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Page 1: Anestesia Ocular
Page 2: Anestesia Ocular

Ophthalmol Clin

Preface

Ocular Anesthesia

Marlene R. Moster, MD Augusto Azuara-Blanco, MD, PhD, FRCS (Ed)

Guest Editors

The goal of this volume is to provide practical

clinical information about anesthesia for ocular sur-

gery. These articles have been written for both anes-

thetists and ophthalmologists, and so we have tried

to integrate the most commonly used techniques

and important recent developments, especially in lo-

cal anesthesia.

We have dedicated an article to each of the types

of anesthesia (eg, general, orbital regional, sub-

Tenon’s) and to different types of ocular surgery

(eg, cataract, glaucoma, vitreoretinal, pediatric) to

help incorporate the latest updated material with cur-

rent usage. The practical approach of this volume

is also reflected in the articles on preparation for

anesthesia and preoperative medical testing, seda-

tion techniques, anesthesia for the open globe, treat-

ment of the blind painful eye, and management of

complications. Numerous illustrations have been

used to provide a natural and easily understandable

flow of information. We believe this volume has

been greatly enriched by the inclusion of articles on

history, pharmacology, and cost-effectiveness of ocu-

lar anesthesia.

0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights

doi:10.1016/j.ohc.2006.02.017

We are indebted to the contributors to this volume

for giving so generously of their time and work. They

are all recognized leaders in ophthalmic anesthesia

and surgery. Our expert collaborators have written

comprehensive articles and have also shared their

personal preferences. We are also extremely grate-

ful to Maria Lorusso, our commissioning editor at

Elsevier, for her help, patience, and advice, and to

Yvette Williams for her expert editorial assistance.

Marlene R. Moster, MD

Wills Eye Hospital

Glaucoma Service

900 Walnut Street

Philadelphia, PA 19107, USA

E-mail address: [email protected]

Augusto Azuara-Blanco, MD, PhD, FRCS (Ed)

Department of Ophthalmology

Aberdeen University Hospital

Foresterhill Road

Aberdeen, AB25 2ZN, UK

E-mail address: [email protected]

N Am 19 (2006) xi

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ophthalmology.theclinics.com

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Ophthalmol Clin N

Seeing an Anesthetic Revolution: Ocular Anesthesia

in History

Douglas R. Bacon, MD, MA

Department of Anesthesiology, Mayo Clinic College of Medicine, Ch1-140, 200 First Street, SW, Rochester, MN 55905, USA

Each surgical procedure places unique demands

on the anesthesiologist to create surgical anesthesia

with minimal physiologic trespass on the patient as

well as the surgical repair. In surgery of the eye, the

quest for an anesthetic that does not harm the eye or

the patient can be a challenge. The removal of cata-

racts is one of the most frequently performed opera-

tions in the United States, and the majority of patients

requiring the procedure are elderly and often have

other significant medical conditions.

Early ocular anesthesia

Historically, ocular procedures have had an enor-

mous influence on the discovery of anesthetic mo-

dalities. Before the discovery of surgical anesthesia in

the 1840s, operations on the eye were difficult, as the

sensitive organ would not willing yield to the sur-

geon’s knife. On October 16, 1846, William Thomas

Green Morton demonstrated the anesthetic effects of

diethyl ether as a jaw tumor was removed from

Gilbert Abbott at the Massachusetts General Hospital

[1]. News of this event traveled around the world, and

operations were soon performed that had only been

dreamed about for centuries before. When Lister

conquered infection some 20 years later, surgery

began an explosive growth, with new, more invasive

operations successfully done around the world.

Ocular surgery began to grow. For example, both

William J. and Charles H. Mayo began to perform

procedures on the eye shortly after their respective

0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights

doi:10.1016/j.ohc.2006.02.014

E-mail address: [email protected]

graduations from medical school. In fact, the first

operation done at St. Mary’s Hospital was an eye

operation [2]. But there was a problem. Before thin

suturing material was available to close the eye, the

wound was left open. Ether was notorious for causing

postoperative retching, and therefore damage to the

eye. A solution was needed.

In Vienna, Sigmund Freud began working with

cocaine. He shared some of the crystals with Carl

Koller (Fig. 1) just before leaving to go on vacation.

Koller noticed that his lips became numb when he put

a solution of cocaine crystals on his tongue. In a

eureka moment, Koller realized that this same

solution ought to make the surface of the cornea

numb. Going into the laboratory, he placed drops of

the cocaine solution on the eyes of several experi-

mental animals, and was able to touch the eye with-

out any reaction. Koller then numbed his own eye,

and that of an assistant. He realized he now had a

topical anesthetic for the eye [3].

Koller quickly took this new anesthetic to the

ophthalmology clinic. He was successful in its use in

eye surgery in a large number of patients. Putting

the results together in a paper, which was accepted

for presentation at the prestigious Congress of Ger-

man Ophthalmologists meeting, September 15 and

16, 1884 in Heidelberg, Koller was anxious to tell his

colleagues of his discovery. Koller, however, could

not afford to go. His friend, Josef Brettauer presented

the paper, which caused a number of people to begin

to see the potential of cocaine as an anesthetic, and a

‘‘rival’’ to ether [4].

William Halstead, who traveled to Europe and

was at the Allgemiene Krankenhouse at the time of

Koller’s discovery, came back to the United States

Am 19 (2006) 151 – 154

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Fig. 1. Carl Koller. (Courtesy of the Wood Library-Museum,

Park Ridge, IL.)

bacon152

and began to work with cocaine. He would infiltrate

the cocaine into the skin and dissect down to nerve

trunks. While looking at the dissected nerve, Halstead

instilled a solution of cocaine to cause blockage in

nerve transmission—the first regional anesthesia. Hal-

stead published the results of his experience [5] be-

fore he entered treatment for a cocaine addiction [6].

Koller’s fellow Europeans picked up on the idea

of regional anesthesia. Schleich began infiltrating

cocaine into the spinal cord when attempting a lumbar

puncture [7]. Bier and Hildenbrand were successful in

injecting cocaine intrathecally, and producing spinal

anesthesia [8]. James Corning, in New York, produced

the first epidural anesthetic [9]. Thus, the quest for

better anesthesia for ophthalmologic surgery resulted

in a new form of anesthesia—regional! And its

founder, Carl Koller, was forced to leave Vienna after

a duel, settled in New York City, and practiced as an

ophthalmologist [4].

Regional blockade of the eye

The blocks in use for ophthalmologic surgery

today have developed in the years since Koller’s

remarkable discovery. Most interestingly, H. Knapp

described a block in the eye using a needle and

syringe, very similar in technique to the retrobulbar

block. Writing in 1884, months after the discovery of

cocaine’s local anesthetic quality, Knapp’s work

never gained popularity [10], most likely because of

the unique properties of cocaine. Blocks are often

patchy, and absorption of the agent causes hyper-

tension and tachycardia, as well as a feeling of

euphoria [11]. Increasing blood pressure may have

contributed to an increase in intraocular pressure, and

without fine suture to close the incision, intraocular

contents may well have been extruded.

However, in 1905, a new local anesthetic,

procaine, was synthesized and used clinically. An

ester, this agent had a predicable onset and duration

of action [12]. Yet this did not change ocular

anesthesia. Gaston Labat, writing in the first textbook

of regional anesthesia published in the United States

believed topical anesthesia was sufficient and com-

mented, ‘‘The following operations need no other

form of anesthesia: superficial interventions on the

conjunctiva, treatment of corneal ulcers by cautery,

removal of foreign bodies from the conjunctiva and

cornea, plastic on the cornea, cataract operations,

iridectomy and other operations on the lens and iris’’

(p. 141) [13].

In 1934, W. S. Atkinson described the classic

retrobulbar block [14]. Atkinson had the patients look

upward and inward before the block was performed.

Using procaine, this form of regional anesthesia of

the eye was very successful and slowly gained

popularity across the United States [15].

However, the retrobulbar block had some signifi-

cant complications associated with it, including dam-

age to the optic nerve. Other options were sought, and

cadaveric study demonstrated that local anesthetics

placed outside intraorbital muscle cone would pene-

trate and create an anesthetic eye. First described in

1986, the peribulbar block is felt to be safer than the

retrobulbar block as the needle is placed at a greater

distance from the eye and optic nerve than with the

retrobulbar block [15].

In the early 1990s, an additional technique was

rediscovered. First described by K. C. Swan in 1956

[16], sub-Tenon’s block involves the injection of

local anesthetic into the episcleral space, which will

create acceptable anesthetic conditions for operations

on the eye. An injection of 6 to 11 milliliters of local

anesthetic is enough to both anesthetize the eye and

the muscles around it, thus making the eye motion-

less. Since the eye muscles are paralyzed, there is no

need for any additional blocks [17].

Since its reintroduction in the 1990s, Koller’s

topical anesthesia for eye surgery has gained in popu-

larity. With improved local anesthetics, the anesthetic

produced by this method was equal, in many

surgeons’ and anesthesiologists’ hand, to that

produced by block, without some of the complica-

tions. However, studies indicate that there may be

some slight increase in postoperative discomfort

Page 5: Anestesia Ocular

ocular anesthesia in history 153

when topical anesthesia is used alone. The experience

of the surgeon is critical in ensuring that the

anesthetic is successful [18].

General anesthesia

In ocular surgery, general anesthesia has been

used, especially since the rise of regional and topical

anesthetics, for those who cannot cooperate in the

operating room or who may have medical conditions,

such as Parkinson’s disease, which cause tremors that

would interfere with the operation. However, in many

ocular trauma cases, the globe is open, and repair

may take longer than regional anesthesia will last.

Thus, a general anesthetic is necessary. In most

trauma cases, because of a ‘‘full stomach’’ rapid se-

curing of the airway is necessary, and the use of

succinylcholine as a quick onset, ultrashort-acting

neuromuscular blocking agent has been recom-

mended. Succinylcholine, however, raises intraocular

pressure [19].

In the 1950s, shortly after the clinical introduction

of succinylcholine, concerns were raised about its use

in open globe procedures. Experimentally, it was

noted that vitreous humor could be extruded while

the eye muscles fasciculated. This potentially had

devastating consequences for the patient. In several

letters to the editor, anecdotal case reports of just such

phenomena occurring were reported. It soon became

widely accepted that succinylcholine was contra-

indicated in the indication of anesthesia when an

open globe was present. Indeed, the combination of

penetrating eye trauma, difficult airway, and a full

stomach became one of the anesthesiologist’s least

favorite nightmares [19].

In the 1990s, however, the trend toward evidence-

based medicine made many physicians’ questions

accepted teaching in anesthesiology. In fully review-

ing the literature, there were no peer-reviewed case

reports of ocular damage when succinylcholine was

used for induction. In point of fact, there were several

large series that pointed in just the opposite direction

[19]. The subject remains controversial.

Subspecialty society

In 1986, the Ophthalmic Anesthesia Society was

formed to ‘‘ensure that the highest quality anesthesia

care is provided to patients undergoing cataract and

other ophthalmic surgical procedures’’ (p. 1) [20].

The society holds 2-day annual meetings where

matters of importance to the field, new research,

and education are presented. More importantly, there

is a community of anesthesia professionals who

can interact with each other and develop this sub-

specialty area. The society’s newsletter, posted on

their Web site, is a marvelous reference for those in-

terested in the field. In 2006, the society will cele-

brate its 20th anniversary with an exciting meeting in

Chicago, Illinois.

Summary

The history of ocular anesthesia reflects the

broader history of anesthesiology and has made

important contributions to the field. Carl Koller’s

search for an anesthetic that was superior to the

general anesthesia available to him led to the creation

of an entire new division of anesthesia. Regional

anesthesia has been used successfully in countless

cases. Specifically, Koller’s demonstration of topical

anesthesia of the eye has remained in use, although

slightly modified, since its inception. The popularity

of cutaneous regional anesthesia in the first four

decades of the twentieth century may have been

responsible for Atkinson’s description and the sub-

sequent popularity of the retrobulbar block. Further

research and cadaveric demonstrations have de-

veloped additional regional anesthetic techniques

including the peribulbar and sub-Tenon’s blocks.

Finally, the use of succinylcholine in open globe

anesthesia is a marvelous example of the continuing

examination of the evidence within medicine. New

conclusions drawn from old data, supplemented by

new investigations can successfully challenge old

accepted ideas in medicine.

References

[1] Fenster J. Ether day. New York7 HarperCollins Pub-

lishers, Inc; 2001.

[2] Clapesattle H. The doctors Mayo. Minneapolis (MN)7

University of Minnesota Press; 1941. p. 252.

[3] Koller C. Personal reminiscences of the first use of

cocain as local anesthetic in eye surgery. Curr Res

Anesth Analg 1928;7:9–11.

[4] Wyklicky H, Skopec M. Carl Koller (1857–1944)

and his time in Vienna. In: Scott DB, Mc Clure J,

Wildsmith JAW, editors. Regional anesthesia 1884–

1984. Sodertalje, Sweden7 ICM; 1984. p. 12–6.

[5] Halstead WS. Practical comments on the use and abuse

of cocaine; suggested by its invariably successful

employment in more than a thousand minor surgical

operaitons. New York Medical Journal 1885;42:294.

Page 6: Anestesia Ocular

bacon154

[6] Olch PD, William S. Halstead and local anesthesia.

Contributions and complications. Anesthesiology

1975;42:479–86.

[7] Goerig M, Schulte am Esch J. Carl-Ludwig Schleich

and the scandal during the annual meeting of the

German Surgical Society in Berlin in 1892. In: Fink

BR, Morris LE, Stephen CR, editors. The history of

anesthesia. Park Ridge (IL)7 The Wood Library-

Museum; 1992. p. 216–22.

[8] Goerig M, Argarwal K, Schulte am Esch J. The

versatile August Bier (1861–1949)—father of spinal

anesthesia. J Clin Anesth 2000;12:561–9.

[9] Marx GF. The first spinal anesthesia. Who deserves the

laurels? Reg Anesth 1994;19:429–30.

[10] Knapp H. On cocaine and its use in ophthalmic and

general surgery. Arch Ophthal 1884;13:402–8.

[11] Bacon DR. Regional anesthesia and chronic pain ther-

apy: a history. In: Brown DL, editor. Regional

anesthesia and analgesia. Philadelphia7 W.B. Saunders

Co; 1996. p. 10–22.

[12] Calatayud J, Gonzalez A. History of the development

and evolution of local anesthesia since the coca leaf.

Anesthesiology 2003;98:1503–8.

[13] Labat G. Regional anesthesia: its techniques and

clinical application. Philadelphia7 WB Saunders; 1924.

[14] Atkinson WS. Retrobulbar injection of anesthetic

within the muscular cone. Arch Ophthal 1936;16:494.

[15] McGoldrick KE, Gayer SI. Anesthesia and the eye.

In: Barash PG, Cullen BF, Stoelting RK, editors.

Clinical anesthesia. 5th edition. Philadelphia7 Lippen-

cott Williams & Wilkins; 2006. p. 974–96.

[16] Swan KC. New drugs and techniques for ocular

anesthesia. Trans Am Acad Ophthalmol Otolaryngol

1956;60:368–75.

[17] Ripart J, Nouvellon E, Chaumeron A. Regional

anesthesia for eye surgery. Reg Anesth Pain Med

2005;30:72–82.

[18] Crandall AS. Anesthesia modalities for cataract sur-

gery. Curr Opin Ophthalmol 2001;12:9–11.

[19] Vachon CA, Warner DO, Bacon DR. Succinylcholine

and the open globe: tracing the teaching. Anesthesiol-

ogy 2003;99:220–3.

[20] Ophthalmic Anesthesia Society. Available at: http://

www.eyeanesthesia.org/index.html. Accessed January

16, 2006.

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Ophthalmol Clin N

Pharmacology of Local Anesthetics

Tim Jackson, MB, ChB, MRCP, FRCAT, Hamish A. McLure, MB, ChB, FRCA

Department of Anesthesia, St James’s University Hospital, Beckett Street, Leeds LS7 9TF, UK

The stimulus for the development of regional

anesthesia was the retreat from poor surgical con-

ditions afforded by primitive general anesthesia in the

latter half of the 19th century. Karl Koller, an eager

young ophthalmic surgeon, was investigating the ef-

fects of cocaine. He found that a few drops instilled

into his own conjunctival fornix produced insensi-

tivity to injury. These magical properties made it pos-

sible to perform painful procedures on patients who

were awake, in quiet surgical conditions without the

systemic toxicity of general anesthesia. However, co-

caine is not without serious adverse effects and

reports of toxicity limited universal uptake by the

ophthalmic community. Two events brought new life

to the field of ophthalmic local anesthesia: (1) the

development of procaine, a much safer alternative to

cocaine, and (2) the description of retrobulbar an-

esthesia by Atkinson [1]. The agents and injection

methods have since been refined and local anesthesia

is now the most common technique used to provide

anesthesia for ocular surgical procedures. Despite

improvements, there is still the potential for compli-

cations, both local and systemic, during routine pro-

cedures. To reduce risks, it is vital for the practitioner

to have a thorough understanding of the physiology

of neuronal function, the chemistry of various local

anesthetic agents, and the pathogenesis of toxicity.

Physiology of nerve conduction

Impulses are transmitted along the nerve in the

form of a wave of electrical activity called an action

potential. This rapid process (1–2 msec) is mediated

0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights

doi:10.1016/j.ohc.2006.02.006

T Corresponding author.

E-mail address: [email protected]

(T. Jackson).

by alterations in the permeability of the neuronal

membrane to various cations, notably sodium and

potassium. In the non-excited resting state, chemical

and electrical gradients exist across the neuronal

membrane. These gradients are established by various

ion channels, which may be passive, active, or voltage

gated. The nerve membrane is relatively imperme-

able to the passage of sodium (Na), but permeable to

potassium (K). In addition to these passive move-

ments, active Na/K-ATPase channels pump potassium

into the cell and sodium outwards, in a molar ratio

of 3:2 respectively. The net effect of these two pro-

cesses, active and passive, is to create a resting po-

tential across the neuronal membrane, in which the

interior is negatively charged (�70 to �90 mV).

The membrane also contains voltage-gated so-

dium channels, which open and close based upon the

membrane potential. Each channel molecule consists

of a pore formed of one a subunit and one or two bsubunits. The a subunit is in turn composed of four

domains (D1–4), each of which comprises six trans-

membrane helical segments (S1–6). These channels

are able to cycle through four states or phases: rest-

ing, activated, inactivated, and deactivated (Fig. 1).

Functionally, the channel can be considered to pos-

sess two gates, an outer m gate and an inner h gate.

At the resting membrane potential, the m gate is

closed, but the h gate is open. On stimulation (ac-

tivation) the m gate opens, and there is an influx of

sodium ions down their electrochemical gradient,

which causes a rise in the membrane potential. If this

occurs with sufficient magnitude, a threshold poten-

tial of about �60 mV is reached, there is widespread

opening of sodium channels, and even greater influx

of sodium ions such that the membrane potential

overshoots neutral to reach a peak of +20 mV. At this

point the h gate closes, which inactivates the channel

and prevents further sodium flux. This process of

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Fig. 1. Diagramatic representation of sodium channel in three main conformational states.

jackson & mclure156

depolarization produces a potential difference rela-

tive to neighboring areas of the neuronal membrane,

which in turn generates an electrical current that tends

to depolarize those neighboring areas of membrane.

Thus, a wave of depolarization flows along the nerve,

propagating the initial stimulus.

During the inactivated phase there is no inward

movement of sodium through the voltage gated chan-

nels, and the resting membrane potential is restored

by continued action of the Na/K-ATPase and pas-

sive potassium leakage. When the membrane potential

reaches �60 mV, the m gate closes and the channel is

said to be deactivated. During these latter two phases

the nerve is refractory to further stimulation, which

prevents rapid re-depolarization of that section of neu-

ronal membrane and retrograde conduction.

Mechanism of action

Local anesthetics reversibly block conduction of

action potentials by interacting with the D4–S6 por-

tion of thea subunit of the voltage-gated sodium chan-

nels. This site of action is intracellular, so the local

anesthetic must first diffuse through the lipophilic

nerve membrane. Local anesthetics are administered

in an acidic solution that causes most of the drug to be

present in the ionized form, which is lipophobic.

Therefore, the drug must first be converted to the un-

ionized form in sufficient quantity to enter the nerve

cell. This depends upon the pKa of the local anesthetic

and the pH of the tissue. Once inside the nerve cell, the

lower pH converts the drug back into the ionized

form, which is then able to block the sodium channels.

This reduces the influx of sodium ions and sub-

sequently, the depolarization of the membrane poten-

tial slows. If sufficient channels are blocked, it will

prevent the threshold potential from being reached,

and prevent propagation of an action potential, with-

out affecting either the resting membrane potential

(which is independent of voltage-gated sodium

channels) or the threshold potential itself.

In addition to the action of the ionized local an-

esthetic moiety on the intracellular portion of the

trans-membrane sodium channel, the non-ionized

form also affects the intra-membrane areas of the

channel: it has direct physical effects on the ex-

pansion of the lipid bilayer. The action of local an-

esthetics is augmented by the blockade of potassium

channels, calcium channels, and G-protein coupled

receptors [2–4].

Local anesthetic agents exhibit differing affinities

with their binding site depending on the state of the

channel, as the conformational changes in the channel

inherent in the cycling of these states reveal or

obscure the binding site. Affinity is greatest when the

channel is open (activated or inactivated) and least

when it is closed (deactivated and resting). Although

this suggests that access of the local anesthetic to its

binding sites will differ based on the frequency of

nerve stimulation, there is no evidence that this use-,

phase-, or frequency-dependent block can be manip-

ulated to alter the quality of the block [5].

In addition to these state-dependent differences in

channel affinity, there are also differences between

local anesthetic agents. Lidocaine binds and disso-

ciates rapidly, whereas bupivacaine dissociates more

slowly. This difference is relatively unimportant for

neuronal conduction, but is crucial to cardiac toxicity.

Conduction of the cardiac impulse is mediated by

voltage-gated sodium channels. Lidocaine binds and

dissociates from these channels quickly; there is little

chance that a frequency-dependent block of the im-

pulse would occur. However, bupivacaine, and part-

icularly the R-isomer, which dissociates more slowly

than the S-isomer, can produce a more profound

frequency-dependent block [6]. Cardiac conduction is

slowed and lethal arrhythmias may occur.

Chemistry

The molecular structure of the standard local an-

esthetics conforms to a similar pattern of a lipophi-

Page 9: Anestesia Ocular

Fig. 2. Generic structure of local anesthetic agents.

pharmacology of local anesthetics 157

lic aromatic ring, linked to a hydrophilic tertiary

or quarternary amine derivative. The intermediate

hydrocarbon chain is joined to the amine moiety by

an ester, amide, ketone or ether, and may be used to

classify the drug as such (Fig. 2). Other dissimilar

compounds may also possess local anesthetic prop-

erties, although they are seldom used in ophthalmic

regional anesthesia (eg, amitryptiline, meperidine)

[7,8]. The clinically used agents are the ester and

amide local anesthetics. The ester bond is relatively

unstable, during hydrolysis, which ensures rapid me-

tabolism in vivo, but shelf life is dramatically short-

ened and autoclave sterilization is impossible.

Ionization

Local anesthetics are weak bases (pKa 7.6–8.9)

(Table 1); poorly soluble in water and therefore

usually presented in acidic hydrochloride salt sol-

utions (pH 3–6). In this form, the local anesthetic

rapidly becomes reduced to a cationic form. This

process is readily reversible, and the relative propor-

tions of neutral base and ionized form develop equi-

Table 1

Physicochemical and clinical properties of local anesthetics

Agent

pKa

(25�C) Speed of onset

Partition

coefficienta

Amide agents

Bupivacaine 8.1 Intermediate 346

Levobupivacaine 8.1 Intermediate 346

Etidocaine 7.7 Fast 800

Lidocaine 7.7 Fast 43

Mepivacaine 7.6 Fast 21

Prilocaine 7.8 Fast 25

Ropivacaine 8.2 Intermediate 115

Ester agents

Cocaine 8.7 Slow Ub

Amethocaine 8.5 Slow 221

Procaine 8.9 Slow 1.7

a Partition coefficient with n-octanol/buffer.b U unknown.

librium as described by the Henderson-Hasselbach

equation. The proportions of each form of the drug

depend on the pH of the solution and the pKa of the

particular drug in question, which is the dissociation

constant and denotes the pH at which the ionized and

neutral forms are present in equal amounts.

pH ¼ pKa þ log base½ �= acid½ �

For a base pH=pKa + log [un-ionized] / [ionized]

Because the pKa for a given local anesthetic agent

is constant, the clinical relevance is in comparing the

speed of onset. Most clinically available local anes-

thetics have pKa values in excess of the pH of extra-

cellular fluid; therefore, the ionized form dominates

after injection, which makes it unable to penetrate the

cell. Those agents with pKa values at the lower end of

the range will have a greater proportion present in the

neutral form, which diffuses more rapidly into the

nerve cell and their site of action. Increasing the pH

of the carrier solution will similarly favor the

formation of a more neutral base, although chemical

stability is reduced by this maneuver. The converse is

true for inflamed tissue, which inherently has a lower

Potency Toxicity

Protein

bound (%) Duration

High High 95 Long

High Intermediate 96 Long

High High 94 Long

Intermediate Low 64 Intermediate

Intermediate Low 75 Intermediate

Intermediate Low 55 Intermediate

Intermediate Intermediate 94 Long

High Very high 98 Long

Intermediate Intermediate 76 Intermediate

Low Low 6 Short

Page 10: Anestesia Ocular

jackson & mclure158

pH than the usual physiological value (7.4), and

renders the local anesthetic less effective.

Lipid solubility

Lipid solubility is a property of the hydrocarbon

chain and aromatic group, and is represented by the

partition coefficient which is a measure of the rela-

tive distribution of agent between an aqueous phase

(eg, buffer at pH 7.4) and non-ionized solvent phase

(eg, octanol, heptane, hexane). As the partition coeffi-

cient gets higher, the drug becomes more lipid solu-

ble, and the concentration of the drug within the

nerve membrane goes up. This is a major determinant

of potency; agents that have high partition coeffi-

cients (eg, bupivacaine, etidocaine) have correspond-

ingly high potency (see Table 1).

Protein binding

Local anesthetics bind to tissue and plasma pro-

teins (albumin, a1-acid glycoprotein). Albumin is

considered high volume, low affinity binding,

whereas, a1-acid glycoprotein is low volume, high

affinity. These proteins represent a reservoir of the

drug, although it is the free drug that is active. The

amount of protein binding correlates well with du-

ration of action of local anesthetic agents; however,

other factors such as potency, dose, presence of vaso-

active substances, and vascularity of the tissue also

have effects. As local anesthetics are absorbed sys-

temically, the binding sites are occupied gradually,

and have apparent stability in free plasma concen-

trations. However, once the binding sites are satu-

rated, toxic levels can be rapidly reached and have

disastrous consequences. This may also occur with

more modest doses in the presence of acidosis, when

local anesthetic dissociates from the binding sites.

Chirality

Organic molecules contain asymmetric carbon

atoms, which may exist as mirror image or stereo-

isomers. They can be identified by the way they

rotate polarized light, and are either R or L, � or + for

dextro- or levorotatory respectively. Bupivacaine,

etidocaine, mepivacaine, prilocaine, and ropivacaine

all have such carbon atoms, and most are produced as

racemic mixtures: composed of equal amounts of

both dextrorotatory and levorotatory isomers. The

exceptions are S-ropivacaine and S-bupivacaine,

which have been marketed separately. They have

similar physicochemical properties, including those

relating to their pharmacokinetics, but behave differ-

ently at biological receptors. As previously men-

tioned, S-bupivacaine (and indeed S-ropivacaine)

demonstrates significantly reduced toxicity.

Metabolism

Ester local anesthetics are hydrolyzed very rapidly

by tissue and plasma cholinesterases. The metabolites

are inactive as local anesthetics, but include para-

aminobenzoic acid (PABA) which can be allergenic.

The rapidity of this metabolism provides some degree

of safety from toxicity, because plasma levels fall so

rapidly. The exception, although no longer used di-

rectly in ophthalmology, is cocaine, which is metab-

olized more slowly in the liver.

Amides are much more stable in plasma than

esters. They are initially absorbed, then distributed to

the pulmonary circulation, where they are temporarily

sequestered by ion-trapping because of the relatively

low pH of extravascular lung water. They are pre-

dominantly cleared by hepatic microsomal phase I

and II reactions, although a small percentage is

cleared by renal mechanisms. The rate of metabolism

depends heavily on liver blood flow, and differs be-

tween agents. Prilocaine and etidocaine are the most

rapid, lidocaine and mepivacaine are intermediate,

and bupivacaine and ropivacaine are the slowest. The

clearance of prilocaine exceeds what the liver could

do alone, which suggests that extra-hepatic mecha-

nisms are also involved, most likely in the lung [9].

Toxicity

Toxic reactions may be local or systemic. Local

toxicity occurs when local anesthetic is injected di-

rectly into a structure, such as a nerve or muscle,

whereas systemic toxicity follows absorption of ex-

cessive amounts or inadvertent intravascular injec-

tion. An exaggerated effect with systemic toxicity may

also occur following accidental sub-dural injection.

Neurotoxicity

Local anesthetics may cause damage to neural

tissue, either by direct injection into a nerve, or in

situations where highly concentrated local anesthetic

solutions bathe nerves for a prolonged period. It

may also occur with concentrations of lidocaine that

would be used in clinical practice. An in vitro squid

Page 11: Anestesia Ocular

pharmacology of local anesthetics 159

axon model showed neurotoxicity with lidocaine 2%

[10]. Lidocaine-induced neurotoxicity has also been

seen in patients with the use of spinal micro catheters

and 5% lidocaine [11]. The presumed mechanism is

relatively concentrated lidocaine that bathes vulner-

able nerves for a prolonged period of time. Fortu-

nately, in ophthalmic regional anesthesia, neither the

concentration, nor the duration of proximity to nerves

of the local anesthetic is sufficiently high, so the local

anesthetic is unlikely to be the sole culprit in neu-

rological damage. In these cases many patients have

coexistent vascular pathology. Highly concentrated

local anesthetic is often used with vasoconstrictors,

and high orbital pressures may develop. It is not sur-

prising that nerve ischemia and subsequent damage

may occur in this adverse environment.

Myotoxicity

Direct injection into muscle can cause muscle

necrosis. The subsequent fibrosis and contracture of

the muscle can significantly impair function and

cause diplopia, which could require surgery. This can

be particularly devastating in elderly patients whose

balance and mobility may already be compromised.

The inferior oblique, inferior rectus, and medial rec-

tus muscles are most frequently involved. This injury

may occur by direct injection into the muscle, but it

has also been reported with sub-Tenon’s injection,

where the mechanism of action may be caused by

local anesthetic that pools around or penetrates the

muscle through small fenestrations in Tenon’s fascia.

It has been suggested that the risks of local anesthetic

induced myotoxicity may be reduced by the addition

of hyaluronidase, which allows dispersal of local

anesthetic away from the muscle [12].

Systemic toxicity

Systemic reactions are uncommon, but may prove

disastrous. In ocular regional anesthesia, systemic re-

actions may occur when anesthetic agent is injected

through the dural cuff into cerebrospinal fluid around

the optic nerve. Brainstem anesthesia could occur

along with loss of consciousness and respiratory and

cardiovascular depression. Supportive treatment is

aimed at securing the airway, providing positive pres-

sure ventilation, and using fluids and vasopressors to

support the circulation. Systemic reactions may also

result from administration of an inappropriately large

dose, or follow intravascular injection of even a small

dose. Intravenous injections of an appropriate dose

may cause significant effects. Reactions can also oc-

cur when much smaller doses are injected at high

pressure into the arterial system, which results in the

retrograde spread of high concentrations of local an-

esthetic solution direct to the brain. The effect of these

mishaps depends upon the drug injected, the speed of

injection, the total dose administered, and the phys-

iology of the patient. Methods aimed at reducing these

complications include techniques to carefully position

the injecting needle, aspiration before every injection

(although a negative aspiration does not exclude the

possibility of intravascular injection), the use of a

test dose, fractionated doses, adequate time between

doses, the use of a less toxic local anesthetic, aware-

ness of maximum doses in different settings, and the

addition of other agents (opioids, clonidine, hyal-

uronidase, bicarbonate, epinephrine) to reduce the

amount of local anesthetic required.

The sequence of toxic phenomena depends upon

the rate of increase in plasma concentration. If the

plasma concentration rises slowly, symptoms develop

such as circumoral and tongue paraesthesiae, a me-

tallic taste, and dizziness, followed by slurred speech,

diplopia, tinnitus, confusion, agitation, muscle twitch-

ing, and convulsions. At even higher plasma levels,

the effects become depressive, and lead to coma and

death. As with direct subarachnoid injection, the treat-

ment is supportive and anticonvulsants are adminis-

tered to control seizure activity.

As plasma levels of local anesthetics increase, neu-

rological effects are accompanied by cardiovascular

complications, which can be difficult to treat. Im-

pending toxicity may be signaled by bradycardia with

prolonged PR interval (the time, in seconds, from the

beginning of the onset of atrial depolarization to the

beginning of the onset of ventricular depolarization)

and broad QRS complex (the EKG representation of

the heart’s electrical impulse as it passes through the

ventricles). This may be followed by a range of dys-

rhythmias, such as heart block, multifocal ectopics,

tachycardia, and ventricular fibrillation. Again, treat-

ment is supportive, but is likely to involve the use of

antiarrhythmics such as amiodarone, phenytoin, and

bretyllium. There is evidence that suggests lipid emul-

sion infusions (intralipid) and clonidine may also

have a supportive role. Although lidocaine has a role

in the treatment of ventricular tachydysrrhythmias, it

would be sensible to avoid it if local anesthetic car-

diotoxicity has been established. Resuscitation is

difficult and may require prolonged efforts, but clini-

cians should remember that the local anesthetic-

induced neuronal depression may be protective

against brain injury.

Page 12: Anestesia Ocular

jackson & mclure160

Increasing laboratory data suggest that modern,

single-isomer local anesthetic preparations provide

improved safety profiles. Nancarrow and colleagues

[13] compared the toxic effects of intravenous bu-

pivacaine, ropivacaine, and lidocaine in sheep, and

found a ratio of lethal doses of 1:2:9. The group that

received lidocaine died with respiratory depression,

bradycardia, and hypotension, but without arrhyth-

mias, whereas, three of four sheep treated with bu-

pivacaine died because of ventricular arrhythmias in

the absence of hypoxia or acidosis. The group treated

with ropivacaine died from a combination of these

causes, or as a result of sudden onset ventricular ar-

rhythmias alone. The arrhythmias precipitated by local

anesthetics are caused by depression of the rapid

depolarization phase (Vmax) of the cardiac action

potential. This leads to slowed conduction, re-entrant

rhythms, and predisposition to ventricular tachycardia.

The effects of arrhythmias on cardiac output are

augmented by myocardial depression, although this

may be offset by the myocardial stimulation asso-

ciated with seizures [14]. In an attempt to isolate the

cardiovascular effects, Chang and colleagues [15]

infused bupivacaine, levobupivacaine, and ropiva-

caine directly into the coronary arteries of conscious

sheep. No significant differences were found in sur-

vival or fatal doses, which indicate that these agents

may have equal cardiac toxicity [16]. Using an

anaesthetised swine model, Morrison and colleagues

[17] administered intracoronary injections of bupiva-

caine, levobupivacaine, and ropivacaine. They found

little difference in fatal dose between levobupivacaine

and ropivacaine, but racemic bupivacaine had greater

cardiotoxicity. Feldman and colleagues [18] showed

that similar doses of ropivacaine and bupivacaine

caused convulsions in dogs, but that the mortality rate

was lower in the animals treated with ropivacaine.

Isolated organ experiments have linked local anes-

thetic toxicity in the brain to disturbances in the heart

[19]. The varied results of these studies may reflect

inter-species variation, or may be a reflection of the

complex interplay between the central nervous sys-

tem, the myocardium, and general anesthesia during

local anesthetic toxicity.

Although the conclusions of these animal studies

are compelling, it is difficult to confirm their results

in human subjects, particularly with respect to lethal

doses. Scott [20] administered a maximum of 150 mg

of ropivacaine and racemic bupivacaine to healthy

volunteers. Of the 12 subjects, 7 tolerated the maxi-

mum dose of ropivacaine, whereas only 1 subject was

able to tolerate 150 mg of bupivacaine. Plasma levels

showed that central nervous system and cardiovas-

cular symptoms occurred at lower plasma levels with

bupivacaine than ropivacaine. In addition, ropiva-

caine reduced myocardial depression and widening of

the QRS (wave) complex. Bardsey and colleagues

[21] used intravenous infusions of lidocaine to fa-

miliarize 12 healthy volunteers with the central ner-

vous system effects of local anesthetic toxicity. A few

days later the volunteers received intravenous infu-

sions of levobupivacaine or bupivacaine at a rate of

10 mg/min until they had received 150 mg, or had

begun to experience central nervous system toxic ef-

fects. Cardiovascular monitoring demonstrated that,

despite higher plasma levels, levobupivacaine de-

pressed myocardial function significantly less than

bupivacaine. Equal doses of intravenous levobupiva-

caine were compared with ropivacaine by Stewart

and colleagues [22]. No differences were found in

terms of central nervous system symptoms or car-

diovascular effects.

Animal and human studies have shown improved

safety with the single-isomer local anesthetics levo-

bupivacaine and ropivacaine. However, they may still

provoke severe toxic reactions. In addition, the mar-

ginally reduced potency of ropivacaine requires a

larger total dose and may reduce any benefit of the

single isomeric form.

Allergy

The first reports of allergy to local anesthesia were

from a dentist who developed contact dermatitis after

repeated exposed to apothesin, an ester local anes-

thetic [23]. Further minor reactions were reported, but

very few individuals developed anaphylaxis. The

trigger for these reactions was found to be PABA, an

intermediate metabolite of ester hydrolysis. Sensitiv-

ity to PABA may also occur as a result of exposure to

certain foodstuffs or cosmetics, and because sulpho-

namides structurally resemble PABA, cross-reactivity

to all these substances may occur.

The development of amide local anesthetics in the

1940s effectively reduced reports of allergic reac-

tions. Amides are now considered to be very rare

allergens; only about 1% of alleged reactions are be-

lieved to be caused by a truly immune-mediated

process [24]. Reports of previous allergic reactions

come largely from the dentist’s surgery. This is likely

to have been a vagal response in a patient who was

anxious and in a semi-upright position, or an in-

advertent intravascular injection of local anesthetic

solution and its associated vasopressor, which pro-

duced some unpleasant cardiovascular effects. Never-

theless, it is important to exclude allergy by referral to

an allergist, who will perform skin-prick tests for

Page 13: Anestesia Ocular

pharmacology of local anesthetics 161

mild reactions or in-vitro testing for patients who

have suffered an anaphylactoid reaction.

Summary

Local anesthesia forms the backbone of all oph-

thalmic anesthetic techniques. From its inception in

the 19th century to the modern era, developments

in the chemistry of local anesthetic agents and im-

provements in operative conditions have led to

reductions in the incidence of adverse reactions. Ne-

vertheless, use of this powerful group of agents is

not without hazard, and it is vital to have a thorough

understanding of the underlying chemistry, and

their potential to cause local and systemic toxicity

when they are used for ophthalmic regional anesthe-

sia. The single-isomer preparations show great pro-

mise in the laboratory, but have yet to demonstrate a

clinical difference.

References

[1] Atkinson WS. Retrobulbar injection of anesthetic within

the muscular cone. Arch Ophthalmol 1936;16:494–503.

[2] Xiong Z, Strichartz G. Inhibition by local anesthetics

of Ca 2+ channels in rat anterior pituatary cells. Eur J

Pharmacol 1998;363:81–90.

[3] Hollman M, Wieczorek K, Berger A. Local anesthetic

inhibition of G protein-coupled receptor signaling by

interference with Galpha(q) protein function. Mol

Pharmacol 2001;59:294–301.

[4] Olschewski A, Hemplemann G, Vogel W. Blockade of

Na + currents by local anesthetics in the dorsal horn

neurons of the spinal cord. Anesthesiology 1998;88:

172–9.

[5] Courtney K. Mechanism of frequency-dependent

inhibition of sodium currents in frog myelinated nerve

by the lidocaine derivative GEA 968. J Pharmacol Exp

Ther 1975;195:225–36.

[6] Vanhoutte F, Vereecke J, Verbeke N, et al. Stereo-

selective effects of the enantiomers of bupivacaine on

the electrophysiological properties of the guuinea-pig

papillary muscle. Br J Pharmacol 1991;103:1275–81.

[7] Sudoh Y, Cahoon E, Gerner P, et al. Tricyclic anti-

depressants as long-acting local anesthetics. Pain 2003;

103:49–55.

[8] Acalovschi I, Cristea T. Intravenous regional anesthe-

sia with meperidine. Anesth Analg 1995;81:539–43.

[9] Tucker G. Local anesthetic drugs: mode of action and

pharmacokinetics. In: Nimmo W, Rowbotham D,

Smith G, editors. Anesthesia, vol. 2. Oxford7 Blackwell

Scientific Publications; 1994. p. 1371.

[10] Kanai Y, Katsuki H, Takasaki M. Lidocaine disrupts

axonal membrane of rat sciatic nerve in vitro. Anesth

Analg 2000;91:944–8.

[11] Lambert L, Lambert D, Strichartz G. Irreversible con-

duction block in isolated nerve by high concentration

of local anesthetic. Anesthesiology 1994;260:121–8.

[12] Brown S, Brooks S, Mazow M, et al. Cluster of dip-

lopia cases after periocular anesthesia without hyal-

uronidase. J Cataract Refract Surg 1999;25:1245–9.

[13] Nancarrow C, Rutten A, Runciman W, et al. Myocar-

dial and cerebral drug concentrations and the mecha-

nism of death after fatal intravenous doses of lidocaine,

bupivacaine, and ropivacaine in sheep. Anesth Analg

1989;69:276–83.

[14] Rutten A, Nancarrow C, Mather L, et al. Hemody-

namic and central nervous system effects of intra-

venous bolus doses of lidocaine, bupivacaine, and

ropivacaine. Anesth Analg 1989;69:291–9.

[15] Chang D, Ladd L, Copeland S, et al. Direct cardiac

effects of intracoronary bupivacaine, levobupivacaine

and ropivacaine in sheep. Br J Pharmacol 2001;132:

649–58.

[16] Huang Y, Pryor M, Mather L, et al. Cardiovascular and

central nervous system effects of intravenous levobu-

pivacaine and bupivacaine in sheep. Anesth Analg

1998;86:797–804.

[17] Morrison S, Dominguez J, Frascarolo P, et al. A

comparison of the electrocardiographic effects of ra-

cemic bupivacaine, levobupivacaie, and ropivacaine in

anesthetized swine. Anesth Analg 2000;90:1308–14.

[18] Feldman H, Arthur G, Pitkanen M, et al. Treatment of

acute systemic toxicity after rapid intravenous injection

of ropivacaine and bupivacaine in the conscious dog.

Anesth Analg 1991;73:373–84.

[19] Heavner J. Cardiac dysrhythmias induced by infusion

of local anesthetic into the lateral ventricles of cats.

Anesth Analg 1986;65:133–8.

[20] Scott D, Lee A, Fagan D, et al. Acute toxicity of

ropivacaine compared with that of bupivacaine.

Anesth Analg 1989;78:1125–30.

[21] Bardsley H, Gristwood R, Baker H, et al. A

comparison of the cardiovascular effects of levobupi-

vacaine and rac-bupivacaine following intravenous

administration to healthy volunteers. Br J Clin Phar-

macol 1998;46:245–9.

[22] Stewart J, Kellet N, Castro D. The central nervous

sytem and acrdiovascular effects of levobupivacaine

and ropivacaine in healthy volunteers. Anesth Analg

2003;97:412–6.

[23] Monk W. Skin reactions to apothesin and quinine (sic)

in susceptible persons. Arch Derrmatol 1920;1:651–5.

[24] Finucane B. Allergies to local anesthetics - the real truth.

Canadian Journal of Anesthetics 2003;50:869–74.

Page 14: Anestesia Ocular

Ophthalmol Clin N

Preoperative Medical Testing and Preparation for

Ophthalmic Surgery

Bobbie Jean Sweitzer, MD

University of Chicago, 5841 S. Maryland Avenue, Chicago, IL 60637, USA

As the practice of medicine becomes more

outcome-driven and cost-conscious, clinicians need

to reevaluate and streamline methods of patient care.

A preoperative evaluation is important to

Screen for and optimize co-morbid conditions.

Assess and lower the risk of anesthesia

and surgery.

Establish baseline results to guide perioperative

decisions.

Facilitate timely care and avoid cancellations on

the day of surgery.

The Australian Incident Monitoring Study (AIMS)

found that adverse events were unequivocally related

to insufficient (3.1%; 197 of the first 6271 reports)

and inadequate (11%) preoperative assessments [1].

More than half the incidents were considered pre-

ventable. Delays, complications, and unanticipated

postoperative admissions have been significantly re-

duced by preoperative screening and patient contact.

Ophthalmologic procedures are considered low

risk because of their general lack of physiologic dis-

turbances such as hemodynamic perturbations, sig-

nificant stress response, hypercoagulable state, blood

loss, or postoperative pain [2]. However, ophthalmic

patients are often elderly and have multiple co-

morbid conditions that are a constant threat to well-

being, even without surgery. If general anesthesia

(GA) is necessary, the risk of the procedure may

increase. In a study of patients who had cataract sur-

gery, there was significantly more myocardial ische-

0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights

doi:10.1016/j.ohc.2006.02.007

E-mail address: [email protected]

mia in the group that was given GA compared with

the group that was given local anesthesia. There

was a surprisingly high incidence (31%) of peri-

operative ischemia detected by Holter monitoring for

24 h after surgery. Interestingly, there was no dif-

ference in occurrence of ischemia between the two

groups (probably because of the high rate of coronary

heart disease in this elderly population) but the GA

group had more episodes per patient, especially intra-

operatively [3]. Patients who undergo retinal surgery

have a particularly increased risk because of their

associated co-morbid conditions [4].

Preoperative assessment

At a minimum, a preoperative visit should include

the following:

Interview the patient to review medical, anesthe-

sia, surgical, and medication history.

Conduct an appropriate physical examination.

Review the pertinent diagnostic data (laboratory,

electrocardiogram).

Refer the patient to primary care or specialist

physicians to manage new or poorly

controlled diseases.

Formulate and discuss care plan with patient or

responsible adult.

Several studies have proven the utility of a pa-

tient history and physical examination when making

a diagnosis. A study of patients in a general medical

clinic found that 56% of correct diagnoses were made

based on the history alone, and rose to 73% based on

Am 19 (2006) 163 – 177

reserved.

ophthalmology.theclinics.com

Page 15: Anestesia Ocular

sweitzer164

history plus physical examination [5]. In patients who

have cardiovascular disease, the history established

the diagnosis two-thirds of the time, and the physical

examination contributed to one-quarter of diagnoses.

Routine investigations, mainly chest radiographs and

ECG, helped with only 3% of diagnoses, and special

tests, mainly exercise ECG, assisted with 6% [5].

History is also the most important diagnostic method

in respiratory, urinary, and neurologic conditions.

The patient’s medical problems, past surgeries,

previous anesthesia or surgical-related complications,

medications, allergies, and use of tobacco, alco-

Patient's Name

Planned Operation

Surgeon Primary Doctor

1. Please list all operations (and approximate dates) a.

b.

c.

d

e

f.

2. Please list any allergies to medicines, latex or other (a.

b.

c

d

3. Please list all medications you have taken in the las drugs, inhalers, herbals, dietary supplements and asp

Name of Drug Dose and how often Na. f.

b. g.

c. h.

d. i.

e. j.

(Please check YES or NO and circle specific problems4. Have you seen your primary care doctor within the las5. Have you ever smoked? (Quantify in packs/day f

Do you still smoke? Do you drink alcohol? (If so, how much?)Do you use or have you ever used any illegal drugs? (

6. Can you walk up one flight of stairs without stopping?7. Can you lie flat (or with only 1-2 pillows) for at least 8. Have you had any problems with your heart? (circle)

abnormal EKG, heart murmur, palpitation, heart failu9. Do you have high blood pressure? 10. Have you had any problems with your lungs or your c

emphysema, bronchitis, asthma, TB, abnormal chest 11. Are you ill now or were you recently ill with a cold, f

Fig. 1. Sample patient preo

hol, or illicit drugs should be documented (Fig. 1).

A screening review of systems should emphasize air-

way abnormalities, personal or family history of ad-

verse events related to surgery, and cardiovascular,

pulmonary, endocrine, or neurologic symptoms. In

addition to identifying the presence of a disease, it

is equally important to establish the severity, the sta-

bility, and any prior treatment of the condition. The

patient’s medical problems, previous surgeries, and

responses, will elicit further questions to establish

the extent of disease, current or recent exacerbations,

and recent or planned interventions.

Age Sex

Date of Surgery

Cardiologist?

.

.

and your reactions to them) .

.

t month (include over-the-counter irin)

ame of Drug Dose and how often

) YES NOt 6 months? or years)

we need to know for your safety)

one hour? (chest pain or pressure, heart attack, re)

hest? (circle) (shortness of breath, x-ray) ever, chills, flu or productive cough?

perative history form.

Page 16: Anestesia Ocular

preoperative assessment & management 165

Knowledge of the patient’s cardiorespiratory fit-

ness or functional capacity can help guide additional

preoperative evaluation, and help predict outcome

and perioperative complications [2,6]. An ability to

exercise is two-pronged; better fitness decreases dis-

eases such as diabetes and hypertension, as well as

mortality, and a patient’s inability to exercise may

be a result of cardiopulmonary disease and therefore

may identify a patient who warrants further inves-

tigation [7]. Several studies have shown that inabil-

ity to perform average levels of exercise (walking

1–2 flights of stairs) identifies patients at risk of

perioperative complications [8].

The important components of the patient history

are shown in Fig. 1. The form can be completed by

the patient in person (paper or electronic version), by

way of web-based programs, by a telephone inter-

view, or by office staff. This form can be used to

identify patients who may be in need of referral to a

primary care physician, an anesthesiologist, or a spe-

cialist, for further evaluation or management be-

fore surgery. Alternately, the form can be forwarded

13. Have you ever had problems with your: (circle)Liver (cirrhosis, hepatitis, jaundice)? Kidney (infection, stones, failure, dialysis)?

14. Have you ever had: (circle)Seizures, epilepsy, or fits? Stroke, facial, leg or arm weakness, difficulty speakin

15. Have you ever been treated for cancer with chemothera16. Women: Could you be pregnant?

Last menstrual period began: 17. Have you ever had problems with anesthesia or surgery (in blood relatives or self) or problems during placemen

12. Have you had any problems with your blood (circle) (ablood clots, transfusions within the last 6 months)?

18. Do you snore? 19. Please list any medical illnesses not noted above:

22. Additional comments or questions for nurse or doctor?

Describe recent changes

Fig. 1 (conti

for an anesthesiologist or a primary care physician to

review and make the determination if an appointment

is needed. A more detailed discussion of important

components of the patient history for specific medical

conditions is presented below.

At a minimum, the preoperative examination

should include vital signs (blood pressure, pulse and

room air oxygen saturation), and a heart and lung

examination. If general anesthesia is not planned,

the ability of the patient to lie flat for the estimated

duration of the procedure is extremely important.

A guide to help determine the patient’s ability to lie

recumbent follows:

Disease. Certain conditions such as heart failure,

lung disease, chronic cough, musculoskeletal

disease like kyphoscoliosis, or a movement dis-

order such as a tremor, may prevent a patient

from lying still during the planned procedure.

Dementia. If the patient’s mental capacity pre-

cludes being able to stay still and follow sim-

ple commands, local anesthesia will likely fail.

g? py or radiation therapy? (circle)

? (circle) (malignant hyperthermia t of a breathing tube)

nemia, leukemia, sickle cell disease,

nued ).

Page 17: Anestesia Ocular

sweitzer166

Dialect. Patients who are unable to communi-

cate because they speak a language different

than operating room personnel may not

be cooperative.

Deafness. Patients who have hearing problems

may have difficultly communicating.

The physical examination contributes one-quarter

of diagnoses in patients who have cardiovascular

disease [5]. Auscultation of the heart, palpation of the

pulses, and inspection of the extremities for the

presence of edema are important diagnostically and

for risk assessment when care plans are developed.

The practitioner should auscultate for murmurs,

rhythm disturbances, and signs of volume overload.

Murmurs, without a previous diagnosis, warrant fur-

ther evaluation. The pulmonary examination should

include auscultation for wheezing, decreased or ab-

normal breath sounds, and notation of cyanosis or

clubbing and effort of breathing. Observing whether

the patient can walk up 1–2 flights of stairs can

predict a variety of medical conditions and post-

operative complications including pulmonary and

cardiac events and mortality.

Preoperative testing

Preoperative testing is performed to evaluate exist-

ing medical conditions and screen for asymptomatic

conditions based on known risk factors for particular

diseases. Diagnostic tests can help assess the risk of

anesthesia and surgery, guide medical intervention to

lower this risk, and provide baseline results to di-

rect intra- and postoperative decisions. The choice of

laboratory tests should depend on the probable

impact of the test results on the differential diagno-

sis and on patient management. A test should be

ordered only if the results will (1) affect the decision

to proceed with the planned procedure, (2) influence

the type of anesthesia used, or (3) alter the care plans.

The history and physical examination should be used

to direct which tests are ordered. (Fig. 2).

Preoperative tests without specific indications lack

clinical utility and may actually lead to patient in-

jury because of unnecessary interventions, delay of

surgery, anxiety, and perhaps even inappropriate

therapies. The patient history is responsible for the

diagnosis 75% of the time and is more important than

the physical examination and laboratory investiga-

tions combined [9]. In addition, the evaluation of

abnormal results is costly. Many studies have eval-

uated the benefits of disease- or condition-indicated

testing versus batteries of screening tests [10]. For-

tunately, without specific clinical indication, few ab-

normalities detected by nonspecific testing have been

shown to result in changes in management and rarely

have such changes been shown to have a beneficial

patient effect [11]. It has been suggested that not

following up on an abnormal test result is a greater

medico-legal risk than not identifying the abnormal-

ity to begin with.

A preoperative ECG is one of the most frequently

ordered and costly noninvasive tests. A preoperative

ECG might be ordered because

Occult heart disease is common in a middle-aged

population and increases with advancing age

Pre-existing heart disease increases periopera-

tive risk

It is useful to establish a baseline.

However, a resting ECG is not a reliable screen

for coronary artery disease and is a poor predictor of

heart disease (without a supporting history) in non-

surgical patients. There is evidence that only some

ECG abnormalities are important in the perioperative

period (eg, new Q waves and arrhythmias). One study

found only 2% of patients had one or both of these

abnormalities [12]. Gold [13] found that in ambu-

latory surgical patients, the incidence of abnormal

ECGs was quite high (43%). However, only 1.6%

had an adverse perioperative cardiac event, and the

preoperative ECG was of potential value in only half

(6/751) of these. It has been suggested that routine

preoperative ECG testing is not indicated in patients

who do not have a history of cardiovascular disease

or significant risk factors [14].

Even though ECG abnormalities are increasingly

more common with advanced age, abnormalities

alone have not been shown to predict postoperative

cardiac complications in the elderly [13,15]. Al-

though abnormal ECG findings are common in the

elderly, significant abnormalities that impact care are

low in the absence of a history or symptoms of car-

diac disease [13]. Centers for Medicare and Medicaid

Services will not provide coverage for age-based

ECGs or ECGs performed simply as a preoperative

test. A practitioner must provide a supporting diag-

nosis with an acceptable ICD-9 code [16]. ECGs are

acceptable if performed within 6 months and the pa-

tient has had no change in symptoms.

Indications for ECG testing include

History of coronary artery disease, myocardial in-

farction, angina or chest pain

History of congestive heart failure

Page 18: Anestesia Ocular

Disease /Therapy/Procedure based Indications

(applies to all patients scheduled for general anesthesia, or newly diagnosed

or unstable conditions only)

Possible pregnancy

BUN; Diabetes; Heart failure; Renal disease; Sickle cell anemia; Use of Diuretics Creatinine

ECG Alcohol abuse; Cardiovascular, Cerebrovascular, Peripheral vascular,

Pulmonary, or Renal disease; Diabetes; Morbid Obesity; Murmurs; Poor exercise

tolerance (unable to walk up a flight of stairs); Poorly controlled hypertension

(BP >180/110 mmHg); Rheumatoid arthritis; Sickle cell anemia; Sleep apnea;

Smoking >40 pk-yr; Systemic lupus; Radiation therapy to chest or left breast; Use

of Digoxin

Electrolytes Cerebrovascular, Hepatic or Renal disease; Diabetes; Sickle cell anemia; Use of

Digoxin, or Diuretics

Glucose Cerebrovascular Disease; Diabetes; Morbid obesity; Steroid use

Platelets; PT; Alcohol abuse; Hepatic disease; Personal or Family history of bleeding; Use of aPTT*

Anticoagulants.

Thyroid Tests Thyroid disease; Use of Thyroid medications

* Only indicated for these conditions if peri- or retrobulbar blocks are planned or bleeding is an issue

Abbreviations: β-hCG=pregnancy test; BUN= blood urea nitrogen; ECG=electrocardiogram; PT= prothrombin time; a-PTT=

activated partial thromboplastin time;

All tests are valid for 6 months before surgery unless abnormal, or patients condition has changed; with the exception of β-hCG for

pregnancy, glucose in diabetics and blood tests in patients with renal failure.

Guidelines may not apply for low-risk procedures without general anesthesia where testing is only

indicated if the medical condition is newly diagnosed or unstable.

β-hCG

Fig. 2. Sample preoperative diagnostic testing order form.

preoperative assessment & management 167

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sweitzer168

History of atrial fibrillation, arrhythmias, irregular

or skipped beats, heart block

History or presence of murmur

Presence of a pacemaker or implantable cardio-

verter-defibrillator

Chronic lung disease, >40 pack-years of tobacco

use or significant shortness of breath

Diabetes mellitus

Cerebrovascular (stroke, TIA) or peripheral vas-

cular disease (claudication)

Renal insufficiency or failure

Age-based recommendations for testing are based

on few data. No correlation has been established,

independent of co-existing disease, a positive history,

or findings on physical examination, between age

and abnormalities in hemoglobin (Hgb), serum chem-

istries, radiographs, or pulmonary function testing

[17–19]. Hemoglobin and hematocrit (Hct) levels are

frequently abnormal in otherwise healthy patients but

rarely impact anesthetic care or management, unless

the planned procedure involves the potential for sig-

nificant bleeding.

Coagulation studies (platelet count, prothrombin

time [PT], or activated partial thromboplastin time

[a-PTT]) are not recommended unless the patient

history is suggestive of a coagulation disorder. It is

generally accepted that the cost of screening co-

agulation tests before minor surgery outweighs the

benefit of non-life threatening bleeding (because of

the minor nature of the procedure) in the rare patient

with what would have to be a minor bleeding dis-

order, if there is a negative history [20].

Healthy patients of any age who undergo low or

intermediate risk procedures (without expected sig-

nificant blood loss) are unlikely to benefit from any

tests. Patients who have stable, well-controlled,

mild to moderate severity co-existing diseases, and

who follow up regularly with primary care or spe-

cialist physicians are unlikely to benefit from addi-

tional diagnostic testing before surgery. In general,

tests are only recommended if they will result in

A change, cancellation, or postponement of the

surgical procedure

A change in anesthesia and medical management

A change in monitoring or guidance of intra- or

post-operative care

Confirmation of a suspected abnormality based on

the patient’s history and physical examination

Generally, test results are valid and acceptable for

up 6 months before surgery if the medical history has

not substantially changed [21]. Suggested tests are

shown in Fig. 2.

Patients who undergo cataract surgery are often

elderly and have extensive co-morbid disease. The

procedure is minor, however, and systemic physio-

logic disturbances or significant postoperative pain

are not expected. Topical anesthesia is commonly

used and because general anesthesia is rarely re-

quired, the risk is lessened. The cost of routine medi-

cal testing before cataract surgery is estimated at

$150 million annually. In one study, more than

18,000 patients were randomly allocated to either a

group that received no routine testing before cataract

surgery or a a group that received a battery of tests

(ECG, complete blood cell count, electrolytes, serum

urea nitrogen, creatinine and glucose levels). No dif-

ferences in postoperative adverse events were found

between the two groups [10].

The study of cataract patients eliminated routine

tests, not tests indicated for a new or worsening

medical problem. All patients underwent a preop-

erative medical assessment. The group that crossed

over from no testing to some testing had significantly

more coexisting illnesses and poor self-reported

health status. This finding suggests that the preop-

erative care provider screen patients to order tests for

those who require them. In the study described, ex-

clusion criteria were general anesthesia or a myocar-

dial infarction within 3 months. More than 85% of

subjects enrolled in the study reported good to ex-

cellent health status, almost 25% reported no coex-

isting illnesses (including hypertension, anemia,

diabetes, and heart or lung disease), almost 30%

were <70 years, and 65% were American Society of

Anesthesiologists physical status (ASA-PS) 1 or 2

(Table 1); all of which suggests a fairly healthy

group. The results of this study do not suggest that

patients who undergo cataract surgery require no

laboratory testing [10]. If patients are comparable to

those in the study, are routinely evaluated by primary

care physicians, have stable mild disease, and will

undergo cataract surgery under topical or bulbar

block, then no special testing is required for cataract

surgery. Serious, poorly controlled conditions must

be normalized before surgery, and selective test-

ing suggested by history and physical examination

may be necessary. Rarely is testing necessary be-

cause of cataract surgery, but patients with limited

access to health care services may benefit from

medical evaluation.

Often physicians are concerned about their failure

to diagnose a condition because a diagnostic screen-

ing test was not ordered, for which legal action can be

brought. The traditional system of ordering routine

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Table 1

American Society of Anesthesiologists physical status

classification

Class Description

ASA 1 Healthy patient without organic, biochemical,

or psychiatric disease.

ASA 2 A patient with mild systemic disease

(eg, mild asthma or well-controlled

hypertension). No significant impact on daily

activity. Unlikely impact on anesthesia

and surgery.

ASA 3 Significant or severe systemic disease that

limits normal activity (eg, renal failure on

dialysis or class 2 congestive heart failure).

Significant impact on daily activity. Likely

impact on anesthesia and surgery.

ASA 4 Severe disease that is a constant threat to

life or requires intensive therapy (eg, acute

myocardial infarction, respiratory failure

that requires mechanical ventilation).

Serious limitation of daily activity. Major

impact on anesthesia and surgery.

ASA 5 Moribund patient who is equally likely to die

in the next 24 hours with or without surgery.

ASA 6 Brain-dead organ donor.

preoperative assessment & management 169

preoperative tests evolved from the mistaken belief

that more information, no matter how irrelevant or

expensive, will improve care, enhance safety, and

decrease liability. In reality, non-selective screening

may actually increase legal culpability. Unanticipated

abnormalities (ie, not suggested by the history or

physical examination) are uncommon and the rela-

tionship between these abnormalities and surgical and

anesthetic morbidity is weak at best. In addition, it

has been documented that over half of all abnormal

test results obtained in routine preoperative screening

are ignored or at least not noted in the medical record,

which is the document of interest to the courts.

Failure to follow up an abnormal result is, from a

legal point of view, probably riskier than failure to

order the test in the first place. AIMS found that

communication problems were predominant in most

reported incidents that involved a failure of preoper-

ative preparation [1].

Risk assessment

Risk assessment is useful to compare outcomes,

control costs, allocate compensation, and assist with

the difficult decision to cancel or recommend that a

procedure not be done when the risks are too high.

Yet risk assessment, at its best, is hampered by in-

dividual patient variability. One of the most com-

mon risk assessment tools used perioperatively is

the ASA-PS scoring system (see Table 1). Though

ASA-PS is usually determined by anesthesiologists

for patients having anesthesia, it is often used for any

comparison of surgical patients. Studies have cor-

roborated an association of mortality and morbidity

with ASA-PS. The other important risk assessment

tool is the joint guideline published by The Ameri-

can College of Cardiology and the American Heart

Association (ACC/AHA), which identifies risk fac-

tors and cardiac complications in noncardiac surgery.

Cardiac complications are the most common cause of

significant perioperative morbidity and mortality. For

the purposes of this article, the ACC/AHA guideline

considers ophthalmic procedures to be low risk and

therefore, further risk assessment is only necessary

for high-risk comorbid conditions [2].

Hypertension

Poorly controlled hypertension (HTN) is one of

the most common reasons for ophthalmic procedures

to be cancelled on the day of surgery. HTN, defined

by two or more measurements of blood pressure (BP)

greater than 140/90 mmHg, affects one billion in-

dividuals worldwide and increases with age. In the

United States, 25% of adults and 70% of patients

older than 70 years have HTN and less than 30% are

adequately treated [22]. The degree of end-organ

damage and morbidity and mortality correlate with

the duration and severity of HTN. Heart failure, renal

insufficiency, and cerebrovascular disease are more

common in hypertensive patients. Ischemic heart dis-

ease is the most common form of organ damage

associated with HTN. Uncontrolled HTN is only a

minor cardiac risk factor and the odds ratio for an

association between HTN and perioperative cardiac

risk is 1.31 [2,23]. There is little evidence of an as-

sociation between preoperative BPs <180/110 mmHg

and perioperative cardiac risk [23].

It is generally recommended that elective surgery

be delayed for severe HTN (diastolic blood pressure

>115 mmHg; systolic blood pressure >200 mmHg)

until BP <180/110 mmHg. If severe end-organ

damage is present, the goal should be to normalize

BP as much as possible before surgery [23]. For BP

<180/110 mmHg there is no evidence to justify can-

cellation of surgery, although if time allows, inter-

ventions preoperatively are appropriate. Severely

elevated BP should be lowered over several weeks.

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Box 1. Preoperative medication guidelines

Continue on the day of surgerya

Antidepressant, anti-anxiety, andpsychiatric medications

Anti-hypertensive medicationsAnti-seizure medicationsAspirin, unless the risk of minor bleed-

ing is significantAsthma medicationsBirth control pillsCardiac medications (eg, digoxin)Cox-2 inhibitorsDiuretics (eg, triamterene or hydrochlo-

rothiazide) for hypertensionHeartburn or reflux medicationsInsulin- all intermediate, combination,

or long-acting insulin, orinsulin pumps� Type 1 diabetics should take asmall amount (one-third to one-half) of their usual morning long-acting insulin (eg, lente or NPH) onthe day of surgery� Type 2 diabetics should take onethird to one-half dose of long-acting (eg, lente or NPH) or com-bination (70/30 preparations) insu-lin on the day of surgery� Patients with an insulin pumpshould continue only their basalrate on the day of surgery

Narcotic pain medicationsStatinsSteroids, oral or inhaledThyroid medications

Discontinue 7 days before surgery

Clopidogrel (Plavix), except patientsscheduled for cataract surgery withtopical or general anesthesia

Herbals and non-vitamin supplementsHormone replacement therapy

Discontinue 4 days before surgery

Warfarin (Coumadin), except for pa-tients scheduled for cataract surgerywith topical or general anesthesia

Discontinue 24 hours before surgery

Erectile dysfunction medications

Discontinue on the day of surgery

Diuretics, except triamterene or hydro-chlorothiazide for hypertension,which should be continued

Insulin- all regular insulin (see insulin tocontinue on day of surgery above)

IronOral hypoglycemic agentsTopical medications (eg, creams

or ointments)Vitamins

Special considerations before surgery

Monoamine oxidase inhibitors: patientstaking these antidepressant medi-cations need an anesthesia consul-tation before surgery (preferably3 weeks before) if general anesthe-sia is planned

a Patients should take medications witha small sip of water even if otherwise in-structions are nothing per mouth.

sweitzer170

Guidelines suggest that cardioselective beta-blocker

therapy is the best treatment preoperatively because

of a favorable profile in lowering cardiovascular risk

[2]. It may take 6–8 weeks of therapy to effectively

lower the risk and to allow regression of vascular

changes, because too rapid or extreme lowering of

BP may increase cerebral and coronary ischemia. The

Antihypertensive and Lipid-Lowering Treatment to

Prevent Heart Attack Trial showed that effective

treatment of HTN is not simply a matter of lowering

BP [24]. Continuation of antihypertensive treatment

preoperatively is critical (Box 1).

Testing should be determined by the history and

physical examination and may include ECG, elec-

trolytes, serum urea nitrogen, and creatinine if gen-

eral anesthesia is planned (see Fig. 2). An elevated

BP during the ophthalmology visit or a history of

poorly controlled HTN should prompt a referral to a

primary care physician for BP control before elec-

tive surgery.

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preoperative assessment & management 171

Cardiac disease

The goals of the ophthalmologist should be to

identify the presence and severity of heart disease

(HD) or significant risk of HD based on associated

conditions, such as diabetes, renal insufficiency or

failure, cerebrovascular or peripheral vascular dis-

ease, and determine the need for preoperative con-

sultation and interventions (almost always medical,

not invasive) to modify the risk of perioperative

adverse events. The basis of cardiac assessment is

the history, physical examination, and ECG. The

most recent guidelines for the cardiac evaluation

for noncardiac surgery from the ACC/AHA have

become the national standard of care [2]. These

guidelines indicate that patients without high-risk co-

morbid conditions defined as unstable or new onset

angina, decompensated heart failure, significant ar-

rhythmias (ventricular tachycardia or atrial fibrilla-

tion with a rapid rate, >100 bpm) or severe valvular

disease (regurgitation or stenosis) can safely undergo

low-risk procedures without stress testing or cardiol-

ogy intervention.

Currently, the benefits of coronary revasculariza-

tion before noncardiac surgery, versus medical risk

modification are controversial [25]. Unless patients

will benefit from revascularization regardless of the

planned procedure, or have unstable angina, revas-

cularization is not indicated before ophthalmic sur-

gery. Noncardiac surgery soon after revascularization

(bypass grafting and percutaneous coronary interven-

tion with or without stents) is associated with high

rates of perioperative cardiac morbidity and mor-

tality [26,27]. Patients who have recently had an-

gioplasty with stent placement (within 6 months),

especially with newer, drug-eluting stents, require

several months of anti-platelet therapy to avoid re-

stenosis or acute thromboses. These patients need to

be identified and close management with a cardiolo-

gist is required. Case reports have indicated that pa-

tients can have stent thromboses perioperatively even

if anti-platelet agents are continued [28].

Patients who have a history of coronary artery

disease or significant risk factors (diabetes, renal in-

sufficiency, cerebrovascular or peripheral vascular

disease) need an ECG within 6 months of a planned

GA (see Fig. 2).

Heart failure affects 4–5 million people in the

United States and is a significant risk factor for post-

operative adverse events [29]. The goal for the

ophthalmologist is to identify patients who have

decompensated heart failure. Recent weight gain,

complaints of shortness of breath, fatigue, orthopnea,

paroxysmal nocturnal dyspnea, edema, hospitaliza-

tions, and recent changes in medication are impor-

tant. Physical findings should focus on examination

for third or fourth heart sounds, rales, jugular ve-

nous distention, ascites, hepatomegaly, and edema

[30]. Decompensated heart failure requires referral

to a cardiologist for optimization preoperatively.

Minor procedures can be done with little risk as

long as heart failure is stable. If GA is planned an

ECG, electrolytes, BUN, and creatinine are required

(see Fig. 2).

New onset or poorly controlled atrial fibrillation

(HR >100 bpm), symptomatic bradycardia, or high-

grade heart block (second or third degree) warrants

postponement of elective procedures and referral to

cardiology for further evaluation. Left bundle branch

block (LBBB) is highly associated with coronary

artery disease and a recent onset, or a patient with-

out a previous evaluation of a LBBB requires stress

testing or cardiology consultation. Right bundle

branch block (RBBB) is more likely to be congenital,

a result of calcification and degeneration of the

conduction system or secondary to pulmonary dis-

ease. If the history and physical examination are

not suggestive of significant pulmonary disease, no

further evaluation is warranted just because of a

RBBB. Patients who have a history of arrhythmias

should be queried about syncope, chest pain, dyspnea

or light-headedness. An ECG is necessary within

6 months or more recently if there has been a change

in symptoms (see Fig. 2).

The quandary with heart murmurs is to distin-

guish between significant murmurs and clinically

unimportant ones. Diastolic murmurs are always

pathologic and require further evaluation. Regurgitant

disease is tolerated perioperatively better than ste-

notic disease.

Aortic stenosis is the most common valvular le-

sion in the United States and affects 2%–4% of

adults >65 years of age; severe stenosis is associated

with a high risk of perioperative complications with

GA [2]. Aortic stenosis was once considered to be a

degenerative lesion that increased with age or a con-

genital bicuspid valve, but is now believed to have

much in common with coronary heart disease and is

an independent marker of ischemic disease [31]. The

classic symptoms of severe aortic stenosis are an-

gina, heart failure, and syncope, though patients

are much more likely to complain of a decrease in

exercise tolerance and exertional dyspnea. Aortic ste-

nosis causes a systolic ejection murmur, which is

best heard in the right upper sternal border and often

radiates to the neck. Any patient with a previously

undiagnosed murmur needs an ECG, and any ECG

abnormality warrants an echocardiogram or a car-

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sweitzer172

diology consultation. Current guidelines recommend

echocardiography annually for patients who have

severe aortic stenosis, every 2 years for moderate

stenosis, and every 5 years for mild stenosis [32].

Aortic sclerosis, which causes a systolic ejection

murmur similar to that of aortic stenosis, is present in

25% of people 65–74 years of age and almost half of

those >84 years. However, there is no hemodynamic

compromise with aortic sclerosis. Aortic sclerosis

is associated with a 40% increase in the risk of

myocardial infarction and a 50% increase in the risk

of cardiovascular death in patients who do not have a

history of heart disease [31].

It is estimated that more than 100,000 pacemakers

and implantable cardiac defibrillators (ICDs) are

implanted annually in the United States. Electro-

magnetic interference (EMI) is likely to occur with

electrocautery and radiofrequency ablation, and result

in malfunction or adverse events [33]. Some patient

monitors and ventilators may cause EMI in patients

who have rate-adaptive pacemakers. The preoperative

evaluation should determine the type of device and

the features (eg, rate-adaptive mechanisms) likely

to malfunction if perioperative EMI should occur.

Consultation with the device manufacturer, cardiolo-

gist, or the electrophysiology service is necessary.

Ideally, patients should have these devices interro-

gated preoperatively. Special features such as rate

adaptive mechanisms and anti-tachyarrhythmia func-

tions need to be disabled or be reprogrammed to an

asynchronous pacing mode before surgical proce-

dures and anesthesia where EMI is anticipated [33].

Newer generation devices are more complex and

reliance on a magnet, except in emergency situations,

is not recommended.

Disabling ICDs will prevent unanticipated dis-

charges during delicate procedures. However, exter-

nal defibrillators must be immediately available. A

baseline ECG is needed in patients who have pace-

makers and ICDs (see Fig. 2).

Pulmonary disease

Patients who have significant chronic obstructive

pulmonary disease (COPD), asthma, or a cough, may

not be able to lie supine for an extended period.

Treating exacerbations of their disease (eg, infection,

bronchospasm) may make it possible for them to

remain recumbent and still, and is necessary to

decrease complications if GA is planned. However,

routine chest radiographs, arterial blood gases, and

the degree of airway obstruction measured by pul-

monary function tests, are not predictive of pulmo-

nary complications.

Sleep-disordered breathing affects up to 9% of

middle-aged women and 24% of middle-aged men;

less than 15% of these cases have been diagnosed.

Obstructive sleep apnea (OSA), the most common

serious manifestation of sleep-disordered breathing,

is caused by intermittent airway obstruction. Car-

diovascular disease is common in patients who have

OSA. These patients have an increased incidence of

hypertension, atrial fibrillation, bradyarrhythmias,

ventricular ectopy, endothelial damage, stroke, heart

failure, dilated cardiomyopathy, and atherosclerotic

coronary artery disease (CAD) [34]. Patients who

have moderate to severe OSA are unlikely to be able

to lie flat without general anesthesia. Mask ventila-

tion, direct laryngoscopy, endotracheal intubation,

and even fiberoptic visualization of the airway are

more difficult in patients who have OSA than in

healthy patients.

The Berlin Questionnaire is useful to identify pa-

tients who have undiagnosed OSA [35]. The presence

of any two of the following is considered a high risk

for sleep apnea: snoring, daytime sleepiness, hyper-

tension, and obesity. Preoperative evaluation should

focus on identifying patients who are at risk for OSA

and improving associated co-morbid conditions. ECG

and echocardiography may be indicated if heart

failure or pulmonary hypertension is suspected or

GA is required (see Fig. 2). Patients should be in-

structed to bring their continuous positive airway

pressure devices to the hospital on the day of surgery.

Obesity

It is estimated that 64% of adults in the United

States are overweight or obese and 4.7% are ex-

tremely obese. Obesity is an independent risk factor

for heart disease. Hypertension, stroke, hyperlipid-

emia, diabetes mellitus, and OSA are more common

in obese people. Morbidly obese patients require spe-

cial operating room tables and gurneys to support

excessive weight. Venous access and invasive and

noninvasive monitoring may be difficult, and air-

ways may require specialized equipment, techniques,

and personnel. Preoperative identification and plan-

ning for these contingencies will avoid delays on the

day of surgery. Preoperative evaluation should be

directed toward identifying significant co-existing

diseases such as OSA, pulmonary hypertension, and

heart failure. Many of these patients will not be able

to lie flat and will require general anesthesia. An

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preoperative assessment & management 173

ECG is indicated preoperatively if GA is required

(see Fig. 2).

Diabetes

An estimated 18 million US adults have diabetes

mellitus, which increases the risk of coronary artery

disease and is considered equivalent to angina for

predicting heart disease [2]. Heart failure is twice as

common in men and five times as common in women

who have diabetes as in individuals who do not have

diabetes. Poor glycemic control is associated with an

increased risk for heart failure and both systolic and

diastolic dysfunction may be present.

Recent studies suggest that tighter perioperative

control is warranted, especially to reduce the risk

of infections. Patients who have poor preoperative

management of glucose are likely to be more out of

control perioperatively. Aggressive management of

hyperglycemia decreases postoperative complications.

The American College of Endocrinologists position

statement recommends a target fasting glucose of

< 110 mg/dL in non-critically ill patients [36].

The focus of the preoperative visit should be

to assess organ damage and control blood sugar.

Cardiovascular, renal, and neurologic systems should

be evaluated. Ischemic heart disease is often asymp-

tomatic in the diabetic patient. An ECG should

be done within 6 months of surgery. Electrolytes,

BUN, and creatinine levels need to be determined

(see Fig. 2). The goal of perioperative diabetic man-

agement should be to avoid hypoglycemia and

marked hyperglycemia (see Box 1).

Anticoagulated patients

There is no consensus on the optimal periopera-

tive management of patients who are taking war-

farin. There are risks if therapy is continued and

risks if it is stopped [37]. The location and extent of

surgery is important and the ability to compress the

bleeding site is a consideration. Warfarin may be

associated with increased bleeding, except for minor

procedures such as cataract surgery without peri- or

retrobulbar blocks. One study found grade 1 hemor-

rhages in 2.3% of patients, grade 2–3 hemorrhages in

2%, and no grade 4 hemorrhages in patients who

were undergoing a variety of ophthalmic procedures

with retro- or peribulbar blocks. However, they con-

cluded that preoperative use of aspirin, other anti-

platelet drugs, and warfarin, (whether they were

continued or not) was not associated with significant

hemorrhage [38]. There have been reports of bleeding

in the anterior eye chamber and subconjunctival

hemorrhages in patients who undergo ophthalmic

surgery while on warfarin. No studies of long-term

visual acuity have been done in patients who con-

tinued warfarin therapy during eye surgery.

A survey of 135 surgeons in the United States

found that 75% stopped anticoagulation 3–5 days

preoperatively. They reported two deaths that were

caused by cerebrovascular accidents, and 7 nonfatal

thromboembolic episodes in the group in which anti-

coagulants were discontinued. No complications were

reported by the 7.4% of surgeons who continued

anticoagulants [39].

There is little harm in continuing aspirin through-

out the perioperative period for ophthalmic patients

and evidence suggests benefit for patients at high risk

for cardiovascular and cerebrovascular complica-

tions [37]. More potent antiplatelet therapy such as

clopidogrel (Plavix) may have a risk of bleeding

intermediate between aspirin and warfarin. Clopidog-

rel or similar drugs should probably be discontinued

for procedures in which one would discontinue war-

farin but do not need to be stopped before cataract

surgery performed with topical anesthesia.

Anemia

Consequences from moderate levels of anemia

and Hgb levels >7.0 g/dL in patients without CAD

are minimal. Transfusion is rarely indicated when the

Hgb is >10 mg/dL and is almost always needed when

the Hgb is <7 mg/dL. The focus of the preoperative

visit is to determine the etiology, duration, and

stability of the anemia, and the patient’s co-morbid

conditions that may impact oxygenation, such as

pulmonary, cerebrovascular, or cardiovascular disease.

Sickle cell disease is a hereditary hemoglobinop-

athy and vaso-occlusion is responsible for most of the

associated complications. Preoperative assessment

should focus on identification of organ dysfunction

and acute exacerbations. Frequent hospitalizations or

a recent increase in hospitalizations, advanced age,

preexisting infections, and pulmonary disease predict

perioperative vaso-occlusive complications [40]. The

preoperative history and physical examination should

focus on the frequency, severity, and pattern of vaso-

occlusive crises and the degree of pulmonary, cardiac,

renal, and central nervous system damage. An ECG,

electrolytes, BUN, and creatinine are necessary

before GA (Table 2). Patients who have significant

pulmonary or cardiac symptoms need an echocar-

diogram. Prophylactic transfusion may be beneficial

Page 25: Anestesia Ocular

Table 2

Guidelines for food and fluids before elective surgery

Time before surgery Food or fluid intake

Up to 8 hours Food and fluids as desired

Up to 6 hoursa Light meal (eg, toast and clear

liquidsb); infant formula; non-

human milk

Up to 4 hoursa Breast milk

Up to 2 hoursa Clear liquidsb only; no solids or

foods that contain fat in any form

During the 2 hours No solids, no liquids

a This guideline applies only to patients who are not

at risk for delayed gastric emptying. Patients who have

the following conditions are at risk for delayed gastric

emptying: morbid obesity, diabetes mellitus, pregnancy,

a history of gastroesophageal reflux, a surgery that limits

stomach capacity, a potentially difficult airway; opiate anal-

gesic therapy.b Clear liquids are water, carbonated beverages, sports

drinks, coffee or tea (without milk). The following are not

clear liquids: juice with pulp, milk, coffee or tea with milk,

infant formula, any beverage with alcohol.

From American Society of Anesthesiologists Task Force on

Preoperative Fasting. Practice guidelines for preoperative

fasting and the use of pharmacologic agents to reduce the

risk of pulmonary aspiration: application to healthy patients

undergoing elective procedures. Anesthesiology 1999;90:

896–905; Available at: http://www.asahq.org. Accessed

October 25, 2005.

sweitzer174

before general anesthesia. Preoperative prophylactic

transfusion is controversial and the decision to

transfuse should be made in concert with a hematol-

ogist who is familiar with sickle cell disease.

Renal or hepatic disease

The focus of the preoperative evaluation of pa-

tients with renal insufficiency or failure should be on

the cardiovascular and cerebrovascular systems, fluid

volume, and electrolyte status. Chronic metabolic

acidosis is common but usually mild and compen-

sated for by chronic hyperventilation. Chronic renal

disease is a significant risk factor for cardiovascular

morbidity and mortality and is an intermediate

cardiac risk factor equal to a history of known

CAD [2]. The annual incidence of death from CAD

in patients with both diabetes and end stage renal

disease and on hemodialysis is 8.2%. In elective

cases, hemodialysis should be performed within

24 hours of surgery but not immediately before.

Hemodialysis is associated with fluid and electrolyte

(sodium, potassium, magnesium, phosphate) imbal-

ance and shifting of electrolytes between intra- and

extracellular compartments. Hemodialysis should be

performed to correct volume overload, hyperkalemia,

and acidosis. Patients with renal insufficiency or

failure undergoing GA need an ECG, BUN, creati-

nine and electrolytes before surgery (see Fig. 2).

It is appropriate to delay elective surgery until

after an acute episode of hepatitis or an exacerbation

of chronic disease has resolved. If GA is planned for

patients who have hepatic or renal disease, electro-

lytes, BUN, and creatinine levels need to be evalu-

ated. If retro- or peribulbar blocks, or a procedure

where bleeding may compromise vision are planned

for patients who have cirrhosis, a PT and a-PTT need

to be determined (see Fig. 2).

Neurologic patients

A history focused on recent events, exacerbations,

or evidence for poor control of the medical condition

is necessary for a patient who has neurologic dis-

ease (eg, stroke, seizure disorder, multiple sclerosis,

Parkinson’s disease). If a stroke or transient neuro-

logic deficit has not been fully evaluated or has oc-

curred within 1 month, elective surgery should be

delayed pending complete evaluation. Patients who

have significant movement disorders or poorly con-

trolled seizures may require general anesthesia.

Consultations

Collaborative care of patients is often neces-

sary and beneficial. Consultation initiated by the

preoperative physician should seek specific advice

regarding diagnosis and status of the patient’s con-

dition(s). The first step is to ask specific questions

such as, ‘‘Is this patient in the best medical condi-

tion for planned vitrectomy under general anesthe-

sia’’? Letters or notes that state ‘‘cleared for surgery’’

are rarely sufficient to design a safe anesthetic. A

letter that summarizes the patient’s medical problems

and condition, along with the results of diagnostic

tests, is necessary.

In many practices, the cardiology service is most

frequently consulted perioperatively. In one survey,

however, the utility of such consultations was ques-

tioned. Forty percent of the consultations contained

only the recommendation to ‘‘proceed with the

case,’’ ‘‘cleared for surgery,’’ or ‘‘continue with cur-

rent medications’’ [41]. Part of this responsibility lies

with the consulting physicians (surgeons or anes-

thesiologists) and the long-standing practice of asking

Page 26: Anestesia Ocular

preoperative assessment & management 175

for, or receiving cardiac clearance. This is a vague

request and often results in a vague response. In gen-

eral, preoperative consultations should be sought for

diagnosis, evaluation, and improvement of a new or

poorly controlled condition.

Close coordination and good communication

among the anesthesiologist, surgeon, and consultant

is vitally important. Miscommunication among care

providers was central to most reported incidents in

the Australian Incident Monitoring Study whenever

preoperative assessment was implicated [1].

Medication instruction

Most medications should be continued on the day

of surgery because of their beneficial effects, al-

though some may be harmful or contraindicated.

Box 1 details classes of drugs and varying protocols

of continuation before surgery. Medications associ-

ated with withdrawal effects (eg, beta-blockers, cen-

trally acting sympatholytics, benzodiazepines, and

opioid analgesics) should be continued through the

preoperative period [42]. Medications used by pa-

tients who have a history of or are at risk for heart

disease, such as beta blockers, digoxin, anti-arrhyth-

mics, and statins should not be withdrawn before

surgery. Not only are they beneficial but risk may

increase when they are not taken [2,42].

Oral hypoglycemic agents should be held the day

of surgery to avoid hypoglycemia unless only local

anesthesia is planned and the patient is instructed to

eat. Patients who have type 1 and type 2 diabetes

mellitus should discontinue all short-acting insulins

on the day of surgery. Type 1 and type 2 diabetics

should take one-third to one-half the dose of long-

acting (eg, lente or Neutral Protamine Hagerdorn) or

combination (70/30 preparations) insulins on the day

of surgery. Small amounts of long-acting insulin on

the day of surgery present little risk of hypoglycemia

but improve perioperative control and avoid diabetic

ketoacidosis. Patients who have an insulin pump

should continue their basal rate only.

It is usually not necessary to discontinue aspi-

rin before ophthalmic surgery [37]. More potent

antiplatelet agents such as clopidogrel (Plavix) need

to be stopped 1 week before surgery if bleeding is a

concern. There is general agreement that aspirin,

nonsteroidal anti-inflammatory drugs and potent

antiplatelet agents (eg, clopidogrel) and warfarin

should be continued in patients who are scheduled

for cataract surgery with general or topical anesthesia.

Most surgeons discontinue warfarin for retinal sur-

gery and practices vary widely as to whether warfa-

rin is discontinued when peri- or retrobulbar blocks

are planned.

If warfarin is stopped it is usually necessary to

withhold four doses before surgery to allow the

International Normalized Ratio to decrease to <1.5, a

level considered safe for surgical procedures. Sub-

stitution with shorter acting anticoagulants such as

unfractionated or low molecular weight heparin,

referred to as bridging, is controversial and should

be individualized [43]. Kearon and Hirsh [43] only

recommend preoperative bridging with intravenous

heparin for patients who have had an acute arterial or

venous thromboembolism within 1 month before

surgery, if surgery cannot be postponed. Patients who

take narcotic pain medications should be told to

continue these medications. Missed doses may result

in withdrawal symptoms and significant pain with the

associated stress response and hemodynamic pertur-

bations. For similar reasons, anti-anxiety and psychi-

atric medications should be continued up until the

time of the procedure.

Herbals and supplements may interact with anes-

thetic agents, alter the effects of prescription medi-

cations, and increase bleeding. Many patients do not

consider supplements medications and will not report

them unless specifically asked. Gingko, echinacea,

garlic, ginseng, kava, St. John’s wort and valerian

may be associated with bleeding and interactions

with anesthetic and sedative medications. It is rec-

ommended that herbals and supplements be stopped

7–14 days before surgery. The exception is valerian,

a central nervous system depressant which may cause

a benzodiazepine-like withdrawal when discontinued.

Patients who are particularly anxious should be

offered a prescription for a short course of benzo-

diazepines such as lorazepam to be taken in the days

preceding surgery as well as on the day of surgery.

Fasting guidelines

If GA is planned, patients should be instructed to

follow the ASA guidelines for preoperative fasting as

shown in Table 2 [44]. Many practitioners allow food

and fluids ad lib if the patient will receive topical or

local anesthesia without sedation.

Future developments

The ophthalmologist is in a unique position during

an ophthalmologic examination to identify patients

who have an increased risk of systemic disease. One

study found an association between retinal arteriolar

Page 27: Anestesia Ocular

sweitzer176

narrowing and coronary heart disease [45]. Another

study found that diabetic retinopathy was associated

with a higher risk of renal failure and death in patients

who had type 2 diabetes mellitus [46]. Ophthalmolo-

gists need to identify at-risk patients and not only

inform the patient of the implications of their findings

but ensure the patient receives appropriate referral

and follow-up.

Summary

The prevention of complications during and after

procedures is the most important goal of preoperative

evaluation. Identification of risk requires fundamen-

tally good medicine, systems of care, clinical and

laboratory assessment, and experienced, knowledge-

able, and dedicated health care providers. Risk

reduction is the ultimate goal of preoperative assess-

ment and management.

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Ophthalmol Clin N

General Anesthesia for Ophthalmic Surgery

Kathryn E. McGoldrick, MDa,b,T, Peter J. Foldes, MDb

aDepartment of Anesthesiology, New York Medical College, Valhalla, NY 10595, USAbWestchester Medical Center, Valhalla, NY 10595, USA

Anesthetic management plays a vital role in con-

tributing to the success or failure of ophthalmic sur-

gery. Patients with eye conditions are often at the

extremes of age, ranging from tiny, fragile infants

with retinopathy of prematurity or congenital cata-

racts to nonagenarians with submacular hemorrhage,

and may have extensive associated systemic or meta-

bolic diseases [1]. Moreover, with more than 13% of

Americans characterized as elderly (older than

65 years), we must acknowledge that the increased

longevity typical of developed nations has produced a

concomitant increase in the longitudinal prevalence

of major eye diseases, including diabetic retinopathy,

primary open-angle glaucoma, and age-related mac-

ular degeneration [2]. Clearly, the challenges of

caring for an aging population with complex coex-

isting diseases undergoing sophisticated and techni-

cally demanding ophthalmic procedures require a

high level of anesthetic expertise.

The objectives of anesthesia for ophthalmic sur-

gery include safety, akinesia, satisfactory analgesia,

minimal bleeding, avoidance or obtundation of the

oculocardiac reflex, prevention of intraocular hyper-

tension, and awareness of potential interactions be-

tween ophthalmic drugs and anesthetic agents. Other

exigencies include an understanding of the anesthetic

implications intrinsic to delicate ophthalmic proce-

dures, including the necessity for an especially

smooth induction, maintenance, and emergence from

anesthesia. Indeed, a closed claims analysis by Gild

0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights

doi:10.1016/j.ohc.2006.02.005

T Corresponding author. Westchester Medical Center,

Macy Pavilion, Room 2389, Valhalla, NY 10595.

E-mail address: [email protected]

(K.E. McGoldrick).

and colleagues [3] disclosed that 30% of eye injury

claims related to anesthesia management were asso-

ciated with patient movement during ocular surgery.

Most of the problems transpired during general an-

esthesia, but in one fourth of the cases the patients

were receiving monitored anesthesia care during pro-

cedures performed under local or regional anesthesia.

Tragically, the outcome was blindness in all cases.

Clearly, strategies to ensure patient immobility during

ophthalmic surgery are mandatory. Moreover, safety

issues are complicated by the logistic necessity for

the anesthesiologist frequently to be positioned at a

considerable distance from the patient’s face, thus

preventing immediate, direct access to the airway. It

is axiomatic that open, clear, and effective commu-

nication among the anesthesiologist, ophthalmologist,

and patient is integral to optimal outcome of oph-

thalmic surgery.

Indications for general anesthesia

In selecting the anesthetic technique for eye sur-

gery, numerous issues must be considered. General

anesthesia remains the technique of choice for chil-

dren, mentally retarded individuals, and demented

or psychologically unstable patients. It is also the

favored technique for patients with suspected or ap-

parent open-globe injuries, although recent literature

supports the use of regional eye blocks in selected

patients with open-eye trauma. Recognizing that there

are several distinct permutations of eye injuries, Scott

and colleagues [4] developed techniques to safely

block patients with certain open-globe injuries. In a

4-year period, 220 disrupted eyes were repaired via

regional anesthesia at Bascom Palmer Eye Institute.

Am 19 (2006) 179 – 191

reserved.

ophthalmology.theclinics.com

Page 30: Anestesia Ocular

mcgoldrick & foldes180

Many of these injuries were caused by intraocular

foreign bodies and dehiscence of cataract or corneal

transplant incisions. Blocked eyes tended to have

smaller, more anterior wounds than those repaired

via general anesthesia. There was no outcome differ-

ence—that is, change of visual acuity from initial

evaluation until final examination—between the eyes

repaired with regional versus general anesthesia.

Additionally, combined topical analgesia and seda-

tion for selected patients with open-globe injuries has

also been reported [5].

General anesthesia is the technique of choice for

removal of infected scleral buckles or for patients

with very high myopia, where a perforating injury

from peribulbar or retrobulbar block is feared. Other

indications may include claustrophobia, deafness, a

language barrier, Parkinson’s disease, and intractable

arthritis or orthopnea, which impair the patient’s abil-

ity to lie flat and remain motionless during surgery.

Furthermore, the anticipated duration of the proce-

dure must be factored into the selection process, be-

cause few geriatric patients under regional anesthesia

can remain comfortable on a narrow, hard operating

table for procedures that exceed 2 or 3 hours.

With general anesthesia the risks of retrobulbar or

peribulbar hemorrhage, globe perforation, myotox-

icity, central spread of local anesthetic with possible

brain stem anesthesia, and inadequate intraoperative

analgesia are virtually eliminated. Nonetheless, gen-

eral anesthesia may be associated with a greater like-

lihood of airway complications and postoperative

nausea and vomiting. Although regional and topical

anesthetic techniques have gained enormous popular-

ity in recent years, it is imperative to appreciate the

vital role that general anesthesia maintains in the care

of certain ophthalmic patients. Major retrospective

and prospective nonrandomized studies have failed to

demonstrate the superiority of one anesthetic ap-

proach over the other in terms of morbidity and mor-

tality [6–10]. Accordingly, the risks, benefits, and

alternatives of all anesthetic options should be ex-

plained clearly to the patient, with the choice deter-

mined after discussion among patient, anesthesiologist,

and surgeon.

Preoperative evaluation

The preoperative evaluation of the geriatric patient

characteristically is more complex than that of the

younger patient owing to the heterogeneity of seniors

and the increased frequency and severity of comor-

bid conditions associated with aging. The process of

aging is highly individualized. Different people age at

varying rates and often in different ways. Typically,

however, virtually all physiologic systems decline

with advancing chronological age. Nevertheless,

chronological age is a poor surrogate for capturing

information about fitness or frailty. Moreover, peri-

operative functional status can be difficult to quanti-

tate because many elderly patients have reduced

preoperative function related to deconditioning, age-

associated disease, or cognitive impairment. Thus, it

is challenging to satisfactorily evaluate the patient’s

capacity to respond to the specific stresses associated

with anesthesia and surgery. How, for example, does

one determine cardiopulmonary reserve in a patient

severely limited by osteoarthritis and dementia? Even

‘‘normal’’ aging results in alterations in cardiac, re-

spiratory, neurologic, and renal physiology that are

linked to reduced functional reserve and ability to

compensate for physiologic stress. Moreover, the con-

sumption of multiple medications so typical of the

elderly can alter homeostatic mechanisms.

Preoperative testing

In the general population there is strong consensus

that most so-called ‘‘routine’’ tests are not indicated.

In the subset of geriatric patients our knowledge is

somewhat more limited. Nonetheless, a recent study

on routine preoperative testing in more than 18,000 pa-

tients undergoing cataract surgery is worthy of com-

ment. Patients were randomly assigned to undergo or

not undergo routine testing (ECG, complete blood

cell count, electrolytes, serum urea nitrogen, cre-

atinine, and glucose) [11]. The analysis was stratified

by age and disclosed no benefit to routine testing for

any group of patients. Similar conclusions were

drawn in a smaller study of elderly noncardiac sur-

gical patients by Dzankic and colleagues [12]. Some

physicians and lay people, however, misinterpreted

the results of Schein and colleagues’ [11] study, be-

lieving that patients having cataract surgery need no

preoperative evaluation. It is vital to note that all

patients in this trial received regular medical care

and were evaluated by a physician preoperatively;

they simply were not subjected to a robotic battery

of routine laboratory testing. Patients whose medical

status indicated a need for preoperative laboratory

tests were excluded from the study. Because ‘‘rou-

tine’’ testing for the more than 1.5 million cataract

patients in the United States is estimated to cost

$150 million annually, the favorable economic im-

pact of this ‘‘targeted’’ approach is obvious.

From these investigations and others, a few con-

cepts emerge. First, routine screening in a general

population of elderly patients does not significantly

Page 31: Anestesia Ocular

general anesthesia for ophthalmic surgery 181

augment information obtained from the patient’s

history and physical examination. Testing should be

selective, based on abnormalities found from the pa-

tient’s history and physical examination. Second, the

positive predictive value of abnormal findings on

routine screening is limited. Third, positive results on

screening tests have modest impact on patient care.

The preoperative period is not the appropriate time to

screen for asympotomatic disease.

The dearth of population studies of perioperative

risk and outcomes specifically addressing the geri-

atric population can make selecting the most appro-

priate course of care challenging. Because age itself

adds very modest incremental risk in the absence of

comorbid disease, most risk-factor identification and

risk-predictive indices have focused on specific dis-

eases [13–15].

Considerations for patients with cardiac disease

It is well known that normal aging produces

structural changes in the cardiovascular system, as

well as changes in autonomic responsiveness/control,

that can compromise hemodynamic stability. The su-

perimposition of such comorbid conditions as angina

pectoris or valvular heart disease can further impair

cardiovascular performance, especially in the periop-

erative period.

According to the guidelines of the American Col-

lege of Cardiology (ACC) and the American Heart

Association (AHA) for preoperative cardiac evalua-

tion, the patient’s activity level, expressed in meta-

bolic units, is a primary determinant of the necessity

for further evaluation, along with the results obtained

from history and physical examination [13]. These

findings are then evaluated in conjunction with due

consideration for the invasiveness of the planned

surgical procedure. Fortunately, most ophthalmic pro-

cedures are typically considered to represent rela-

tively noninvasive, low-risk surgery.

Clearly, the goal of the preoperative evaluation

should be the identification of major predictors of

cardiac risk such as unstable coronary syndromes (for

example, unstable angina or myocardial infarction

[MI] less than 30 days ago), decompensated conges-

tive heart failure (CHF), severe valvular disease, and

significant arrhythmias. These patients have a pro-

hibitive rate of perioperative morbidity and mortality,

and are inappropriate candidates for elective outpa-

tient surgery. They deserve the benefit of further car-

diology consultation and optimization. In patients

with intermediate clinical predictors (mild angina,

previous MI more than 30 days ago, compensated or

prior CHF, diabetes mellitus, or renal insufficiency),

the invasiveness of the surgery and the functional

status of the patient will play major roles in de-

termining the nature and extent of preoperative

testing or intervention. Importantly, no preoperative

cardiovascular testing should be performed if the

results will not change perioperative management.

Patients with minor clinical predictors, such as ad-

vanced age, ECG abnormalities, rhythm other than

sinus, low functional status, history of stroke, or hy-

pertension, who are having low- or intermediate-risk

surgery typically will not require further cardiovas-

cular testing.

For those in whom further testing is warranted,

there are several options including Holter monitor-

ing, radionuclide ventriculography, thallium scintigra-

phy, dobutamine stress echocardiography, and coronary

angiography. The use of perioperative b-blockade in

intermediate or high-risk patients undergoing vascu-

lar surgery can be beneficial and may obviate the

need for more invasive interventions [16]. A recent

study demonstrated that perioperative b-blockertherapy is associated with a reduced risk of in-

hospital death among high-risk, but not low-risk,

patients undergoing major noncardiac surgery [17].

However, there is an absence of data pertaining to the

use of perioperative b-blockade in patients under-

going less invasive outpatient surgery that is charac-

teristic of most ophthalmic procedures.

Increasingly, patients with coronary artery disease

are undergoing stent placement. A frequently asked

question in this context is how long should one wait

after stent placement before scheduling a patient for

elective surgery under general anesthesia. Kaluza and

colleagues [18] in 2000 published a recommendation

(based on a study of 40 patients) that elective surgery

should be postponed for 2 to 4 weeks after stent

placement to allow completion of the antiplatelet pro-

tocol. A few years later, however, Wilson and col-

leagues [19] studied more than 200 patients and

recommended that nonemergency surgery should be

delayed for 6 weeks after stent insertion to permit

completion of the antiplatelet therapy and to allow for

endothelialization of the stent.

It should be emphasized that diabetes mellitus is

an intermediate predictor of such adverse cardiac

outcomes as perioperative MI and CHF after elective

surgery because of the accelerated atherosclerosis that

occurs with associated aberrations of lipid and cho-

lesterol metabolism. The Diabetes Control and Com-

plications Trial, a clinical study of young (average

age 27 years) diabetic patients, showed that intensive

treatment delayed the onset and severity of retinop-

athy, nephropathy, and neuropathy [20]. However, the

cohort was probably too young to demonstrate a

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mcgoldrick & foldes182

reduction in cardiovascular complications with ag-

gressive insulin therapy, but the results suggest that a

well-controlled diabetic patient may be at lesser risk

than a poorly controlled diabetic patient. Nonetheless,

this issue is not addressed in the ACC/AHA guide-

lines. It is important to appreciate that the diagnosis

of myocardial ischemia may be more challenging in

a diabetic patient owing to the high incidence of au-

tonomic neuropathy. Patients with autonomic neu-

ropathy may not complain of chest pain even when

experiencing an acute MI.

General anesthesia: physiologic principles and

pharmacologic agents

Those patients who require or prefer general an-

esthesia for eye surgery experience a favorable

outcome provided the airway is satisfactorily main-

tained, hemodynamic stability is achieved, and the

eye is kept motionless with a constant intraocular

pressure (IOP). The latter is especially critical during

open-eye operations such as corneal transplantation

or open-sky vitrectomy procedures when the risk of

vitreous loss or expulsive choroidal hemorrhage is

present. Moreover, it is important to appreciate that

drugs administered to produce pupillary dilation or to

reduce IOP may be absorbed systemically from the

conjunctiva or (predominantly) from the nasal mu-

cosa after drainage through the nasolacrimal duct.

Such systemic absorption has important anesthetic

implications. Nasolacrimal duct occlusion is an ef-

fective way to minimize systemic absorption, and this

maneuver is important in small children who are ex-

tremely vulnerable to the toxic effects of such drugs

as scopolamine or phenylephrine. Additionally, top-

ical administration of these drugs should be avoided

in eyes with open conjunctival wounds. Examples

of potentially worrisome topical ocular drugs include

cyclopentolate, echothiophate iodide, epinephrine,

and timolol.

Intraocular drugs also have important anesthetic

implications. Nitrous oxide, for example, should not

be used concomitantly in eyes that receive intraocular

air or gas. To avoid significant changes in the volume

of the injected bubble and associated dangerous

changes in IOP, nitrous oxide should be discontinued

15 to 20 minutes before an intravitreous air or gas

injection administered to tamponade a detached retina

[21]. Furthermore, if a patient requires a repeat op-

eration after intravitreous gas injection, the typical

recommendation is that nitrous oxide should be

omitted for 5 days after an air injection and for

10 days after a sulfur hexafluoride injection [22]. In

cases where perfluoropropane has been injected, the

nitrous oxide proscription should be in effect for

longer than 30 days [23]. It is important to point out,

however, that resorption time is not uniform or al-

ways predictable. For example, reports have appeared

where a 19-year-old woman with type 1 diabetes

injected with sulfur hexafluoride 25 days before sub-

sequent surgery and a 37-year-old male with insulin-

dependent diabetes injected with perfluoropropane

gas 41 days before subsequent surgery were given

nitrous oxide and developed central retinal artery

occlusion and permanent blindness in the affected eye

[24]. Because the pressure in retinal arterial vessels is

lower in patients with diabetes, the elderly, and those

with atherosclerosis, these patients are probably at

higher risk for this devastating complication [25–29].

The international distributor of medical-grade gases,

in cooperation with the American distributors and the

US Food and Drug Administration (FDA), has begun

to provide hospital band-type warning bracelets for

patients who receive intraocular gas injection to alert

other health professionals to the presence of the bub-

ble and the need to avoid nitrous oxide administration.

Because many eye surgery patients are elderly,

they may have arthritic involvement of the cervi-

cal spine and the temporomandibular joint, which

can make laryngoscopy difficult or, occasionally,

impossible. Thus, equipment designed to facilitate

intubation, such as gum elastic bougies, fiberoptic

endoscopes, laryngeal mask airways, and a variety of

laryngoscope blades and endotracheal tube sizes,

should be readily available.

The logistic exigencies of ophthalmic anesthesia

are such that the anesthesiologist is positioned remote

from the patient’s airway. It is, therefore, essential to

meticulously secure the endotracheal tube. Addition-

ally, the anesthetic tubing should be positioned so that

torsional strains do not occur that might inadvertently

occlude the endotracheal tube by causing it to kink

or twist. All connections should be firmly secured

because movement of the head by the surgeon might

dislodge a weak connection. Finally, the eye that is

not undergoing surgery should be taped shut and a

shield applied to prevent injury. Many ophthalmolo-

gists request that the patient’s nares be packed with

gauze to prevent nasal secretions from contaminating

the eye during surgery.

The laryngeal mask airway (LMA) has gained

great popularity in the past 15 years. Having the

advantage of being easy to position without laryngos-

copy or muscle relaxants, the LMA does not produce

the same marked degree of vasopressor and oculo-

tensive reflexes associated with endotracheal intuba-

tion and is less apt to cause dental damage. Initially, it

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general anesthesia for ophthalmic surgery 183

was thought that the LMA was less likely to produce

a sore throat [30,31], but more recent prospective

investigations question the purported advantage of

the LMA versus an endotracheal tube in regard to

minor laryngopharyngeal morbidity [32]. The classic

LMA does not protect against aspiraton, however,

and many geriatric patients have an incompetent

esophagogastric junction that may allow reflux of

gastric contents. Moreover, many patients with dia-

betes mellitus also have gastroparesis. These patients,

and others with significant risk factors for aspiration,

are managed prudently by intubation with a cuffed

endotracheal tube to protect the lungs.

A wide assortment of anesthetic agents can be

administered safely and effectively in ophthalmic

surgery. Virtually any of the inhalation agents can be

administered after intravenous induction with a

barbiturate or propofol. Similarly, a total intravenous

anesthetic technique with a propofol infusion and

other intravenous medications as needed can be ad-

ministered. Because it is consistently associated with

less postoperative nausea and vomiting than other

agents [33–35], propofol is an excellent drug for

patients undergoing ophthalmic surgery. Recovery

from propofol is rapid and typically associated with a

sense of well-being [36], even euphoria, making it a

very suitable drug for ambulatory surgery. Moreover,

propofol attenuates the hypertensive response to

intubation and reduces IOP, similar to most intra-

venous anesthetic drugs commonly used during eye

surgery, such as narcotics and other sedative-hypnotics

[37,38]. Propofol, however, frequently produces dis-

comfort or pain when injected into small veins. This

complication can be minimized or prevented by

preadministration of, or admixing with, 20 mg li-

docaine. Moreover, new formulations of propofol

designed to be less irritating to veins are currently

being evaluated. In patients with significant coronary

artery or other types of heart disease, the cardiode-

pressant effects of barbiturates or propofol are un-

welcome. Induction with intravenous etomidate may

be more benign in terms of the cardiovascular system

but, unfortunately, can trigger postoperative nausea

and vomiting and possibly also result in short-term

depression of adrenocortical function. The selection

of the optimal muscle relaxant to facilitate intubation

is made after assessing the patient’s airway and the

probable degree of difficulty of intubation, the pres-

ence of symptomatic reflux, the hemodynamic con-

sequences of the neuromuscular blocking agent, and

the estimated duration of the surgery.

Satisfactory control of arterial blood pressure is

always important, but it has special implications for

retinal perfusion in patients having vitreoretinal sur-

gery. If the patient’s mean arterial pressure is mark-

edly reduced, the retinal perfusion may be inadequate

and compromise the visual outcome of surgery.

Alternatively, marked elevation of retinal arteriole

pressure can be dangerous. Therefore, it behooves the

anesthesiologist to be cognizant of the patient’s nor-

mal blood pressure and endeavor to maintain hemo-

dynamic variables within an acceptable range for

each individual patient.

Various inhalation agents are available for intra-

operative maintenance of anesthesia, including iso-

flurane, desflurane, and sevoflurane. All these agents

lower IOP in a dose-dependent fashion, provided

oxygenation and ventilation are satisfactorily main-

tained. Desflurane and sevoflurane, the two newest

inhalation agents in widespread use, have lower

blood-gas solubilities than all previously used potent

inhaled agents. In theory, this solubility advantage

allows greater control of anesthetic depth and more

rapid recovery from general anesthesia. Desflurane

has the lowest blood-gas solubility of all volatile

agents and is associated with the fastest immediate

awakening after surgery. Data indicate that desflurane

resists in vivo degradation more than any other potent

halogenated agent. The limited biodegradation that

does occur appears to be approximately one tenth that

of isoflurane, the least degraded of the other available

halogenated agents. This lack of significant biotrans-

formation suggests relative safety in terms of po-

tential toxicity from metabolites.

The cardiovascular effects of desflurane involve

the direct effects of the agent, and a transient response

linked to sympathetic nervous system activation. The

direct hemodynamic effects of desflurane are quite

similar to those of isoflurane, including a reduction in

peripheral vascular resistance and blood pressure.

Prolongation of the QTc interval has been reported

with many anesthetic drugs including isoflurane,

sevoflurane, and desflurane [39]. However, the tran-

sient sympathetic activation seen with desflurane

administered in combination with nitrous oxide is not

encountered with isoflurane, but had been reported

with diethyl ether. Although the precise mechanism

responsible for this response has not been definitively

established, beta-adrenergic activation leading to

major increases in blood pressure and heart rate

through increased plasma epinephrine and norepi-

nephrine levels has been postulated [40]. The extent

of sympathetic activation is related, at least partially,

to the absolute concentration of desflurane as well as

to the rapidity of increase in the concentration of

desflurane. Thus, an extremely rapid progression to

high concentrations of desflurane triggers more dra-

matic sympathetic stimulation [40,41]. This sympa-

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mcgoldrick & foldes184

thetic response can be attenuated by pretreatment

with clonidine or intravenous fentanyl, esmolol, or

propofol. Nonetheless, many clinicians think it is best

to avoid desflurane in patients with a history of myo-

cardial ischemia, or else to administer only relatively

low concentrations of the agent and to increase the

concentration gradually as indicated.

Many of the physicochemical characteristics and

pharmacologic properties of sevoflurane suggest that

it is well suited for use in ophthalmic surgery. Com-

pared with desflurane, sevoflurane has the advantage

of being nonirritating to the airway. Inhalational in-

duction of anesthesia with sevoflurane is accom-

plished smoothly and quickly, making it the agent of

choice in young children who are afraid of needles

and would, therefore, prefer to avoid an intrave-

nous induction. Coughing, laryngospasm, and breath-

holding are lesser problems than they are with

isoflurane or desflurane, even with so-called single

breath inductions. Additionally, sevoflurane, unlike

desflurane, has a cardiovascular profile that is quite

predictable, and it does not activate the sympathetic

nervous system [42]. The incidence of bradycar-

dia and arrhythmias during inhalation induction in

children is also much lower than with halothane

[43]. Occasionally, the occurrence of opisthotonic

and seizurelike activity with sevoflurane has been

noted [44–46]. The seizurelike activity has been re-

ported at variable sevoflurane concentrations and

during induction, maintenance, and recovery. The

phenomenon has been observed in adults as well as

children. It is reassuring that all of the patients who

demonstrated the seizurelike activity recovered with-

out incident. Nonetheless, clinicians should be aware

of this problem, which is listed in the drug insert

provided by Abbott Pharmaceuticals [47].

Sevoflurane is unstable under in vitro and in

vivo conditions, producing compound A and fluo-

ride. Compound A has been shown to be nephro-

toxic in rats, and high fluoride concentrations can be

nephrotoxic in humans. However, despite extensive

clinical investigations, multiple studies have not

demonstrated any clinically significant renal or he-

patic dysfunction in humans, even at very low gas

flows [48,49]. Indeed, sevoflurane has been admin-

istered to more than 120 million patients worldwide

with an impressive safety record. It appears that the

likelihood of long-term toxicity in humans from

sevoflurane administered according to the guidelines

in the package insert is extremely low, even when

given for prolonged procedures. Similar to desflur-

ane, awakening and emergence from sevoflurane are

rapid and complete. However, emergence excitement

or agitation is not uncommon with desflurane and

sevoflurane. The times until discharge for ambulatory

patients in whom desflurane or sevoflurane was used

are comparable with more soluble agents like iso-

flurane or enflurane [50]. Whether this finding re-

flects a true lack of improvement in recovery time, or

merely inertia in the ambulatory center system, re-

mains to be determined.

Regardless of which agent is selected, it should be

carefully titrated and, because akinesia is important

for delicate ocular surgery, administration of a non-

depolarizing muscle relaxant is advised, in conjunc-

tion with peripheral nerve monitoring to ensure a

twitch height suppression of 90% to 95% during

open-eye surgery. Ventilation should be controlled

and continuously monitored by end-tidal CO2 deter-

mination to avoid hypercarbia and its ocular hy-

pertensive effect as well as to detect inadvertent

disconnection of the endotracheal tube from the an-

esthesia circuit, a dangerous event that can be ob-

scured by the surgical drapes. Continuous monitoring

of arterial oxygen saturation by pulse oximetry is also

essential. After completion of surgery, any residual

neuromuscular block should be reversed. Intravenous

lidocaine can be administered a few minutes before

extubation to prevent or attenuate periextubation

coughing. Depending on such factors as the patient’s

airway anatomy, NPO (nil per os) status, and history

of reflux, either awake or deep extubation may be

selected. In skilled hands, either technique is sat-

isfactory for patients who were fasting, who have

normal airway anatomy, and who have no risk factors

for reflux.

Postoperative nausea and vomiting: prevention

and therapy

Postoperative nausea and vomiting (PONV) ac-

count for a major proportion of unanticipated ad-

missions to the hospital after intended ambulatory

surgery, especially in children. Fortunately, after age

50 the incidence of PONV declines by more than

10% during each subsequent decade. The incidence

of PONV is higher with narcotic-based anesthesia and

with volatile agents. The incidence is lowest with a

total intravenous anesthetic technique using propofol.

The emetic effect of anesthetics are modulated in the

chemoreceptor trigger zone, where serotonergic, his-

taminic, muscarinic, and dopaminergic receptors are

found [34]. Input also comes from vagal and other

stimulation directly to the emetic center.

Although pharmacologic agents that act on the

chemoreceptor trigger zone are well represented

in our antiemetic armamentarium, the neurokinin1

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general anesthesia for ophthalmic surgery 185

(NK1) antagonists are the only available antiemetics

that act on the vomit center. Traditional antiemetics

include benzamides such as metoclopramide, buty-

rophenones such as droperidol, and phenothiazines

such as prochlorperazine. These three classes of drugs

antagonize dopamine receptors. Scopolamine and

atropine are anticholinergics that antagonize musca-

rinic receptors. Dimenhydrinate, diphenhydramine,

and hydroxyzine antagonize histamine receptors.

Other useful antiemetics include steroids such as

dexamethasone and assorted agents such as ephedrine

and propofol. Newer drugs include the 5-HT3 sero-

tonergic receptor antagonists, such as ondansetron,

tropisetron, and granisetron, which are expensive but

generally effective. The 5-HT3 blockers are attractive

because of the paucity of side effects associated with

their use. Unlike many other antiemetics, which can

cause drowsiness, dry mouth, or extrapyramidal

symptoms, the 5-HT3 antagonists have a clean profile,

except for headache and mild effects on liver function

tests. However, similar to droperidol, some of the

drugs in this category can prolong the QT interval.

Unlike droperidol, however, these drugs have not

been subject to a black box warning from the FDA.

Our knowledge concerning the pathophysiology

and management of PONV has grown impressively in

the past 15 years. We now believe, for example, that

universal PONV prophylaxis is not cost-effective.

Rather, prophylactic treatment should be directed to-

ward those at increased risk for the complication.

Apfel and colleagues have developed a simplified

risk score that identifies four major risk factors: fe-

male gender, nonsmoking status, history of PONV,

and opioid use [51]. In this investigation of inpatients

receiving balanced inhaled anesthesia the incidence

of PONV with none, one, two, three, or all four risk

factors was approximately 10%, 20%, 40%, 60%, and

80%, respectively. Apfel and colleagues claimed that,

for inpatients, the type of surgery was not an inde-

pendent risk factor. Sinclair and colleagues, however,

reported that certain ophthalmic procedures, such as

strabismus correction, were predictive of an increased

risk of PONV [52].

Recently, guidelines have been developed to pro-

vide a comprehensive, evidence-based reference tool

for the management of patients at moderate or high

risk for PONV [53]. Double and triple antiemetic

combinations (each with a different mechanism of

action) are recommended prophylactically for pa-

tients at high risk for PONV. All prophylaxis in chil-

dren at moderate or high risk for postoperative

vomiting should be with combination therapy using

a 5-HT3 antagonist and a second drug from a different

category. Antiemetic rescue therapy should be admin-

istered to patients who have an emetic episode after

surgery. If PONVoccurs within 6 hours after surgery,

patients should not receive a repeat dose of the pro-

phylactic antiemetic(s). Rather, a drug from another

class should be given.

Guidelines for diabetic patients undergoing

general anesthesia

Estimates reflect that as many as 15 million

people in the United States have diabetes mellitus.

Ninety percent of diabetic individuals have non-

insulin-dependent, or type 2, diabetes mellitus, and

10% have insulin-dependent, or type 1, diabetes mel-

litus requiring exogenous insulin to prevent keto-

acidosis. Diabetes affects virtually every tissue of the

body and shortens average life expectancy by up to

15 years. The emotional toll and financial costs

of diabetes and its complications are an estimated

$132 billion annually. This estimate reflects both

direct health care costs as well as lost productivity.

More than one of every four Medicare dollars is spent

on people with diabetes. It is sobering to realize that

diabetes and its complications rank as the third lead-

ing cause of death by disease in the United States.

Given the pandemic of obesity currently afflicting our

country, one can anticipate that the number of dia-

betic individuals will continue to climb.

End-organ disease

The renal, neurologic, cardiovascular, and oph-

thalmic complications of diabetes mellitus have been

well described. Both the presence and extent of end-

organ disease in an individual diabetic patient and the

metabolic perturbations induced by the stress of

anesthesia and surgery must be thoroughly compre-

hended if one is to formulate a rational and effective

perioperative management plan.

Cardiovascular abnormalities include coronary

artery disease, hypertension, cardiac autonomic neu-

ropathy, and impaired ventricular function. Occa-

sionally, unexpected sudden death may occur in

association with autonomic nervous system dysfunc-

tion. Because atherosclerosis and microangiopathy

occur at an earlier age in diabetic patients compared

with nondiabetic individuals, a diabetic patient’s

physiological age is much older than the stated

chronologic age. Thus, coronary artery disease is

common in long-standing type 1 diabetes, even at age

25 or 30 years. Myocardial infarction is 5 to 10 times

more common in type 1 and type 2 diabetic in-

dividuals with end-organ disease than in the general

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mcgoldrick & foldes186

population. Because diabetic adults are considered at

high risk for perioperative myocardial ischemia, a

baseline ECG should be obtained on all adult diabetic

individuals. Anesthetic management is then adjusted

appropriately to the results of preoperative assess-

ment and intraoperative hemodynamic performance.

Hypertension is extremely common in diabetic

patients, and may be a marker for possible coronary

artery disease. The presence of left ventricular hy-

pertrophy suggests impaired autoregulation of coro-

nary perfusion, rendering these patients vulnerable to

ischemia with even a moderate reduction in blood

pressure. Satisfactory control of blood pressure be-

fore surgery should foster stable intraoperative and

postoperative hemodynamic function. However,

perioperative hemodynamic instability may occur ow-

ing to altered sympathetic tone, reduced barorecep-

tor function, relative hypovolemia associated with

chronic vasoconstriction, and anesthetic interactions

with some antihypertensive medications. Because of

the diabetic patient’s limited ability to autoregulate

coronary perfusion, the anesthesiologist should

attempt to maintain blood pressure within ±20% of

baseline values.

The presence of orthostatic hypotension, an ele-

vated resting heart rate, or a reduction or absence of

a normal beat-to-beat variation of heart rate during

deep breathing suggests the possibility that the patient

may have cardiac autonomic neuropathy. This con-

dition manifests as an impaired cardiovascular stress

response and may be accompanied by painless

myocardial ischemia. Additionally, diabetic patients

with autonomic neuropathy may have abnormal

hypoxic drive mechanisms centrally or peripherally

and hence are at greater risk for sudden, unexpected

cardiac and respiratory arrest in the setting of hypoxia

[54,55].

Those with painless myocardial ischemia may

also have occult left ventricular dysfunction, which

can result in CHF if the patient is given a volume

overload perioperatively. Impaired gastric emptying

is also a consequence of autonomic dysfunction, and

can increase the risk of perioperative aspiration and

PONV. Administration of IV metoclopramide to fa-

cilitate gastric emptying may be helpful.

Diabetic renal disease, including renal papillary

necrosis and glomerulosclerosis, renders the diabetic

patient susceptible to perioperative acute renal failure.

Additionally, a diabetic patient is at greater risk for

urosepsis, which may contribute to systemic sepsis

and acute renal failure.

Fixation of the atlanto-occipital joint with limi-

tation of head extension may make endotracheal

intubation difficult [56]. ‘‘Stiff joint syndrome’’ typi-

cally occurs in type 1 diabetic patients and is as-

sociated with short stature, small joint contractures,

and tight, waxy skin. The etiology is thought to be

abnormal collagen cross-linking by nonenzymatic

glycosylation, which may occur in up to 25% of

juvenile diabetic individuals [57]. This abnormal

collagen glycosylation may also lead to possible

atlanto-occipital dislocation. A defective palm print

or ‘‘prayer sign’’ in these patients (owing to an in-

ability to approximate the interphalangeal joints of

the hand) is often associated with difficult intubation

and, therefore, should be assessed preoperatively so

that appropriate airway management can be planned,

enabling the necessary equipment to be immedi-

ately available.

Clearly, meticulous attention must be paid to a

thorough preoperative assessment and optimization

of the patient’s medical condition, as well as careful

titration of the drugs and fluids administered peri-

operatively. Attention must also be paid to proper

positioning and padding intraoperatively, because the

diabetic patients are especially vulnerable to pressure

ischemia of nerves and vasculature.

A retrospective study assessed perioperative risk

of nonocular surgery in diabetic patients [58]. Over-

all, 15% of patients had significant complications,

and there were major differences in outcome depend-

ing on the presence or absence of end-organ damage.

Patients with serious cardiac disease were more prone

to major perioperative cardiac complications. Non-

cardiac complications, including infection, renal in-

sufficiency, and cerebral ischemia, occurred in 24% of

patients with end-organ disease (retinopathy, neu-

ropathy, or nephropathy), in 29% of those with CHF,

and in 35% of those with peripheral vascular disease.

In patients without preexisting conditions, noncardiac

complications (6%) and cardiac complications (4%)

were rare. Moreover, the type of anesthetic selected

was not predictive of risk of complications. The study

emphatically underscored, however, that increased

morbidity and mortality occur in diabetic patients

with cardiac and end-organ disease.

Control of glucose

Despite the known advantages of ‘‘tight’’ or near

euglycemic control in the chronic diabetic state, the

concept of rigidly tight control is controversial in the

perioperative period. Aggressive attempts to achieve

euglycemia may result in dangerous episodes of

hypoglycemia that may be masked by anesthesia

and sedation. Therefore, the perioperative blood

sugar level should be maintained in the range of ap-

proximately 100 to 180 mg/dL. Patients with insulin-

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general anesthesia for ophthalmic surgery 187

dependent diabetes mellitus (type 1) tend to be more

‘‘brittle’’ than those with type 2 diabetes, and surgery

for type 1 patients should be scheduled as early in the

day as possible. Several regimens for insulin and

substrate infusions have been advocated, but one of

two protocols is generally followed. All treatment

options require frequent measurement of blood glu-

cose and treatment of hypoglycemia and hyper-

glycemia as needed. The blood glucose level is

determined preoperatively, and an intravenous infu-

sion of dextrose 5% (D5) and 0.25 normal saline

is begun. One half of the usual neutral protamine

Hagedorn (NPH) insulin dosage is administered,

provided the blood sugar level is above 150 mg/dL.

Blood glucose levels are monitored frequently (usu-

ally hourly) during the intraoperative period. Regular

insulin doses of 0.1 unit/kg are given when the

plasma glucose level exceeds 200 mg/dL. In contrast,

if the blood glucose level is below 100 mg/dL, more

intravenous dextrose is administered.

Alternatively, a simultaneous insulin and glucose

infusion may be given to a type 1 patient after a

preoperative blood sugar level has been established.

The infusion contains 1 to 2 units of insulin per

100 mL of 5% dextrose in water, and the infusion rate

allows for 0.2 to 0.4 units of insulin per gram of

glucose. Blood glucose levels are maintained in the

desired range by titrating the infusion rate.

Type 2 diabetic patients taking daily insulin are

managed in a manner analogous to that for type 1

diabetic individuals. Those patients on oral hypogly-

cemics should refrain from taking the hypoglycemic

agent on the day of surgery. After the fasting blood

sugar level has been established an appropriate intra-

venous infusion is initiated. A postoperative blood

sugar level is determined, with therapeutic and die-

tary instructions provided accordingly. An ophthal-

mic patient is usually able to tolerate oral intake

within a relatively brief period after surgery. When

oral intake is adequate, the patient may resume his or

her usual diabetic regimen.

Considerations for select high-risk patients

Marfan syndrome

Marfan syndrome is a disorder of connective

tissue, involving primarily the cardiovascular, skel-

etal, and ocular systems. However, the skin, fascia,

lungs, skeletal muscle, and adipose tissue may also be

affected. The etiology is a mutation in FBNI, the gene

that encodes fibrillin-1, a major component of extra-

cellular microfibrils, which are the major compo-

nents of elastic fibers that anchor the dermis, epi-

dermis, and ocular zonules [59]. Connective tissue in

this disorder has decreased tensile strength and elas-

ticity. Marfan syndrome is inherited as an autosomal

dominant trait with variable expression.

Ocular manifestations of the syndrome include

severe myopia, spontaneous retinal detachment, lens

displacement, and glaucoma. Cardiovascular mani-

festations include dilation of the ascending aorta and

aortic insufficiency. The loss of elastic fibers in the

media may also account for dilation of the pulmonary

artery and mitral insufficiency resulting from ex-

tended chordae tendinae. Myocardial ischemia owing

to medial necrosis of coronary arterioles as well as

dysrhythmias and conduction disturbances have been

well documented. Heart failure and dissecting aortic

aneurysms or aortic rupture are not uncommon.

The patients are tall, with long, thin extremities

and fingers (arachnodactyly). Joint ligaments are

loose, resulting in frequent dislocations of the man-

dible and hip. Possible cervical spine laxity can also

occur. Kyphoscoliosis and pectus excavatum can

contribute to restrictive pulmonary disease. Lung

cysts have also been described, causing an increased

risk of pneumothorax. A narrow, high-arched palate

is commonly found.

The early manifestations of Marfan syndrome

may be subtle, and therefore the diagnosis may not

yet have been made when the patient comes for initial

surgery. The anesthesiologist, however, should have a

high index of suspicion when a tall young patient

with a heart murmur presents for repair of a spontane-

ously detached retina. These young patients should

have a chest radiograph as well as an electrocardio-

gram and echocardiogram before surgery. Antibiotics

for subacute bacterial endocarditis prophylaxis

should be considered, as well as b-blockade to miti-

gate increases in myocardial contractility and aortic

wall tension (dP/dT).

The anesthesiologist should be prepared for a

potentially difficult intubation. Laryngoscopy should

be carefully performed to circumvent tissue damage

and, especially, to avoid hypertension with its atten-

dant risk of aortic dissection. The patient should be

carefully positioned to avoid cervical spine or other

joint injuries, including dislocations. The dangers of

hypertension in these patients are well known.

Clearly, the presence of significant aortic insuffi-

ciency warrants that the blood pressure (especially

the diastolic pressure) be high enough to provide

adequate coronary blood flow but should not be so

high as to risk dissection of the aorta. Maintenance

of the patient’s normal blood pressure is typically a

good plan. No single intraoperative anesthetic agent

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mcgoldrick & foldes188

or technique has demonstrated superiority. If pulmo-

nary cysts are present, however, positive pressure ven-

tilation may lead to pneumothorax [60]. At extubation,

one should take care to avoid sudden increases in

blood pressure or heart rate. Adequate postoperative

pain management is vitally important to avoid the

detrimental effects of hypertension and tachycardia.

Myotonic dystrophy

Myotonic dystrophy, also known as myotonia

dystrophica or Steinert’s disease, is a genetically trans-

mitted autosomal dominant disease with variable and

unpredictable penetrance and phenotypic presenta-

tion. Myotonia denotes a characteristic persistent

contracture after cessation of voluntary contraction or

electrical or percussive stimulation. This inability of

skeletal muscle to relax is diagnostic. Electromyog-

raphy is corroborative and pathognomonic, showing

continuous, low-voltage activity with high-voltage,

fibrillation-like potential bursts. Myotonia can be

initiated or exacerbated by exercise or cold temper-

ature and a host of other conditions and drugs. The

most common form of myotonic dystrophy is lo-

calized to chromosome 19, locus q12.3, the gene that

codes for serine/threonine kinase. An abnormally

long trinucleotide repeat is thought to lead to the

disease. Moreover, within a given patient there is

mosaicism in the aberrant repeat sequences in differ-

ent tissues. A defect in sodium and chloride channel

function produces electrical instability of the muscle

membrane and self-sustaining runs of depolarization.

Additionally, abnormal calcium metabolism may be

involved. In contrast to most myopathies, the distal

muscles are more affected than proximal muscles.

Although patients can present at any age from infancy

to late life, typically myotonic dystrophy manifests in

the second or third decade. Myotonia is the predom-

inant manifestation early in the disease, but as the

condition progresses, muscle weakness and atrophy

become more apparent. Facial muscles (orbicularis

oculi and oris, masseter, and so forth) frequently

develop marked atrophy, producing a characteristic

expressionless facial appearance sometimes described

as ‘‘hatchet face.’’

Multiple organ systems are affected. Cardiac mani-

festations, which are often noted before the appear-

ance of other clinical symptoms, consist of atrial or

ventricular tachyarrhythmias, conduction abnormal-

ities including varying degrees of heart block, and,

less frequently, impaired ventricular function [61,62].

Mitral valve prolapse is said to occur in approxi-

mately 15% of myotonic patients [62]. Respiratory

involvement consists of a restrictive pattern of dis-

ease, with respiratory and sternocleidomastoid mus-

cle weakness leading to reduced vital capacity.

Patients typically develop a weak cough, dyspnea,

and frequent episodes of pneumonia. Alveolar hypo-

ventilation is caused by either pulmonary or central

nervous system dysfunction. Chronic hypoxemia may

result in cor pulmonale. Assorted other stigmata in-

clude presenile cataracts, ptosis, strabismus, and pre-

mature frontal balding. Endocrine dysfunction leads

to adrenal [63], thyroid, pancreatic [64], and gonadal

insufficiency. Central nervous system manifestations

include mental retardation, central sleep apnea, and

hypersomnolence, as well as psychiatric aberrations.

Delayed esophageal and gastric emptying [65], in

combination with compromised ability to swallow

[66], can predispose patients to pulmonary aspiration.

Moreover, uterine atony can retard labor and increase

the likelihood of retained placenta.

Treatment of myotonic dystrophy can be under-

taken with membrane-stabilizing medications, such

as phenytoin, quinine sulfate, and procainamide. Al-

though phenytoin has not been implicated in the

exacerbation of cardiac conduction abnormalities,

quinine and procainamide may prolong the P-R inter-

val. A cardiac pacemaker should be inserted in pa-

tients with significant conduction defects, even if they

appear to be asymptomatic.

Patients with myotonic dystrophy offer multiple

challenges to the anesthesiologist because they are at

high risk for serious perioperative respiratory and

cardiac complications. (Apparently, this condition can

also complicate surgical results. Three case reports,

for example, describe seemingly uneventful cataract

surgery that was complicated postoperatively by re-

current opacifications and intraocular fibrosis [67].) It

is vital to appreciate that a small number of patients

with this condition may be presymptomatic and un-

diagnosed. Indeed, although rare, there are reports of

patients with myotonic dystrophy in whom the diag-

nosis was made only after an episode of prolonged

apnea occurred following general anesthesia. Typi-

cally, however, the patient’s diagnosis is known, and

that individual suffers from a host of associated con-

ditions including restrictive lung disease, conduction

defects, cardiomyopathy, hypothyroidism, diabetes,

dysphagia, and delayed gastric emptying.

Patients with myotonic dystrophy have altered re-

sponses to a vast spectrum of anesthetic drugs. They

are frequently extremely sensitive to even small doses

of opioids, sedatives, and inhalation agents, all of

which may trigger prolonged apnea. Succinylcholine

is considered relatively contraindicated because it can

precipitate intense myotonic contractions. Moreover,

trismus can abolish the ability to open the mouth for

Page 39: Anestesia Ocular

general anesthesia for ophthalmic surgery 189

oral intubation. Myotonic contraction of respiratory,

chest wall, or laryngeal muscles can render ven-

tilation difficult or impossible. Additionally, hypo-

thermia, shivering, struggling during an inhalation

induction, application of a tourniquet, performing a

painful needle stick for intravenous induction, surgi-

cal manipulation, and using electrocautery or a pe-

ripheral nerve stimulator can all trigger myotonic

contractions. Other drugs that act at the motor end

plate, such as neostigmine and physostigmine, can

exacerbate myotonia. Regional anesthesia can be ad-

ministered but does not reliably prevent myotonic

contractions, which do respond to intramuscular

injection of procaine or intravenous administration

of 300 to 600 mg quinine hydrochloride. Even non-

depolarizing muscle relaxants do not consistently

prevent myotonic contractions. Because reversal

agents can theoretically trigger myotonic contrac-

tions, the use of relatively short-acting nondepolariz-

ing drugs, such as mivacurium, is recommended.

Small doses of meperidine may be judiciously ad-

ministered to prevent the shivering commonly asso-

ciated with hypothermia and the use of volatile

anesthetics. Short-acting opioids, such as alfentanil

or remifentanil, are recommended to avoid prolonged

postoperative respiratory depression and obtundation.

Obviously, temperature monitoring is important, as is

the use of warmed IV fluids, warmed humidified

inhaled gases, and use of a warming blanket. More-

over, aspiration prophylaxis is probably prudent.

Aggressive pulmonary hygiene with physical ther-

apy, incentive spirometry, and vigilant postopera-

tive monitoring are warranted. In the past, there was

speculation about an association between myotonic

dystrophy and malignant hyperthermia. This possible

link has not been confirmed, however. Interestingly,

both conditions map to chromosome 19, but have

different loci.

The literature suggests that there is no association

between the type of anesthesia administered and any

postoperative complications. Risk of pulmonary com-

plications appears to be greatest in those with severe

disability and those having upper abdominal surgery.

Because a variety of approaches have been used

successfully, there is no single best method. The risks

and benefits should be assessed individually to tailor

an appropriate anesthetic plan.

Summary

Skillful anesthetic management is integral to op-

timal outcomes after ophthalmic surgery. Although

the majority of ophthalmic operations in the United

States are performed with local anesthetic techniques,

nonetheless general anesthesia may be either nec-

essary or advisable in several challenging circum-

stances. Ophthalmic patients are often at the extremes

of age, and not uncommonly have extensive asso-

ciated systemic or metabolic diseases. Because the

complications of ophthalmic anesthesia can be vision

threatening or life threatening, it is imperative that the

ophthalmologist and the anesthesiologist understand

the complex and dynamic interaction among patient

disease(s), anesthetic agents, ophthalmic drugs, and

surgical manipulation. Effective communication and

planning among all involved are essential to safe

and efficient perioperative care.

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Ophthalmol Clin N

Sedation Techniques in Ophthalmic Anesthesia

Shireen Ahmad, MD

Northwestern University, Feinberg School of Medicine, Department of Anesthesiology, 251 East Huron Street, F5-704,

Chicago, IL 60611, USA

The majority of ophthalmologic surgeries are

performed with regional nerve block anesthesia.

Preoperatively, sedation may be required during the

placement of the nerve block to decrease the dis-

comfort of the injection, limit patient motion, relieve

anxiety, and produce amnesia about the procedure.

Intraoperatively, sedatives may also be administered

to relieve anxiety and prevent uncontrolled and

unexpected movement. However, it is also important

during surgery for the patient be calm, cooperative,

and aware; reflexes should not be obtunded; and the

airway should not be obstructed. Ideal sedation levels

can be achieved by careful intravenous titration of

suitable agents while monitoring the effect of the

sedative and analgesic agents.

Evidence-based medicine

Sedation practices for ophthalmologic surgery

range from none to multiple drug combinations that

result in a level of sedation that borders on general

anesthesia. There are limited data regarding the

question of whether there is a sedation strategy that

is safer and more effective, with most studies, despite

being randomized and placebo controlled, not having

a large enough sample size to detect any adverse

medical event with a low incidence. One study of

90 subjects who underwent cataract surgery follow-

ing intramuscular analgesic agents found that intra-

muscular sedation was associated with a higher

incidence of bradycardia compared with no sedation

[1], and another found an increased need for sup-

plemental oxygen when intramuscular sedative use

0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights

doi:10.1016/j.ohc.2006.02.004

E-mail address: [email protected]

was compared with placebo [2]. Oral sedatives were

not associated with any adverse events in two studies

[3,4], neither was intravenous propofol [5,6]. Barbi-

turates have been evaluated also and revealed no

hemodynamic complications [7,8]. A large cohort

study of 19,354 patients reported a 1.95% and 1.23%

incidence of intraoperative and postoperative adverse

events, respectively [9]. There was a strong associa-

tion between the use of intravenous agents in con-

junction with topical or nerve block anesthesia and

intraoperative adverse medical events after adjusting

for age, gender, length of surgery, and American

Society of Anesthesiologists Physical Status classi-

fication [10]. Use of more than one agent also was

associated with an increased risk of adverse events,

suggesting that use of multiple agents may not be

advisable. Most of the events were bradyarrhythmias

and hypertension.

Levels of sedation

The American Society of Anesthesiologists has

defined the levels of sedation [11,12] that are

commonly used to monitor patients perioperatively

and have also been used by the Joint Commission on

Accreditation of Healthcare Organizations (JCAHO)

to establish standards and guidelines on sedation.

These levels of sedation are as follows.

Minimal sedation (anxiolysis)

Minimal sedation (anxiolysis) produces a drug-

induced state during which patients respond normally

to verbal commands. Although cognitive function

and coordination may be impaired, ventilatory and

cardiovascular functions are unaffected.

Am 19 (2006) 193 – 202

reserved.

ophthalmology.theclinics.com

Page 43: Anestesia Ocular

ahmad194

Moderate sedation or analgesia (‘‘conscious

sedation’’)

Moderate sedation or analgesia (‘‘conscious seda-

tion’’) is a drug-induced depression of conscious-

ness during which patients respond purposefully to

verbal commands, either alone or accompanied by

light tactile stimulation. No interventions are required

to maintain a patent airway, and spontaneous venti-

lation is adequate. Cardiovascular function is usu-

ally maintained.

Deep sedation and analgesia

Deep sedation and analgesia is a drug-induced

depression of consciousness during which patients

cannot be easily aroused but respond purposefully

following repeated or painful stimulation. The ability

to independently maintain ventilatory function may

be impaired. Patients may require assistance in main-

taining a patent airway and spontaneous ventilation

may be inadequate. Cardiovascular function is usu-

ally maintained.

Anesthesia

General anesthesia is a drug-induced loss of con-

sciousness during which patients are not arousable,

even by painful stimulation. The ability to indepen-

dently maintain ventilatory function is often impaired.

Patients often require assistance maintaining a patent

airway, and positive-pressure ventilation may be re-

quired because of depressed spontaneous ventilation

or drug-induced depression of neuromuscular func-

tion. Cardiovascular function may be impaired.

The JCAHO standards require that moderate or

deep sedation be administered by a practioner with

‘‘appropriate credentials’’ who can ‘‘rescue’’ the pa-

tients from deep sedation and general anesthesia.

Monitoring level of sedation

Patients undergoing surgery may become sedated

as a result of the effects of regional blockade. Spinal

anesthesia is known to be accompanied by significant

sedation [13] and both spinal and epidural anesthesia

reduce hypnotic requirements for midazolam [14,15]

and thiopental [16]. Patients undergoing ophthal-

mologic surgery under regional block may also fall

asleep during the procedure. The mechanism for this

effect is not completely understood, but it has been

demonstrated that temporary peripheral denervation

decreases the excitability of the cuneate nucleus in the

brainstem [17] and acute block of retinal discharges

results in synchronization of cortical electroencepha-

logram (EEG), which is normally desynchronized

[18]. More recently it has been suggested that de-

crease in ascending somatosensory transmission can

modulate the activity of the reticulo-thalamo-cortical

mechanisms that regulate arousal [19,20] and thus

neuraxial blockade could result in a reduced level

of consciousness.

Ongoing assessment of the level of conscious-

ness throughout the surgical procedure is essential

to prevent the patient from progressing into deep

sedation with loss of protective airway reflexes. The

accurate assessment of the depth of sedation re-

quires a tool that is reliable and valid, and at the same

time is easy to use in the clinical arena. Various such

tools have been developed [21–29]. The Ramsay

sedation scale is a commonly used subjective assess-

ment of level of consciousness that uses an ordinal

scaling system to describe the level of conscious-

ness [21]:

� Level 1: Patient awake, anxious/restless, or both� Level 2: Patient awake, cooperative, orientedand tranquil� Level 3: Patient awake responds to

commands only� Level 4: Patient asleep, brisk response to light

glabellar tap or loud auditory stimulus� Level 5: Patient asleep, sluggish response to

light glabellar tap/loud auditory stimulus� Level 6: Patient asleep, no response to light

glabellar tap or loud auditory stimulus

The Observer’s Assessment of Alertness/Sedation

Scale (OAA/S) was designed to measure changes

in the level of consciousness during procedures,

but it is limited with deeper levels of sedation

(Table 1) [22].

The Neurobehavioral Assessment Scale [23] and

the Vancouver Sedative Recovery Scale (VSRS) [30]

are better at assessing the patient at the two extreme

ends of the scale. Children may progress rapidly from

light to deeper levels of sedation and greater vigilance

is necessary. The University of Michigan Sedation

Scale (UMSS) [31] is a validated scoring system that

has been used in children undergoing nonpainful

procedures and may be useful in the child undergoing

minor ophthalmologic surgery:

� 0, Awake and alert� 1, Minimally sedated: tired/sleepy, appropriate

response to verbal conversation and/ or sound

Page 44: Anestesia Ocular

sedation techniques in ophthalmic anesthesia 195

� 2, Moderately sedated: somnolent/sleeping,

easily aroused with light tactile stimulation or a

simple verbal command� 3, Deeply sedated: deep sleep, arousable only

with significant physical stimulation� 4, Unarousable

Conscious sedation versus sedation/analgesia

The term conscious sedation was coined by

the American Dental Association to describe the

practice of using sedatives and analgesics to alleviate

the fear, anxiety, and pain of dental surgery. Deeper

levels of sedation induced by an anesthesiologist are

referred to as sedation/analgesia or ‘‘monitored

anesthesia care.’’

Route of administration

The intravenous route is the preferred method of

administration, however in some very young chil-

dren, oral and inhalation agents may be necessary.

The enteral, subcutaneous, or intramuscular routes

are best avoided whenever possible because of unpre-

dictability of absorption and distribution of the drugs.

Choice of drugs

The drugs commonly used fall into two main

categories, namely sedatives and analgesics. When

Table 1

Observer’s Assessment of Alertness/Sedation Scale

(OAA/S) [22]

Subscore Responsiveness Speech

5 Responds readily to

name in normal tone

Normal

4 Lethargic response to

name spoken loudly

repeatedly

Mild slowing

or thickening

3 Responds only after

name spoken loudly

or repeatedly

Slurring or slowing

2 Responds after mild

prodding or shaking

Few recognized

words

1 Does not respond to

mild prodding or shaking

used in combination these drugs have a synergistic

effect and need to be titrated carefully [32–34].

Additionally, it is important to differentiate between

patient movement as a result of anxiety and that as a

result of pain. Administration of additional sedatives

in the presence of pain resulting from inadequate

regional block will only worsen the situation and

result in a deeply sedated, uncooperative patient with

uncontrolled movement.

Sedative agents

Benzodiazepines

Benzodiazepines are the most commonly used

drugs for peri-operative sedation. They act by binding

to the g-aminobutyric acid (GABA) complex and in-

hibit neuronal transmission. These drugs exhibit hyp-

notic, anxiolytic, and amnestic properties and lower

intraocular pressure. Cardiovascular and respiratory

depression is seen with excessive doses. Diazepam

has a long half-life, which is further prolonged in the

elderly. Its original formulation (Valium; Roche

Laboratories, Nutley, NJ), which contained propylene

glycol, was associated with venous irritation and phle-

bitis [35]. The newer lipid-based formulation (Dizac;

Ohmeda, Liberty Corner, NJ) is less irritating [36].

Midazolam is a water-soluble imidazo-benzodia-

zepine, with a rapid onset and short duration of effect.

The half-life of midazolam is 1.7 to 2.6 hours,

whereas that of diazepam is 20 to 50 hours [37].

Midazolam is metabolized in the liver by hydrox-

ylation to 1-hydroxy-midazolam, which has 20% to

30% the activity of midazolam and a shorter dura-

tion of action. It is excreted by the kidneys and could

have a prolonged effect in patients with renal failure

[38]. Respiratory depression and apnea occurs with

all benzodiazepines and is more likely to occur in the

presence of opioids, old age, and debilitating dis-

ease. Low doses of midazolam (0.075 mg/kg) do not

affect the ventilatory response to carbon dioxide,

suggesting that clinically significant respiratory

depression is unlikely at that dose range [39]. In a

study of midazolam in male volunteers, the elimi-

nation half-life was prolonged more than twofold in

the elderly group as compared with the young males

[40]. This study also revealed that the volume of

distribution was increased in the elderly, the obese,

and in women. Used alone, the benzodiazepines have

modest hemodynamic effects. The predominant

hemodynamic change is a slight reduction in arterial

blood pressure that results from a decrease in sys-

temic vascular resistance. The hemodynamic effects

of midazolam are dose related: the higher the plasma

level, the greater the decrease in systemic blood

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ahmad196

pressure [41]. The amnesic effect of midazolam has

been compared with diazepam and it was found to

produce better antegrade amnesia and faster recovery,

making it a more suitable drug for the elderly patient

having outpatient surgery than diazepam [42]. Mid-

azolam has been administered in small doses in the

range of 0.015 mg/kg, before administration of local

anesthetic in patients undergoing phacoemulsification

and lens implant surgery [43–45] and resulted in

high patient satisfaction scores and low levels of in-

traoperative anxiety.

In children ranging from 2 to 10 years of age,

midazolam has been administered orally (0.5 mg/kg)

before diagnostic and minor ophthalmologic surgical

procedures [46]. Administration of intranasal midazo-

lam has been reported in pediatric patients aged

3.5 months to 10 years for sedation before ocular

examination. This method of administration was as-

sociated with a rapid onset and was preferable to the

rectal route [47].

Lorazepam has twice the sedative potency of

midazolam, a slower onset of action, and longer du-

ration of action. A prospective randomized placebo-

controlled study of sublingual lorazepam 1 mg

administered an hour before peribulbar block for

cataract or glaucoma surgery resulted in good patient

comfort and amnesia related to the injection [48].

Propofol

Propofol (2, 6-di-isopropylphenol) is an alkylphe-

nol nonbarbiturate sedative-hypnotic that modulates

the GABAA receptor. It is rapidly metabolized in

the liver by conjugation to glucuronide and sulfate to

produce water-soluble compounds, which are ex-

creted by the kidneys [49]. The elimination half-life

of propofol is 4 to 23.5 hours [50,51]. Propofol phar-

macokinetics are affected by age, with elderly hav-

ing decreased clearance rates [52] and children a

more rapid clearance [53]. The degree of sedation and

reliable amnesia, as well as preservation of respira-

tory and hemodynamic function, are better overall

with benzodiazepines than with other sedative-

hypnotic drugs used for conscious sedation. When

midazolam is compared with propofol for sedation,

the two are generally similar except that emergence

or wake-up is more rapid with propofol. Because of

the potential for significant respiratory depression it

is recommended that propofol be administered under

close medical supervision by physicians with airway

management skills [54].

Propofol in small incremental intravenous doses

(20 mg) has been used to achieve amnesia for re-

gional eye blocks [55]; however, propofol provides

no analgesia for insertion of the block needle and

therefore semiconscious patients may have a startle

response to needle insertion. A single dose of pro-

pofol (0.98 mg/kg) has been shown to reduce intra-

ocular pressure (IOP) by 17% to 27%, which is

also beneficial during ophthalmologic surgery [56].

This change occurs immediately following injec-

tion and may be related to relaxation of the ex-

traocular muscles. Continuous infusion of propofol

(1.5 mg/kg/hour) has been found to be effective

during cataract surgery under topical anesthesia

but does require close monitoring for signs of respi-

ratory depression [57]. Patient-controlled sedation

using propofol (0.3 mg/kg, lockout interval of

3 minutes) in 55 elderly patients undergoing cataract

surgery has been reported [58]. Patients used less

than 1 mg/kg and reported a high degree of satis-

faction. One patient developed excessive sedation and

transient respiratory depression, which responded to

patient stimulation.

Ketamine

Ketamine is a phenylcyclidine derivative and dif-

fers from other sedative-hypnotic agents in that it also

has significant analgesic effects. It is metabolized by

hepatic microsomal enzymes to form norketamine

(metabolite I), which has been shown to have sig-

nificantly less (between 20% and 30%) activity than

the parent compound [59]. Ketamine produces a dis-

sociative state in which patients have profound anal-

gesia but keep their eyes open and maintain their

corneal, cough, and swallow reflexes. Ketamine ad-

ministration results in pupillary dilation, nystagmus,

lacrimation, salivation, and increased skeletal muscle

tone, often with coordinated but seemingly purpose-

less movement of the arms, legs, trunk, and head.

Ketamine is associated with psychic emergence reac-

tions, including excitement, confusion, euphoria, and

fear, which usually abate within 1 to several hours

[60]. The incidence of emergence reactions is higher

in adults [61], women [62], and with larger doses [63]

and can be reduced by concomitant use of benzodiaze-

pines [64].

Ketamine has minimal effect on the central respi-

ratory drive [65] and does not usually depress the

cardiovascular system [63]. Early studies reported an

increase in IOP after intramuscular or intravenous

administration of ketamine. However, subsequent

studies of ketamine given with diazepam and meper-

idine showed no affect on IOP, and intramuscularly

administered ketamine may even lower IOP in chil-

dren [66]. The use of ketamine in conjunction with

droperidol and diazepam has been reported to be a

useful adjunct in patients undergoing cataract surgery

with regional block [67].

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sedation techniques in ophthalmic anesthesia 197

Barbiturates

Barbiturate compounds such as methohexital and

thiopental have been used for sedation in ophthalmo-

logic surgery in the past, but have been replaced by

newer agents such as propofol and midazolam, which

have better pharmacologic profiles and fewer side

effects. Methohexital is administered in incremental

doses of 10 to 20 mg [68]. Residual sedation is

greater with methohexital than with propofol [69].

Chloral hydrate

Chloral hydrate has been used in children under-

going diagnostic procedures in offices and outpatient

clinics [70] and in elderly patients before cataract

surgery [71]; however, midazolam was found to be

preferable for the amnesic properties.

Dexmedetomidine

Dexmedetomidine is an a2-adrenergic agonist andproduces a sedative-hypnotic effect by an action on

a2-receptors in the locus ceruleus and an analgesic

effect by its action on a2-receptors within the locus

ceruleus and the spinal cord [72]. In volunteers, dex-

medetomidine sedation reduced minute ventilation

but did not alter the slope of the ventilatory response

to increasing CO2 [73]. The effects on the cardiovas-

cular system are a decreased heart rate; decreased

systemic vascular resistance; and indirectly decreased

myocardial contractility, cardiac output, and systemic

blood pressure [74]. Used as a premedicant at intra-

venous doses of 0.33 to 0.67 mg/kg given 15 minutes

before surgery, dexmedetomidine appears to be effi-

cacious with minimal cardiovascular side effects [75].

When used for intraoperative sedation, dexmedeto-

midine (0.7 mg/kg/hr) had a slower onset than pro-

pofol but had similar cardiorespiratory effects. With

continuous infusion sedation after termination of the

infusion was more prolonged, as was recovery of

blood pressure; however, lower doses of opioid were

needed in the first hour postoperatively [76]. A

double-blind placebo-controlled comparative study of

intramuscular dexmedetomidine (1 mg/kg) and mid-

azolam (20 mg/kg) before peribulbar block for cata-

ract surgery revealed comparable sedation in both

groups, but dexmedetomidine was more effective at

lowering IOP [77].

Opioid Analgesic Agents

Analgesic agents may be administered before

performing regional nerve block to decrease the pain

associated with the injection. Additionally, pain may

occur intraoperatively as a result of the light from the

operating microscope, iris manipulation, irrigation-

aspiration, and intraocular lens manipulation [78,79]

necessitating intraoperative analgesics.

Fentanyl

Fentanyl is the opioid analgesic most commonly

used to supplement regional blockade. It is usually

administered intravenously, in small doses in the

range of 50 to 100 mg. Onset of action is within 3 to

5 minutes but fentanyl has a relatively long half-life,

in large part because of this widespread distribution

in body tissues. The elimination half-life is 2 to

3 hours. Fentanyl is primarily metabolized in the liver

by N-dealkylation and hydroxylation to norfentanyl,

which is detectable in the urine for up to 48 hours

after intravenous administration [80]. Elderly pa-

tients are more sensitive to fentanyl and lower doses

(0.7 mg/kg) have been recommended in this age

group [81,82].

Fentanyl is available for oral transmucosal admin-

istration and results in reasonably rapid absorption,

with peak blood levels achieved within 15 to 30 min-

utes [83]. A recent study found that the liquid

intravenous formulation administered orally was rap-

idly absorbed and may be a reasonable substitute for

intramuscular opioid administration in children who

do not have intravenous access. An advantage of this

method may be the shorter and less variable con-

sumption time and greater versatility in dosing in

comparison to the Fentanyl Oralet [84].

Alfentanil

Alfentanil is a more rapid and shorter-acting

analog of fentanyl [85].The main metabolic pathways

of alfentanil include oxidative N-dealkylation and

O-demethylation, aromatic hydroxylation, and ether

glucuronide formation. The degradation products of

alfentanil have little, if any, opioid activity. Human

alfentanil metabolism may be predominantly, if not

exclusively, by cytochrome P-450 3A4 /5. Alfentanil

has been reported to have fewer side effects and simi-

lar or shorter recovery times than fentanyl [86,87].

Onset of action is in 1 to 3 minutes and the elimi-

nation is 1 to 2 hours [80]. The elderly exhibit an

increased sensitivity to the opioids and the dose of

alfentanil should be reduced by half [88].

Remifentanil

Remifentanil is chemically related to the fentanyl

congeners, but it is structurally unique because of

its ester linkages that render it susceptible to hydroly-

sis—primarily by enzymes within the erythrocytes—

resulting in its rapid metabolism. Remifentanil has a

30- to 60-second onset time and a 5- to 10-minute

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ahmad198

duration. The primary metabolic pathway of remifen-

tanil is de-esterification to form a carboxylic acid

metabolite, GI90291, which is 0.001 to 0.003 times as

potent as remifentanil. Excretion of GI90291 is

dependent on renal clearance mechanisms [89]. Its

pharmacokinetics are not appreciably influenced by

renal or hepatic failure [90,91]. Remifentanil (0.3 to

0.6 mg/kg IV) has been used to prevent the pain

associated with placement of the peribulbar block

[92]. A double-blind, randomized study of remi-

fentanil (remifentanil 1 mg/kg, remifentanil 1 mg/kg +

infusion of 0.2 mg/kg/min) administered before per-

forming peribulbar block found it to be more effective

than alfentanil (0.7 mg/kg) [93]. It was noted that the

patients were calm and cooperative, although aware

during the eye block and did not move or startle. In

this study the group that had the bolus dose followed

by an infusion had a higher incidence of respiratory

depression; however, in clinical situations the bolus

dose alone would be adequate.

Combinations of sedatives and analgesics

It is a common practice to combine sedatives and

analgesics in an attempt to minimize the side effects

of the individual agents by using smaller doses than

would be necessary if they were used alone. In most

situations the drugs have synergistic effects and may

result in significant hemodynamic and respiratory

depression, especially in the elderly patient. Propofol

has been used in combination with alfentanil [94] and

a combination of midazolam, propofol, and alfentanil

revealed the increased risk of apnea with multiple

drug combinations [95]. A combination of propofol

and ketamine provided better analgesia and sedation

than propofol alone and was not associated with an

increase in IOP [96].

Patient-controlled sedation and analgesia

The level of stimulation and discomfort may vary

during the peri-operative period and the need for

sedation/analgesia varies considerably among pa-

tients, making the patient-controlled administration a

useful alternative [97,98]. Successful use of the tech-

nique in patients undergoing ophthalmologic surgery

has been reported [99–101]. The main advantage with

this technique is the increased patient satisfaction;

however, it is important that patients be appropriately

monitored to prevent excessive sedation.

Nonpharmacologic measures

It has been suggested that music may be able to

modulate the human stress response [102] and studies

have suggested that music may be used as an adjunct

to sedatives. It has also been shown that music can

reduce pain reported by patients [103] and may

decrease analgesic requirements. The music selected

needs to have specific characteristics, namely, the

music needs to be of the patients choice, tracks need

to be mixed to convey homogeneous ambience, and

the playing device needs to be of good quality to

avoid auditory fatigue [104–106].

Type of surgery

Besides cataract surgery, regional anesthesia and

sedation has been used for trabeculectomy [107],

keratoplasty [108], vitreoretinal surgery [109], open

globe injuries [110], and enucleations and eviscera-

tions [111].

Summary

Sedation/analgesia for ophthalmologic surgery is

safe and effective [9]. The choice of sedation/an-

algesia strategy should be based on patient preference

and the assessment of risk for adverse events. Pre-

operative screening and preparation of the patient

is most important in obtaining cooperation and pa-

tient acceptance.

Despite the obvious effectiveness of the various

strategies, there is a small group of patients who are

not suitable for regional anesthesia with sedation.

Patients with chronic spontaneous cough, shortness

of breath while lying flat, parkinsonian head tremor,

Alzheimer’s disease, or claustrophobia may be very

difficult to manage with regional anesthesia and light

sedation. These patients may best be managed with a

general anesthetic.

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Ophthalmol Clin N

Choices of Local Anesthetics for Ocular Surgery

Gary D. Cass, MD

Tampa Eye and Specialty Surgery Center, 4302 N. Gomez Avenue, Tampa, FL 33607, USA

The choice of local anesthetic solution to perform

either topical anesthesia or conduction blockade for

ocular surgery is made based on the specific require-

ments of the patient, the surgical procedure, and the

properties of the local anesthetic. It is important for

clinicians to be aware of the options before selecting

an ophthalmic anesthetic delivery system. This arti-

cle discusses the rationale for using different local

anesthetics, anesthetic combinations, and additives, in

different clinical situations and with different anes-

thetic deliveries.

Topical ocular anesthesia

Topical ocular anesthesia has been demonstrated

to be a safe and effective alternative to retro or peri-

bulbar anesthesia [1]. However, topical anesthesia

does not provide ocular akinesia and may provide

inadequate sensory blockade for the iris and ciliary

body. Therefore, topical techniques are best reserved

for short surgeries and cooperative patients who have

low to moderate anxiety. Sedation should be carefully

administered to help relieve anxiety but not affect the

patient’s cooperation and movement. Topical anes-

thesia can be successfully achieved by several dif-

ferent methods and combinations of these methods. A

few popular approaches to topical ocular anesthesia

will be discussed, although there are many variations

of these practices.

The first approach simply involves administering

local anesthetic eye drops, most commonly pro-

paracane, tetracaine, lidocaine, or bupivacaine, to the

operative eye three or four times, usually separated by

0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights

doi:10.1016/j.ohc.2006.02.011

E-mail address: [email protected]

a few minutes just before surgery. The choice of which

anesthetic to use can be based on concerns regarding

corneal epithelial toxicity, patient comfort, and the

patient’s history of local anesthetic allergies.

High doses or prolonged use of local anesthetics

are toxic to the corneal epithelium, which prolongs

wound healing and causes corneal erosion [2,3]. All

of these local anesthetics are safe and effective in

brief perioperative exposure. Tetracaine is the most

irritating of the eye drop anesthetics mentioned; it is

an ester anesthetic and should be avoided in patients

allergic to that family of local anesthetics. Propara-

cane is also an ester anesthetic, but it is not metabo-

lized to the p-aminobenzoate (PABA) moiety and,

therefore, may be safely used in patients who are al-

lergic to other ester anesthetics.

It is common practice to administer topical anes-

thesia using viscous lidocaine gel instead of drops.

Often this gel is mixed with dilating medications,

antibiotics, and non-steroidal anti-inflammatory

agents. An anecdotal description of such a mixture

is 5 mL 2% lidocaine gel with 4 gtts tropicamide

(Mydriacyl), 4 gtts 1% cyclopentolate (Cyclogel),

4 gtts 10% phenylephrine (Neosynephrine), 10 gtts

moxifloxacin (Vigamox) and 4 gtts ketorlac (Acular).

This mixture applied to the operative eye twice before

surgery reportedly achieves excellent results in both

dilation and anesthesia [4]. Predictability of drug ab-

sorption or corneal epithelial safety with this mixture

has not been well investigated.

A common adjunct to topical anesthetic eye drops

is intracameral injection of local anesthetics. Intra-

cameral anesthetics have included preservative free

1% lidocaine and preservative free 0.5% bupivacaine

injected in doses of 0.1 to 0.5 mL instilled into the

anterior chamber. Intracameral injection may provide

sensory blockade for the iris and ciliary body, which

Am 19 (2006) 203 – 207

reserved.

ophthalmology.theclinics.com

Page 53: Anestesia Ocular

cass204

relieves discomfort that patient’s may have when the

intraocular lens is placed.

This topic has been the subject of many studies.

In 2001, in a report by the American Academy of

Ophthalmology, Karp and colleagues [5] reviewed

over 180 literature citations to address questions

about intracameral anesthesia’s efficacy and safety in

regard to possible corneal endothelial and retinal

toxicity. Regarding efficacy, the ideal timing and

placement of intracameral anesthesia was not deter-

mined. Some of the articles reviewed in this report

showed efficacy of intracameral injection whereas

others did not. The authors concluded that because

topical anesthesia alone is effective, surgeons may

elect to use intracameral anesthesia to manage

patients that had incremental pain with topical anes-

thesia alone.

Regarding the safety of intracameral anesthesia,

short-term studies seem to indicate that preservative-

free 1% lidocaine is well tolerated by the corneal

endothelium, whereas higher concentrations are

toxic. Retinal toxicity is another concern because

local anesthetics diffuse posteriorly to the retina.

There have been reports of patients loosing light per-

ception temporarily after intracameral anesthesia.

Several in vitro studies suggest lidocaine and bupiva-

caine may be toxic to the retina. This report suggests

that minimal amounts and concentrations of local

anesthetic be used. Preservative-free 1% lidocaine in

doses of 0.1ml to 0.5 mL has not been associated

with corneal endothelial toxicity, but studies suggest

that higher concentrations may be toxic. Intracameral

bupivacaine is not as well studied as lidocaine and

it may be more toxic to the corneal endothelium than

1% lidocaine. The authors suggested, therefore, that

the local anesthetic of choice for intracameral

anesthesia is preservative-free 1% lidocaine.

Intracameral lidocaine alone has been shown to

dilate the pupil well [6]. This may be because of

its direct action on the iris which causes muscle

relaxation. A recent practice of using intracameral

preservative-free 1% lidocaine with 1:100,000 epi-

Table 1

Properties of local anesthetics for ocular conduction blockade

Generic name Brand name Class

2-chloroprocaine Nesacaine Ester

Articaine Septocaine Amide

Lidocaine Xylocaine Amide

Ropivacaine Naropin Amide

Bupivacaine Marcaine Amide

Levobupivacaine Chirocaine Amide

nephrine is reported to enhance the pupillary dilation

more than 1% lidocaine alone, and may obviate the

need for preoperative dilating drops [7].

Conduction ocular anesthesia

The most common choices of local anesthetics for

either retro or peribulbar (intra or extraconal) or sub-

Tenon’s (episcleral) technique are bupivacaine, lido-

caine, ropivacaine, levobupivacaine, articaine, and

2-chloroprocaine. The following discussion considers

the pros and cons of each of these local anesthetics

and the indications for their use. Considerations

include cardiovascular and central nervous system

safety, family of local anesthetics, and onset and

duration of each agent. Properties of local anesthetics

for ocular conduction blockade are summarized in

Table 1.

When reviewing the literature about onset and

duration times of local anesthetics in ocular anes-

thesia, it is very difficult to make comparisons be-

cause shorter acting local anesthetics with faster onset

times are often combined with longer acting anes-

thetics. In addition to combining local anesthetics,

hyaluronidase is frequently added to the mix, which

also confounds the true onset time and duration of a

specific local anesthetic. Hyaluronidase shortens the

onset and duration of local anesthetics used for ocular

conduction blockade. Another variable from study to

study is the volume and concentration of anes-

thetic injected.

Bupivacaine and lidocaine are familiar local anes-

thetics that have been used for many years in retro

and peribulbar anesthesia as well as sub-Tenon’s

technique. Studies regarding the onset and duration

of lidocaine and bupivacaine in ocular anesthesia

compare them to the newer local anesthetics. The

onset time to ocular akinesia of a 50:50 mixture of

2% lidocaine and 0.5% bupivacaine with 1:200,000

epinephrine and 30 IU/mL hyaluronidase is reported

to be 7.2 minutes with a 5.7 minute standard devia-

Onset Duration Toxicity

Rapid Short Low

Rapid Short Intermediate

Rapid Intermediate Intermediate

Slow Long Intermediate

Slow Long High

Intermediate Long Intermediate

Page 54: Anestesia Ocular

local anesthetics 205

tion [8]. The duration is not so well investigated.

A patient can usually remove their eye patch in 4 to

6 hours after a block where bupivacaine was used

and not be troubled by diplopia. Many practitioners,

however, report instances where the diplopia did not

resolve until the next day.

Ropivacaine is a long-acting, pure S-enantiomer,

amide local anesthetic similar to bupivacaine in

duration. The use of ropivacaine is attractive because

it is less cardiotoxic than equal concentrations of

racemic bupivacaine and has a significantly higher

threshold for central nervous system toxicity than

bupivacaine. Ropivacaine and bupivacaine were

compared with each other when mixed with 2% lido-

caine and hyaluronidase and both mixtures were

equally effective in peribulbar anesthesia [9]. In this

study, the median time at which the block was

adequate to start surgery was 8 minutes. This com-

paratively quick onset is representative of the quicker

acting lidocaine with hyaluronidase rather than the

ropivacaine. Another recent study compared onset

and duration of different concentrations of ropiva-

caine with hyaluronidase. At 15 minutes ropivacaine

0.75% had an 82% complete motor block, whereas

the 0.5% ropivacaine had a 55% complete motor

block. Complete recovery of motor function 1 hour

after surgery was 37% with 0.5% ropivacaine with

hyaluronidase, whereas complete motor recovery was

only 5% in the 0.75% ropivacaine with hyaluroni-

dase group [10]. Another study reported that diplopia

lasted up to 30 hours past peribulbar block when

1% ropivacaine was used [11]. Ropivacaine would be

a good clinical choice when longer anesthesia is

needed and a large enough dose will be used that

there is concern about toxicity.

Levobupivacaine is the S enantiomer of racemic

bupivacaine. Because of findings that cardiotoxicity

observed with racemic bupivacaine, although infre-

quent, is based on entantioselectivity, the S enan-

tiomer, levobupivacaine, was developed for use as a

long acting, local anesthetic that shows reduced

cardiotoxicity. Recently McLure and colleagues [12]

compared the onset of 2% lidocaine with 0.75%

levobupivacaine, both with hyaluronidase, in sub-

Tenon’s block. The speed of onset for the lidocaine

group was 3.02 minutes, which statistically was

significantly faster then the onset time for the

levobupivacaine group, which was 5.06 minutes.

The authors concluded, however, that this difference

in onset time was not clinically significant. Levo-

bupivacaine 0.75% was compared with bupivacaine

0.75%, each with hyaluronidase, in peribulbar anes-

thesia [13]. After a 5 cc injection, both agents re-

portedly achieved satisfactory anesthesia in a median

time of 2 minutes. The authors concluded that both

levobupivacaine and bupivacaine are equally suc-

cessful in achieving clinically satisfactory peribulbar

anesthesia with few adverse effects. The most com-

mon post operative adverse effect reported was

prolongation of the block in 15% of the patients.

Bupivacaine, ropivacaine, and levobupivacaine all

have clinically acceptable onset times when mixed

with lidocaine. However, the duration can be up to

30 hours when most surgeries last only 15 minutes.

Prolonged diplopia is disturbing to the patients and

dissatisfying to the clinician.

Articaine is a comparatively new local anesthetic.

It is chemically unique and offers a shorter duration

than the previously discussed drugs. In a number of

European countries, articaine is the most widely used

local anesthetic in dentistry. Articaine is classified as

an amide local anesthetic but is structurally different

from other amide local anesthetics in that it contains

a thiophene ring. It also contains an ester linkage

which is quickly hydrolyzed by esterase to inactive

artinic acid.

In 2001, Allman and colleagues [14] compared

the onset of 2% articaine mixed with epinephrine

(1:200,000), with the onset of a mixture of 0.5%

bupivacaine and 2% lidocaine in peribulbar anes-

thesia, where a single medial canthus injection is

used. Hyaluronidase was added to both solutions.

The degree of akinesia was measured at 1, 5, and

10 minutes after block, at the end of surgery, and at

discharge from the day unit. At 1 minute the score in

both groups was the same, but at 5 minutes articaine’s

onset was significantly greater. At discharge it was

apparent that the articaine group regained extraocular

motion quicker. The authors, however, don’t specify

how much time elapsed between initial injection and

discharge. Eyelid motion was the same for both

groups at all measurements. A similar study [8] was

repeated at the same institution and compared the

same agents, but used an inferotemporal injection

with similar results. In 2004, 2% articaine was com-

pared with a mixture of 0.5% bupivacaine and 2%

lidocaine in a sub-Tenon’s approach, and once again

articaine had the faster onset times and appeared to be

a safe agent to use [15].

Articaine appears to have a desirable onset and

duration for shorter ocular surgeries. In the United

States articaine is prepared in a solution that contains

both epinephrine and sodium metabisulfate as a pre-

servative. Currently articaine has only been approved

in the United State for dental use.

For shorter surgeries, 2-choloroprocaine is a desir-

able choice of a local anesthetic for conduction block-

ade. Cass and colleagues [16] compared 2% versus 3%

Page 55: Anestesia Ocular

cass206

preservative-free 2-cholroprocaine in peribulbar anes-

thesia. Onset time of ocular akinesia and surgical

anesthesia was <4 minutes in the 2% group and 6 min-

utes in the 3% group. Full recovery of extraocular

muscle and eyelid motion was less than 85 minutes in

the 2% group and was less than 100 minutes in the 3%

group. Both 2% and 3% 2-cholroprocaine were safe

and effective in peribulbar aesthesia.

Modern ophthalmic surgeries are being performed

faster and faster. At the typical outpatient surgery

center where cataract surgery takes 20 minutes or

less, a patient can be blocked in a preoperative area,

moved to the operating room, have surgery, then go

to a recovery area where they can have a cup of

coffee or juice. By the time postoperative instructions

are given, the patient has regained full extraocular

and eyelid motion. This allows the patient to be

discharged without an eye patch and with good vi-

sion. Although the duration of 2-cholroprocaine is

relatively short, it still affords the surgeon enough

time to handle circumstances such as an unanticipated

anterior vitrectomy. A particular circumstance where

rapid vision recovery is extremely advantageous is in

the monocular patient having surgery on their better

seeing eye. This is very satisfying to both the patient

and the clinical staff.

Because it is an ester anesthetic, 2-choloropro-

caine is quickly hydrolyzed by plasma cholinester-

ase, which makes it a safe local anesthetic that has

a high therapeutic index. Clinicians should avoid

2-choloroprocaine in patients who report allergies to

ester local anesthetics.

Use of additives

Anesthetic solutions often contain preservatives,

enzymes that aid the spread of the local anesthetic,

and drugs that increase the duration of action. It is

important for clinicians to choose whether or not to

use these additives because they can affect local

anesthetic toxicity both locally and systemically.

Preservatives in local anesthetics are considered

to be toxic to the retina. In many ophthalmology

practices all local anesthetics used are preservative-

free, although in many other practices, with the

exception of intracameral administration, topical and

injected local anesthetics are used with preservatives

and without apparent retinal problems.

Hyaluronidase is a proteolytic enzyme which is

often added to local anesthetic solutions to aid the

spread of the anesthetic. The enzyme hydrolyses

hyaluronic acid which limits diffusion by binding

cells together. The addition of hyaluronidase shortens

the time of onset of the local anesthetic solution as

well as its duration. In retro or peribulbar anesthesia,

the addition of hyaluronidase is presumed to decrease

the time of exposure of the local anesthetic to the

extraocular muscles, which decreases the incidence

of myotoxicity that results in diplopia. In a retro-

spective chart review, Brown and colleagues [17]

postulated that the absence of hyaluronidase was

responsible for a cluster of diplopia. In a response

to this paper, Miller [18] reported a series of over

7000 cases of periocular injections without hyal-

uronidase which resulted in no incidence of diplopia.

It is important to point out that anesthetic myotoxicity

is not the only cause of diplopia after periocular

block. The extraocular muscle can be directly in-

jured by the injection or indirectly injured by ische-

mia secondary to pressure on the muscle from a high

volume of injectate.

Epinephrine is a common additive to local anes-

thetic solutions for periocular block. It augments

anesthetic duration. In the borderline patient small

amounts of epinephrine can cause untoward hemody-

namic consequences.

Clonidine has also been added to local anesthetic

solutions used for periocular block to lengthen the

duration of the anesthesia [19]. Vecuronium has been

added to periocular local anesthetic solutions to en-

hance the ocular and eyelid akinesia [20]. Adding

these medicines to periocular anesthetic solutions is

potentially harmful because these agents have power-

ful systemic actions.

Summary

There are many choices of local anesthetic solu-

tions and additives for both topical anesthesia and

conduction blockade. The differing onset and dura-

tion, toxicity, and pharmacology of local anesthetics

must be considered when making a choice of which

agent to use. Additives to local anesthetic solutions

must also be considered. Clinicians should make their

ocular anesthetic plan based on the specific require-

ments of the patient, the surgical procedure, and the

properties of the local anesthetic.

References

[1] Patel BCK, Byrnes TA, Crandall A, et al. A com-

parison of topical and retrobulbar anesthesia for cata-

ract surgery. Opthalmology 1966;103:1196–203.

[2] Grant RL, Acosta D. Comparative toxicity of tetra-

caine, proparacane and cocaine evaluated with primary

Page 56: Anestesia Ocular

local anesthetics 207

cultures of rabbit epithelial cells. Exp Eye Res 1994;

58(4):469–78.

[3] Bisla K, Tanelian DL. Concentration-dependent effects

of lidocaine on corneal epithelial wound healing.

Invest Ophthalmol Vis Sci 1992;33:3029–33.

[4] Fanning GL. You asked for it. Ophthalmic Anesthesia

Society In-Sight 2005;Summer:7.

[5] Karp CL, Cox TA, Wagoner MD, et al. Intracameral

anesthesia: a report by the American Academy of

Opthalmology. Opthalmology 2001;108(9):1704–10.

[6] Lee JJ, Moster MR, Henderer JD, et al. Pupil dilation

with intracameral 1% liodocaine during glaucoma fil-

tering surgery. Am J Opthalmol 2003;136(1):201–3.

[7] Cionni RJ, Barros MG, Kaufman AH, et al. Cataract

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[8] Allman KG, Barker LL, Werrett GC, et al. Comparison

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2002;88(5):676–8.

[9] Nicholson G, Sutton B, Hall GM. Ropivacaine for

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[10] Gioa L, Fanelli G, Casati A, et al. A prospective ran-

domized, double- blinded comparison of ropivacaine

0.5%, 0.75%, and 1% ropivacaine for peribulbar block.

J Clin Anesth 2004;16(3):184–8.

[11] Wells AP, Maslin K. Diplopia from peribulbar ropi-

vacaine. Clin Experiment Ophthalmol 2000;28(1):

32–3.

[12] McLure HA, Kumar CM, Ahmed S, et al. A com-

parison of lidocaine 2% with levobupivacaine 0.75%

for sub-Tenon’s block. Eur J Anaesthesiol 2005;22(7):

500–3.

[13] Birt DJ, Cummings GC. The efficacy and safety of

0.75% levobupivacaine vs 0.75% bupivacaine for peri-

bulbar anaesthesia. Eye 2003;17(2):200–6.

[14] Allman KG, McFadyen JG, Armstrong J, et al. Com-

parison of articaine and bupivacaine/lidocaine for

single medial canthus peribulbar anaesthesia. Br J

Anaesth 2001;87(4):584–7.

[15] Gouws P, Galloway P, Jacob J, et al. Comparison of

articaine and bupivacaine/lidocaine for sub-Tenon’s

anaesthesia in cataract extraction. Br J Anaesth

2004;92(2):228–30.

[16] Cass G, Reynolds W, Lorenzen T, et al. Randomized

double-blind study of the clinical duration and efficacy

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thesia. J Cataract Refract Surg 1999;25(12):1656–61.

[17] Brown SM, Brooks SE, Mazow ML, et al. Cluster of

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[18] Miller RD. Hyaluronidase and diplopia [letter]. J Cata-

ract Refract Surg 2000;26:478.

[19] Bharti N, Madan R, Kaul HL, et al. Effect of addition

of clonidine to local anaesthetic mixture for peribulbar

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Ophthalmol Clin N

Sub-Tenon’s Anesthesia

Chandra M. Kumar, MBBS, MSc, FFARCS, FRCAa,b,T,Chris Dodds, MBBch, MRCGP, FRCAa,b

aSchool of Health and Social Science, University of Teesside, Middlesbrough, TS4 3BW, UKbDepartment of Anaesthesia, The James Cook University Hospital, Middlesbrough, TS4 3BW, UK

The sub-Tenon’s anesthesia block was reintro-

duced as a simple, safe, effective, and versatile alter-

native to a sharp needle block for orbital anesthesia.

After topical anesthesia has been instilled, Tenon’s

capsule is dissected, a blunt cannula is introduced

into the sub-Tenon’s space, and a local anesthetic

agent is administered [1]. It is not known how fre-

quently this technique has been used. Seven percent

of ophthalmic departments in the United Kingdom

used this technique in 1997 [2] but its use appears to

have increased [3]. In the United Kingdom, only

trained ophthalmologists or anesthesiologists perform

needle orbital local anesthetic injections [2], but in

some centers nurses have been trained to perform the

sub-Tenon’s block [4]. It is essential for any practi-

tioner to have a comprehensive understanding of the

basic sciences and techniques behind regional orbital

blocks. Before any technique is used, the knowledge

of globe anatomy, especially Tenon’s capsule and the

surrounding structures, must be mastered.

The regional orbital block was first described by

Turnbull in 1884 [5]. More recently Mein and

colleagues [6], Hansen and colleagues [7] and

Stevens [8] have popularized this block. The tech-

nique is also known as pinpoint anesthesia [9],

parabulbar block [10], and episcleral block [11].

0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights

doi:10.1016/j.ohc.2006.02.008

T Corresponding author. Department of Anaesthesia,

The James Cook University Hospital, Middlesbrough, TS4

3BW, UK.

E-mail address: [email protected]

(C.M. Kumar).

Anatomy

There are many excellent books on ophthalmic

anatomy [12–15] and these are recommended as a

source of reference.

Globe movements are controlled by both the

rectus muscles (inferior, lateral, medial, and superior)

and the oblique muscles (superior and inferior). The

rectus muscles arise from the annulus of Zinn near

the apex of the orbit and insert anterior to the equator

of the globe to form an incomplete muscle cone.

The optic nerve (II), oculomotor nerve (III, contains

both superior and inferior branches), abducens nerve

(VI), nasociliary nerve (branch of nerve V), ciliary

ganglion, and vessels all lie within the muscle cone.

The superior branch of the oculomotor nerve supplies

the superior rectus and the levator palpebrae mus-

cles. The inferior branch of the oculomotor nerve

supplies the medial rectus, the inferior rectus, and

inferior oblique muscles. The abducens nerve sup-

plies the lateral rectus. The trochlear nerve (IV) runs

outside and above the annulus, and supplies the

superior oblique muscle (the anesthetic agent may

fail to block this nerve and the oblique muscle will

retain activity).

Corneal and perilimbal conjunctival sensation and

the superonasal quadrant of the peripheral conjunc-

tival sensation are mediated through the nasociliary

nerve. The remainder of the peripheral conjunctival

sensation is supplied through the lacrimal, frontal,

and infraorbital nerves which run outside the muscle

cone. Intraoperative pain may be experienced if these

nerves are not blocked.

The fascial sheath (Tenon’s capsule) is a thin

membrane that envelops the eyeball and separates it

Am 19 (2006) 209 – 219

reserved.

ophthalmology.theclinics.com

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Fig. 1. Sub-Tenon’s space shows multiple connective tissue bands (From Gray, H. Anatomy of the human body. Philadelphia:

Lea & Febiger; 1918; Bartleby.com, 2000. Available at www.bartleby.com/107/. Accessed September 14, 2005; with permission.)

kumar & dodds210

from the orbital fat [14]. It thus forms a socket for the

eyeball. The inner surface is smooth and shiny and is

separated from the outer surface of the sclera by a

potential space, the episcleral space (sub-Tenon’s

space). Numerous delicate bands [15] of connective

tissue (Fig. 1) cross the space and attach the fascial

sheath to the sclera. Anteriorly, the fascial sheath is

firmly attached to the sclera (Fig. 2) about 3–5 mm

posterior to the corneoscleral junction [16,17].

Posteriorly, the sheath fuses [13] with the meninges

around the optic nerve and with the sclera around the

exit of the optic nerve (see Fig. 1). However, the

description varies and a major textbook of anatomy

[15] suggests that the space under the Tenon capsule

Fig. 2. Tenon’s capsule is shown underneath the conjunctiva

when dissected 5 mm posterior to limbus.

is a lymph space, and this follows the optic nerve and

continues with the subarachnoid space. The tendons

of all six extrinsic muscles of the eye pierce the

sheath as they pass to their insertion on the globe. At

the site of perforation, the sheath is reflected back

along the tendons of these muscles to form a tubular

sleeve. The superior oblique muscle sleeve extends as

far as the trochlea, and the inferior oblique muscle

sleeve extends to the origin of these muscles. The

tubular sleeves for the four recti muscles have

expansions. Expansions for the medial and lateral

recti are strong, are attached to the lacrimal and

zygomatic bones, and are called medial and lateral

check ligaments respectively. The superior rectus

expansion is thinner, less distinct, and extends from

the superior rectus tendon to the levator palpebrae

superioris. Similarly, the expansion from the inferior

rectus extends to the inferior tarsal plate. The inferior

part of the fascial sheath is thickened and is con-

tinuous, both medially and laterally, with the medial

and lateral check ligaments.

Assessment of patients

The preoperative assessment and preparation of

patients who have ophthalmic surgery under local

anesthesia varies worldwide. There are evidence-

based guidelines [18] and reports [19] available on

this subject. The Joint Colleges Working Party Report

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Fig. 3. Essential (right) and non-essential (left) equipment which may be required during sub-Tenon’s anesthesia.

sub-tenon’s anesthesia 211

[18] has recommended that patients not be starved but

starvation policies vary considerably [20]. Complica-

tion rates as a result of starvation or aspiration in

ophthalmic regional anesthesia are unknown but

dangers remain if a patient vomits while undergoing

anesthesia and surgery. According to guidelines and

evidence reports, routine investigation of patients who

undergo cataract surgery is not essential and does not

improve health or outcome of surgery, but tests can

be done to improve general health of the patient

if required.

The preoperative assessment should always in-

clude specific enquiry about bleeding disorders and

drugs. There is increased risk of hemorrhage in pa-

tients receiving anticoagulants and a clotting profile

assessment is required before injection. Patients who

receive anticoagulants are advised to continue medi-

cation [21]. Clotting results should be within the

recommended therapeutic range [21,22]. Because of

a lack of data, currently there are no recommenda-

tions for patients who receive antiplatelet agents [22].

Sub-Tenon’s block is a favored technique for these

patients [21].

Fig. 4. Upwards and outwards rotation helps to expose the

area of dissection.

Monitoring during block

Once the decision is made to operate, anesthetic

and surgical procedures are explained to the patient,

and informed consent is obtained and recorded. All

monitoring and anesthetic equipment in the operating

environment should be fully functional [18]. Blood

pressure, oxygen saturation, and ECG leads are

connected to the patient, and baseline recordings are

obtained [18]. Although, the insertion of an intra-

venous line has been questioned [23], it is always a

good clinical practice to secure an intravenous line,

because serious complications can occur regardless of

the anesthetic technique being used (eg, anaphylactic

reaction to antibiotics).

Standard sub-Tenon’s technique

Access to the space by the inferonasal quadrant is

the most commonly described approach, because the

placement of the cannula in this quadrant allows good

fluid distribution superiorly, avoids the area of

surgery, and reduces the risk of damage to the vortex

veins [1]. The equipment that may be required during

sub-Tenon’s blocks is shown in Fig. 3. After instil-

lation of local anesthetic eye drops (proxymetacaine

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Fig. 5. The place of incision for dissection during infero-

nasal sub-Tenon’s anesthesia.

kumar & dodds212

0.5% or tetracaine 1%), the eye is cleaned with spe-

cially formulated 5% aqueous povidone iodine solu-

tion. An eyelid speculum or an assistant’s finger is

used to keep the eyelids apart. The patient is asked to

look upwards and outwards, to expose the inferonasal

quadrant (Fig. 4). The conjunctiva and Tenon’s cap-

sule are gripped with non-toothed forceps 5–10 mm

away from the limbus. A small incision is made

Fig. 6. Different types of sub-Tenon’s cannulas. (A) A standard pos

mid sub-Tenon’s cannula, 21 gauge and 1.8 cm long; (C) an anter

ultra-short cannula, 14 gauge and 0.6 cm long.

through these layers with scissors and sclera is ex-

posed (Fig. 5).

A blunt, curved (Fig. 6A), metal sub-Tenon can-

nula, (19 gauge, 25 mm long, curved, a flat profile

with end hole) that is securely mounted onto a 5 mL

syringe, which contains the local anesthetic solution,

is inserted through the hole along the curvature of the

sclera. If resistance is encountered, a gentle pressure

is applied and hydro-dissection usually helps to ad-

vance the cannula. The resistance felt during insertion

of the cannula is caused by the intermuscular septum,

but usually the cannula passes into the posterior sub-

Tenon’s space. If the hydro-dissection does not help,

or the resistance encountered is too great, it is ad-

visable to reposition or reintroduce the cannula.

Muscle insertions vary and the cannula may be tran-

versing the muscle’s Tenon’s sheath rather than

following the globe surface. The local anesthetic

agent of choice is injected slowly and the cannula is

removed. A gentle pressure is applied over the globe

to help spread the local anesthetic agent.

There are many variations of the sub-Tenon’s

technique that relate to route of access, type of can-

nula, local anesthetic agent, volume of anesthetic, and

the adjuvant used.

terior sub-Tenon’s cannula, 19 gauge and 2.54 cm long; (B) a

ior sub-Tenon’s cannula, 14 gauge and 1.2 cm long; (D) an

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sub-tenon’s anesthesia 213

Variations of technique

Access to sub-Tenon’s space

Access to all other quadrants has been reported:

the superotemporal by Fukasaku [9], the superonasal

and inferotemporal by Roman and colleagues [24]

and McLure and colleagues [25], and the medial

canthal side by Ripart [11]. It is not known how

frequently these quadrants are used for access. In

addition, there are no comparative data to support the

ease of access to any particular quadrant. However,

the supernasal route is potentially more hazardous

because of the vascular, neuronal, and muscular

contents in that area.

Varieties of cannulae

There are several alternative cannulae available

for this block. Some are specifically designed for this

purpose while others have a different primary pur-

pose. The specifically designed cannulae may be

made of either metal or plastic. The metal cannulae

vary in gauge, length, curvature, and the position of

the end holes. A plastic cannula advocated by Green-

baum [10] is known as an anterior sub-Tenon’s can-

nula and is 15 gauge, 1.2 cm long, blunt, D shaped,

and has a flat bottom (see Fig. 6C). The opening on

the flat bottom is designed to face the sclera after

insertion. Non-specific sub-Tenon’s cannulae include

the metal Southampton cannula [8], metal ophthalmic

irrigation cannula [26], plastic intravenous cannula

[27], and plastic mid sub-Tenon’s cannula [28] (see

Fig. 6B). Recently an ultrashort metal cannula,

(16 gauge, 6 mm with blunt end hole) has been de-

scribed [29] (see Fig. 6D). The placement of a poly-

ethylene catheter into sub-Tenon’s space has been

described for long surgeries [30]. Additionally, access

to the sub-Tenon space through the medial canthal

approach has been described using needles without

dissection [11,31]. The selection of a cannula or

needle depends on the availability, cost, and the skills

and expertise of the clinician. However, the commer-

cially manufactured, posterior metal sub-Tenon’s

cannula is the type that is most commonly featured

in published studies.

Choice of local anesthetic agent

Anesthesia and akinesia are determined by the

properties of the local anesthetic agent, but more

directly, by the proximity to the sensory and motor

nerves. Lidocaine 2% is the most commonly used

agent and is considered the gold standard [32]. Vari-

ous local anesthetic agents such as articaine 2% [33],

etidocaine [34], prilocaine [35], mepivacaine [36],

levobupivacaine [37], and a mixture of lidocaine and

bupivacaine [38], have been used but there are few

comparative data available on the relative effec-

tiveness of various agents.

Volume of local anesthetic agent

There is a wide variation in the volume of local

anesthetic used in sub-Tenon’s block and this has

been a subject of debate. The volumes vary from 1 to

11 mL [10,39] but 3 to 5 mL are generally used [40].

Smaller volumes will usually provide globe anes-

thesia but larger volumes are required if akinesia is

desirable [41].

Adjuvant and sub-Tenon’s block

Vasoconstrictor

Vasoconstrictors are commonly mixed with local

anesthetic solution to increase intensity and duration

of the block, and to minimize bleeding from small

vessels [32]. Because vasoconstrictors reduce absorp-

tion of local anesthetic, a surge in plasma levels is

avoided. However, epinephrine may cause vasocon-

striction of the ophthalmic artery, which compromises

the retinal circulation [32]. The use of solutions that

contain epinephrine is usually avoided in elderly

patients who suffer from cerebrovascular and car-

diovascular diseases. The role of epinephrine in sub-

Tenon’s block has been questioned [42]. This is

because ophthalmic surgery does not usually take a

long time and the duration of the block achieved

by lidocaine without epinephrine suffices for modern

minimally invasive cataract surgery.

Hyaluronidase

Hyaluronidase is an enzyme, which reversibly

liquefies the interstitial barrier between cells by depo-

lymerization of hyaluronic acid to a tetrasaccharide,

and enhances the diffusion of molecules through tis-

sue planes [32]. The amount of hyaluronidase

mixed with the local anesthetic varies from 0.5 to

150 IU/mL. There is conflicting evidence that hyal-

uronidase (30 IU/mL) improves the effectiveness and

the quality of sub-Tenon’s block [43,44]. If hyal-

uronidase is to be used, 15 IU/mL is the recom-

mended amount in the United Kingdom [45]. It is an

expensive drug [46] and although side effects are

rare, allergic reactions [47], orbital cellulites [48], and

the formation of pseudotumors [49] have been re-

ported after its use.

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kumar & dodds214

pH alteration

Commercial preparations of lidocaine and bupiva-

caine are acidic solutions in which the basic local

anesthetic exists predominantly in the charged ionic

form [32]. It is only the non-ionized form of the agent

that traverses the lipid membrane of the nerve to

produce the conduction block. At higher pH values a

greater proportion of local anesthetic molecules exist

in the non-ionized form, which facilitates more rapid

influx into the neuronal cells. Alkalinisation of the

local anesthetic agent has been shown to decrease the

onset and prolong the duration of needle blocks

[50,51] but no such benefit has been observed in sub-

Tenon’s block [52].

Passage of local anesthetic agent during injection

The passage of the local anesthetic during sub-

Tenon’s block has been studied using different

imaging techniques [53–55]. These studies confirm

that when the anesthetic agent is injected into the sub-

Tenon’s space, it opens the space to form a character-

istic T sign (Fig. 7). As the local anesthetic agent

spreads through the sub-Tenon’s space, it diffuses

into intraconal and extraconal areas and results in

anesthesia and akinesia of the globe and eyelids.

Intense analgesia is produced by blockade of the

short ciliary nerves as they pass through the Tenon’s

capsule [53]. Akinesia is caused by a blockade of

the motor nerves present in the intraconal and extra-

conal compartments.

Fig. 7. Ultrasound image shows the opening of the s

Complications of sub-Tenon’s anesthesia

Minor complications

Pain during injection

The pain experienced during ophthalmic blocks is

multi-factorial. Up to 44% of patients report pain

during sub-Tenon’s injection in which a posterior

metal cannula is used [8]. Pain scores on a visual ana-

log scale [0 = no pain, 10 =worst imaginable] have

been reported as high as 5, and smaller cannulae offer

a marginal benefit [56]. Premedication or sedation

of patients during sub-Tenon’s injection does not

seem to be beneficial [57]. To reduce the patient’s

discomfort and anxiety, it is important to give a thor-

ough preoperative explanation of the procedure, use a

good surface anesthesia, use gentle technique, slowly

inject the warm local anesthetic agent, and pro-

vide reassurance.

Chemosis

Chemosis signifies anterior injection of the anes-

thetic agent. This usually occurs if a large volume of

local anesthetic is injected and if the Tenon’s cap-

sule is not dissected properly [41]. The incidence of

chemosis varies from 25% to 60% [24,58] with

posterior cannula and to 100% with shorter cannulae

[41]. Chemosis may not be confined to the site of

injection and has been known to spread to other

quadrants [8,41]. This usually resolves after the

application of digital pressure, and no intraoperative

problems have been reported. Surgeons who per-

ub-Tenon’s space and the characterstic T-sign.

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sub-tenon’s anesthesia 215

form glaucoma surgery may believe that significant

chemosis compromises the surgical procedure.

Subconjunctival hemorrhage

Fine vessels are inevitably severed during the

conjunctival dissection, which causes a degree of

subconjunctival hemorrhage. The incidence (and

severity) of subconjunctival hemorrhage varies from

20% to 100% and depends on the cannula used

[8,41]. This can be minimized by careful dissection

that avoids damage to fine vessels. The use of cau-

tery has been advocated [10] but no benefit was

seen when a disposable diathermy was used by

anesthesiologists [59]. Patients should receive ade-

quate warning about the possibility of subconjunc-

tival hemorrhage.

Overspill of anesthetic

Overspill of the local anesthetic agent during its

administration is commonly observed [8,41]. This is

likely to occur if the dissection of the sub-Tenon’s

capsule is not complete or if there is a resistance to

injection. Traction during injection may cause en-

largement of the initial dissection and large injection

volume also cause overspill. Careful dissection and

use of diathermy may minimize the loss. Gentle pres-

sure over the insertions site with a surgical sponge

might also help [1].

Akinesia and anesthesia

Akinesia is volume dependent and if 4–5mL of

local anesthetic agent is injected, most patients de-

velop akinesia [41]. However, superior oblique mus-

cle and lid movements may remain active in a small

but significant number of patients. Many published

studies on the subject report good results when an-

esthesia accompanies sub-Tenon’s block. However,

akinesia is variable and may not be complete [41,57].

Serious complications

Sight- and life-threatening complications have

been reported. These include short-lived muscle

paresis [60] as well as orbital and retrobulbar hem-

orrhage [61,62]. Recently, a scleral perforation during

sub-Tenon’s block was reported in a patient who had

previously undergone retinal surgery [63]. Damage to

the inferior and medial rectus muscles, caused by

trauma from metal cannula, has led to restrictive

functions that result in diplopia [64]. Other compli-

cations relate to optic neuropathy [65], afferent

papillary, and accommodation defects [66]. Retinal

and choroidal vascular occlusion has been reported

[67] as has one case where central spread of the local

anesthetic agent led to cardio-respiratory collapse

[68]. The mechanism of central spread is not clear but

possible explanations include spread of the injected

anesthetic agent into the subarachnoid space (see

discussion above) through the optic nerve sheath, or

back-tracking of the local anesthetic agent through

one of the orbital foramina [1]. The later can happen

if there is an unintentional perforation of the Tenon’s

capsule, which leads to the deposition of the local

anesthetic agent into the intraconal compartment.

Retained visual sensations

Published studies have reported that patients who

have phacoemulsification cataract surgery under topi-

cal, retrobulbar, peribulbar, and sub-Tenon’s blocks,

experience light and other visual sensations during

surgery [69]. Although most of the patients felt

comfortable with the visual sensations they experi-

enced, a proportion of patients (up to 16%) found the

experience to be unpleasant or frightening [70,71].

Preoperative counseling benefits these patients [69].

Patients who receive sub-Tenon’s block should be

offered preoperative advice which may alleviate fear

of this experience.

Intraocular pressure and role of ocular

compression

The rise in intraocular pressure (IOP) after ad-

ministration of sub-Tenon’s block is small or even

insignificant [72,73]. There was a numerically sig-

nificant reduction in intraocular pressure using a

Honan balloon, but this did not make a clinical

difference in the effectiveness of anesthesia [74].

Pulsatile ocular blood flow during sub-Tenon’s

block

It is known that retrobulbar and peribulbar

injections decrease pulsatile ocular blood flow, at

least for a short time [75]. In a recent study [73], the

changes in IOP and ocular pulsatile amplitude (OPA)

were compared during peribulbar and sub-Tenon’s

blocks. The IOP remained stable with both blocks

throughout the study. One minute after injection of

the anesthetic agent, the OPA decreased significantly

in the injected eyes in both the sub-Tenon’s (24%)

and peribulbar (25%) groups. The OPA decrease in

the sub-Tenon’s group (14%) was also detectable

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kumar & dodds216

after 10 minutes in the control group. Therefore,

caution is required in the management of patients

whose ocular circulation may be compromised and an

alternative anesthesia, such as general anesthesia,

may be desirable.

Presence of anesthesiologists

The presence of anesthesiologists during sub-

Tenon’s block may not be required [18] but the

ability to manage life-threatening cardio-respiratory

events must be available from the other staff in

theater. A member of the staff whose sole responsi-

bility is to the patient, should be responsible for

monitoring and should remain with the patient at all

times throughout the monitoring period. This person

must be trained to detect and act on any adverse

events, and may be an anesthesiologist, nurse, or

operating department practitioner who is trained in

life support [18].

Intraoperative monitoring

The patient should be comfortable and soft pads

should be placed under the pressure areas. All

patients who experience major eye surgery under

local anesthesia should be monitored with pulse

oximetry, ECG, non-invasive blood pressure mea-

surement, and verbal contact [18]. Patients should

receive an oxygen-enriched breathing atmosphere to

prevent hypoxia, and a flow rate high enough to

prevent hypercarbia if enclosed in surgical drapes.

ECG and pulse oximetry should be continued. Once

the patient is under the drapes, verbal and tactile

contacts are maintained [18].

Sedation during sub-Tenon’s block

A patient who undergoes ophthalmic surgical

procedures, regardless of the type of regional

anesthesia used, should be fully conscious; respon-

sive; and free of anxiety, discomfort, and pain [18].

The aim of sedation is to minimize anxiety and pro-

vide the maximum degree of safety. Sedation is com-

monly used during cataract surgery under topical

anesthesia [76], but selected patients who receive a

sub-Tenon’s or another type of orbital regional block,

may benefit from sedation if explanation and

reassurance are inadequate [17]. Short acting benzo-

diazepines, opioids, or intravenous anesthetic agents

in minimum dosages are used. However, there is an

increased risk of an intraoperative event when seda-

tion is used [77,78]. A means of providing sup-

plemental oxygen must be available when sedation

is administered.

Advantages of sub-Tenon’s block

A sub-Tenon’s block eliminates the risks of sharp

needle techniques, provides reliable anesthesia, can

be supplemented for prolonged anesthesia and post-

operative pain relief, and can be safely used in pa-

tients who have a long globe [1]. There are numerous

studies that demonstrate its effectiveness compared

with retrobulbar, peribulbar, and topical anesthesia

alone [1]. Sub-Tenon’s block has been used mainly

for cataract surgery, but also vitreoretinal surgery

[79–81], panretinal photocoagulation [82], strabis-

mus surgery [83], trabeculectomy [42,84], optic nerve

sheath fenestration [85], chronic pain management

[86], and therapeutic delivery of drugs [87]. Recent

reviews suggest that sub-Tenon’s block may be used

safely in patients who receive anticoagulants and

antiplatelet agents, as long as clotting results are in

the normal therapeutic range [21,22]. Despite reports

of a few major complications, sub-Tenon’s block has

one of the highest safety profiles of any regional

anesthetic technique.

Limitations of sub-Tenon’s block

Subconjunctival hemorrhage and chemosis are

common. Residual muscle movement or incomplete

akinesia do not cause intraoperative difficulties and

are generally acceptable to surgeons. The block may

be difficult to perform in patients who have had

previous sub-Tenon’s block in the same quadrant,

previous retinal detachment and strabismus surgery,

eye trauma, and infection to the orbit. Some

glaucoma surgeons may dislike sub-Tenon’s block,

although it has been used successfully for glaucoma

surgery [1].

Summary

Currently there is no absolutely safe orbital re-

gional block technique. Sub-Tenon’s block is a

simple, effective, safe, and versatile technique,

although rare complications can occur. To perform a

sub-Tenon’s block, a thorough knowledge of anat-

omy and understanding of the underlying principles

is essential.

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sub-tenon’s anesthesia 217

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Page 68: Anestesia Ocular

Ophthalmol Clin N

Orbital Regional Anesthesia

Gary L. Fanning, MD

Hauser-Ross Eye Institute, P.O. Box 406, Sycamore, IL 60178-0406, USA

Topical and sub-Tenon’s local anesthetic tech-

niques have rapidly gained popularity for cataract [1]

and other ophthalmic surgical procedures (ie, stra-

bismus and retinal surgery) both here and abroad,

largely because of their perceived margins of safety.

In Great Britain, sub-Tenon’s anesthesia in particular

has risen in popularity and now is used for a large

percentage of cataract surgeries. However, there re-

mains a place for orbital regional anesthesia or gen-

eral anesthesia in ophthalmic surgery, because topical

and sub-Tenon’s techniques are not suitable for every

patient, every procedure, nor every surgeon.

The goals of this article are to examine the no-

menclature of orbital blocks, to review orbital anat-

omy as it relates to the safe performance of orbital

regional anesthesia, and to describe two specific

block techniques and contrast them with others.

Nomenclature

Nomenclature for orbital blocks is imprecise and

can be confusing [2]. Currently, the term retrobulbar

is applied to a block for which a long, apically

directed needle is used. Actually, all orbital blocks are

retrobulbar because the term simply means behind the

globe. In many patients it is possible to be behind the

globe with a 0.5-in needle. Similarly, the term peri-

bulbar is used to describe a block in which the intent

is to stay out of the muscle cone with the needle. In

fact, all blocks should be peribulbar (ie, around the

globe), because the only alternative is transbulbar,

something to avoid. More recently, the term para-

bulbar has been used to describe sub-Tenon’s blocks.

0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights

doi:10.1016/j.ohc.2006.02.009

E-mail address: [email protected]

This seems reasonable, because parabulbar has the

connotation of being next to and close to the globe.

Use of the terms retrobulbar and peribulbar to

describe different block techniques seems unsuitable

on at least two grounds: they are imprecise and they

do not actually describe the anatomical spaces they

are meant to describe. It would be more precise and

anatomically correct to substitute the term intraconal

for retrobulbar, because the block is designed to go

into the muscle cone. Instead of peribulbar, the term

extraconal better describes the type of block intended

to inject anesthetic into the extraconal space. In this

article, therefore, the terms intraconal and extraconal

will be used instead of the more widely used

expressions retrobulbar and peribulbar, respectively.

Anatomy for orbital regional anesthesia

To best understand the anatomy of the orbit for the

purpose of doing blocks, one should have a thorough

knowledge of the frontal anatomy of the orbit at

various depths from the orbital rim back to the optic

canal. This anatomy is best illustrated in the works of

Leo Koornneef [3] and Jonathan Dutton [4].

The orbit is an irregularly shaped pyramid; the

base faces anteriorly, roughly on the frontal plane.

The apex (the optic canal) lies at the posterior end of

the medial wall. Because of the irregular shape of the

orbit, the lateral wall is longer than the medial wall.

As a result, a long (1.5 in) needle that is inserted

along the medial wall can easily reach the optic canal

in most patients.

The globe is situated in the orbit such that it is

slightly closer to the roof and lateral wall than to the

floor and medial wall. The lateral rectus muscle lies

against the orbital wall until quite far anteriorly

Am 19 (2006) 221 – 232

reserved.

ophthalmology.theclinics.com

Page 69: Anestesia Ocular

Fig. 1. A frontal section through the posterior half of the

globe. The open star indicates the fat-filled space at the

extreme inferotemporal corner of the orbit. The inferior

rectus muscle is located at the junction of the lateral one-

third and medial two-thirds of the inferior orbital rim. The

neurovascular bundle to the inferior oblique lies just lateral

to it. The filled star lies in the medial canthal fat-filled

space, another relatively safe entry point for an orbital

block. IRM, inferior rectus muscle; LPM, levator palpebrae

muscle; LRM, lateral rectus muscle; MRM, medial rectus

muscle; SOM, superior oblique muscle; SRM, superior

rectus muscle. (Adapted from Dutton JJ. Atlas of clinical

and surgical orbital anatomy. Philadelphia: W.B. Saunders

Company; 1994; with permission.)

Fig. 2. Frontal section at a level about 5–10 mm behind the

hind surface of the eye. The tip of a 1-in needle should just

reach this level and lie in the fat medial to the lateral rectus,

and lateral and inferior to the optic nerve. It is unnecessary

to be deeper than this in the orbit to achieve an excellent

block. IRM, inferior rectus muscle; LRM, lateral rectus

muscle; MRM, medial rectus muscle; OA, ophthalmic

artery; ON, optic nerve; SOM, superior oblique muscle;

SRM, superior rectus muscle. (Adapted from Dutton JJ.

Atlas of clinical and surgical orbital anatomy. Philadelphia:

W.B. Saunders Company; 1994; with permission).

fanning222

where its tendon then passes medially to insert on the

globe. The medial rectus muscle, in contrast, begins

to angle laterally to join the globe relatively close to

its origin at the annulus of Zinn. As a result, there is a

sizable fat-filled space between the medial rectus

muscle and the medial orbital wall for most of its

length, especially in the anterior half of the orbit

(Fig. 1). This extraconal space is an excellent site for

the injection of local anesthetic, as it communicates

freely with the intraconal space and is virtually devoid

of easily damaged structures if appropriately ap-

proached. Some practitioners use this as the site of their

primary orbital block.

At the extreme inferotemporal corner of the orbit

there is another extraconal, fat-filled space that is

easily entered and is devoid of other structures. It,

too, communicates with the intraconal space between

the lateral rectus muscle and inferior rectus muscle. A

frontal section just posterior to the equator of the

globe (see Fig 1) invariably shows this space to be

large and filled with fat. Actually, both the inferior

rectus muscle and the neurovascular bundle to the

inferior oblique are quite close to this spot. This can

be seen by looking at the junction of the lateral third

and medial two-thirds of the lower orbital rim. For

decades, this point has been recommended as the

needle entry point for an orbital block. Atkinson [5] is

often credited with suggesting this entry point, but in

his original 1936 paper, he recommended ‘‘. . .theinferior temporal margin of the orbit.’’ An illustration

in his paper shows a skin wheal at the inferotemporal

margin of the orbit.

It is not surprising that the inferior rectus com-

monly suffers dysfunction after orbital regional anes-

thesia. This point is significantly closer to the globe

than a point at the inferotemporal corner of the orbit.

Thus, for clear anatomical reasons, the classic inser-

tion point for orbital regional anesthesia (junction of

the lateral third and medial two-thirds of the lower

orbital rim) would seem to be a less desirable entry

point than the extreme inferotemporal corner of

the orbit.

A frontal section of the orbit 5–10 mm behind the

hind surface of the eye (Fig. 2) shows a fat-filled,

intraconal space that is relatively devoid of structures

other than the optic nerve; the bellies of the extra-

ocular muscles are close to the orbital walls at

this level. Vascular structures are small and widely

spread. The space between the lateral rectus and

Page 70: Anestesia Ocular

Fig. 3. Frontal section 15–20 mm behind the hind surface of

the eye shows how closely packed structures become as the

apex of the orbit is approached. There is little room for error

here and a needle can damage any of the structures seen in

this section. A 1.5-in needle can reach this level in at least

20% of patients. There is no need to be this deep in the orbit

when doing orbital regional anesthesia. IRM, inferior rectus

muscle; LPM, levator palpebrae muscle; LRM, lateral rectus

muscle; MRM, medial rectus muscle; ON, optic nerve;

SOM, superior oblique muscle; SRM, superior rectus

muscle. (Adapted from Dutton JJ. Atlas of clinical and sur-

gical orbital anatomy. Philadelphia: W.B. Saunders Com-

pany; 1994; with permission.)

Fig. 4. The white line in this drawing divides the orbit

into superior and inferior halves. Most large arterial vessels

are seen in the superior and deep areas of the orbit. To

avoid injuring them, keep needles out of these areas. Note

the course of the ophthalmic artery that leaves the optic

canal and goes into the superonasal quadrant. (Adapted

from Dutton JJ. Atlas of clinical and surgical orbital

anatomy. Philadelphia: W.B. Saunders Company; 1994;

with permission.)

orbital regional anesthesia 223

inferior rectus muscles is fairly large, but the space

between the medial rectus muscle and the medial

orbital wall is narrower than in the previous section.

These spaces behind the globe are reachable with

a 1-in needle. If a sufficient volume of anesthetic is

injected, it is unnecessary to place a needle any

further back into the orbit to achieve a good block.

There is no intermuscular septum between the rectus

muscles to define the intraconal from the extraconal

space. In fact, anesthetic injected into either space

flows readily into the other, as clearly demonstrated

by Ripart and coworkers [6]. Some practitioners rely

on feeling a pop when the needle is inserted, and

believe that they have traversed the (non-existent)

septum. When a sharp needle is inserted into a fat-

filled space, little, if any, sensation will be felt. A

popping sensation may mean that one of the tiny

connective tissue septa described by Koornneef [3]

and that are found throughout the orbit, has been

punctured. It may also indicate, however, a punctured

vessel, nerve, muscle, optic nerve, or globe.

A frontal section, about 20 mm behind the hind

surface of the globe (Fig. 3), shows that the amount

of fat in the intraconal space is now much less and

there are other structures that fill it. These include the

branches of the motor nerves that supply the ex-

traocular muscles, the arteries and veins to those

muscles, and the optic nerve. The subarachnoid space

between the dural sheath and optic nerve is impres-

sive in this section. The bellies of the extraocular

muscles are also much larger at this level. Myotox-

icity, which is often irreversible, may occur when

local anesthetic is injected directly into a muscle belly

[7,8]. The part of the orbit where the structures are

closely packed and easily impaled is reached by a

1.5-in needle in at least 15%–20% of eyes, as dem-

onstrated by Katsev and colleagues [9]. To avoid

damage to any of the structures seen in the frontal

section, it would seem wise to use a shorter needle.

Three special anatomical details are worth dis-

cussion. First is the vascular tree of the orbit. Both the

largest arteries (Fig. 4) and largest veins (Fig. 5) lie in

the superior half of the orbit. In addition, the vessels

that have the largest diameter lie in the deep portion

of the orbit. To avoid a major retrobulbar hemorrhage

or intravascular injection, the needle tip should be

kept out of the upper half and out of the deep portion

of the orbit. Second is the superonasal quadrant of the

orbit, which is an especially dangerous place to put a

needle. The terminal branches of the ophthalmic

artery are here, an artery that is often large and tor-

tuous in elderly, hypertensive individuals. A needle

placed in this artery may result in a sight-threatening

Page 71: Anestesia Ocular

Fig. 5. This figure shows the venous drainage of the orbit.

The major vessels are in the superior and deep portions of

the orbit. The superior ophthalmic vein begins in the su-

peronasal quadrant. Needles should not enter that quadrant.

(Adapted from Dutton JJ. Atlas of clinical and surgical or-

bital anatomy. Philadelphia: W.B. Saunders Company; 1994;

with permission.)

fanning224

hematoma or intravascular injection of anesthetic that

causes immediate seizure activity. In addition, the

terminal branches of the nasociliary nerve lay in the

superonasal quadrant and can be damaged. The supe-

rior oblique muscle and its trochlear mechanism

are also located in the superonasal quadrant. Third is

the dural sheath that surrounds the optic nerve. A

needle tip placed within that sheath will result in

local anesthetic being injected retrograde into the

cerebrospinal fluid surrounding the brainstem, caus-

ing brainstem anesthesia. This complication may

largely be avoided by the use of short needles that

are not apically directed.

Patient preparation

Before performing an orbital block, it is wise to

review the patient’s medical history and conduct a

directed physical examination to be sure that the

patient is a suitable candidate on the day of surgery.

Routine assessment of vital signs and an ECG moni-

tor will help determine if patients have fevers,

arrhythmias, or hypertension, conditions that may

require the procedure to be cancelled. At the Hauser-

Ross Eye Institute patients are routinely treated who

have blood pressures >170 mm Hg systolic and/or

105 mm Hg diastolic. Judicious doses of intravenous

labetalol (10–20 mg) are commonly used, but other

agents are available to patients who must avoid beta-

blockers. Great care is taken to avoid suddenly low-

ering the blood pressure in patients who have angina,

aortic stenosis, renal vascular disease, or carotid ste-

nosis. In order to prevent hypotension, administer

small, divided doses and monitor carefully.

It is also important to examine the eyes for in-

fectious, traumatic, or even malignant lesions. The

patient’s record should be examined for evidence of

the length of the eye. In the case of cataract sur-

gery, each patient should have had an axial length

measurement and this should be noted and recorded

by the person who performs the orbital block. If the

anesthesia provider is performing the block, the

ophthalmologist should be certain that they know

the axial length. If the axial length is not available,

the spherical equivalent in the patient’s eyeglass

prescription should be reviewed. High myopes tend

to have exceptionally long eyes, so when the

spherical equivalent is as high as �6.00 or �7.00,it is advisable to measure the axial length before

performing an orbital block. Fig. 6 demonstrates the

relationship between axial length and spherical

equivalent as measured in 1325 eyes. Patients who

have axial lengths �27 mm are at risk for posterior

staphylomata [10] and should have been carefully

examined for their presence preoperatively. After the

patient’s eye length has been determined or estimated,

the relationship of the eye within the orbit should be

examined. Is it a long eye sunk deeply into a very

tight orbit? Is it a short, proptotic eye in a large but

potentially shallow orbit? Knowledge of this relation-

ship is used to determine the angle of the block

needle as it enters the desired orbital space in order to

avoid penetrating the sclera.

Sedation

An orbital block can result in a great deal of pain

and many practitioners use deep sedation, equivalent

to a brief period of general anesthesia, when they

perform a block. Pain on injection is likely to occur

when a needle is placed deeply into the orbit, because

pressure is generated when the anesthetic is injected

rapidly into a tight space that is filled with delicate

structures. Deep sedation is not without its risks, and

a number of unwanted events can occur, including ap-

nea, hypoxemia, uncontrolled movements, and even

vomiting or aspiration. Some practitioners believe

that it is important not to sedate the patient deeply for

an orbital block, because they want the patient to be

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Fig. 6. Axial length versus spherical equivalent in 1325 eyes. Patients who are highly myopic (and have eyeglass prescriptions

with large negative spherical equivalents), tend to have very long eyes. Axial length is plotted against spherical equivalent. The

bars represent two standard deviations from the averages. When performing a block on a patient who has not had an their axial

length measured, it is useful to look at the spherical equivalent in the eyeglass prescription to estimate the length of the eye.

(Gary L. Fanning, MD, unpublished data, 2000.)

orbital regional anesthesia 225

able to give notice if excessive pain occurs. Such pain

might indicate that the anesthetic is not being injected

into a fat-filled space but rather into an extraocular

muscle, the globe, a nerve, or under the periosteum. It

is possible to have a patient who is sedated to the

point of anxiolysis and still remain cooperative. Small

intravenous doses of midazolam (1–2 mg) coupled

with small, divided doses of a short-acting barbiturate

(thiopental [Pentothal] 25–75 mg or methohexital

[Brevital] 10–30 mg) or with a rapid, short-acting

opioid (remifentanil [Ultiva] 20–40 mcg, alfentanil

[Alfenta] 250–500 mcg, or fentanyl [Sublimase]

50–100 mcg) can produce a patient who is re-

laxed, submissive, and cooperative. Sedative doses

of propofol are preferred by many, but it can be dif-

ficult to titrate due to its slow onset of action, and in

some patients it results in a great deal of unwanted

movement unless sleep doses are given. Nonetheless,

it is an appropriate agent for many patients when

administered by those skilled in its use. Strict attention

to the patient’s reaction to the sedatives is important to

avoid over-sedation. The patient’s response to sedation

for the block provides advanced knowledge of their

reaction to the sedatives before the onset of surgery. If

additional sedation is believed to be required during

surgery, the practitioner will be able to avoid excessive

sedation and its attendant dangers. To render the in-

jection of a block virtually painless in a patient who

is awake, three precautions must be taken: (1) use a

fine, short needle (ie, 25 gauge, 1 in), (2) use an anes-

thetic solution that has been heated to about 35�C, and(3) inject the anesthetic at a slow rate (15–20 s/mL).

Studies [11,12] that have examined warming the

anesthetic solution have often failed to include the

other two precautions, and over-warming the solution

often produces increased pain. Any solution injected

deeply and rapidly into the orbit will cause intense

pain. Warmed solutions injected slowly and more

anteriorly do not. Conscious sedation along with a

painless injection technique has another benefit:

patients may be allowed to have a light breakfast

before cataract surgery. The author has used this

technique in more than 22,000 patients without a

single instance of regurgitation or aspiration. When

a painless injection technique is used, only small

amounts of sedation, if any, are necessary.

Needles

Before discussing the details of block techniques,

it is necessary to examine what kind of needle should

be used to perform a block. Many, if not most,

practitioners still use the 23-gauge, 1.5-in needle that

has been used for decades. In 1989, Katsev and

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fanning226

coworkers [9] published an anatomical study of the

orbit with regard to needle length. They measured the

distance from the junction of the lateral third and

medial two-thirds of the inferior orbital rim to the

optic canal. In the 120 skulls that were examined, this

measurement varied from about 42 mm to 54 mm

(Fig. 7). They postulated that the most dangerous part

of the orbit, where structures are densely packed and

vulnerable to damage, is the portion within 7 mm of

the annulus of Zinn. Thus, the tip of a 1.5-in needle

(38 mm) would reach this dangerous portion in any

orbit shorter than 45 mm. In their specimens this

would be about 15%–20% of the total. If a needle

�1.25-in (32 mm) in length is used, the danger area

would not be reached in any of the skulls examined

by Katsev and coworkers. Although the study was

published in a prominent journal, many practitioners

still use a long needle. Having used a 1-in needle

for 2 years with great success and having used a

1.25-in needle for 12 years before that, it is the au-

thor’s opinion that the incidence of all of the fol-

lowing complications of orbital regional anesthesia

would be significantly reduced by using a shorter

needle: retrobulbar hemorrhage, brainstem anesthe-

sia, optic nerve damage, intravascular injection, and

extraocular muscle dysfunction. With regard to nee-

dle gauge, the needle should be 25 gauge, no bigger.

Some prefer a 30-gauge, 1-in needle although others

find it too flexible. Many would prefer a 27- or

Fig. 7. Orbital length in 120 skulls. Orbital length is plotted again

20% of orbits are short enough that a 1.5-in needle can reach within

(Adapted from Katsev DA, Drews RC, Rose BT. An anatomical st

96:1221–4; with permission.)

28-gauge, 1-in needle, but these are no longer avail-

able commercially in the United States; a 25-gauge,

1-in needle is a compromise.

There is a great debate about whether the bevel of

the needle should be sharp or blunt. Some of this

discussion revolves around feel: many practitioners

believe that a blunt-beveled needle offers a better tac-

tile signal than the sharp-beveled one; others believe

just the opposite. Proponents of the blunt-beveled

needle believe that it is less likely to inadvertently

puncture the sclera than is the sharp-beveled needle.

Although this may be true, it is also true that any

needle that is capable of going through the intact skin

is also able to go through the sclera of the eye in situ

(as opposed to an enucleated eye, where it can be

demonstrated that a blunt-beveled needle requires

more force than a sharp one to penetrate the globe).

There is some evidence that scleral puncture with a

blunt-beveled needle results in more retinal damage

than puncture with a sharp-beveled one [13]. One

group has suggested that in patients with a long eye,

the blunt-beveled needle should always be used

because it is less likely to puncture the sclera [14].

However, the longest eyes have the most delicate

sclera, which makes it easy for any needle to pene-

trate. If penetration did occur, it would seem pref-

erable to have used a needle that would result in less

retinal damage. Furthermore, it is not rational to rely

on the shape of the needle to avoid penetration of

st the percentage of orbits that have specific lengths. About

7mm of the optic canal where structures are tightly packed.

udy of retrobulbar needle path length. Ophthalmology 1989;

Page 74: Anestesia Ocular

orbital regional anesthesia 227

the sclera. Instead, thorough knowledge of orbital

anatomy and examination of the patient’s globe-orbit

relationship should prevent this complication. One

thing that is not disputed is that the sharp needle

enters the skin more easily and with less pain. No

matter what needle the practitioner uses, the length,

gauge, and bevel shape must be documented in the

patient’s record.

Fig. 9. Line A represents the diagonal of the orbit from the

superotemporal to the inferotemporal corner. The block

needle is aligned with line A and is inserted at the infero-

temporal corner. Dotted line B represents a sagittal plane

that goes through the lateral limbus. The block needle is

angled (angle C) so that the tip will just intersect plane B

about 5–10 mm behind the hind surface of the eye when

inserted. The value of this angle is different for each patient.

Technique

Intraconal block

For an intrconal block, the patient should be in the

supine position, the chin held up, and the eyes in a

neutral gaze. A skin wheal is made with a 0.5-in,

30-gauge needle using 0.1% lidocaine solution in-

jected at the extreme inferotemporal corner of the

orbit (Fig. 8). The lidocaine solution is prepared by

adding 1.5 mL 2% lidocaine with preservative to a

30 mL bottle of 0.9% saline solution with preserva-

tive. The final solution contains about 0.1% lido-

caine, which provides excellent anesthesia for about

5–10 min but is virtually painless to inject. This

solution given through a 30-gauge 0.5-in needle is

also used to anesthetize the intravenous catheter’s

insertion site, which makes starting the intravenous

line painless as well. In many patients a distinct notch

is felt in the lower orbital rim at the inferotempo-

ral corner. It is worthwhile to search for this notch,

Fig. 8. A skin wheal is raised at the inferotemporal corner of

the orbit. A 30-gauge needle is used to inject 0.1% lidocaine

solution, which is virtually painless on injection. The same

solution also is used before starting an intravenous to render

it painless.

because inserting the needle here increases one’s

chances of entering into the intraconal space keeping

well away from the extraocular muscles and the

globe. While an assistant steadies the patient’s head

and holds the upper lid open, a 25-gauge 1-in needle

is inserted through the skin wheal at the inferotem-

poral corner (notch) of the orbit on a line that con-

nects the inferotemporal corner with the superonasal

corner (line A, Fig. 9) and is aimed posteriorly to pass

tangential to the globe and intersect a sagittal plane

(line B, Fig. 9) to pass through the lateral limbus. The

angle formed by the needle shaft and the frontal

plane on which line A lies (angle C, Fig. 9) will vary

in each patient. The degree of angulation is deter-

mined by the eye’s axial length and how deeply set

or proptotic the eye is. In Fig. 10, the two deep-set

eyes can be compared with two more proptotic eyes.

The angulation necessary to pass tangentially to the

globe will differ in each of these patients. The

patient’s eye should be watched constantly during

the initial insertion, at which time it should not move

at all as the needle passes the globe. Although the

patient’s eye should be in neutral gaze during the

initial insertion and should not move, it is helpful to

have the patient gaze toward the ipsilateral side once

the needle is slightly beyond the equator. This insures

that the globe is free and also moves the posterior

pole of the eye away from the needle tip. Some

practitioners prefer to have the patient continue in

neutral gaze, which is also acceptable. It is not ac-

Page 75: Anestesia Ocular

Fig. 10. The depth of the eye with respect to the lower orbital rim varies from patient to patient. The length of the eye, how

deeply it is set, and how tightly it is placed within the orbit constitute the globe-orbit relationship. This relationship must be

carefully considered for each patient in order to angle the needle safely to pass tangentially to the globe.

Fig. 11. The tip is more anterior when a short needle is used

and injection may cause anesthetic solution to pass retro-

grade into the lower eyelid instead of behind the eye. To

lessen this tendency, the assistant is directed to place two

fingers along the lower orbital rim and to apply gentle

pressure to encourage flow of the injectate behind the globe.

It is an easy and harmless maneuver that results in a higher

rate of successful blocks.

fanning228

ceptable to move the needle back and forth in order

to see if it is in the globe or not. This has been termed

by some as stirring the orbital contents, a practice to

be avoided. For most patients, the tip of the fully

inserted 1-in needle will lie just behind the posterior

surface of the globe and no deeper than 5–10 mm

behind it. The bevel of the needle should at first be

pointing toward the globe so that during insertion the

tip of the needle will tend to move away from the

globe. After the tip of the needle is well beyond

the equator of the globe (about half inserted), the

needle can be spun 180� so that the bevel faces

away from the globe. This will tend to move the tip

medially into the intraconal space behind the globe.

Properly placed, the tip of the needle should now be

in the intraconal space of the inferotemporal quadrant

of the orbit, just behind the globe. Before injecting,

the assistant places two fingertips along the lower

orbital rim to bolster the inferior orbital septum

(Fig. 11). Gentle pressure applied here during injection

promotes flow of anesthetic upward and posteriorly

instead of retrograde into the lower lid through the

ever-present gaps in the orbital septum. Local anes-

thetic is injected slowly (1 mL every 15–20 seconds)

and the globe is periodically palpated to insure that

there is no excessive pressure. In most patients 7 mL

can be injected safely, a volume that will provide total

akinesia and anesthesia in well over 90% of patients.

After injection, an orbital compression device is ap-

plied for 10 min. This can be a soft plastic ball or a

Honan balloon [15]. This compression helps to

disperse the anesthetic throughout the orbit and helps

to prevent excessive intraocular pressure caused by the

presence of the anesthetic within the orbit.

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Fig. 12. If a supplemental block is required to achieve

complete akinesia, a medial canthal block is performed.

First, identify the small tunnel or dimple that lies anterior

to the caruncle and just behind the medial canthus. The tip

of the needle is placed in that tunnel.

orbital regional anesthesia 229

It is important to emphasize the insertion point

described in this technique. For decades, common

practice has been to insert the needle at the junction

of the lateral third and medial two-thirds of the lower

orbital rim (the classic point). As explained above,

this insertion site is nearer the globe, is close to

the inferior rectus muscle, and is also close to the

neurovascular bundle of the inferior oblique. Because

it is so close to the globe, it is also difficult from

this point to place the needle tip within the muscle

cone without trying to redirect it after insertion.

From the extreme corner, it is easier to stay far away

from the globe and the angle of insertion does not

have to change to enter the intraconal space. In fact,

a needle only has to be angled 10� medial to a sagit-

tal plane tangential to the globe (ie, to the optic axis)

to enter the intraconal space [16]. If the needle is

angled as described in the paragraph above, this

should happen virtually every time. When performing

an extraconal block, it is acceptable to enter at the

classic point if the needle remains low and parallel to

the orbital floor and is not redirected once inserted.

A large volume of anesthetic injected through a

short needle in this way will often provide a satis-

factory block.

Some practitioners prefer to insert the needle into

the orbit through the inferior conjunctiva instead of

transcutaneously as described above. This is an ac-

ceptable technique, especially since the conjunctiva

can be anesthetized with topical anesthetic, which

avoids the need to inject a skin wheal. Transconjunc-

tival injection can be difficult for some patients,

however, especially for those who are very protective,

have short palpebral fissures, or have exceptionally

deep-set eyes. In these patients, the transcutaneous

approach may be easier and perhaps safer.

The block technique described above should be

contrasted with the classic technique that has been

taught, practiced, and described in the literature

[17]. In the older technique, the needle enters more

medially, as has been mentioned, and is redirected

to be aimed toward the apex of the orbit when it is

an inch or so into the orbit. It is during this redi-

rection of the needle, especially in patients with long

eyes (26–27 mm or longer), that perforation of the

globe probably occurs. Perforation is less likely to

occur if the needle is inserted further away from

the globe, not aimed at the apex, and not redirected.

In the apex, structures are tightly packed together,

and a long needle aggressively aimed in that di-

rection has a real chance of causing a major com-

plication. The complication rate is, in fact, relatively

low, but it could be even lower with the use of im-

proved techniques.

Extraconal block

After 10 min, the patient’s eye should be evalu-

ated for movement. When significant movement

occurs, it is most often medial, torsional, or superior.

If there is a lot of movement, it may be wise to re-

peat the inferotemporal, intraconal injection, which is

often necessary in patients with large orbits. If there is

less movement, a supplement in the medial canthal

extraconal space is recommended. The purpose of

this injection is to deposit anesthetic into the fat-filled

space between the medial rectus muscle and the

medial orbital wall (see Fig. 1). Anesthetics placed

here flow unimpeded into the posteromedial aspect of

the intraconal space as well as into the posterosu-

perior extraconal space. This block, described by

Hustead and colleagues [18], is preferred by some for

the primary block. For this procedure, a 25-gauge,

1-in needle (some practitioners use a 30-gauge 0.5-in

needle) is inserted into the tunnel that lies between

the caruncle and the medial canthus (Fig. 12). This is

usually painless because of the inferotemporal block.

The needle tip is directed at first toward the medial

wall (Fig. 13). The orbital wall is extremely thin here

and is called the lamina papyracea (paper layer). If

inserted too aggressively, the needle tip ends up in the

ethmoid sinus and after injection the patient will feel

the anesthetic running down the back of the nose and

into the throat. After touching the wall, the needle is

withdrawn slightly (1 mm) and is redirected so that it

can be inserted into the orbit parallel to the medial

wall and the floor (Fig. 14). The needle should be

Page 77: Anestesia Ocular

Fig. 14. The needle has been redirected and inserted into the

fat-filled space medial to the medial rectus. The shaft of the

needle should be parallel to the medial wall and to the floor

of the orbit. No attempt should be made to angle it supe-

riorly or inferiorly. No needle longer than 1 in should be

used, and the shoulder (where hub and shaft meet) of the

needle should not go deeper than the plane of the iris.

Fig. 13. The tip of a 1-in needle is inserted into the tun-

nel until it just touches the periosteum of the medial wall

(lamina papyracea). The tip is then withdrawn just 1–2 mm,

and the needle is redirected.

fanning230

aimed straight posteriorly to stay in the fat-filled,

avascular space medial to the medial rectus muscle. A

needle longer than 1 inch should never be used here,

because the optic canal lies directly posterior and can

be impacted by overly aggressive insertion. The

shoulder (where the hub and shaft join) of a 1-in

needle should not go deeper than the plane of the iris.

The bevel of the needle during insertion should face

the orbital wall to keep the tip of the needle away

from the wall. It is not unusual to see the globe move

medially and then move back to neutral gaze during

insertion of the needle. This is because the needle will

pass through the medial check ligament, and, in some

patients, the globe will turn. Properly placed, how-

ever, the needle is safely medial to the globe in

spite of the movement. After aspirating, 2–5 mL is

injected while the globe is frequently palpated to in-

sure that excessive pressure does not develop. The

orbital compression device is reapplied for another

5–10 min. It is rare to have to give more than one

supplement and then only when absolute akinesia is

required. As mentioned, some practitioners use this

approach for their primary block, inject up to 10 mL,

and are happy with their results.

An alternative approach to the medial canthal

block has been suggested by Jacques Ripart and his

colleagues in Nimes, France [19,20]. Instead of in-

serting the needle in front of the caruncle, they insert

it between the caruncle and the globe. The globe turns

severely medially during insertion and then pops

suddenly back to neutral gaze as the needle goes back

further. They have promoted this technique as a way

of entering the sub-Tenon’s space, which they un-

doubtedly do when short needles (0.5 in) are used. If

longer needles are used, the needle probably enters

the medial canthal space [21]. Ripart and colleagues

have reported excellent results with their blocks, and

their technique should be respected and considered.

Block mixtures

A variety of anesthetic agents are acceptable for

performing orbital regional anesthesia; they range

from 1% lidocaine for short procedures that do not

require complete akinesia to 0.75% bupivacaine for

long procedures that do. The higher concentrations of

local anesthetics are known to be significantly myo-

toxic in laboratory investigations [7,8] and may be

so in selected patients [22]. They will certainly be

toxic if injected directly into a muscle. In addition,

bupivacaine may exhibit significant neurotoxicity

and cardiotoxicity when injected intravascularly.

Although 4% lidocaine has been marketed and used

for deep intraconal blocks for many years, some [23]

believe that it is too myotoxic and should be avoided

when doing orbital regional anesthesia. For the most

part, however, the choice of anesthetic agent is only

critical when deciding how long the patient needs to

be anesthetized.

Hyaluronidase has been used for years in orbital

regional anesthesia, perhaps the only regional block

where it has been shown to be beneficial, although

not all investigators agree regarding its effectiveness

[24–26]. Hyaluronidase does slightly speed the on-

set of block and perhaps improves the quality of the

Page 78: Anestesia Ocular

orbital regional anesthesia 231

block, but it also facilitates more rapid diffusion of

the anesthetic bolus within the orbit, which reduces

vitreal pressure during cataract and other intraocular

procedures [27]. In addition, during a recent lack of

hyaluronidase in the commercial market in America,

a rise in extraocular muscle dysfunction was noted in

some institutions [28,29]. Lack of the agent may have

caused high concentrations of anesthetic to remain

close to a muscle for a longer period, which resulted

in toxicity, although such a mechanism is hypotheti-

cal. Nonetheless, the question remains as to whether

or not myotoxicity is seen more frequently when

hyaluronidase is not added to orbital block mixtures.

The amount of hyaluronidase needed has been

the subject of clinical investigations. Many practi-

tioners use large amounts of the agent: 150 units per

5–10 mL of anesthetic mixture (15–30 units per mL).

A study from Finland [30] showed that a mixture

containing 3.5 units per mL is quite effective. This

author has used 1 unit per mL for many years

[31]. Hyaluronidase is also an expensive agent and

150 units is more than sufficient for a dozen patients,

a significant savings compared with giving 150 units

to each patient.

The use of epinephrine in the block mixture is

controversial. Some believe that it is dangerous and

results in retinal vascular problems [23,32]. High

concentrations (�1:200,000) are to be avoided and it

should probably not be used for patients who have

known severe, generalized peripheral vascular dis-

ease. The reasons to add epinephrine are to prolong

the block and to improve its quality. In the author’s

experience, small quantities of epinephrine (1:300,000

or 1:400,000 concentrations) have not resulted in

retinal vascular problems in over 22,000 patients and

have added significant duration to the block. Epi-

nephrine, however, is not absolutely necessary to

obtain a good block, and high concentrations should

not be used.

Summary

Orbital regional anesthesia is a useful and safe

modality to provide excellent operating conditions for

the surgeon and painless, pleasant circumstances for

the patient. It is especially suited for patients who are

extremely sensitive and who could not tolerate topi-

cal anesthesia or a sub-Tenon’s block without deep

sedation. Both intraconal and extraconal techniques

can be used safely and effectively if proper precau-

tions are taken to enter the safest areas of the orbit in

order to avoid the vascular areas and the deep orbit

where structures are tightly packed and thus more

easily harmed. Thorough knowledge of orbital anat-

omy and understanding of the globe-orbit relation-

ship of every patient are necessary to perform this

form of regional anesthesia. In addition, knowledge

of the effects and side effects of the anesthetics and

adjuvants is also required.

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icity as a cause of restrictive strabismus after scleral

buckling surgery. Retina 2000;20:478–82.

[23] Hamilton RC. Complications of ophthalmic regional

anesthesia. Ophthalmol Clin North Am 1998;11:99–114.

[24] Johansen J, Kjelgard M, Corydon L. Retrobulbar anaes-

thesia. A clinical evaluation of four different anaesthetic

mixtures. Acta Ophthalmol (Copenh) 1993;71:787–90.

[25] Crawford M, Kerr W. The effect of hyaluronidase

on peribulbar block. Anaesthesia 1994;49:907–8.

[26] Bowman R, Newman D, Richardson E, et al. Is hyal-

uronidase helpful for peribulbar anaesthesia? Eye 1997;

11:385–8.

[27] Ripart J, Nouvellon E, Chaumeron A. Regional anes-

thesia for eye surgery. Reg Anesth Pain Med 2005;30:

72–82.

[28] Brown SM, Brooks SE, Mazow ML, et al. Cluster of

diplopia cases after Periocular anesthesia without hyal-

uronidase. J Cataract Refract Surg 1999;25:1245–9.

[29] Troll G, Borodic G. Diplopia after cataract surgery

using 4% lidocaine in the absence of Wydase (sodium

hyaluronidase) [Letter]. J Clin Anesth 1999;11:615–6.

[30] Kallio H, Paloheimo M, Maunuksela EL. Hyaluroni-

dase as an adjuvant in bupivacaine-lidocaine mixture

for retrobulbar/peribulbar block. Anesth Analg 2000;

91:934–7.

[31] Fanning G. Hyaluronidase in ophthalmic anesthesia

[Letter]. Anesth Analg 2001;92:560.

[32] Ahmad S, Ahmad A. Complications of ophthalmologic

nerve blocks: a review. J Clin Anesth 2003;15:564–9.

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Ophthalmol Clin N

Choosing Anesthesia for Cataract Surgery

Joselito S. Navaleza, MDa, Sagun J. Pendse, MDa, Mark H. Blecher, MDb,TaWills Eye Hospital, 840 Walnut Street, Philadelphia, PA 19107, USA

bCataract and Primary Eye Care Service, Wills Eye Hospital, 840 Walnut Street, Philadelphia, PA 19107, USA

Advances in cataract surgery techniques have pre-

sented surgeons with new options for ocular anes-

thesia. As cataract removal has become faster, safer,

and less traumatic, the need for akinesia and anes-

thesia has declined significantly. The use of general

anesthesia or retrobulbar block has largely been re-

placed with other safer and equally effective means of

local anesthesia, including peribulbar, sub-Tenon’s,

and topical. These newer and less invasive methods

have not only reduced the potential for catastrophic

surgical complications, but also increased the effi-

ciency of cataract surgery and hastened the process of

visual rehabilitation. Today there are numerous modes

of anesthesia from which a surgeon can choose. There

is not one type of anesthesia right for all cases. The

best choice varies from surgeon to surgeon, and pa-

tient to patient. The goal of this article is to review

the current choices for ocular anesthesia, compare

their efficacies, and provide a framework, helping to

select the most appropriate type of anesthesia for

each patient.

Although general anesthesia was first used in

surgery in 1846 by William Morton, it was not used

for cataract surgery until 1954 [1]. Retrobulbar block

was first described in 1884 by Knapp who injected

4% cocaine before enucleation surgery [2]. The mod-

ern technique used by most ophthalmologists today

was described by Atkinson in 1948, and until re-

cently served as the most commonly used technique

for intraocular surgery [3]. Davis and Mandel are

credited with introducing the peribulbar block in

0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights

doi:10.1016/j.ohc.2006.02.001

T Corresponding author. Cataract and Primary Eye Care

Service, Wills Eye Hospital, 840 Walnut Street, Philadel-

phia, PA 19107.

E-mail address: [email protected] (M.H. Blecher).

1986 as a less dangerous alternative to retrobulbar

anesthesia [4].

The decision between retrobulbar anesthesia and

peribulbar anesthesia presents the surgeon with a

choice between speed and safety. With a retrobulbar

block a surgeon can ensure that adequate akinesia and

anesthesia will result for cataract surgery; however, a

blind injection into the orbit poses several potential

complications, including, but not limited to retro-

bulbar hemorrhage, globe perforation, optic nerve

damage, and brainstem anesthesia. Peribulbar anes-

thesia, involving the injection of local anesthetic

external to the muscle cone, is thought to decrease the

likelihood of optic nerve and globe perforation while

maintaining the desirable qualities of excellent

akinesia and anesthesia. However, the potential need

for reinjection, the higher volume of injectate re-

quired, and the longer duration of onset associated

with peribulbar blocks may make it a less attractive

alternative. In a prospective, randomized controlled

trial involving 100 patients undergoing elective cata-

ract surgery, Whitsett and colleagues compared retro-

bulbar anesthesia with one injection site peribulbar

anesthesia [5]. They evaluated the two methods based

on three criteria that were considered critical to in-

traocular surgery: lid akinesia, globe akinesia, and

ocular anesthesia. Following administration of the

block, an independent observer rated each of these.

The authors concluded that one injection site peri-

bulbar anesthesia appeared to have a similar range

of efficacy in all three categories as compared with

standard retrobulbar anesthesia. There were no

anesthetic-related complications in either group.

As documented by Leaming [6] in his annual

surveys of ASCRS members, the current trend for

cataract surgery has shifted away from retrobulbar

and peribulbar anesthesia toward topical anesthesia.

Am 19 (2006) 233 – 237

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navaleza et al234

Karl Koller was the first to describe the use of

cocaine as a topical anesthetic for ocular surgery

in 1884 [7]. Topical anesthesia, however, did not

gain popularity until recently when it was reintro-

duced in the early 1990s by groups that used topical

medications. Subsequently, topical anesthesia was

modified by Gills and colleagues in 1997 with the

introduction of nonpreserved intracameral lidocaine

[8,9] and by Barequet et al [10] with the introduction

of lidocaine gel.

Given the recent trend toward the use of topical

anesthesia, perhaps of more significance would be

a comparison of retrobulbar and topical anesthesia

for cataract surgery. In 1993, Kershner evaluated

100 patents undergoing cataract surgery with topical

anesthesia and concluded that topical anesthesia was

safe, decreased complication rates, and hastened

patients’ return to normal vision [11]. However, the

following year, however, Fukasaku and Marron

[12] compared topical and retrobulbar anesthesia

and found that patients had unacceptable amounts of

intraoperative pain with the topical technique and

abandoned its use altogether. They, however, did not

mention the use of preoperative counseling or IV

sedation. Patel and collegaues completed a random-

ized controlled trial comparing the clinical efficacy of

retrobulbar versus topical anesthesia in patients

undergoing temporal clear corneal cataract extraction

[13]. Patients were given IV sedation (Midazolam)

in this study. They used a visual pain analog scale to

evaluate patient discomfort preoperatively, intraop-

eratively, and postoperatively, and concluded that the

degree to which patients experience pain is only

marginally higher for the topical group during the

administration of the anesthetic, intraoperatively, and

postoperatively. There was no statistically significant

difference in pain scores (P=.35). They also con-

cluded that no statistically significant (P=.5) differ-

ence in operative conditions were experienced by the

surgeon because of lack of globe akinesia. The im-

portance of careful patient selection with regard to

patient anxiety and cooperation was emphasized.

In a follow-up study by Crandall and colleagues,

the efficacy of topical anesthesia with and without

intracameral lidocaine was assessed [14]. In this

study no intravenous sedation was used. The authors

found that there was no statistically significant

difference in patients’ assessments of pain preopera-

tively, intraoperatively or postoperatively between

those who received intracameral lidocaine and those

in the control group. There did exist, however, a

statistically significant difference in patients’ percep-

tion of tissue handling (P=.021). This outcome

measure did not incorporate pain, but rather the

sensation that the eye or surrounding tissue is being

manipulated. Of perhaps greatest importance was the

finding of a statistically significant difference in the

surgeon’s assessment of patient cooperation (P = .043)

between the two groups. Those patients who received

intracameral lidocaine more readily followed sur-

geon commands. It was postulated that this ability

to cooperate was a result of the patient being less

bothered by tissue manipulation. The authors argue

that this finding alone justifies the use of intracameral

lidocaine to enhance topical anesthesia given the

importance of patient cooperation to successful topi-

cal cataract surgery. And to take the current trend

of less anesthesia to its most absolute, Pandey and

associates compared no anesthesia to topical and

topical with intracameral and found that for a highly

experienced surgeon, with a carefully selected patient

population, the pain scores for all three groups were

the same. The only difference was the discomfort

level of the surgeon [15].

In the most recent published study of the practice

styles and preferences of ASCRS members [6], it was

found that retrobulbar block without facial block was

used by 11% of surgeons and retrobulbar injection

with facial block by 9% (down from 76% in 1985,

32% in 1995, and 14% in 2000). The peribulbar

block was used by 17% of surgeons (down from

38% in 1995). Topical anesthesia was used by 61%

(up from 8% in 1995 and 51% in 2000). Of those

surgeons electing to use topical, 73% of surgeons also

used concomitant intracameral lidocaine. The use of

topical also varied with surgical volume. Those per-

forming 1 to 5 cataract procedures per month used

topical 38% of the time and those doing more than

75 procedures used it in 76% of cases. Clearly the

trend has been to transition from retrobulbar anes-

thesia to topical, and this pattern parallels the increase

in the use of temporal clear corneal incisions.

Given the choices for ocular anesthesia today, one

thing remains clear: no single mode of anesthesia can

serve as a universal choice for all patients and all

surgeons. The literature reveals that each of the major

modes of ocular anesthesia—retrobulbar, peribulbar,

and topical—are essentially equally effective in con-

trolling patient pain and allowing a surgeon to have

a successful surgical outcome. The decision to choose

one of these methods ultimately falls on the surgeon,

and the surgeon should carefully tailor his or her

approach to each individual patient. The decision of

which type of anesthesia to use is not only dependent

on a number of patient factors, but is also dependent

on the surgeon and the surgeon’s level of expertise

and facility with the surgery to be performed. With

this in mind, we present a short discussion that

Page 82: Anestesia Ocular

choosing anesthesia for cataract surgery 235

addresses the decisions involved in choosing the

mode of anesthesia best suited for each patient.

The ideal surgery is conducted under the safest

conditions, is cost- and time-efficient, and ultimately

results in excellent outcomes as well as patient sat-

isfaction. These are our goals with regard to the use

of anesthesia for cataract surgery as well. We group

anesthesia into three categories: general, regional

(retrobulbar, peribulbar, and sub-Tenon’s), and topical

(with and without intraocular anesthetics).

Risks and benefits

General anesthesia provides excellent anesthesia,

analgesia, and akinesia. In addition, the duration of

anesthesia can be varied to accommodate the length

of surgery. This provides the most controlled environ-

ment for surgery and may result in fewer ocular

complications and, ultimately, a satisfied patient.

Systemic risks include malignant hyperthermia,

hemodynamic fluctuation, postoperative nausea and

vomiting, and allergic reactions. There may also be

increased risk of cardiac complications under general

anesthesia. In 1980, Backer and colleagues [16]

published a study suggesting elderly patients with a

history of myocardial infarction were at a higher risk

for another myocardial infarction under general

anesthesia. Lang [17] did not find similar results in

their review of 15,000 cases between 1977 and 1979

comparing regional with general anesthesia. There

was one death in each group and the only two myo-

cardial infarctions occurred in the regional group.

Lynch and colleagues [18] found similar rates of

mortality and major complications including vitreous

loss with general and regional anesthesia in 2217

consecutive patients. Ocular complications such as

intraocular pressure fluctuation, Valsalva retinopathy,

corneal abrasions, and chemical injury also occur

more frequently.

General anesthesia requires more medication,

equipment, and personnel than topical anesthesia.

As a result, it is the most costly form of anesthesia.

The time required for induction, intubation, and ex-

tubation also contributes to its inefficiency. Modern

health care, where time and cost efficiency are sig-

nificant factors, renders general anesthesia unlikely

for the bulk of cataract surgeries.

Regional anesthesia also provides excellent anes-

thesia, analgesia, and akinesia. The duration of effect

varies with the anesthetic mixture used but can easily

last for most cataract surgeries. While the eye is not

able to move, the patient may still move, as a result, it

is not quite as controlled as general anesthesia. The

cost of the medications and equipment are much less

than with general anesthesia. Injections themselves take

very little time, making this method more time and cost

efficient than general anesthesia. There are systemic

risks such as allergic reactions, brainstem anesthesia,

and oculocardiac reflex. In addition, the complications

of a blind injection into the orbit present additional

risks discussed earlier. The incidence of retrobulbar

hemorrhage has been reported as low as 0.44% of cases

[19], up to 3% of cases [20]. Peribulbar anesthesia,

involving the injection of local anesthetic external to

the muscle cone, is thought to decrease the likelihood

of optic nerve and globe perforation while maintaining

the desirable qualities of excellent akinesia and

anesthesia. However, the higher volume of injectate

required and the longer duration of onset may make it a

less attractive alternative. Sub-Tenon’s injections with

blunt cannulas have an even lower risk of local

complications [21]. With all orbital block anesthesia,

cosmetic complications such as localized swelling,

bruising, and subconjuctival hemorrhage may lead to

reduced patient satisfaction. In addition, eye movement

and vision are affected for some time after surgery.

Topical anesthesia is the most cost and time

efficient. Topical does not affect vision or motility, so

patients may have improved and useful vision almost

immediately after surgery. There are also minimal

cosmetic changes. As a result, if patients have no pain

or discomfort during surgery, patient satisfaction may

be improved. Topical also avoids the systemic risks

of general anesthesia and the risk of local trauma that

occurs with regional blocks. Rare local allergic reac-

tions do occur. The disadvantage to topical anesthesia

is that it provides the least controlled environment for

cataract surgery. Patients are able to move their eyes

as well as any other part of their bodies. They per-

ceive visual phenomena as the case proceeds. Pain

and pressure may be experienced with intraocular

pressure changes as the lens– iris diaphragm move.

These sensations may be reduced with intravenous

sedation or analgesia, maneuvers such as entering the

eye with low bottle height, or with the use of intra-

cameral anesthetics [22]. However, even with all of

the above, patients may still experience some dis-

comfort. In addition, the duration of anesthetic effect

is typically less than an hour. Even in uncomplicated

cases there may be a loss of effect by the end of a case.

Choosing anesthesia

It is essential that the surgeon, patient, and

anesthesia staff work together and be involved in

Page 83: Anestesia Ocular

navaleza et al236

the selection and execution of anesthesia during the

surgery. Involving the patient in this decision by

describing the patient experience before and during

surgery is critical. Fear and anxiety result when things

are unknown or unexpected. If patients are prepared,

they are better equipped to cope with the sensations

they may feel during and after surgery. Anesthesia

staff, whether a physician or nurse anesthetist should

also be involved and know the patient. Modulation

of intravenous sedation can play a key role during

surgery. Increasing sedation as needed during surgery

can reduce discomfort, provide akinesia, and ulti-

mately may result in some amnesia that can result in

better outcomes. This may be particularly important

with topical anesthesia, and the degree of intravenous

sedation may vary widely from surgeon to surgeon,

and from case to case.

Some of the indications for general anesthesia for

cataract surgery include pediatric patients, patients

who are unable to cooperate, lengthy procedures

(> 3 hours), and patient or surgeon preference. Most

surgery in children is performed under general anes-

thesia. Patients with psychiatric disorders, dementia,

tremor, and inability to lie flat are at risk to move

or even attempt to sit up during surgery. Longer pro-

cedures may exceed the duration of action of regional

blocks; some complex anterior segment surgeries

such as suturing lenses can take hours in some hands.

Patients may ultimately feel that they will not be able

to cooperate during surgery and request general anes-

thesia. Finally, the surgeon may choose general an-

esthesia for certain patients. Again, general does

provide the most controlled environment. This may

be ideal for the beginning surgeon. In teaching

institutions, it would also allow the attending surgeon

and the resident surgeon to communicate more freely

during surgery.

General and topical anesthesia should also be

considered in patients on anticoagulation treatment;

general is preferable when complete ocular akinesia is

desired. Patients with nystagmus may not be able to

fixate and ocular akinesia can only be attained with

regional or general anesthesia. Anatomic abnormali-

ties such as an abnormally long axial length may

make topical or general anesthesia a safer alternative.

There are patients in which general anesthesia is

contraindicated or should be undertaken with caution.

Myotonic dystrophy patients develop cataracts at a

younger age; these patients are at risk of cardiac and

respiratory complications under general anesthesia

[23,24]. Marfan’s patients are subject to lens sub-

luxation and dislocation; they are also at increased

risk of cardiac and pulmonary complications under

general anesthesia [25,26]. Other modes of anesthesia

should be considered in patients with a family his-

tory of malignant hypertension. Thorough review

of medications is necessary, because some ocular

medications may interfere with general anesthesia.

Topical epinephrine used to treat glaucoma may

interact with halogenated hydrocarbon anesthetics

leading to ventricular fibrillation [27]. Echothiophate,

which in the past was used to treat glaucoma, inhibits

plasma pseudocholinesterase, which also metabolizes

anesthetics including succinylcholine leading to over-

dosing [28].

Regional blocks provide some benefit over topical

for patients who are unable to follow directions, such

as when the patient is hearing impaired or there is a

language barrier. It obviously does not prevent patient

movement. The ocular akinesia and longer duration of

effect make it a more ideal mode of anesthesia in cases

in which the primary surgeon is a physician in training.

Topical anesthesia provides the least controlled

environment for cataract surgery. The surgeon must

be able to tolerate some ocular motility, the patient

should be able to follow directions, and the anesthe-

sia staff must be willing to modulate intravenous

sedation. Topical has the shortest duration of action.

If the surgeon anticipates that he or she can complete

the case in a reasonable time frame and the other

conditions are met, topical anesthesia may ultimately

be the safest mode of anesthesia as it avoids the

systemic risks of general anesthesia and the risk of

local trauma that accompanies regional blocks. For

many patients and surgeons this mode of anesthe-

sia fulfills all of the goals of anesthesia in cataract

surgery. This is perhaps the reason that it has become

the most popular form of anesthesia.

It seems every few years we further perfect the

cataract operation. We make it safer, faster, better, and

more atraumatic. And just when we think we cannot

improve it any more, we do. Hand in hand with our

evolving surgical technique has come concepts in

ocular anesthesia that bring these surgical advances to

our patients in the safest and most efficient manner.

While it seems unbelievable that we can further re-

duce the stress of cataract surgery and cataract sur-

gery anesthesia any further, our history should tell

us otherwise.

References

[1] Esser A. The first cataract surgery under general

anesthesia. Klin Monatsbl Augenheilkd 1954;125(5):

610–4.

[2] Knapp H. On cocaine and its use in ophthalmic and

general surgery. Arch Ophthalmol 1884;18:402–48.

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[3] Atkinson WS. Local anesthesia in ophthalmology. Am

J Ophthalmol 1948;31:1607–18.

[4] Davis DB, Mandel MR. Posterior peribulbar anesthe-

sia: an alternative to retrobulbar anesthesia. J Cataract

Refract Surg 1986;12:182–4.

[5] Whitsett J, Baleyat H, McClure B. Comparison of one-

injection-site peribulbar anesthesia and retrobulbar

anesthesia. J Cataract Refract Surg 1990;16:243–5.

[6] Leaming D. Practice styles and preferences of ASCRS

members—2003 survey. J Cataract Refract Surg 2004;

30:892–900.

[7] Koller C. On the use of cocaine for producing

anaesthesia on the eye. Lancet 1884;2:990–2.

[8] Fichman R. Use of topical anesthesia alone in cataract

surgery. J Cataract Refract Surg 1996;22:612–4.

[9] Gills JP, Cherchio M, Raanan MG. Unpreserved

lidocaine to control discomfort during cataract surgery

using topical anesthesia. J Cataract Refract Surg 1997;

23:545–50.

[10] Barequet IS, Soriano ES, Green WR, et al. Provision of

anesthesia with single application of lidocaine 2% gel.

J Cataract and Refract Surg 1999;25:626–31.

[11] Kershner R. Topical anesthesia for small incision self-

sealing cataract surgery. A prospective evaluation of

the first 100 patients. J Cataract Refract Surg 1993;18:

290–2.

[12] Fukasaku H, Marron J. Pinpoint anesthesia: a new ap-

proach to local ocular anesthesia. J Cataract Refract

Surg 1994;20:468–71.

[13] Patel B, Burns T, Crandall A, et al. A Comparison of

topical and retrobulbar anesthesia for cataract surgery.

Ophthalmology 1996;103:1196–203.

[14] Crandall A, Zabriskie N, Patel B. A comparison of

patient comfort during cataract surgery with topical

anesthesia versus topical anesthesia and intracameral

lidocaine. Ophthalmology 1999;6:60–6.

[15] Pandey SK, Werner L, Apple DJ, et al. No-anesthesia

clear corneal phacoemulsification versus topical and

topical plus intracameral anesthesia: randomized

clinical trial. J Cataract Refract Surg 2001;27(10):

1643–50.

[16] Backer CL, Tinker JH, Robertson DM, et al. Myo-

cardial reinfarction following local anesthesia for

ophthalmic surgery. Anesth Analg 1980;59:256–62.

[17] Lang DW. Morbitity and mortality in ophthalmology.

In: Bruce RA, McGoldrick KE, Oppenheimer P,

editors. Anesthesia for ophthalmology. Birmingham

(AL)7 Aesculapius Publishing; 1982. p. 195.

[18] Lynch S, Wolf GL, Berlin I. General anesthesia for

cataract surgery: a comparative review of 2217

consecutive cases. Anesth Analg 1974;53:909–13.

[19] Edge KR, Nicoll JM. Retrobulbar hemorrhage after

12,500 retrobulbar blocks. Anesth Analg 1993;76(5):

1019–22.

[20] Morgan CM, Schatz H, Vine AK, et al. Ocular

complications associated with retrobulbar injections.

Ophthalmology 1988;95:660–5.

[21] Greenbaum S. Ocular anesthesia. Philadephia7 W B

Saunders Company; 1997. p. 1–57.

[22] Fichman RA. Topical anesthesia. Ophthalmol Clin

North Am 1998;11:60.

[23] Luntz MH. Clinical types of cataracts. In: Duane TD,

editor. Clinical ophthalmology. Philadelphia7 JB Lip-

pincott; 1988. p. 14.

[24] Aldridge LM. Anaesthetic problems in myotonic

dystrophy: a case report and review of the Aberdeen

experience comprising 48 general anesthetics in a

further 16 patients. Br J Anaesth 1985;57:1119–30.

[25] Wells DG, Podolakin W. Anesthesia and Marfan’s

syndrome: case report. Can J Anesth 1987;34:311–4.

[26] Mostafa SM. Anaesthesia for ophthalmic surgery.

Oxford7 Oxford University Press; 1991.

[27] Janssens ML, Cockx F. A case of ventricular fibrilla-

tion during halothane anesthesia caused by eye drops.

Acta Anaesthesiol Belg 1979;30(4):273–5.

[28] DeRoeth A, Dettbar WD, Rosenberg P. Effect of

phospholine iodide on blood cholinesterase levels.

Am J Ophthalmol 1963;59:586– 92.

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Ophthalmol Clin N

Anesthesia Considerations for Vitreoretinal Surgery

Steve Charles, MDa,b,T, Gary L. Fanning, MDc

aUniversity of Tennessee, College of Medicine, 6401 Poplar Avenue, Suite 190, Charles Retina Institute,

Memphis, TN 38119, USAbColumbia University, New York, NY, USA

cHauser-Ross Eye Institute, 2240 Gateway Drive, Sycamore, IL 60178, USA

Regardless of the type of anesthesia contemplated

for vitreoretinal (VR) surgery, the patient should

undergo a thorough preoperative evaluation before

the procedure. Under most circumstances this eval-

uation should occur well before the day of surgery so

that required adjustments can be performed in ad-

vance to help ensure that the patient is in optimal

condition before surgery. Specific investigations, such

as chest radiography, electrocardiogram, and blood

chemistries, should be performed only when dic-

tated by the findings of thorough history and physical

examinations. So-called ‘‘screening labs’’ are not in-

dicated when the appropriate history and physical

examinations are negative [1].

General versus local anesthesia

Both general and local anesthetic techniques are

acceptable for VR surgery; however, many retinal

surgeons prefer to do the vast majority of these cases

using monitored local anesthesia for the following

reasons: (1) local anesthesia offers increased safety

for patients, especially those in high-risk categories;

(2) local anesthesia saves time and reduces cost; and

(3) local anesthesia provides rapid recovery and pro-

longed analgesia, both of which are especially im-

portant in the outpatient population.

0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights

doi:10.1016/j.ohc.2006.02.002

T Corresponding author. University of Tennessee, Col-

lege of Medicine, 6401 Poplar Avenue, Suite 190, Charles

Retina Institute, Memphis, TN 38119.

E-mail address: [email protected] (S. Charles).

Not all patients are appropriate candidates for VR

surgery under local anesthesia. Immature, mentally

deficient, claustrophobic, and uncooperative patients

are best managed with general anesthesia. Patients

with language barriers, however, can frequently be

managed extremely well with local anesthesia if a

competent translator can be found. Estimated surgical

time is an additional consideration when choosing

general versus local anesthesia. Surgeons requiring

more than 90minutes for a given VR procedure should

consider general anesthesia over local anesthesia,

because patients may become restless and uncomfort-

able when asked to lie completely still for such long

periods. An additional indication for general anesthesia

is the patient who insists on it, although these patients

will be rare if properly informed and reassured by a

sympathetic surgical team.

Monitoring during surgery

Regardless of the type of anesthesia used, the

patient must be carefully monitored during surgery.

Appropriate monitoring begins with the continuous

presence of an anesthesiologist or certified registered

nurse anesthetist (CRNA) during the entire proce-

dure. If sedation is being given, it is not in the pa-

tient’s best interest to have the surgeon or circulating

nurse monitoring the patient, as may be the case in

a brief procedure performed under strictly local

anesthesia without sedation. Basic monitoring in-

cludes continuous electrocardiogram, noninvasive

blood pressure (NIBP), and pulse oximetry. End-tidal

CO2 monitoring is additionally essential during

Am 19 (2006) 239 – 243

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charles & fanning240

general anesthesia and can also be helpful during

local anesthesia, especially when continuous sedation

techniques are used. Core temperature monitoring is

indicated during longer procedures under general

anesthesia to help ensure that thermal preservation

procedures are successful and to help in monitoring

for the rare occurrence of malignant hyperthermia.

In diabetic patients, the ability to monitor blood

glucose in the intra- and perioperative periods is also

important to recognize and treat extremes of both

hyper-and hypoglycemia.

Blood pressure considerations during general

anesthesia

It is common for VR surgeons to become

angry if the patient moves at all during surgery. An

unintended consequence of this tendency is for the

anesthesia provider to maintain deeper levels of

anesthesia to prevent movements, which may result

in systemic blood pressures that are low enough to

compromise cerebral, myocardial, and retinal perfu-

sion. During VR surgery, intraocular pressure (IOP)

should be controlled in the 35-45 mm Hg range.

Ocular ischemia and central retinal artery occlusion

can occur if low systemic blood pressures are allowed

to persist during the procedure. To ensure adequate

levels of general anesthesia and immobility of the

patient, adequate, monitored muscular paralysis com-

bined with processed electroencephalogram (ie, bi-

spectral analysis) monitoring should be considered

so that excessively deep levels of general anesthesia

can be avoided.

Sedation during local anesthesia

In general, patients having VR surgery under local

anesthesia should have minimal sedation, most of

which should be given at the time of the block.

Patients should not be sedated too deeply during VR

surgery for a number of reasons. In the first place,

airway obstruction may occur, requiring manual

support and interruption of the procedure. This has

been described as AWAC (anesthesia without airway

control). Second, respiratory movements during sleep

or near sleep often result in magnified movements of

the head, which greatly hinder the progress of the

surgeon who is seeing these movements magnified

20 to 40 times through the operating microscope.

Third, some patients become quite talkative and social

when overly sedated. It may be impossible for them to

quit talking and moving despite the most vigorous

admonitions to do so. The only way to manage these

patients is to stop all sedation completely or to convert

to general anesthesia. Finally, patients who are asleep

or nearly asleep are prone to awakening suddenly

and completely unpredictably and being totally

disoriented, resulting in movements that can be devas-

tating, even in the hands of the finest surgeon.

Judicious amounts of sedatives or opioid agents can

be helpful during local anesthesia for VR surgery,

especially in the patient who is very apprehensive

or slightly claustrophobic. Methohexital, thiopental,

midazolam, propofol, alfentanil, remifentanil, keta-

mine, and others have been promoted to provide good

operating conditions and acceptable patient satisfac-

tion for a variety of procedures performed under lo-

cal anesthesia. For VR surgery, the emphasis must be

placed on balancing patient comfort and satisfaction

while providing the most stable conditions for surgery.

In general this means using small doses of rapid- and

short-acting drugs given continuously with very care-

ful monitoring of effect. The goals are to assist the

patient in lying perfectly still for 60 to 90 minutes

without falling asleep, to enhance analgesia, and to

provide a measure of amnesia. These goals are not

easily achieved, but they can be accomplished in most

patients by an experienced and knowledgeable anes-

thesia team.

Psychological preparation for local anesthesia

In preparing patients for VR surgery under some

form of local anesthesia, it is important to give them

specific details about the experience so that they will

suffer no surprises. They need to know about the

drape and about not being able to see during the

procedure. They also need to know that plenty of fresh

air will be provided for them under the drape and that

breathing under the drape will not be a problem. This

is the perfect opportunity to discuss the patient’s fears,

such as claustrophobia, positional dyspnea, positional

pain, and similar concerns. One may discover during

these discussions that a particular patient might be

better managed with general anesthesia.

The patient should also be given a realistic es-

timate of the length of time for the procedure and the

need for lying extremely still. Almost anyone can lie

still for 30 to 45 minutes, but for longer procedures

the patient must be reassured that short ‘‘time outs’’

can be arranged to allow for some movement.

Patients must also be aware that an anesthesia

provider will be constantly present and dedicated to

monitoring their condition and to act as liaison with

the rest of the team. It is extremely important for the

Page 87: Anestesia Ocular

anesthesia considerations for vitreoretinal surgery 241

anesthesia provider and surgeon to communicate

freely during the procedure, both with each other

and with the patient. Simple means for communica-

tion with minimal movement, such as hand-holding

or hand-held signaling devices, give the patient a

feeling of comfort in knowing that it is possible to

alert the team to a problem while not jeopardizing the

surgical field. If the patient cannot speak English, it

is imperative to have a translator in the room who

is fluent in the patient’s native language.

Choice of local anesthesia

There are essentially four types of local anesthesia

commonly used in ophthalmic surgery: topical, retro-

bulbar, peribulbar, and sub-Tenon’s. Topical anesthe-

sia is useful in a variety of operations, but it has

limitations in VR surgery because of the need for

complete akinesia during many VR procedures, such

as macular surgery and membrane peeling. The terms

retrobulbar and peribulbar are confusing and impre-

cise, and they should perhaps be replaced by the

terms intraconal and extraconal, which more accu-

rately describe the intended location of the needle in

the orbit. These techniques carry a risk, albeit small,

of major complications, such as ocular perforation,

bleeding, and brainstem anesthesia, but both are very

useful for VR surgery, providing excellent akinesia,

anesthesia, and prolonged postoperative analgesia.

Sub-Tenon’s anesthesia offers an increased level

of safety over intraconal and extraconal techniques.

Sub-Tenon’s may not be appropriate for patients who

have had previous scleral buckling, as scleral per-

foration with a sub-Tenon’s cannula has been re-

ported in such a patient [2]. A recent report by Lai

et al [3] compared the use of orbital regional anes-

thesia with sub-Tenon’s anesthesia for retinal surgery

and found that both had similar efficacy profiles.

Technique for intraconal anesthesia

A 25- or preferably a 27-gauge sharp needle is

preferred over larger needles and blunt so-called

‘‘retrobulbar’’ needles, which cause much more pain

when entering the orbit. [4] In addition, retrobulbar

needles often penetrate the septum abruptly after

considerable force is applied and may then perforate

the eye. The conventional 1.5-inch needle is too long

for many orbits and should be replaced by a 1- to

1.25-inch needle to avoid impaling the optic nerve in

the orbital apex. The entry point should be at the

outer ‘‘corner’’ of the orbital rim, not at the outer one

third, inner two thirds junction to reduce potential

damage to the eye and inferior oblique muscle. The

needle should not be directed apically but rather

posteromedially to intersect a sagittal plane through

the lateral limbus about 5 to 10 mm behind the pos-

terior surface of the eye [4]. The authors use 2% plain

lidocaine without epinephrine to reduce the risk of

arrhythmias and hypertension and avoid using bicar-

bonate because of reports and personal experience

with lateral rectus paralysis for months after surgery.

The author recommends applying pressure on the

entire orbit with the palm of the hand immediately

after withdrawing the needle to reduce bleeding and

disperse the anesthetic agent. If hyaluronidase is used

in the block mixture, its concentration should be

limited to 1 unit per milliliter, as higher concentra-

tions are not necessary [5].

Reblocking during the procedure

Sometimes local anesthesia must be supplemented

during surgery. This can occasionally be accomplished

with topical anesthesia, but we most commonly

supplement intraoperatively by placing a flexible

cannula into Tenon’s space and injecting additional

local anesthetic. An additional intraconal injection can

also be performed by placing the needle between

Tenon’s capsule and the sclera to enter the intraconal

space. Most often reblocking is necessary when the

block has been inadequate, when the patient is a

reoperation, and when the procedure is prolonged.

Facial nerve blocks

Separate facial nerve blocks are rarely indicated,

especially if a well-performed extraconal or high-

volume intraconal block is used. Avoiding a facial

nerve block spares the patient a painful injection and

prevents the bleeding, swelling, and other complica-

tions that occasionally accompany these blocks. If the

patient is a marked ‘‘squeezer,’’ the orbicularis oculi

can be easily and effectively blocked by inserting a

one-half-inch 30-gauge needle transconjunctivally

into the lower lid just beneath the orbicularis and

injecting about 1.5 mL of local anesthetic.

Sources of pain during VR surgery

Local anesthesia needs to be quite complete if the

experience is to be pain-free. Manipulation of the iris,

ciliary body, and sclera can all be painful, especially

Page 88: Anestesia Ocular

charles & fanning242

if blunt instruments are being used. Thermal stim-

ulation is also an important source of discomfort.

Cryopexy is very painful, more so than laser or even

radiofrequency cautery (bipolar diathermy). Lasers in

the near-infrared range are more painful than the ar-

gon laser at 514 nm or the diode-pumped, frequency-

doubled CW YAG laser at 532 nm. As one or

more of these modalities may be used during VR sur-

gery, it is important that the patient receives ade-

quate anesthesia.

Carbon dioxide issues

Patients lying awake under the drape frequently

complain that they ‘‘cannot get enough air.’’ Because

pulse oximetry routinely records normal oxygen

saturation in these patients, their complaints are

frequently attributed to anxiety. In fact, CO2 often

builds up under the drape, resulting in hypercarbia

and a feeling of air hunger. This may be noted by a

rise in the baseline if capnography is being used,

even though the peak expired CO2 may be normal

or only slightly elevated. An easy solution to this

problem is to ensure adequate air/oxygen supplemen-

tation near the patient’s nose and mouth as well as

active evacuation of the exhaled gases by way of a

large bore vacuum line placed under the drapes. The

vacuum line also facilitates cooling, which can be an

issue as well. If laser or electrocautery are to be

used, it is important to use only air under the drape to

avoid the dangers of fires attended by an oxygen-

enriched atmosphere.

Air/gas and general anesthesia

If gas or air are introduced into the eye during VR

surgery, nitrous oxide should be turned off at least

10 minutes beforehand and fresh gas flow into the

anesthesia machine should be increased to ensure

adequate washing out before introduction of the gas.

Failure to do so results in a smaller-than-desired gas

bubble within the eye and lower-than-desired IOP

postoperatively when nitrous oxide diffuses out of the

bubble. Conversely, if a patient has a bubble in the

eye from a previous procedure, nitrous oxide should

be avoided from the beginning to prevent expansion

of the bubble by diffusion of nitrous oxide into it,

thus raising IOP. In fact, patients must be warned

both verbally and in writing to alert physicians to the

presence of the bubble should they require emergency

surgery for a nonophthalmic condition and of the

dangers of air travel for as long as the bubble is

present [6].

Anesthetic considerations for specific procedures

Endophthalmitis

Endophthalmitis is an acute situation in which

cultures must be taken and therapy instituted as

quickly as possible. In many situations, cultures and

even core vitrectomy can be performed under topical

anesthesia. If general anesthesia is required, surgery

cannot be delayed to allow the stomach to empty.

The open globe

Each patient must be thoroughly evaluated, as

choice of anesthesia will depend on the extent of the

injury and the ability of the patient to cooperate.

Often initial wound closure can be accomplished

under topical and intracameral anesthesia. In cooper-

ative patients with limited damage, orbital regional

anesthesia can be safely used [7], provided that the

person performing the block has had sufficient

experience, uses limited volumes of anesthetic, and

injects very slowly (ie, 1 mL every 30 to 60 seconds)

while closely watching the eye. When general

anesthesia is required, the issue of whether or not to

use a depolarizing muscle relaxant arises. Because

there are advocates on both sides of this issue, the

choice must be left to the anesthesia provider who

will make a decision based on the total clinical pic-

ture. If general anesthesia is required, allowing suf-

ficient time (6 to 8 hours) for the stomach to empty

should be seriously considered.

Scleral buckles

Many presenting for scleral buckling procedures

will be high myopes. These patients have long axial

lengths, often accompanied by posterior staphylomata

and scleral thinning. Sub-Tenon’s cannula techniques

might be considered in these patients to lessen the

risk of perforation, provided that long cannulae ap-

proaching the posterior half of the globe are avoided.

Regional anesthesia for scleral buckling proce-

dures may be complicated by the fact that the orbital

retractor can cause significant orbital rim pain even in

the presence of complete ocular anesthesia. Addi-

tionally, with traction of the extraocular muscles the

oculocardiac reflex may occur. Most commonly the

resulting bradycardia will return to normal when

traction is released, and the reflex will diminish over

Page 89: Anestesia Ocular

anesthesia considerations for vitreoretinal surgery 243

time. Intravenous atropine is more effective than gly-

copyrrolate in blocking the reflex, but its use is as-

sociated with the higher incidence of subsequent

tachyarrhythmias. Local anesthetic injection may

block the bradycardia, but the reflex is also seen in

the presence of a complete block.

Patients who have had previous scleral buckles

and present for another procedure may be difficult to

block. Because the buckling may slightly elongate

the eye, one must be aware of an increased danger

for perforation. Because scarring occurs, normally

‘‘safe’’ procedures may be come less safe, and ocular

perforation has been reported with sub-Tenon’s anes-

thesia in a patient with a previous scleral buckle [2].

Anticoagulation issues

In our practice we virtually never stop anti-

coagulation before VR surgery, although it is wise

to ensure that the patient taking warfarin compounds

has an International Normalized Ratio in the thera-

peutic range (generally 2 to 3). Stopping anticoagu-

lants risks causing morbidity or mortality from a

variety of causes, including stroke, myocardial in-

farction, pulmonary embolism, and deep venous

thrombosis. In our opinions the dangers of intra-

operative hemorrhage are grossly overemphasized

when compared with the dangers of stopping thera-

peutic anticoagulation. Use of cannula techniques for

local anesthesia greatly reduces the risk of hemor-

rhage in these patients, as does the use of short

needles (1 to 1.25 inches) placed in the less vascular

areas of the orbit (ie, avoiding the superior half of

the orbit in general and especially the superonasal

quadrant) for orbital blocks.

Postoperative pain

One source of postoperative pain is the injection

of antibiotics and steroids into the periocular tissues

at the end of the procedure. This pain can be reduced

by injecting these substances into the sub-Tenon’s

space with a cannula if conjunctival incisions have

been made, which is not the case with 25-gauge,

sutureless surgery. In addition, injection of a long-

acting local anesthetic, such as bupivacaine, at the

end of the procedure with a flexible cannula can

greatly reduce postoperative pain. This is especially

important in the occasional patient who requires

general anesthesia for VR surgery and those under-

going scleral buckles.

Summary

The vast majority of VR procedures can be safely,

comfortably, and efficiently performed under local

anesthesia with minimal sedation. Compared with

general anesthesia, properly performed monitored

local anesthesia offers the patient an increased level

of safety, reduced recovery times, and prolonged

postoperative pain relief. Nonetheless, the choice of

anesthesia technique must be based on the needs of

the patient, the requirements of the surgeon, and the

skills of the anesthesia provider, ever keeping in mind

that our ultimate goal is a satisfied patient with a good

visual outcome.

References

[1] Schein OD, Katz J, Bass EB, et al. The value of routine

preoperative medical testing before cataract surgery.

Study of medical testing for cataract surgery. N Engl J

Med 2000;342:168–75.

[2] Frieman BJ, Friedberg MA. Globe perforation asso-

ciated with subtenon’s anesthesia. Am J Ophthalmol

2001;131:520–1.

[3] Lai MM, Lai JC, Lee WH, et al. Comparison of retro-

bulbar and sub-Tenon’s capsule injection of local anes-

thetic in vitreoretinal surgery. Ophthalmology 2005;112:

574–9.

[4] Kumar CM, Fanning GL. Orbital regional anaesthesia.

In: Kumar CM, Dodds C, Fanning GL, editors. Oph-

thalmic anaesthesia. Lisse (The Netherlands)7 Swets &

Zeitlinger B.V.; 2002. p. 61–88.

[5] Fanning GL. Hyaluronidase in ophthalmic anesthesia

[letter]. Anesth Analg 2001;92:560.

[6] Seaberg RR, FreemanWR, GoldbaumMH, et al. Perma-

nent postoperative vision loss associated with expansion

of intraocular gas in the presence of a nitrous oxide-

containing anesthetic. Anesthesiology 2002;97:1309–10.

[7] Scott IU, Gayer S, Voo I, et al. Regional anesthesia with

monitored anesthesia care for surgical repair of selected

open globe injuries. Ophthalmic Surg Lasers Imagining

2005;36:122–8.

Page 90: Anestesia Ocular

Ophthalmol Clin N

Anesthesia for Glaucoma Surgery

Tom Eke, MA (Cantab), MD, FRCOphth

Norfolk & Norwich University Hospitals NHS Trust, Colney Lane, Norwich NR4 7UY, UK

Glaucoma surgery can be done using any of

the established anesthesia techniques. Each technique

has its advantages and disadvantages, as outlined in

Tables 1 and 2. Retrobulbar and peribulbar injections

are particularly associated with the risk of sight-

threatening and life-threatening complications, in any

patient. Glaucoma patients may be at increased risk of

sight-threatening complications from orbital injec-

tions because the optic nerve is already compromised

and vulnerable to pressure/ischemic damage (Table 3).

Therefore, there has been much interest in the less

invasive techniques of local anesthesia for glaucoma

patients, with anterior placement of local anesthesia

(anterior sub-Tenon, subconjunctival, topical, and

intracameral techniques) [1]. These ‘‘newer’’ tech-

niques appear to be successful in terms of safety and

patient acceptability. However, there is some uncer-

tainty regarding the effect of different anesthesia

techniques on complication and failure rates for

glaucoma surgery.

Factors influencing the choice of anesthesia

In planning any ocular surgery, it is appropriate to

ask ‘‘which is the most appropriate anesthetic, for this

operation, for this patient?’’ Numerous factors must

be considered, including nature of the operation to be

done; efficacy of the various anesthetic techniques;

acceptability to both patient and surgeon; safety is-

sues (ocular, orbital, and systemic complications of

anesthesia or per-operative and later surgical compli-

cations associated with each anesthetic technique);

demand on staff, hospital beds, and other resources;

speed, efficiency, and throughput of patients in the

0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights

doi:10.1016/j.ohc.2006.02.003

E-mail address: [email protected]

operating room; and financial issues (Tables 1 and 2).

The patient’s general health may influence the choice

of anesthesia, particularly the choice between general

anesthesia (GA) and local anesthesia (LA). Ocular

conditions themselves may also influence the choice

of anesthetic technique, and this is especially true in

the case of glaucoma (Table 3). Glaucoma is a

chronic condition characterized by progressive pres-

sure/ischemic damage to the optic nerve head, so it

would be logical to choose an anesthetic technique

that has a low risk of causing further damage to the

optic nerve. It is common for glaucoma patients to

require filtering surgery (eg, trabeculectomy) and

also cataract surgery, and many eyes with glaucoma

will require two or more operations. Therefore, the

long-term functioning of any previous or future

filtering surgery should also be considered when

deciding on the appropriate anesthesia technique for a

glaucoma patient.

In this article, the issues specific to glaucoma

patients are discussed. Other articles have discussed

the generic problems associated with each of the

LA techniques, which can be briefly summarized as

sight-threatening complications, life-threatening com-

plications, and surgical complications related to the

LA technique used (Table 2). General anesthesia has

the potential for various life-threatening complica-

tions, as discussed in any textbook of anesthesia.

Table 3 summarizes the concerns related to anesthesia

and glaucoma surgery, and the relative merits and

demerits of the various anesthesia techniques.

Optic nerve damage from anesthesia

If anesthetic agents are placed into the orbit be-

hind the globe, there is potential for damage to the

optic nerve. This damage could occur as a result of

Am 19 (2006) 245 – 255

reserved.

ophthalmology.theclinics.com

Page 91: Anestesia Ocular

Table 1

Factors influencing the choice of anesthesia technique for

any ocular surgery

Operation

to be done

How much of the eye/orbit needs to

be anesthetised?

Is total akinesia needed?

Any specific anesthetic requirements

for this operation? (see Tables 2, 3)

Patient factors

and comorbidity

General (eg, child; adult with very

poor general health)

Ocular (eg, glaucoma (see Table 3),

severe nystagmus)

Acceptability

of technique

To patient

To surgeon

To managers/providers

Use of

resources

Efficiency

Staff (eg, anesthetist, trained

assistants)

Hospital accommodation (eg, beds for

GA patients)

Back-up facilities required (eg, cardiac

arrest team, intensive care)

Cost (consumables, staffing costs, and

so forth)

Time taken per case

Number of cases done per operating

list

Safety Ocular/orbital complications of

LA/GA technique

Systemic complications of LA/GA

technique

Surgical complications related to

LA/GA technique

Late complications related to LA/GA

technique

Abbreviations: GA, general anesthesia; LA, local anesthesia.

eke246

direct trauma from a retrobulbar or peribulbar needle,

pressure on the nerve, or ischemia [2]. Potential

mechanisms are summarized in Table 3. For patients

whose optic nerve is already damaged by glaucoma,

this could result in further loss of vision.

The phenomenon of severe visual loss after sur-

gery, with no obvious cause, is known as ‘‘wipe-out’’

or ‘‘snuff syndrome.’’ Wipe-out is generally seen in

patients who already have a severe glaucomatous

visual field defect [3,4]. Local anesthetic injections

into the orbit have been postulated as a likely cause

for many cases of wipe-out [4]. Possible mechanisms

include unnoticed trauma to the optic nerve from the

anesthetic needle, or pressure on the optic nerve

owing to either a hematoma in the optic nerve sheath,

a retrobulbar hematoma, or simply from the volume

of anesthetic injected. High pressure around the nerve

could potentially occur even with a low volume of

LA, if the LAwere to become trapped between fascial

layers to give a ‘‘compartment syndrome.’’ This pres-

sure may also induce ischemia of the nerve, as may

epinephrine (adrenaline) in the LA mixture. While the

term ‘‘wipe-out’’ is reserved for severe loss of vision

after surgery, glaucoma patients are also at risk of

suffering a milder form of this condition.

There is a wealth of indirect evidence to support

the concept of orbital LA as a cause for wipe-out

syndrome. There have been numerous case-reports of

visual loss as a result of direct needle trauma to the

optic nerve, or secondary to high orbital pressure

from LA-induced orbital hemorrhage [2]. In a series

of 3 cases of hyaluronidase-associated orbitopathy,

the most severe and long-lasting visual loss occurred

in the one patient who had glaucoma [5]. Doppler

imaging studies have shown that retrobulbar injec-

tions can cause a marked reduction in blood flow

in the arteries supplying the anterior optic nerve,

particularly if epinephrine is included in the LA

mixture [6,7]. This effect is not seen with anterior

placement of LA, for example by subconjunctival

anesthesia [8]. A retrospective study of 508 trabecu-

lectomies identified four cases of wipe-out, all of

which had retrobulbar anesthesia [3].

The problems described above could potentially

occur with retrobulbar, peribulbar, or posterior sub-

Tenon’s LA. It would be very difficult to prove a

definite association between LA technique and wipe-

out or increasing field defects, because of difficulties

in case definition, the rarity of the condition, and the

problems encountered with any large randomized

prospective trial. However, the high index of suspi-

cion means that many glaucoma specialists now try to

avoid using these LA techniques for any surgery on

glaucoma patients [1]. Preferred techniques are GA,

anterior sub-Tenon’s, subconjunctival, topical, and

intracameral anesthesia. Small case-series indicate

that these techniques are acceptable to patients and

surgeons, but data are lacking as regards long-term

pressure control, complications, and visual field.

Effect of LA on the conjunctiva, and outcome of

filtering surgery

Conjunctival scarring, as a result of previous sur-

gery or topical medication, may significantly increase

the risk of trabeculectomy failure [9,10]. These

insults initiate an inflammatory response in the con-

junctiva and Tenon’s capsule, making a trabeculec-

tomy more likely to fail because of further scarring.

It would be logical to infer that any LA technique

that induces chemosis or subconjunctival hemorrhage

could increase the risk for failure for any future

trabeculectomy. Chemosis and hemorrhage are fre-

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Table 2

Safety factors to be considered when choosing an anesthesia technique for any patient undergoing intraocular surgery, and relative risk of each anaesthesia technique

General anesthesia

(GA)

Peribulbar local

anesthesia (LA)

Retrobulbar

LA

Sub-Tenon’s

LA

Subconjunctival

LA

Topical

LA

Topical-intracameral

LA

Sight-threatening

complications

Globe penetration or perforation � ++ ++ +/� + � �Optic nerve penetration or perforation � ++ ++ � � � �Severe orbital hemorrhage � ++ ++ +/� � � �Hyaluronidase orbitopathy � + + + � � �

Life-threatening

complications

Brainstem anesthesia � ++ ++ � � � �Oculo-cardiac reflex + �? �? �? +? +? +?

Other life-threatening adverse event ++ � � � � � �See text for fuller discussion.

Abbreviations: ++, significant potential risk of sight-threatening or life-threatening adverse event; +, lower potential risk; +/�, this adverse event is very rare with this technique, or

theoretical risk only; �, ‘no risk’ of this event occurring.

anesthesiaforglaucomasurgery

247

Page 93: Anestesia Ocular

Table 3

Additional safety concerns for the glaucoma patient when choosing anesthesia techniques for ocular surgery, and relative risk for each anesthesia technique

General

anesthesia

Peribulbar local

anesthesia (LA)

Retrobulbar

LA

Sub-Tenon’s

LA

Sub-conjunctival

LA

Topical

LA

Topical-intracameral

LA

Avoid risk of

further damage

to optic nerve

Direct trauma Inadvertent trauma from

LA needle

� ++ ++ � � � �

Pressure damage Volume effect of periocular LA � ++ + +/� � � �‘compartment syndrome’

(esp. if no hyaluronidase)

� + + +/� � � �

Hyaluronidase orbitopathy � + + + � � �Severe orbital haemorrhage � ++ ++ +/� � � �

Ischemic damage Pressure (see above) � ++ ++ +/� � � �Epinephrine � + + + � � �Systemic hypotension ++ � � � � � �

Consider functioning

of filtering surgery

Future filter Induction of conjunctival

scarring

� +/� +/� +? +? � �

Previous filter Re-activation of conjunctival

scarring

� +/� +/� +? +? � �

Filtering surgery

today

Induced scarring? (controversial,

see text)

� �? �? �? +? �? � �

See text for fuller discussion, and see also Table 2.

Abbreviations: ++, significant potential risk of sight-threatening adverse event; +, lower potential risk; +/�, very rare, or theoretical risk only; �, ‘no risk’ of this event occurring.

eke

248

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anesthesia for glaucoma surgery 249

quently seen with peribulbar, retrobulbar, and sub-

Tenon’s injections [2], particularly if the sub-Tenon’s

injection is more anterior or of larger volume [11].

For this reason, many glaucoma specialists prefer to

avoid these LA techniques for any surgery in patients

who may need filtering surgery in the future.

Some studies have suggested that the outcome of

trabeculectomy surgery itself may be influenced by

the anesthetic technique used, although published evi-

dence is inadequate at present. Observational studies

have suggested that subconjunctival LA may be

associated with an increased risk of bleb failure or

leakage, although there is no definite evidence to sup-

port this and some of the evidence is contradictory.

Noureddin and colleagues [12] published a study

that appeared to show a link between subconjunctival

anesthesia and thin-walled, leaking trabeculectomy

blebs. In a retrospective, nonrandomized observa-

tional study, they looked at 29 patients who had under-

gone trabeculectomy with GA approximately 1 year

previously, and compared them with 19 patients who

had LA with 2 mL of subconjunctival 2% lidocaine.

Intraocular pressure (IOP) control was good in both

groups, with better IOP in the subconjunctival anes-

thesia group. However, the incidence of thin-walled,

leaky (Seidel-positive) blebs was higher, at 77% in

the subconjunctival lidocaine group as opposed to

25% in the GA group. Leaky blebs are undesirable,

because they predispose the eye to bleb-related infec-

tion and potential blindness. The authors postulated

that lidocaine might have an inhibitory effect

on fibroblasts.

Edmunds and colleagues [13–16] found a possi-

ble link between subconjunctival anesthesia and poor

IOP control, although they did not report any

problems with late bleb leakage. They performed a

large prospective observational study of routine prac-

tice, which looked at 1450 primary trabeculectomies

performed by 382 surgeons [13]. ‘‘Success’’ was de-

fined as a one-third reduction in IOP, without the use

of antiglaucoma medications. At 1 year, ‘‘success’’

rate was 65.6% for the 555 peribulbar LA cases,

69.5% for the 424 GA cases, 65.7% for the 105 ret-

robulbar LA cases, 69.0% for the 59 sub-Tenon’s

cases, 39.5% for the 38 subconjunctival LA cases,

and 100% for the 6 topical LA cases. Multiple lo-

gistic regression compared ‘‘success’’ rates for sub-

conjunctival and peribulbar LA, and indicated an odds

ratio of 0.172 (95% confidence interval: 0.065–0.459,

P<.0001) [16], suggesting that subconjunctival anes-

thesia is associated with worse surgical outcome.

There was no further detail on the number of surgeons

who did the 38 cases (possibly as few as 10 surgeons),

or the specific techniques used for subconjunctival

LA. The authors speculated that subconjunctival LA

could possibly stimulate conjunctival fibroblasts or

cause hemorrhage, thus predisposing to a higher

failure rate. They concluded that the association

deserved further examination, and suggested a pro-

spective randomized trial of the type of LA in

trabeculectomy [16]. Edmunds and colleagues’ series

appears to have a much lower rate of bleb leak than

Noureddin and colleagues’. The actual rate of bleb

leakage at 1 year is not given, although the paper

implies that the overall rate was below 3% [15]. In

another study, Vicary and colleagues [17] looked at

1-year outcomes for phaco-trabeculectomy using

small volume (0.1- to 0.2-mL) subconjunctival 2%

lidocaine with epinephrine: IOP control was described

as ‘‘excellent,’’ with 72% of patients requiring no

glaucoma medication at 1 year. Thus, there appears to

be no agreement between these studies that looked at

anesthesia technique and trabeculectomy outcomes.

Each of these studies is observational in nature with

small numbers of subconjunctival anesthesia cases, so

these results should be interpreted with caution. In a

recent clinical audit, my colleagues and I looked at

results of primary trabeculectomy, using the same

criteria as Edmunds and colleagues’ study. We looked

retrospectively at the 1-year outcomes for two glau-

coma surgeons at the same institution, one of whom

routinely used peribulbar anesthesia, the other sub-

conjunctival lidocaine 0.5% (Rai C et al, submitted for

publication). Both techniques showed 1-year ‘‘suc-

cess’’ rates that were better than Edmunds’ series.

There was no bleb leakage at 1 year, but the

subconjunctival anesthesia group did appear to have

a higher rate of early leakage. We will be conducting a

prospective audit to see if this is a genuine phenome-

non, or simply reflects a higher degree of concern

about bleb leakage in patients who have had subcon-

junctival anesthesia.

There is some evidence that subconjunctival lido-

caine may indeed have an inhibitory effect on con-

junctival healing, as suggested by Noureddin and

coworkers. Studies on other tissues have found a

dose-dependent effect of lidocaine on wound

strength. The tensile strength of skin wounds has

been studied, following infiltration of the wound with

lidocaine 2%, 1%, 0.5%, and saline. Wound strength

was the same when 0.5% lidocaine or saline was

used, but 1% and 2% lidocaine gave significantly

weaker wounds [18,19]. Lidocaine 1% infiltration

was associated with decreased vascularity and fewer

collagen fibers, when compared with saline [18].

These findings could possibly explain Noureddin

and colleague’s high rate of bleb leakage with large

volumes (2 mL) of strong (2%) lidocaine [12]. It may

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be that lidocaine exhibits a dose-dependent inhibi-

tory effect on conjunctival healing, analogous to

the antimetabolites.

Data on specific LA techniques

Since the early 1990s, there have been numerous

papers describing ‘‘less invasive’’ LA techniques for

glaucoma surgery. Most have been either case-series

or small randomized trials of a few dozen patients.

Numerous techniques have been described, mainly

for trabeculectomy or combined cataract and tra-

beculectomy (phaco-trabeculectomy) surgery. They

include various methods of administering topical,

subconjunctival, anterior sub-Tenon’s, and intra-

cameral anesthesia. Most publications concentrate on

per-operative complication rates and acceptability to

patient and surgeon.

Studies on patient/surgeon acceptability should be

interpreted with caution, because it is difficult to

avoid bias. Even in prospective randomized studies,

both patient and surgeon are likely to be aware

whether they are using a periocular injection or one of

the ‘‘newer’’ techniques. This lack of masking may

influence acceptability scores. It is best if pain/

acceptability data are collected by an independent

person, who is unaware of the LA technique used and

without the presence of the surgeon or other person-

nel connected with the surgery. This means that pain

scores collected at the time of surgery may be biased

by the patient not wanting to displease the surgical

team, and pain scores collected after surgery may be

subject to recall bias. Most or all published studies

show good acceptability to the surgeon, but this may

simply reflect that the authors want to prove the

effectiveness of their favored technique, and tend to

recruit surgeons who feel likewise. In addition,

there is publication bias in that unfavorable studies

are less likely to be submitted and published. Despite

these caveats, it does appear that the ‘‘newer’’ LA

techniques are acceptable to most patients, and to

many surgeons.

The current literature should be considered in-

adequate, for several reasons. Terminology is not

consistent, with some authors using the terms ‘‘sub-

conjunctival’’ and ‘‘sub-Tenon’s’’ for what appears to

be the same technique, and others creating new terms

for minor variations on established techniques (peri-

limbal, contact, and so forth). Most of the safety

concerns outlined in Tables 2 and 3 cannot be ad-

dressed by these small studies, although it is possible

to infer from the larger studies of cataract patients that

these ‘‘newer’’ techniques ought to be safer than pe-

riocular injections [20,21]. Most studies have looked

at LA for trabeculectomy, with very few studies

looking at other glaucoma procedures such as cyclo-

ablation, glaucoma drainage devices, or nonpenetrat-

ing surgery. There is no direct evidence regarding the

possible effect of LA technique on the visual field, as

discussed in the section ‘‘Optic nerve damage from

anesthesia.’’ There is a definite need for studies that

look at success rates for filtering surgery and late

complication rates.

Subconjunctival anesthesia and anterior

sub-Tenon’s anesthesia

These two techniques will be considered together,

because of confusing use of terminology in the

glaucoma literature. In the literature related to cata-

ract surgery, there is a clear difference between the

two techniques, but the terms ‘‘sub-conjunctival’’ and

‘‘sub-Tenon’s’’ appear to be used interchangeably by

some authors in the glaucoma literature.

Both techniques were popularized by publications

in the early 1990s. Sub-Tenon’s LA for cataract

surgery was described by several authors, all of

whom used similar techniques [22–24]. A small cut

is made through conjunctiva and Tenon’s capsule, so

that a blunt cannula can be passed into the sub-

Tenon’s space, between Tenon’s capsule and sclera.

The LA agent can easily reach the back of the globe,

even with an anterior injection [25], and chemosis is

unlikely if small volumes are injected posteriorly via

a long cannula [11]. By contrast, subconjunctival LA

[26,27] is administered by means of a sharp needle,

the aim being to infiltrate the conjunctiva/Tenon’s

layer with the anesthetic agent. Therefore, subcon-

junctival LA will always induce chemosis in the area

where the LA is injected, and the LA is not expected

to reach the back of the globe. A sharp-needle sub-

Tenon’s (episcleral) LA technique has been described

[28], although some have raised concerns about the

risk of globe penetration by the needle. Many of

the descriptions of ‘‘sub-Tenon’s’’ anesthesia in the

glaucoma literature would be more accurately de-

scribed as ‘‘sub-conjunctival’’ anesthesia.

Ritch and Liebmann [29] were among the earliest

to describe this technique for glaucoma surgery. Their

original report was entitled ‘‘Sub-Tenon’s anesthesia

for trabeculectomy,’’ although they later referred to it

as a ‘‘subconjunctival’’ technique [30]. They used a

lid block, topical tetracaine, and then injected about

1 mL of 2% lidocaine or 2% mepivacaine via a

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anesthesia for glaucoma surgery 251

30-gauge needle, ‘‘beneath Tenon’s capsule over the

anterior portion of the superior rectus muscle,’’ with

smaller injections over the medial and lateral recti.

They wrote that ‘‘concerns regarding sensation

during iridectomy have proven to be unfounded,

and only rarely do patients complain of pain at

the time.’’

Buys and Trope [31] used a similar technique to

that of Ritch and Liebmann, and performed a

prospective randomized comparison with retrobulbar

anesthesia. All 39 patients had sedation using a

standard technique. Pain scores collected during and

after surgery were similar, and ‘‘creation of an

iridectomy was not associated with discomfort or a

response in the sub-Tenon’s group.’’ The ‘‘sub-

Tenon’s’’ group was less likely to require additional

LA during surgery (9% versus 60%), or analgesia

after surgery (32% versus 71%), and these differences

were both statistically significant.

Azuara-Blanco and colleagues [32] reported a

prospective randomized trial of ‘‘sub-conjunctival

versus peribulbar anesthesia in trabeculectomy.’’ All

patients had intravenous sedation and a facial nerve

block, using an identical technique. The LA agent

was the same for the 30 peribulbar and 30 subcon-

junctival injections (2% mepivacaine with 0.75%

bupivacaine), except for the omission of hyaluroni-

dase from the subconjunctival group. Subconjuncti-

val injections were given in the supero-temporal

quadrant, 8 to 10 mm posterior to the limbus, ‘‘bal-

looning the superior conjunctiva.’’ During surgery,

patients were asked to grade their pain as none, mild,

moderate, or severe. There was a low pain score for

both groups, with all episodes of pain (20% in the

subconjunctival group and 7% in the peribulbar

group) rated as mild. This difference did not reach

statistical significance. The authors concluded that

their technique was well tolerated, although ‘‘mild

intra-operative discomfort and eye movements should

be expected.’’

Anderson [33] described a modification of the

subconjunctival LA technique, which he called

‘‘circumferential perilimbal anesthesia.’’ A small in-

jection of 0.25 mL lidocaine 4% was injected through

the inferior conjunctiva, ‘‘to avoid the possibility of a

button-hole in the superior conjunctiva.’’ The anes-

thetic was then spread subconjunctivally around the

limbus for 360 degrees, using smooth forceps. All pa-

tients were sedated, and 1 of 34 phaco-trabeculectomy

patients complained of pain during surgery.

Vicary and colleagues [17] looked at surgical

outcomes 1 year after phaco-trabeculectomy using

subconjunctival anesthesia. They used topical lido-

caine 4% and a small volume (0.1 to 0.2 mL) of

subconjunctival 2% lidocaine with 1:200,000 epi-

nephrine. Charts were reviewed retrospectively for 38

consecutive cases. At 1 year, 72% of patients had

‘‘controlled IOP without additional medication’’ and

overall IOP control was described as ‘‘excellent.’’

Bleb leak is not mentioned.

Bellucci and colleagues [34] described a ‘‘true’’

sub-Tenon’s anesthesia technique for phaco-

trabeculectomy. A conjunctival limbal incision was

commenced as for a standard fornix-based trabecu-

lectomy using topical lidocaine 4% anesthesia. A

plastic cannula was then passed into the sub-Tenon’s

space near to the superior rectus, to inject 1.5 mL of

mepivacaine 2%. Retrospective review of 50 cases

showed that only one patient required supplementary

sub-Tenon’s anesthesia, and the per-operative and

early complication rates were similar to a cohort of

50 patients who had peribulbar anesthesia.

Kansal and colleagues [35] describe a similar

technique in which ‘‘true’’ sub-Tenon’s anesthesia is

augmented with intracameral anesthesia. This is

discussed in the ‘‘Combined LA techniques’’ section

later in this article.

Topical anesthesia techniques

Several studies have described using topical

anesthesia for trabeculectomy, with or without the

use of sedation. Techniques include LA drops alone,

application of LA in gel form, or via an applicator

made of spongelike material. Topical anesthesia may

be combined with any of the other LA techniques

discussed below.

Jonas [36] describes using topical oxybuprocaine

0.4% (Benoxinate) eyedrops, followed by topical

cocaine 10%, for all of his routine trabeculectomy

surgery. Patients are instructed to gaze in the desired

direction, so that superior rectus or corneal traction

sutures are not used. An earlier study compared this

technique with retrobulbar anesthesia in a prospective

randomized study of 20 patients [37]. Intravenous

infusion was set up, but the authors do not state

whether the patients had any sedation. Pain scores

were similarly low in both groups, and none of the

topical anesthesia patients thought that the surgery

was more painful than having the intravenous needle

put into the back of their hand. In a subsequent series

of 69 consecutive cases, there were no per-operative

complications that could be attributed to a mobile

eye, and ‘‘when asked which type of anesthesia they

would prefer if the same type of surgery would have

to be repeated, the patients answered they preferred

topical anesthesia’’ [36].

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eke252

Ahmed and colleagues published randomized

trials comparing topical bupivacaine drops with

retrobulbar anesthesia, for trabeculectomy [38] and

for phaco-trabeculectomy [39]. All patients were se-

dated. Different sedative agents were used for each

group and pain scores were collected postoperatively,

therefore the results are difficult to interpret. The

authors felt that both techniques were similarly well

tolerated by patients.

Pablo and colleagues [40] described a technique of

‘‘contact-topical’’ LA for trabeculectomy. An absorb-

able gelatin sponge was soaked in lidocaine 2%

solution, and inserted into the superior fornix for

5 minutes before surgery. Intravenous sedation was

given ‘‘as required,’’ and the technique was compared

with peribulbar LA in a randomized trial of 100 cases.

Pain scores and use of sedation were similarly low in

both groups.

Lai and colleagues [41] looked at using 2% lido-

caine gel without sedation. They prospectively eval-

uated 22 consecutive cases of phaco-trabeculectomy,

all of whom had surgery under topical anesthesia

without sedation. Lidocaine 2% gel was applied to

the conjunctival fornices for 5 minutes before sur-

gery. They looked at patients’ pulse rate and blood

pressure, and per-operative pain scores were recorded

immediately after surgery. Using a pain scale of 0 to

10, mean reported pain was 0.9, with a range of 0 to

3, and only three patients reported having pain

or discomfort during surgery. They concluded that

the technique provided adequate analgesia for

the surgery.

Carrillo and colleagues [42] reported a prospec-

tive randomized trial comparing topical lidocaine 2%

gel with ‘‘sub-Tenon’s’’ LA for trabeculectomy. As

discussed in the previous section, the LA technique

for the control group would be described as ‘‘sub-

conjunctival’’ by some other authors. All 59 cases

received a standardized sedative, and the ‘‘topical’’

group received about 1 mL of nonpreserved lidocaine

2% gel to the conjunctival fornices 5 minutes before

surgery commenced. The control group LA was

similar to the ‘‘sub-conjunctival’’ technique described

by Azuara-Blanco and colleagues [32] (see previous

section). Mean pain scores (recorded postoperatively)

and surgeon satisfaction scores were similar in the

two groups. Supplemental anesthesia (as determined

by the surgeon) was required in 4 of the 29 sub-

Tenon’s cases, and none of the lidocaine gel cases.

The authors concluded that topical 2% lidocaine gel

was ‘‘as effective’’ as the sub-Tenon’s (subconjunc-

tival) technique.

Lidocaine 2% gel has also been used for implan-

tation of glaucoma drainage devices. Rebolleda and

colleagues [43] describe using lidocaine 2% gel

without sedation for implanting Ahmed valves. In a

prospective randomized trial, the technique was com-

pared with retrobulbar anesthesia. Pain scores were

similarly low, although surgical times were longer in

the topical group and the authors concluded that

lidocaine 2% gel offered ‘‘a reasonably safe and

comfortable surgical environment’’ for experienced

surgeons and selected patients.

Topical-intracameral anesthesia

Rebolleda and colleagues [44] described topical-

intracameral LA for phaco-trabeculectomy. Tetracaine-

oxybuprocaine drops were supplemented with 1%

nonpreserved intracameral lidocaine; sedation was

not used. The technique was compared with retro-

bulbar anesthesia in a prospective randomized study

of 60 patients. Pain scores were significantly higher in

the topical-intracameral group, in that 93% of the

topical-intracameral anesthesia patients required fur-

ther LA in the form of extra drops or application of a

sponge soaked in 1% lidocaine. By contrast, only

17% of the retrobulbar LA group needed any addi-

tional LA. Pain scores showed that discomfort was

rated as none/mild by 67% of the topical group and

93% of the retrobulbar group. Four patients had

retrobulbar anesthesia for their first eye and topical-

intracameral for the second; three of these pa-

tients stated that they preferred topical-intracameral

anesthesia. The authors concluded that, despite

the higher levels of per-operative discomfort, the

technique was well tolerated and ‘‘provides a safe

and comfortable surgical environment for experi-

enced surgeons.’’

Pablo and colleagues [45] described a technique

of ‘‘contact-topical plus intracameral’’ LA for phaco-

trabeculectomy. An absorbable gelatin sponge was

soaked in lidocaine 2% and inserted into the superior

fornix for 5 minutes before surgery, and intracameral

lidocaine 1% was used for phaco-emulsification. No

sedation was used. In a prospective trial, 80 patients

were randomized to topical-intracameral or peribul-

bar LA. During surgery, there were no significant

differences in vital signs, patients’ pain evaluation, or

surgeon stress.

If intracameral anesthesia is used for trabecu-

lectomy surgery, it may cause the pupil to dilate in

many patients [46]. This may make it difficult

to do the peripheral iridectomy, but the phe-

nomenon can be prevented by using pilocarpine

drops preoperatively.

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anesthesia for glaucoma surgery 253

Combined LA techniques

Kansal and colleagues [35] described a combined

sub-Tenon’s (subconjunctival), topical, and intracam-

eral LA with intravenous sedation. The technique,

referred to as ‘‘blitz’’ anesthesia, involved topical

bupivacaine or mepivacaine, intracameral 1% lido-

caine, and a sub-Tenon’s injection of 1% lidocaine

via a 30-gauge needle (for limbus-based filters) or

via a cannula in fornix-based filters. Acceptability was

assessed in a prospective series of 139 consecutive

cases of trabeculectomy, phaco-trabeculectomy, and

aqueous shunt surgery. Results were compared with a

parallel case-series of 139 patients who had similar

surgery by different surgeons using retrobulbar

anesthesia and sedation. Pain scores were similarly

low in both groups, with no intraoperative complica-

tions. The authors concluded that the technique was

‘‘a safe and effective alternative to retrobulbar

anesthesia’’ for glaucoma surgery.

This author’s favored technique for trabecu-

lectomy surgery is a combined subconjunctival-

intracameral anesthesia without sedation (Burnett

and Eke, submitted for publication). After instilling

topical oxybuprocaine or tetracaine, around 0.5 mL

of 0.5% lidocaine is infiltrated subconjunctivally in

the area of the proposed drainage bleb. The bleb of

anesthetic is then massaged (through the lid), so that

it covers the entire surgical area. Additional tetracaine

drops are instilled onto the sclera before cautery, and

intracameral 0.5% lidocaine is used before the

peripheral iridectomy. Patients’ acceptability is good,

with low pain scores for the surgery. Average pain

scores for surgery are lower than the average pain

scores for removing the sticky surgical drape at the

end of the procedure. When asked, all patients stated

they would have the same LA technique again if

further surgery was required.

Summary

While glaucoma surgery can be done using any of

the established anesthesia techniques, many glau-

coma specialists prefer to avoid using retro-ocular

injections (peribulbar, retrobulbar, posterior sub-

Tenon’s) for their glaucoma patients. Peribulbar and

retrobulbar injections can have sight-threatening or

life-threatening complications in any patient (Table 2),

and glaucoma patients may be at further risk of vision

loss because of more subtle pressure/ischemic effects

of LA injected around the optic nerve (Table 3). For

this reason, anterior application of LA agents has

become popular, using combinations of topical, sub-

conjunctival, anterior sub-Tenon’s, and intracameral

LA. These ‘‘newer’’ LA techniques should avoid the

potential for optic nerve damage, and they have been

shown to be acceptable to patients and surgeons.

However, there have been some concerns regarding

long-term outcomes of trabeculectomy surgery, par-

ticularly with subconjunctival anesthesia. There is

little evidence in the literature regarding this, and

further research is needed.

The author’s personal practice is to use LA with-

out sedation for virtually all patients. Filtering sur-

gery is performed using a combined subconjunctival/

intracameral technique, with 0.5% nonpreserved lido-

caine as described in ‘‘Combined LA techniques.’’

Cyclo-ablation (cyclo-diode laser) is performed using

a small volume posterior sub-Tenon’s LA. Cata-

ract surgery is performed using topical-intracameral

LA and a clear-corneal incision. This approach is

designed to give a good balance of safety and pa-

tient acceptability.

The doctor-patient relationship is particularly im-

portant in glaucoma. Treatment goals are, first,

lifelong maintenance of normal vision, and second,

freedom from concern regarding eyes and vision. A

painful operation could result in a breakdown in trust

between the patient and his or her ophthalmologist,

so it is important to use an appropriate mode of

anesthesia for each individual patient. Preopera-

tive counseling should therefore include an expla-

nation of the degree of awareness that the patient

should expect.

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Refract Surg 2002;28(4):631–8.

[40] Pablo LE, Perez-Olivan S, Ferreras A, et al. Contact

versus peribulbar anaesthesia in trabeculectomy: a

prospective randomized clinical study. Acta Ophthal-

mol Scand 2003;81(5):486–90.

[41] Lai JS, Tham CC, Lam DS. Topical anesthesia in

phacotrabeculectomy. J Glaucoma 2002;11(3):271–4.

[42] Carrillo MM, Buys YM, Faingold D, et al. Prospective

study comparing lidocaine 2% jelly versus sub-Tenon’s

anaesthesia for trabeculectomy surgery. Br J Ophthal-

mol 2004;88(8):1004–7.

[43] Rebolleda G, Munoz-Negrete FJ, Benatar J, et al.

Comparison of lidocaine 2% gel versus retrobulbar

anaesthesia for implantation of Ahmed glaucoma

drainage. Acta Ophthalmol Scand 2005;83(2):201–5.

[44] Rebolleda G, Munoz-Negrete FJ, Gutierrez-Ortiz C.

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anesthesia for glaucoma surgery 255

Topical plus intracameral lidocaine versus retrobulbar

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1214–20.

[45] Pablo LE, Ferreras A, Perez-Olivan S, et al. Contact-

topical plus intracameral lidocaine versus peribulbar

anesthesia in combined surgery: a randomized clinical

trial. J Glaucoma 2004;13(6):510–5.

[46] Lee JJ, Moster MR, Henderer JD, et al. Pupil dilation

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Ophthalmol Clin N

Oculoplastic and Orbital Surgery

Adam J. Cohen, MDT

Eyelid and Facial Aesthetic and Reconstructive Surgery, Craniofacial Surgery, Elmhurst Hospital, Elmhurst, IL 60126, USA

Successful surgical outcomes are not based solely

on the knowledge and skill level of a surgeon. Pa-

tient comfort and cooperation along with minimiz-

ing bleeding are paramount to achieving successful

surgical outcomes. Few things in a surgeon’s life

can be more frustrating than a patient who is not

adequately anesthetized and is uncooperative during

an operation.

The majority of oculoplastic and facial surgical

procedures are performed in outpatient settings under

local or regional anesthesia with sedation via oral or

intravenous routes. To achieve maximal patient com-

fort, familiarity with regional neuroanatomy, anes-

thetic agents, and techniques of delivery are salutary.

Because large numbers of these procedures are

performed with an anesthesiologist, this article will

be geared toward delivery of anesthesia from the

surgeon’s standpoint.

Anatomy

Sensory innervation of the craniofacial region is

most easily broken down by the well-recognized der-

matomes [1]. The major sensory innervation of the

face; a large portion of the scalp, teeth, and oral

and nasal regions; and dura mater is the trigeminal or

fifth cranial nerve. This nerve transmits information

on light touch, pain, temperature, and propioception

to the ventral, mid-lateral pons. After leaving its

nucleus the nerve divides into three branches: the

ophthalmic nerve (V1), the maxillary nerve (V2), and

the mandibular nerve (V3) (Fig. 1).

0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights

doi:10.1016/j.ohc.2006.02.016

T 2720 S. Highland Avenue, Lombard, IL 60148.

E-mail address: [email protected]

The ophthalmic nerve (V1) is the smallest branch

of the trigeminal nerve and is a purely sensory nerve.

After traversing the lateral wall of the cavernous sinus

the ophthalmic nerve divides into the lacrimal, fron-

tal, and nasociliary nerves just before entering the

orbit through the superior orbital fissure (Fig. 2).

The lacrimal nerve enters the orbit laterally via

the superior orbital fissure and travels in proximity

to the lacrimal artery to supply the lacrimal gland

and surrounding conjunctiva, terminating in the upper

eyelid septum.

The frontal nerve enters the orbit through the

superior orbital fissure and continues anteriorly. It lies

between the periosteum of the orbital roof and the

levator palpebralis superioris and divides into the

supraorbital and supratrochlear bundles.

The supraorbital branch of the frontal nerve con-

tinues along the orbital roof exiting from the supra-

orbital notch radiating branches to the upper eyelid

and conjunctiva. The supraorbital notch can usually

be palpated at the medial one third of supraorbital

rim. Moving cephalad it ascends with the supraorbital

artery to a level in the vicinity of the lambdoid su-

ture supplying sensation to the forehead and a large

portion of the scalp (Fig. 3). An in-depth study of

this nerve by Knize [2], found two distinct branches

after it exits the supraorbital foramen: a superficial

(medial) branch, which supplies the anterior scalp

margin and forehead skin, and a deep (lateral) branch

supplying the frontoparietal scalp. In addition, this

nerve also supplies the mucosa of the frontal sinus.

The supratrochlear nerve exits the orbit medial to

the supraorbital notch and travels along the frontal

bone to supply the upper eyelid skin and conjunctiva.

Moving superiorly below the corrugator supercilii

and frontalis muscles it terminates to innervate the

glabelar region.

Am 19 (2006) 257 – 267

reserved.

ophthalmology.theclinics.com

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Fig. 1. The distribution of ophthalmic and maxillary nerves.

The mandibular nerve is not shown because it is usually not

of consequence during oculoplastic procedures. (Courtesy of

Mark R. Levine.)

Fig. 3. Deep branch of supraorbital nerve with artery.

cohen258

The nasociliary branch of the ophthalmic nerve

(V1) enters the orbit through the annulus of Zinn and

travels to the medial orbital wall. Here it enters the

cranium via the anterior ethmoidal foramen and canal

as the anterior ethmoidal nerve. Before entering the

anterior ethmoidal foramen, the infratrochlear nerve

offshoots to supply the skin of the medial canthal

region including the caruncle and nasal skin superior

to the medial canthal tendon along with nasolacrimal

sac. Moving extracranially it then enters the nasal

cavity innervating the mucosa and upper lateral nasal

sidewall terminating as the external nasal nerve to par-

tially supply the skin of nasal columella, ala, and tip.

Before leaving the orbit this nerve provides sev-

eral branches of the long ciliary nerves that supply the

ciliary body, iris, cornea and post-ganglionic sym-

pathetic fibers of the dilator pupillae.

The posterior ethmoidal nerve innervates the mu-

cosa of ethmoidal and sphenoid sinuses.

Fig. 2. The ophthalmic nerve exiting the superior orbital

fissure and its branches. (Courtesy of Mark R. Levine.)

The maxillary nerve (V2) provides sensory neural

branches emanating at four distinct craniofacial sites:

the cranial cavity, pterygopalatine fossa, infraorbital

canal, and face. Because the oculoplastic surgeon

rarely performs intracranial surgery I will limit my

description to the latter three.

At the pterygopalatine fossa the maxillary nerve

gives off the zygomatic nerve, which enters the or-

bit through the inferior orbital fissure. Before leaving

the orbit it divides into the zygomaticotemporal and

zygomaticofacial nerves. Both of these nerves emerge

through their respective foramina with the zygo-

maticotemporal nerve supplying the skin of the tem-

poral region and the zygomaticofacial supplying the

skin of malar region.

Within the infraorbital canal the superior alveolar

nerves (anterior, middle, and posterior) arise before

the infraorbital nerve and its accompanying vessels

exit the infraorbital foramen located approximately

6 mm below the inferior orbital rim and parallel to the

mid-pupillary axis. They supply the lower eyelid and

lateral canthal region; the skin of the nasal sidewall

and anterior portion of its mucosa; the nasal septum;

maxillary sinus; upper gingiva and teeth; and the skin

of the anterior cheek, upper lip, and oral mucosa

(Fig. 4).

The palatine branch of the maxillary nerve is of

importance to the oculoplastic surgeon when harvest-

ing hard palate grafts for eyelid reconstruction.

It should be recognized that there is overlap of

the ophthalmic and maxillary nerve branches in the

medial and lateral canthal regions. This overlap may

explain patients’ discomfort when operating in these

areas after local anesthetic infiltration.

The mandibular nerve (V3), the largest division of

the trigeminal nerve, is composed of a large sensory

and smaller motor root. The sensory branch supplies

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Table 1

Commonly used ophthalmic topical anesthetic agents

Anesthetic agent

Available

strengths, %

Duration of

action, min

Proparacaine HCL 0.5 5–20

Tetracaine HCL 0.5–2.0 15–20

Lidocaine HCL 2.0 or 5.0 20–30

Abbreviation: HCL, hydrochloride.

Fig. 4. The infraorbital and zygomaticofacial nerves exiting

the infraorbital and zygomaticofacial foramina respectively.

(Courtesy of Mark R. Levine.)

oculoplastic & orbital surgery 259

the teeth and gums of the mandible, the skin of the

temporal region, the otic auricle, the lower lip, and

the lower part of the face. The smaller motor branch

innervates the muscles of mastication. Branches of

the mandibular nerve pertinent to the oculoplastic and

facial surgeon include the inferior alveolar nerve and

its branch the mental nerve.

The largest branch of the mandibular nerve is the

inferior alveolar nerve. Descending with the inferior

alveolar artery, it passes between the sphenomandib-

ular ligament and the ramus of the mandible into

the mandibular foramen. It then passes forward in

the mandibular canal, beneath the teeth, as far as the

mental foramen, where it divides into two terminal

branches, the incisive and mental nerves.

The mental nerve exits at the mental foramen, and

divides into three branches. These branches provide

sensation to the skin of the chin and the skin and

mucous membrane of the lower lip.

Inferior alveolar nerve injury can occur during a

sagittal split osteotomy while dissections for allo-

plastic chin implantation or mandibular protuberance

reshaping can insult the mental nerves.

The cervical plexus is formed by the anterior

divisions of the upper four cervical nerves. Each

nerve, except the first, divides into an upper and a

lower branch, and the branches unite to form three

loops. These branches are divided into superficial and

deep groups.

The great auricular nerve is the largest of the

superficial ascending branches. It arises from the

second and third cervical nerves and divides into an

anterior and a posterior branch. The anterior branch

supplies the skin of the face over the parotid gland

and communicates in the substance of the gland with

the facial nerve. The posterior branch supplies the

skin over the mastoid process and the posterior au-

ricle, except at its superior most aspect. The posterior

branch communicates with the smaller occipital nerve

and the auricular branch, which also supplies the skin

of the upper and back part of auricle. The poste-

rior branch of the greater auricular nerve can be

damaged during elevation of the retroauricular flap

during rhytidectomy.

Pharmacology

Topical anesthetic agents

Commonly used topical ocular anesthetic agents

include proparacaine hydrochloride, tetracaine hydro-

chloride, and lidocaine hydrochloride jelly. Their side

effects include ocular discomfort before onset of ac-

tion and punctate keratopathy [3] (Table 1).

EMLA (Astra Zeneca Pharmaceuticals, Wilming-

ton, Delaware) (lidocaine 2.5% and prilocaine 2.5%)

and ELA-Max (Ferndale Laboratories, Inc., Ferndale,

Michigan) (4% lidocaine) are topical skin anesthetics.

These creams can lessen the discomfort associated

with needle insertions and superficial cutaneous sur-

gery when applied approximately 15 to 60 minutes

before the procedure. Corneal or conjunctival contact

should be avoided with these agents. Ramos-Zabala

and colleagues [4] reported adequate anesthesia with

EMLA cream and remifentanil during full face la-

ser resurfacing with the Erbium:yttrium-aluminum-

garnet (Er:YAG) laser.

Reducing the temperature of the skin with ice or

cool compresses often provides adequate anesthesia

to reduce discomfort associated with needle insertion

and removal of small acrochordons. Placement of ice

for 5 minutes before injection of botulinum toxin to

the lateral orbital region resulted in a statistically

significant decrease in pain when compared with non-

iced regions [5].

Infiltrative anesthetic agents

Local anesthetic agents are usually of the amino

amide class and have a relatively rapid onset of ac-

tion. Commonly used agents include lidocaine, bupi-

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Table 2

Commonly used infiltrative anesthetic agents

Anesthetic agent Onset of action Dosage ceiling Duration of action

Lidocaine Rapid 7.0 mg/kg with EPI 2–4 h with EPI

4.5 mg/kg without EPI 1–2 h without EPI

Bupivacaine Slow 3.0 mg/kg with EPI 8 h with EPI

2.5 mg/kg without EPI 4 h without EPI

Prilocaine Moderate 7.5 mg/kg with EPI 6 h with EPI

5.0 mg/kg without EPI 90 min without EPI

Mepivacaine Rapid 7.0 mg/kg with EPI 6 h with EPI

5.0 mg/kg without EPI 3 h without EPI

Etidocaine Rapid 8.0 mg/kg with EPI 8 h with EPI

6.0 mg/kg without EPI 4 h without EPI

Cocaine Rapid 2.8 mg/kg without EPI 45 min without EPI

Abbreviation: EPI, epinephrine.

cohen260

vacaine, prilocaine, mepivacaine, and etidocaine. The

potency, onset, toxicity level, and duration of action

of these agents vary (see Table 2) [6].

Local anesthetic agents of the amino ester class

include procaine, chloroprocaine, cocaine, and tetra-

caine. This class of agents is uncommonly used ex-

cept for cocaine during surgery of the lacrimal system.

Toxicity of infiltrative anesthetics is related to sys-

temic absorption, distribution, and metabolism that

vary considerably among individual compounds and

patients. Infiltrative anesthetic adverse reactions are

almost always the result of an excessively large dose

or oversight of an intravascular injection [7].

Toxic signs and symptoms of local anesthetic are

usually limited to cardiovascular and central nervous

system dysfunction. Cardiac dysfunction is related

to direct myocardial depression, which may lead to

arrthymia, hypotension, and asystole. Intravascular

injection of bupivicaine and etidocaine has been

reported to result in cardiovascular collapse unre-

sponsive to resuscitative attempts [8]. Central ner-

vous system signs and symptoms include circumoral

paresthesias, light-headedness, tinnitus, metallic taste,

auditory or visual hallucinations, dysarthria, nystag-

mus, and tremors. At higher toxicity levels grand

mal seizures, apnea, and loss of consciousness may

result [8].

Allergic reactions may occur with infiltrative

anesthetics [9]. Para–aminobenzoic acid (PABA) is

thought to play a role in hypersensitivity [10]. Be-

cause ester amides produce a PABA metabolite the

incidence of hypersensitivity is greater versus amino

amides [11], albeit the overall frequency of these

reactions is uncommon in either class. Preservatives

such as methylparaben are found in the amino amide

class of agents and are metabolized to PABA [10].

One should use preservative-free amino amide agents

when anesthetizing a patient with a known allergy to

ester amide agents to avoid indirect patient exposure

to PABA.

Hypersensitivity reactions can manifest as mild

rashes, hives, angioedema, dyspnea, tachycardia, hy-

potension, or anaphylactia. Antihistamines and corti-

costeroids are usual treatment options in mild cases,

while cardiopulmonary compromise necessitates

ACLS measures [11].

Additives to infiltrative anesthetics

Epinephrine’s vasoconstrictive properties pro-

vide hemostatis and impede the systemic absorption

of infiltrative agents by one third [10], prolonging

their effect. This reduced systemic absorption al-

lows for a greater maximal safe dose. Most commer-

cially available injectable agents contain 1:100,000 or

1:200,000 strengths. Care should be taken to avoid

use of epinephrine in patients with thyroid storm or

advanced cardiac disease.

Sodium bicarbonate has been used to reduce the

acidic pH of infiltrative anesthetics. This is thought to

improve patient comfort associated with irritation of

infiltration of low pH solutions. Risks of alkaliniza-

tion include precipitation of anesthetics [12]. Addi-

tion of 1 cc of a 1 mEq/mL solution of bicarbonate

for every 9 cm3 of local anesthetic can alleviate

burning and improve patient comfort [13]. It should

be remembered that increasing the pH reduces the

shelf life of infiltrative anesthetic agents [14].

Ovine testicular hyaluronidase (Vitrase, Irvine,

CA, USA) increases the permeability of connective

tissue by the hydrolysis of hyaluronic acid [15]. This

allows for more rapid diffusion of injectable solutions

Page 105: Anestesia Ocular

oculoplastic & orbital surgery 261

thereby reducing the amount of anesthetic needed and

increasing the rate of onset. Symptoms of overdose

include edema, urticaria, nausea, chills, and tachy-

cardia [15].

Tumescent anesthesia

Tumescent anesthesia has been well described to

provide excellent anesthesia of superficial and deep

tissue structures and vasoconstriction [16]. This mo-

dality allows for the use of large amounts of anesthetic

solution because of the extremely low concentration

of lidocaine. Klein’s solution is a well- recognized

mixture that includes 50 mL of lidocaine hydro-

chloride, 1 mL of 1:1000 epinephrine, 12.5 mL of

8.4% sodium bicarbonate, and 1000 mL of normal

saline with a final concentration of 0.05% lidocaine

hydrochloride and 1:100,000 epinephrine [17]. Klein

reported a safe upper limit of 35 mg/kg when using

tumescent solution and postoperative analgesia for

up to 18 hours obviating the need for postoperative

analgesic medications [18]. Tumescent solutions are

infused into the subcutaneous adiposity via a cannula

in a subcutaneous plane. This is especially useful

with facial procedures such as rhytidectomy or lipo-

suction because of the creation of a tissue plane that

aids in dissection and a relatively bloodless field

provided by vasoconstriction. Tumescence may also

be used when performing laser or chemical skin re-

surfacing. Because of skin creep, optimal exposure

to laser energy or chemical agents can be achieved.

Although some support the use of tumescent solution

for facial reconstruction with flaps, I personally do

not use this technique [19]. Use of injectable anes-

thetic agents has yielded excellent results in my ex-

perience without compromise of flap vascularity.

Oral sedatives

The use of and selection of these agents are based

on the comfort level of the surgeon. A commonly

used class of medication is the benzodiazepines,

which provide excellent sedative and antianxiety

affects. One must use caution when prescribing these

since age, weight, and history of patient use of these

medications and drug interactions can alter metabo-

lism of these drugs. Diazepam, 5 to 20 mg and

alprozolam 0.25 to 0.50 mg [20] are two commonly

used drugs and can be given to patients on arrival for

their procedure.

Intravenous sedative and anesthetic agents

Because profound cardiovascular and pulmonary

effects are avoided with intravenous sedatives in most

cases, this class of agents is extremely popular. They

produce excellent analgesia and amnesia without the

need for laryngeal mask or general endotracheal

anesthesia. Several are discussed below.

Propofol (Diprivan, AstraZeneca Pharmaceuticals

LP, Wilmington, DE, USA) is a widely used sedative-

hypnotic agent [21]. Its rapid onset of action and

superlative level of hypnosis make for an excellent

choice when coupled with an opioid before local

anesthetic infiltration or as maintenance of monitored

anesthesia care sedation during prolonged proce-

dures. The author has found this agent to be of ex-

cellent value when repairing traumatic eyelid and

facial lacerations in the pediatric population in an

emergency department setting.

Midazolam is a benzodiazepine with a short half-

life. Given in slow, incremental 1-mg doses this agent

produces deep semiconscious sedation [22]. Intra-

venous use of this agent has been described to cause

impairment of memory for several hours [23].

Another useful attribute is its antianxiolytic effect.

Morphine sulfate, alfentanil hydrochloride, and

remifentanil hydrochloride (Ultiva, GlaxoWellcome,

Inc., Research Triangle, NC, USA) can provide out-

standing analgesia. The author has found alfentanil

hydrochloride (Alfenta, Taylor Pharmaceutical, De-

catur, IL, USA) at an induction dose of 3 to 8 mg/kgprovides effective pain control when used in a moni-

tored anesthesia care setting. Maintenance dosing

of 0.25 to 1 mcg/kg/min may be required during

protracted procedures. Care should be taken in pa-

tients with respiratory compromise because decreased

respiratory drive and increased airway resistance oc-

cur with increasing doses of alfentanil. Avramov and

White suggested healthy outpatients premedicated

with 2 mg of intravenous midazolam, receive a prop-

ofol and alfentanil infusion dose as calculated by

their formula for sedation and analgesia during

monitored anesthesia care (MAC) in the ambulatory

setting [24].

Remifentanil hydrochloride is a rapid onset, short-

acting m-opioid. Philip and colleagues [25] compared

this agent to alfentanil. They found remifentanil may

be used in a 1:4 ratio compared with alfentanil for

total IV anesthesia in ambulatory surgery patients pre-

medicated with midazolam. Remifentanil was more

effective in suppression of intraoperative responses

and did not result in prolonged awakening or

discharge times. Another study compared propofol

and remifentanil in patients who received 2 mg of

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Fig. 5. Cornwall syringe system.

cohen262

midazolam before the procedure [26]. It found remi-

fentanil to provide comparable intraoperative con-

ditions and patient comfort at a lower sedation level

compared with propofol. Remifentanil did result in

increased respiratory depression and longer discharge

times in these patients.

General anesthetic agents

Familiarity and administration of general inhala-

tion anesthetic agents is not usual practice for the vast

majority of oculoplastic surgeons and is beyond the

scope of this manuscript.

Applied anatomy

The vast majority of oculoplastic procedures are

performed with direct infiltration or regional blocks

in conjunction with conscious sedation. This section

will deal with these direct infiltrative and regional

block techniques in a structured anatomical fash-

ion. Although many commercially available inject-

able anesthetics are available, I prefer a mixture of

0.75% bupivicaine, 1:400,000 epinephrine, and hyal-

uronidase (Vitrase, Ista Pharmaceuticals, Irvine, CA)

(1 unit/mL). In my experience this melange offers

excellent and prolonged analgesia, hemostatis, and

tissue diffusion.

Fig. 6. Local infiltration in a subcutaneous, avascular plane.

Scalp, forehead, and eyebrow surgery

Anesthesia of this region can be achieved by di-

rect infiltration alone or in combination with su-

pratrochlear and supraorbital nerve blocks. Direct

infiltration provides the additional advantage of vaso-

constriction, especially advantageous in this highly

vascular region. A Cornwall syringe system (Becton

Dickinson and Co, Franklin Lakes, NJ) system can

assist in delivering anesthetic agents to large areas

such as the scalp and forehead (Fig. 5).

Usually the supraorbital foramen can be palpated

approximately parallel to the midpupillary axis, al-

though others have described it to be parallel to

the medial iris [27]. Once this landmark is found, a

30-gauage, one-half-inch needle is advanced to a

level beneath the periosteum just lateral to the fora-

men. The foramen itself should not be entered. One

should remember to draw back on the syringe be-

fore injection because inadvertent intravascular place-

ment of the needle may occur. One to 2 mL of

solution is injected and the needle withdrawn followed

by digital pressure.

The supratrochlear nerve may be anesthetized by

inserting a needle in a perpendicular fashion at the

junction of the nasal root, medial orbital wall, and

roof. A similar injection technique as described above

should be used.

Upper eyelid surgery

Anesthetizing the upper eyelid is achieved with

direct infiltration in most cases. The solution should

be injected in a subcuticular plane and unhurriedly to

reduce patient discomfort (Fig. 6). If possible, the

needle should pierce the skin in an avascular region

to avoid hematoma formation, which can lead to

perioperative eyelid distortion. Application of digital

pressure following injection can help to evenly dis-

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Fig. 7. Insertion of needle with bevel facing orbital peri-

osteum. Eyelid crease has been exaggerated to better define

the needle placement site.

oculoplastic & orbital surgery 263

tribute the solution and reduce focal swelling. Local

anesthetic agents should be used sparingly to mini-

mize Muller’s muscle overactivity and levator palpe-

bralis superioris underactivity due to epinephrine

and bupivicaine respectively. Focal swelling and mus-

cle under- or overactivity may result in imprecise

results during repair of blepharoptosis. If medial fat

extirpation is planned one should be cognizant that

both the supratrochlear and infratrochlear nerves may

supply this area necessitating additional anesthetic.

Oliva and colleagues [28] reported a case of transient

visual impairment and internal and external ophthalmo-

plegia following injection for blepharoplasty reaffirming

the need for gentle infiltration and minimal anesthetic

doses. In addition, central retinal artery occlusion has

been reported following local anesthesia for blepharo-

plasty [29].

A frontal nerve block is usually performed during

Muller’s muscle-conjunctival resection for blepharo-

ptosis. A 25-gauge, 1.5-inch sharp needle is used. It

is passed below the midsuperior orbital rim with the

needle lumen facing the orbital roof (Fig. 7). One

should feel the needle passing along the orbital roof

to a depth of 1.5 inches. Then, 1.5 to 2 mL of anes-

thetic solution is infiltrated followed by gentle digital

pressure. If the patient is adequately blocked, a com-

plete ptosis will result with the inability to open his

or her eye.

Lower eyelid and midface surgery

Direct anesthetic technique for the lower eyelids is

similar to that for the upper eyelids. If desired, this

direct infiltration of subcutaneous structures can be

combined with a conjunctival approach for lower eye-

lid and upper midface analgesia. After instillation

of a topical anesthetic onto the patient’s eye, a

corneoscleral shield should be placed over the globe.

The lower eyelid should be retracted away from the

globe exposing the tarsal conjunctiva. A 30-gauge

0.5-inch or 25-gauge 5/8-inch needle should be

directed at a 45 degree angle directly below the

inferior tarsal border to a point just anterior to the

inferior orbital rim. Once the initial injection is

performed the needle may be slightly withdrawn

and directed laterally and medially to further anes-

thetize the entire eyelid.

Infraorbital nerve blocks provide excellent anes-

thesia when operating on the lower eyelid, central and

medial midface, lateral aspect of the nose, and upper

lip. Blocking of this nerve may be approached via

a cutaneous or intraoral route. Whichever route is

chosen, one should be certain the needle is placed

beneath the periosteum to achieve the maximum dis-

tribution of the anesthetic.

If a cutaneous route is taken, the infraorbital

foramen is palpated approximately 6 mm below the

inferior orbital rim and parallel to the mid-pupillary

axis. A 30-gauge 0.5-inch or 25-gauge 5/8-inch

needle should be directed perpendicular to, without

entering, the foramen. Several boluses of 0.5- to

1.0-mL injections can be placed around the foramen

by repositioning the needle. Care should be taken to

avoid entering the orbit, which can lead to diplopia,

hemorrhage, and loss of vision.

The intraoral approach begins with palpation of

the infraorbital foramen with the middle finger and

elevation of the lip with the thumb and index finger

of the same hand. A 30-gauge 0.5-inch or 25-gauge

5/8-inch needle should be introduced into the

gingival sulcus above at the superior aspect of the

canine fossa. One to 2.0 mL of anesthetic solution

should be placed around the foramen.

Lower facial and mandibular surgery

Excellent analgesia can be achieved with mental

nerve blocking. The mental nerve exits the mandible

via the mental foramen, which is located approx-

imately within the midpupillary line. This nerve may

be blocked by a cutaneous or intraoral route. Which-

ever route is chosen, one should be certain the needle

is placed beneath the periosteum to achieve the maxi-

mum distribution of the anesthetic as described with

the infraorbital block.

After palpating the mentalis foramen the needle

should be advanced without entering the foramen.

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cohen264

Then 1.5 to 2.0 mL of solution anesthetic solution

should be infiltrated. When an intraoral route is taken

a similar technique as describe for the infraorbital

block is used for exposing the injection site.

The needle then pierces the inferior labial sulcus

at the top of the first bicuspid followed by anes-

thetic infiltration.

Fig. 9. Infraorbital nerve block.

Lacrimal system surgery

Innervation of this system stems from the oph-

thalmic and maxillary divisions of the trigeminal

nerve [30]. Achieving adequate anesthesia of medial

canthal and intranasal structures is essential for opti-

mal patient comfort during dacryocystorhinostomy,

conjunctivodacryocystorhinostomy, dacryocystectomy,

balloon dacryoplasty, or lacrimal system intubation.

Nasal passageway anesthesia has typically been

described to consist of preoperative packing of the

middle turbinate region with neurosurgical cottonoids

soaked in a 4% cocaine solution (Fig. 8). Others

espouse the use of a mixture of phenylephrine and

cocaine [31] to reduce untoward side effects while

others support the use of oxymetazoline and lidocaine

[32] for intranasal anesthesia. Pelletier and colleagues

[33] suggest coating the nasal vault with 2% lidocaine

hydrochloride jelly via a 22-gauge angiocatheter to

reduce the discomfort of placement of the nasal

packing and to aid passage of the cottonoids into

the nose.

Blocking of the nasolacrimal sac and duct and

medial canthal and external nasal regions can be

achieved by the elegant technique described by

Fanning [31]. Fanning’s technique is composed of

Fig. 8. Packing of the nasal vault with neurosurgi-

cal cottonoids.

four blocks. The first block is a standard cutaneous

infraorbital block as described previously using a

27-gauage, 1-inch needle (Fig. 9). Following the in-

fraorbital block the needle is withdrawn completely

and is directed toward the medial canthus and placed

beneath the periosteum (Fig. 10). One to 1.5 mL of

anesthetic is instilled and the needle withdrawn

completely. The needle should then be reinserted be-

low the periosteum at a point midway between the

original injection site and the medial canthus, directed

at the medial canthus. Injection at this site results in a

subperiosteal tumescent effect moving toward the

medial canthus (Fig. 11). Once this effect is seen the

injection is stopped. Gentle massage for 1 minute

allows for further anesthetic dissemination and

reduction of edema at the injection site.

The second block is a medial compartment block.

The same caliber and length needle is used as before

and is directed at a 30-degree angle to the coronal

plane between the caruncle and medial canthus

toward the medial wall stopping just at the perios-

Fig. 10. Reinsertion of the needle toward the medial canthus

followed following infraorbital nerve blocking.

Page 109: Anestesia Ocular

Fig. 13. Intranasal injection.

Fig. 11. Reinsertion of the needle at a point half way

between the medial canthus and insertion site depicted in

Fig. 10.

oculoplastic & orbital surgery 265

teum (Fig. 12A). Once this point is reached the

needle is withdrawn 1 or 2 mm and then redirected

becoming parallel with the medial orbital wall. The

bevel of the needle should be facing the orbital bone

and the needle should be inserted until the shoulder

(hub-needle junction) of the needle meets the iris

plane (Fig. 12B). The needle should remain medial to

the medial rectus at all times. Slowly inject 2 to 4 mL

of anesthetic while monitoring the tension of the

globe with your fingertip. This technique will

produce transient extraocular and orbicularis muscle

weakness necessitating gentle patching for several

hours postoperatively.

The third block is an optional lacrimal canal

block. A 30-gauge 0.5-inch needle is inserted per-

pendicular to the coronal plane entering the medial

aspect of the lower eyelid stopping at the level of

the infraorbital rim periosteum. The needle should be

gently rolled until it falls off the posterior aspect

Fig. 12. (A) Insertion of the needle between the medial canthus an

plane. (B) Redirection of the needle in a plane parallel to the med

of the infraorbital rim. The needle is now within

the lacrimal canal and 2 mL of anesthetic should be

injected. If reflux is noted from the punctum the

needle should be slightly withdrawn, removing it

from the lacrimal sac, and the area re-infiltrated.

The fourth block is performed after temporarily

removing the previously placed nasal packing. A

27-gauge 1-inch needle is used to directly infiltrate

anterior to the middle turbinate in a submucosal plane

(Fig. 13). Slow instillation of anesthetic results in a

spreading effect posteriorly along the middle turbi-

nate and lateral nasal wall. The nasal packing is then

replaced and left until intranasal access is needed

during the procedure.

Adequate anesthesia for less invasive procedures

involving the puncta or canaliculi can be realized

with topical and local infiltration in most instances.

d caruncle at a 30-degree angle with respect to the coronal

ial orbital wall.

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cohen266

Orbital surgery

Although most orbital surgery is performed with

general anesthesia, several authors have reported

successful outcomes with regional anesthetic blocks.

Burroughs and colleagues [34]described successful

outcomes in 158 patients when performing enucle-

ation and evisceration with retrobulbar blocks and

monitored anesthesia care . In addition, Kezirian and

colleagues [35] reported four cases of successful

orbital floor repair with peribulbar and infratrochlear

nerve blocks.

Postoperative pain control following enucleation,

evisceration and orbital implant placement may

be difficult even with narcotics. Several authors have

described success in such scenarios with placement

of orbital catheters [36,37]. Garg and colleagues

[38] reported one case of death of a patient with

Stickler’s syndrome following placement of a flexible

orbital catheter.

Summary

Awide variety of anesthetic agents and techniques

are available. No one combination of agents or tech-

niques is accepted as dogma. Experience and knowl-

edge with these agents will optimize anesthetic

effects, surgical outcomes, and patient satisfaction

and will reduce the risk of complications.

References

[1] Gray H. Gray’s anatomy. 38th edition. London7 Chur-

chill Livingstone; 1999. p. 1230–40.

[2] Knize DM. A study of the supraorbital nerve. Plast

Reconstr Surg 1995;96(3):564–9.

[3] Katzen LB. Anesthesia, analgesia and amnesia. In:

Putterman AM, editor. Cosmetic oculoplastic surgery.

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[4] Ramos-Zabala A, Perez-Mencia MT, Fernandez-

Garcia R, et al. Anesthesia techniques for outpatient

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[5] Sarifakioglu N, Sarifakioglu E. Evaluating the effects

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[13] Brogan Jr GX, Giarrusso E, Hollander JE, et al.

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for anesthesia of traumatic wounds. Ann Emerg Med

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[14] Bartfield JM, Homer PJ, Ford DT, et al. Buffered

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[16] Namias A, Kaplan B. Tumescent anesthesia for der-

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[18] Klein JA. Tumescent technique for regional anesthesia

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J Dermatol Surg Oncol 1990;16(3):248–63.

[19] Coleman 3rd WP, Klein JA. Use of tumescent tech-

nique for scalp surgery, Dermabrasion and soft tissue

reconstruction. Dermatol Surg Oncol 1992;18(2):130–5.

[20] Moody BR, Holds JB. Anesthesia for office-based ocu-

loplastic surgery. Dermatol Surg 2005;31(7):767–9.

[21] Hickey KS, Martin DF, Chuidian FX. Propofol-

induced seizure-like phenomena. J Emerg Med 2005;

29(4):447–9.

[22] Biswas S, Bhatnagar M, Rhatigan M, et al. Low-dose

midazolam for oculoplastic surgery under local anes-

thesia. Eye 1999;13(Pt. 4):537–40.

[23] Baker TJ, Gordon HL. Midazolam (Versad) in ambu-

latory surgery. Plas Reconstr Surg 1988;82:224 – 6.

[24] Avramov MN, White PF. Use of alfentanil and

propofol for outpatient monitored anesthesia care: deter-

mining the optimal dosing regimen. Anesth Analg 1997;

85(3):566–72.

[25] Philip BK, Scuderi PE, Chung F, et al. Remifentanil

compared with alfentanil for ambulatory surgery

using total intravenous anesthesia. The Remifentanil/

Alfentanil Outpatient TIVA Group. Anesth Analg 1997;

84(3):515–21.

[26] Smith I, Avramov MN, White PF. A comparison of

propofol and remifentanil during monitored anesthesia

care. J Clin Anesth 1997;9(2):148–54.

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[27] Cuzalina AL, Holmes JD. A simple and reliable

landmark for identification of the supraorbital nerve in

surgery of the forehead: an in vivo anatomical study.

J Oral Maxillofac Surg 2005;63(1):25–7.

[28] Oliva MS, Ahmadi AJ, Mudumbai R, et al. Transient

impaired vision, external ophthalmoplegia and internal

ophthalmoplegiaafter blepharoplasty under local anes-

thesia. Am J Ophthalmol 2003;135(3):410–2.

[29] Brancato R, Pece A, Carassa R. Central retinal ar-

tery occlusion after local anesthesia for blepharoplasty.

Graefes Arch Clin Exp Ophthalmol 1991;229:593–4.

[30] Dutton JJ. Atlas of clinical and surgical orbital anat-

omy. Philadelphia7 Saunders; 1994.

[31] Fanning GL. Local anesthesia for dacryocystorhinos-

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[32] Meyer DR. Comparison of oxymetazoline and lido-

caine versus cocaine for outpatient dacryocystorhinos-

tomy. Ophthalmic Plast Reconstr Surg 2000;16(3):

201–5.

[33] Pelletier CR, Jordan DR, Hamilton PP. Intranasal ap-

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undergoing dacryocystorhinostomy. Can J Ophthalmol

1996;31(5):245.

[34] Burroughs JR, Soprakar CNS, Patrinely JR, et al.

Monitored anesthesia care for enucleation and eviscer-

ations. Ophthalmology 2003;110:311–3.

[35] Kezirian GM, Hill FD, Hill FJ. Peribulbar anesthesia

for the repair of orbital floor fractures. Ophthalmic Surg

1991;22(10):601–5.

[36] Fezza JP, Klippenstein KA, Wesley RE. Use of an or-

bital epidural catheter to control pain after orbital im-

plant surgery. Arch Ophthalmol 1999;117(6):1306–7.

[37] Merbs SL, Grant MP, Iliff NT. Simple outpatient

postoperative analgesia using an orbital catheter after

enucleation. Arch Ophthamol 2004;122(3):349–52.

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Ophthalmol Clin N

Anesthesia for Pediatric Ocular Surgery

Steven Gayer, MD, MBAa,b,T, Jacqueline Tutiven, MDa

aUniversity of Miami Miller School of Medicine, 900 Northwest 17th Street, Miami, FL 33136, USAbDirector of Anesthesia Services, Bascom Palmer Eye Institute, 900 Northwest 17th Street, Miami, FL 33136, USA

Ophthalmic pathology in infants and children un-

dergoing eye surgery ranges from the rare and atypi-

cal to the commonplace. These pathologies include

nasolacrimal duct obstruction, strabismus, congenital

or traumatically induced cataracts, penetrating eye

injuries, glaucoma, retinopathy of prematurity, intra-

orbital tumors, and more. Nasolacrimal duct stenosis,

cataracts, and traumatic eye injuries often occur in

otherwise healthy pediatric patients; however, many

ophthalmopathies can be associated with other con-

genital disorders that may have important anesthesia

implications. In this article, we will review pertinent

anesthesia issues within the context of various

ophthalmic diseases.

The vast majority of adult eye surgery patients

have regional or topical anesthesia with sedation.

Pediatric patients lack the maturity to remain still and

are readily traumatized by unfamiliar environments

and separation from parents, so general anesthesia is

de rigueur. It may be difficult for children up to the age

of 5 or 6 to cooperate for the most basic ophthalmic

examination. Therefore, general anesthesia is also

often used to accomplish simple refraction; measure

intraocular pressure (IOP); and obtain photographs,

ultrasound examination, or electroretinography.

The preoperative anesthesia evaluation is crucial.

The timeline is dependent on degree of prematurity

and existing comorbidities. Congenital aberrancies

and degrees of previously unviable prematurity are

now frequently survivable. Additionally, frail and

0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights

doi:10.1016/j.ohc.2006.02.012

T Corresponding author. University of Miami Miller

School of Medicine, 900 Northwest 17th Street Miami,

FL 33136.

E-mail address: [email protected] (S. Gayer).

sickly neonates often mature to become frail, sickly

children [1]. Societal pressures have caused the venue

for ophthalmic surgery to migrate from hospital oper-

ating room suites to freestanding eye surgery centers.

Many such facilities lack depth of services and may

perform only a modest amount of pediatric surgery

per year. Caring for the infant or child with signifi-

cant comorbidities puts greater demands on the

anesthesiology staff as well as the facility [2]. The

preoperative examination is a key point in the con-

tinuum of care to assess if the perioperative anes-

thesia environment will ensure a safe course for the

individual patient.

Separation anxiety is a well-described concern of

pediatric patients (and their parents). A small dose of

benzodiazepine may be helpful in transitioning a

child into the operating room. Anxiolytics can be

administered intramuscularly, intranasally, by mouth

or rectum, or intravenously. Older children may ac-

quiesce to placement of an IV, particularly if the

cannulation site has been anesthetized with EMLA

(eutectic mixture of local anesthetics) cream. For

younger children, the oral route is more readily ac-

cepted. Because of variability in first-past absorption

through the hepatic circulation, timing and extent of

response to oral midazolam is less predictable. Intra-

nasal midazolam can be painful and is poorly tol-

erated [3]. Premedication with midazolam prolongs

neither emergence from general anesthesia nor dis-

charge from the hospital [4].

Surgical access is improved with pupil dilation.

Because of prolonged latency of onset, drops are

often instilled preoperatively, but may be given in the

operating room as well. They can migrate through the

puncta into the nasolacrimal duct and on to the nasal

mucosa with subsequent absorption into the systemic

Am 19 (2006) 269 – 278

reserved.

ophthalmology.theclinics.com

Page 113: Anestesia Ocular

gayer & tutiven270

circulation. Sequelae from phenylephrine, an alpha

agonist mydriatic, range from transient hypertension

to pulmonary edema and cardiac arrest [5]. Over 100

severe or fatal reports have been documented. Addi-

tionally, intravenous administration of beta-blockers

given in response to iatrogenic hypertension can

induce unopposed alpha-adrenergic stimulation,

exacerbate symptoms, and produce life-threatening

consequences [6]. Therefore, full strength, 10%

phenylephrine should be avoided in pediatric patients

[7,8]. Ideally, parasympatholytic mydriatic agents

should be used instead of phenylephrine. Otherwise

judicious instillation of 2.5% phenylephrine with ac-

tive occlusion of the nasal puncta to minimize

unintentional rerouting of drug through the naso-

lacrimal duct is advisable. Sufficient time for onset of

effect is warranted before placing additional drops.

The anesthesiologist must be informed so that he or

she may monitor for a hypertensive response and

react appropriately.

Retinopathy of prematurity

Retinopathy of prematurity (ROP), a disease of

neovascularization of the retina, is a leading cause of

infant blindness. Primary risk factors for ROP are

birth weight of less than 1500 g and prematurity with

a postconceptual age less than 32 weeks. Together,

the least mature, lowest weight infants are at highest

risk of developing the disease. Oxygen administration

in the first few weeks of life may be associated with

ROP; however, there are confounding case reports of

newly born infants who have never had exposure to

exogenous oxygen yet have evidence of ROP [9–11].

The improved survival rate of very low birth weight

and highly premature infants has increased the inci-

dence of ROP surgery in developed countries [12].

These infants have markedly higher incidence of

bronchopulmonary dysplasia, cardiac anomalies, epi-

sodic bradydysrhythmias, anemia, intraventricular

hemorrhage, and necrotizing enterocolitis.

In normal development, retinal vessel formation

and growth begins at the optic disc and continues

concentrically, reaching the periphery by 36 to

40 weeks of gestation. It is a dynamic process—

vessels develop or resorb as a function of changes in

local tissue oxygen availability. ROP results from

aberrant formation of blood vessels within the eye in

response to fluctuating levels of oxygen. It develops

in a two-step manner: During the period of early

vascular development, blood vessels in the retina

diminish as an autoregulatory response to high

oxygen tension. Later, in response to the increased

metabolic demands of the developing retina in a

milieu of relative avascularity, endothelial growth

factors are secreted that, in turn, induce vasoprolifera-

tion [13,14]. This neovascularity causes poor visual

acuity, tractional retinal detachment, amblyopia, and

ultimately, blindness.

Neonatologists attempt to maintain preterm in-

fants’ oxygen saturation below the level that is usu-

ally considered to be physiologically normal to

prevent further neovascularization and advancement

of ROP [15]. Intraoperatively, anesthesiologists have

adhered to this practice as well. The Supplemental

Therapeutic Oxygen for Prethreshold Retinopathy

(STOP-ROP) multicenter study sought to determine

if use of exogenous oxygen during the ischemic

phase of ROP could correct local tissue hypoxia,

blunt the secretion of vascular endothelial growth

factors, and prevent formation of new vessels [16].

Threshold disease, typically stage 3 retinopathy, is the

point at which treatment should be administered.

Premature infants with prethreshold ROP and oxygen

saturation below 94% were randomized to maintain

oxygen saturation between 89% and 94% or 96%

and 99%. Although the STOP-ROP study did not find

clear evidence that staged oxygen administration

attenuated development of ROP, it was significant

in that it found that provision of supplemental oxygen

to saturations up to 99% did not cause greater

progression to threshold ROP. During surgery and

anesthesia, higher FI O2 reduces the likelihood of

severe hypoxemia, lowers pulmonary arterial pres-

sure, and decreases airway resistance in infants with

chronic lung disease [17]. Thus, one may consider

that if higher oxygenation is warranted because of

other patient comorbidities, maintaining a relatively

hypoxic state intraoperatively may not be crucial to

the management of neonates with ROP. On the other

hand, some studies have found that episodic cycling

between hypoxia and hyperoxia produces greater re-

tinal neovascularization than exposure to either

hypoxic or hyperoxic environments [18,19]. Many

neonatal intensive care units (NICUs) have adopted

policies that strive to keep oxygen saturation within a

restricted, tight range [20]. The anesthesiologist may

consider keeping perioperative oxygen saturations

within the NICU’s proscribed boundary. Thus, since

concentration, duration, timing, and fluctuation of

oxygen all may have a role in ROP; the optimal in-

traoperative oxygen saturation for these patients has

yet to be clearly elucidated.

The same risk factors that predispose a neonate to

develop ROP, namely low birth weight, prematurity,

and exogenous oxygen, may also promote broncho-

pulmonary dysplasia. This form of chronic lung

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anesthesia for pediatric ocular surgery 271

disease is associated with increased airway resistance

and reactivity, diminished lung compliance, and hyp-

oxemia. In the operating room, endotracheal intu-

bation has been the traditional means of obtaining

control of premature and ex-premature ROP patients’

airways; however, barring specific contraindications,

supraglottic devices may provide suitable airways,

even for those patients with history of mild to mod-

erate bronchopulmonary dysplasia [21,22]. For short

procedures, placement of a laryngeal mask airway

(LMA) causes less cardiovascular stimulation than

laryngoscopy and endotracheal intubation. It does not

impede the ophthalmologist’s access to the eyes, and

is associated with a reduced incidence of coughing

and Valsalva [23].

Postoperative breath-holding and apnea are poten-

tial serious complications for premature and ex-

premature infants undergoing surgery for ROP. It

may be associated with episodic bradycardia [24].

Perioperative risk of apnea is dependent on post-

conceptual age, gestational age, and prior history of

apnea at home, with the incidence strongly correlat-

ing inversely with postconceptual and gestational

age. Combined analysis of several studies has found

that at 48 weeks postconceptual age, neonates have

an approximately 5% risk of postoperative apnea,

whereas those at approximately 55 weeks have a less

than 1% probability [25]. Apnea at emergence from

anesthesia, periodic breathing in the recovery room,

and history of anemia confer moderate additional risk

for delayed breath-holding [26]. Intravenous caffeine

or theophylline may attenuate the likelihood of

postoperative apnea [27]. Ophthalmologists should

consider delaying ROP surgery until after 48 to

55 weeks postconceptual age when feasible. Alterna-

tively, examination and minor procedures on ex-

tremely premature patients may be performed bedside

in the NICU [28]. Preterm infants should be observed

after surgery with pulse oximetry and apnea monitor-

ing in an inpatient setting [29]. If the surgical venue is

a freestanding ophthalmic specialty center, arrange-

ments for a bed in an inpatient, monitored facility

as well as for a pediatric transport team must be

coordinated with sufficient time before the day of

surgery [30].

Patients may be brought to the operating room

for diagnostic or surgical interventions. Advances in

photography and ultrasonography now allow for

improved imaging of the eye’s posterior segment.

Cryotherapy, and more recently, laser photocoagula-

tion are common minimally invasive procedures.

Retinal detachment is managed with vitrectomy,

injection of intravitreal gas, and scleral buckle

surgery. General anesthesia with nitrous oxide should

be avoided if use of intravitreal gas is intended

[31,32].

Glaucoma

Congenital glaucoma is caused by aberrant de-

velopment of the trabecular mesh network with

obstruction of flow of aqueous humor. It may be

primary or secondary, infantile or juvenile. Infantile

glaucoma has onset within the first 3 years of life and

is commonly associated with elevated intraocular

pressure (IOP), enlargement of the eyes, and cloudy

corneas. Neonates have elastic, immature tissue that

stretches in response to increased pressure, so larger-

sized, buphthalmic ‘‘ox-like’’ eyes and are common,

while juvenile glaucoma patients do not have this

feature. The classic triad of symptoms for congenital

glaucoma includes tearing, photophobia, and blepha-

rospasm [33].

Corrective surgery to establish paths for aqueous

humor outflow include goniotomy, trabeculotomy,

and implantation of synthetic drainage devices. Aque-

ous humor production can be abated by destruction of

the ciliary body with laser in refractory cases. The

key to good outcome is prompt diagnosis because

early surgery is highly successful at curtailing prog-

ress of disease. On several occasions we have

operated on days-old neonates who have been diag-

nosed by astute parents and pediatricians. Because of

immaturity and inability to cooperate, older infants

and small children may not tolerate the initial diag-

nostic ophthalmoscopic examination and IOP mea-

surement, thus general anesthesia to accomplish a

meticulous eye assessment is warranted. Concomitant

congenital abnormalities such as craniofacial dysto-

ses, various chromosomal trisomies, and other

syndromes are not uncommon and may have sig-

nificant anesthesia implications [34,35]. After defini-

tive surgery, many pediatric patients return to the

operating room periodically for examination under

anesthesia until they are sufficiently mature to be

examined in an office setting.

Assessment of IOP is crucial to both diagnosis

and determination of response to treatment. Anes-

thetic intervention introduces variables that may taint

the accuracy of IOP measurements. Most anesthetics,

including inhalation and induction agents as well as

benzodiazepines and narcotics, lower ocular pressure

[36]. A number of etiologies, including depression of

central nervous system (CNS) activity, induction

of extraocular muscle tone relaxation, reduction of

aqueous humor production while enhancing aqueous

flow, and lowering of venous/arterial blood pressure

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gayer & tutiven272

have been postulated. Recent studies have disputed

the traditional notion that ketamine raises IOP. Some

have found that pretreatment with benzodiazepines or

narcotics prevents change in eye pressure with

ketamine, while others have determined that ketamine

may actually decrease IOP [37,38]. Although non-

depolarizing neuromuscular blocking agents do not

increase IOP, succinylcholine may transiently do so

by as much as 10 mm Hg. Debate exists as to whether

or not pretreatment with a small dose of nondepo-

larizing agent ablates this effect [39].

Compression of the eye by an anesthesia face-

mask may lead to spuriously high IOP measurement

[40]. Laryngoscopy and intubation raise IOP through

sympathetic nervous system stimulation; however,

this may be attenuated by achieving a deep plane of

anesthesia before attempting airway manipulation

[41]. Supraglottic airway placement is not accom-

panied by significant increase of IOP and may have

comparable effect on pressure as use of a facemask

[42,43]. Both pediatric as well as glaucoma patients

experience less change in IOP with placement of a

laryngeal mask airway than with laryngoscopy and

intubation [44,45].

Because there are a number of confounding intra-

operative variables that may affect IOP, we believe that

it is important to achieve consistency of technique such

that the patient’s IOP is assessed under similar

conditions with each visit to the operating room [46].

Intraocular tumors

In adults, orbital tumors most commonly result

from secondary metastasis from other areas. The

major primary eye cancer is uveal tract melanoma. In

children, retinoblastoma is the predominant primary

eye neoplasm. It accounts for nearly 3% of all child-

hood cancers and, in the past, was the cause of almost

1% of all pediatric cancer deaths. Untreated, it is a

fatal disease; however, with therapy survival rates

exceed 90%. Retinoblastoma is caused by an abnor-

mality in a specific tumor suppressor gene. This

defect may occur spontaneously or be inherited. More

than half of the children of a parent with bilateral

retinoblastoma will develop ocular malignancy. Ini-

tial clinical diagnosis is made within the first 2 years

of age by observing leukocoria on gross examination

or via indirect ophthalmoscopy of the fundus [47,48].

Earlier detection and newer modalities of treat-

ment have led to improved survival and more

conservative approaches to retinoblastoma than the

traditional enucleation and external beam radiother-

apy [49]. Currently, enucleation is reserved for

patients with extensive disease or those who have

not responded to other therapeutic interventions. The

majority of patients, however, come to the operating

room for minimally invasive procedures. Often there

is no ‘‘surgery’’ on the day of surgery. Typical inter-

ventions are fundoscopic examination, photography,

ultrasound, laser, cryotherapy, and thermotherapy.

Owing to the need to document and follow progress/

regress of disease and provide therapy on a con-

tinuous basis, patients may return to the operating

room regularly over the course of their early child-

hood. The psychosocial aspect of care for both the

patient and parents should not be ignored. Small

children tend to begin fearing trips to the hospital and

develop ‘‘white coat’’ syndrome. Providing a relaxed

atmosphere with interesting toys along with age-

appropriate preoperative tours of the operating room

suite and videos for viewing at home can help belay

the onset of ‘‘blue scrubs’’ anxieties. Premedication

with benzodiazepines may also be beneficial [50,51].

Atraumatic, smooth induction of anesthesia reduces

the incidence of postoperative emotional conse-

quences by half [52]. Parental presence in the

operating room at the time of induction is somewhat

controversial. Although it has no impact on infant

distress during induction of anesthesia, it may allay a

small child’s anxiety and ease the experience [53]. On

the other hand, some children are not calmed by their

parents’ presence and staff and physicians may be

uncomfortable. Some parents are distressed by the

foreign environment. Each care team and institution

needs to develop its own suitable policy [54].

Preoperative labs are generally unnecessary for

children with retinoblastoma who return to the

operating room episodically for tailored, focused

interventions; however, a complete blood count may

be indicated for those who have received recent

chemotherapy. Inhalation induction of general anes-

thesia with maintenance of airway patency via a

facemask is typical. Access to the eye for the surgeon,

photographer, and ultrasonographer can be improved

with use of a mask such as a Rendell-Baker mask,

tailored to hug the bridge of the nose and taper away

from the eyes. If a brief procedure is anticipated,

assuming an otherwise healthy child without pro-

longed fasting, we often forgo intravenous cannula-

tion. If actual surgery is planned or if multiple

procedures are foreseen, an IV and supraglottic

airway such as an LMA are placed.

To avoid laryngospasm or the oculocardiac reflex,

particularly without an indwelling IV, sufficient depth

of anesthetic should be ensured before any manipu-

lation of the eye. Atropine, epinephrine, and succi-

nylcholine doses are calculated and drawn up before

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anesthesia for pediatric ocular surgery 273

induction of anesthesia and are immediately available

for intramuscular injection should circumstances

require them. Materials for IV access are also placed

proximate to the patient. An indicator of insufficient

degree of anesthesia is the upward rolling of the eyes

in response to pressure on the eyelids by an eye

speculum. Normally, a natural protective reflex, this

so-called Bell’s phenomenon, causes the eye to gaze

cephalad when the lid begins to close. Since this

reflex is lost under deep general anesthesia and the

eyelids are open with the eye readily visible

throughout the procedure, ‘‘Belling’’ of the eye may

be a useful monitor of anesthetic depth [55,56].

Currently, there is debate as to whether bispectral

index data correlate with depth of anesthesia of

pediatric patients [57].

Sevoflurane is an ideal inhalation agent for

children undergoing examination under anesthesia

because of its favorable cardiovascular profile and

lack of respiratory irritation. One drawback, however,

is emergence delirium, most often encountered in

children younger than 6 years of age [58]. Post-

sevoflurane agitation occurs whether or not actual

surgery has occurred and is not caused by post-

operative pain [59]. It may, however, be related to a

child’s level of preoperative anxiety [60].

The child with retinoblastoma presenting for

examination under anesthesia is at enhanced risk of

post-sevoflurane agitation because his or her general

anesthetic primarily consists of high-dose sevoflurane

via facemask and little else. Some studies have found

that addition of midazolam, propofol, narcotics, or

nonsteroidal anti-inflammatory drugs (NSAIDS) to

the anesthetic regimen decreases the likelihood of

emergence delirium [58,61]. Preoperative narcotics

confer no advantage over midazolam, providing

further justification for our inclination to use oral

benzodiazepines before surgery [62]. Some consider

switching to an alternative inhalation agent after

induction. Fortunately, while acutely distressing to

patient and parents, there are no long-term behavioral

ramifications of sevoflurane-induced emergence

delirium [63].

Electroretinograms and visual evoked potentials

Electroretinography and visual evoked potentials

(VEPs) are used to assess the function of the visual–

cortical axis from the level of the photoreceptors to

the visual cortex. The examination is fairly brief and

noninvasive, requiring placement of a contact lens

electrode on each eye and subsequent exposure to

pulses of flashing light. For adults, this is an office

procedure. Infants and small children, however, often

will not tolerate the procedure and may require anes-

thesia. Traditionally, bulky electroretinogram (ERG)

equipment has been fixed in specialized lightproof

suites where patients’ retinal cells can be dark-

adapted before the examination. Older inhalational

anesthetics such as halothane and isoflurane, as well

as newer agents, sevoflurane and desflurane, are

known to decrease amplitude and prolong latency of

ERG/VEPs when given in high doses typically

needed for mask-induction of anesthesia, so their

use has been typically avoided for these studies

[64–67].While VEPs are exquisitely sensitive to inha-

lation agents, ERGs may be less so [68]. Methohexi-

tal, an ultrashort-acting barbiturate that has a rapid

recovery profile, provides effective sedation. It can be

administered rectally, obviating need for intravenous

access. Onset of effect occurs quickly with 15 to

30 mg/kg of a 10% solution [69]. Owing to potential

apnea of variable duration, post-procedure monitor-

ing is requisite [70]. Propofol may have less effect

upon the ERG than barbiturates and is associated

with a very rapid recovery, but requires cannulation

of a vein [71,72].

Although there are multiple techniques for seda-

tion of pediatric patients outside of the operating

room setting, customary use of rectally administered

barbiturate-based anesthesia for ERG/VEP examina-

tions evolved as a direct consequence of the need to

avoid inhalation agents for anesthesia of infants and

small children in an artificially darkened area remote

from the operating room [73]. Recently there have

been acute shortages of methohexital. The manufac-

ture of small portable ERG machines allow for dark-

adapted pediatric patients to undergo the examination

as scheduled cases in the operating room suite.

Strabismus

Strabismus is a misalignment disorder of extra-

ocular muscles characterized by amblyopia with or

without anisometropia. Surgery, including intramus-

cular placement of adjustable or semi-adjustable

sutures, resections, or direct injection of the par-

alytic botulinum toxin, often yields immediate

rectification of symptoms. Strabismus may be in-

herited, developmental, or acquired, and can have

associated comorbidities—particularly other neuro-

muscular disorders. Children with strabismus or pal-

pebral ptosis may be at increased risk for malignant

hyperthermia or harbor an undiagnosed cardiomy-

opathy, so a thorough preanesthesia examination is

warranted [74,75]. The incidence of malignant

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gayer & tutiven274

hyperthermia, intraoperative hyperkalemic arrest, or

rhabdomyolysis has decreased with improved iden-

tification of highly susceptible patients, avoidance of

succinylcholine and other triggering agents, and use

of total intravenous anesthesia with nontriggering

anesthetics [76].

Usually elicited by traction on extraocular mus-

cles and their adnexa or by sudden pressure applied to

the eye or orbit, the oculocardiac reflex (OCR) is not

infrequently encountered in infants and children

having ophthalmic procedures under general anes-

thesia. It is fairly commonly experienced during

strabismus surgery. The stimulus is initially mediated

by the trigeminal nerve, with a vagal efferent re-

sponse that can produce abrupt changes in heart rate.

The cardiac response may be attenuated by a timely

prestimulus IV dose of anticholinergics, use of

sevoflurane instead of halothane, use of neuro-

muscular blocking drugs with vagolytic effects,

and gentle surgical handling of the extraocular

muscles [77]. Since the OCR displays tachyphy-

laxis, repeated stimuli are often accompanied by

attenuated responses—or extinguishment of symp-

toms. First response should be cessation of the

surgical stimulus, allowing the heart rate and rhythm

to return to baseline while simultaneously reassur-

ing adequate patient oxygenation, ventilation, and

depth of anesthesia. Mild hemodynamic instability

of brief duration may not require anticholinergics;

however, compromising bradycardia warrants the

use of atropine. Atropine, not glycopyrrolate or epi-

nephrine, is the appropriate initial agent for vagal-

induced symptomatic bradycardia [78]. Glycopyrrolate

may produce a similar cardiac effect with less pro-

arrhythmic consequences and is used prophylacti-

cally by some after induction of anesthesia, before

surgical stimulation [79].

Strabismus surgery is often accompanied with

postoperative nausea and vomiting (PONV). The

reported incidence of nausea and emesis ranges wide-

ly, no doubt because of differences in patient pop-

ulations as well as surgical and anesthetic techniques

[80]. The increased probability of PONV above

baseline may be a result of an oculo-gastric reflex

that is a vagally mediated response to surgical ma-

nipulation of extraocular muscles. Supporting this

notion, an association between the intraoperative

occurrence of another vagus nerve-mediated re-

sponse, the OCR, and PONV has been described

[81]. Following surgery, motion sickness because of

diplopia may also produce nausea and emesis.

While symptoms are usually self-limiting, serious

ramifications may occur. Delayed eating and drinking

may lead to dehydration, electrolyte imbalance, and

prolonged stay in the recovery room. Unanticipated

admission to an inpatient facility may be necessary.

PONV is distressing and its curtailment is valued

[82]. Avoidance of emesis and nausea after surgery is

a greater patient priority than prompt wakefulness,

rapid discharge from same-day surgery, cost, or even

pain itself [83].

Strategies to minimize PONV include adjustment

of the anesthetic plan as well as the use of anti-

emetics. Preoperative anxiety may contribute to

postoperative nausea/vomiting, so benzodiazepines

or clonidine may be beneficial [84,85]. Narcotics are

highly proemetic and newer agents such as remifen-

tanil may not confer advantage over fentanyl [86].

Conflicting reports regarding nitrous oxide exist.

Higher oxygen concentrations allay PONV in adults

after gastrointestinal (GI) surgery, however, increased

FI O2 has not been found to have similar effect in

pediatric and adult strabismus patients [87,88].

Anticholinesterases used for reversal of neuromus-

cular blocking agents promote nausea, so preintuba-

tion use of an ultrashort neuromuscular blocking

agent that does not require reversal, such as miva-

curonium, is warranted [89]. Supraglottic airways

obviate the need for paralysis altogether. Propofol

may reduce the incidence of nausea and vomiting, but

is associated with the oculo-cardiac reflex and

bradydysrythmias [90,91]. Peribulbar or sub-Tenon’s

block before emergence from general anesthesia

lessens PONV [92,93]. Nonpharmacologic tech-

niques such as acupressure may be helpful [94].

Postoperatively, premature inducement to eat and

drink should be avoided [95].

Antiemetics can be administered during surgery or

once symptoms arise after emergence. Since strabis-

mus surgery is, in and of itself, a notable independent

risk factor for PONV in children, prophylactic admin-

istration of antiemetics is warranted [84]. Surgery in

excess of 30 minutes, as well as a family history of

PONV confer additional risk and further justify

intraoperative antiemetics [96]. Additionally, in this

setting, prophylactic antiemetics may be more cost-

effective than symptomatic treatment of nausea and

vomiting [97].

PONV after strabismus surgery has been studied

with all classes of antiemetics, including butyrophe-

nones, benzamides, histamine and muscarinic receptor

antagonists, steroids, and serotonin 5-HT3 receptor

antagonists [98,99]. Use of combinations of anti-

emetics with differing mechanisms of action may be

more effective for those eye muscle surgery patients

at highest risk of PONV. One such combination

includes droperidol, a 5-HT3 receptor agonist, or ste-

roid. Droperidol has a marked anti-nausea effect

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anesthesia for pediatric ocular surgery 275

while the serotonin receptor antagonists are better

suppressers of vomiting than nausea, and dexametha-

sone has a prolonged duration of action [98].

Traumatic eye injuries

Traumatic eye injuries are relatively common with

small children and adolescents. Reparative surgery

occurs more frequently in community-based facilities

than trauma centers [100]. Open eye injuries are

either ruptures from blunt objects or lacerations from

sharp projectiles. Lacerating injuries may be pene-

trating, with single full-thickness lesions, or perforat-

ing, with entrance and exit wounds. An intraocular

foreign body may also be present. Anesthesia strate-

gies for management of open-globe patients are de-

scribed elsewhere in this text. In the otherwise healthy,

normovolemic, fasted child, a gentle inhalation-based

induction may be considered since squeezing of the

eyelids owing to attempted IVaccess can cause IOP to

exceed 70 mm Hg, potentially precipitating extrusion

of globe contents [101]. Although general anesthesia

remains conventional, anesthesia for select patients

with open globe injuries can be accomplished with

regional anesthesia [102,103]. In the pediatric

population, with the possible exception of older

more-mature teenagers, general anesthesia is most

appropriate. Nonetheless, an eye block before con-

clusion of surgery provides effective postoperative

analgesia for the child having repair of a traumatic

eye injury under general anesthesia. Emergence from

anesthesia is more quiescent, with less PONV than

encountered with opiates, and the child is less likely

to rub or squeeze an eye that has been rendered

insensate with local anesthetics [104]. Appropriate

dosing can be achieved with proportionally smaller

volumes and lower concentrations of local anes-

thetic. Alternatively, intravenous, but perhaps not

topical, ketorolac as well as oral or rectal acetami-

nophen may also attenuate postoperative pain with-

out enhancing the potential for PONV [105–107].

Summary

The intent of this article was to shed light on

important issues in pediatric ophthalmic anesthesia

within the constraints of the space allotted. A timely

and detailed history and physical examination com-

plimented with indicated diagnostic tests generally

ensures a safe anesthetic course. Preterm and ex-

premature infants as well as syndromic children un-

dergoing eye surgery require proper institutional

support, and may also need postoperative trans-

portation from the ophthalmology specialty center

to a pediatric intensive care unit for further monitor-

ing. Anesthesia implications for particular ophthalmic

pathologies including retinopathy of prematurity,

glaucoma, retinoblastoma, strabismus, and traumatic

eye injuries were discussed. We reviewed peri-

operative considerations including the preoperative

examination, evaluation of comorbidities and syn-

dromes, preoperative labs, premedication, separation

anxiety, systemic effects of ophthalmic medications,

emergence delirium, the increasing use of supra-

glottic airways, IOP, OCR, PONV, and pain manage-

ment strategies including intraoperative eye block.

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Ophthalmol Clin N

Succinylcholine and the Open Eye

Elie Joseph Chidiac, MDa,b,T, Alex Oleg Raiskin, MDa

aDepartment of Anesthesiology, Wayne State University School of Medicine, Anesthesiology Education Office,

Room 2901, 2-Hudson, 3990 John R., Detroit, MI 48201, USAbKresge Eye Institute, 4717 St. Antoine, Detroit, MI 48201, USA

The use of succinylcholine in ocular trauma is

controversial. This article reviews the determinants

of intraocular pressure (IOP), the effects of succinyl-

choline on IOP, and the advantages and disadvantages

of alternatives to succinylcholine, including regional

anesthesia for open globe injuries. We review various

methods to attenuate the effect of succinylcholine on

IOP, if it is to be used. Finally, we suggest an algo-

rithm for airway management of patients with pene-

trating eye injuries, highlighting circumstances where

succinylcholine may be the safest muscle relaxant.

Intraocular pressure

Normal IOP is 10 to 22 mm Hg, with diurnal

variations (ie, 2 to 3 mmHg higher in the daytime) and

positional changes (ie, 1 to 6 mm Hg higher if su-

pine).It is physiologically determined by aqueous hu-

mor dynamics, changes in choroidal blood volume,

central venous pressure, and extraocular muscle tone

[1]. The most important determinant of IOP is the

balance between production and elimination of aque-

ous humor, maintaining an average volume of 250mL.

Aqueous humor is formed in the ciliary process from

capillaries by diffusion, filtration, and active secretion

[2]. It flows through the posterior chamber, around the

0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights

doi:10.1016/j.ohc.2006.02.015

T Corresponding author. Department of Anesthesiology,

Wayne State University School of Medicine, Anesthesiology

Education Office, Room 2901, 2-Hudson, 3990 John R.,

Detroit, MI 48201.

E-mail address: [email protected]

(E.J. Chidiac).

iris, and into the anterior chamber. It is eliminated

through the spaces of Fontana and Schlemm’s canal

at the iridocorneal angle, where it flows into the

episcleral venous system. Any increase in venous

pressure (eg, cough, strain, head-down position) will

increase IOP. Additionally, any decrease in cross-

sectional area of the spaces of Fontana (eg, mydriatic

drugs) will increase IOP.

The choroid is a meshwork of arterial anasto-

moses in the posterior chamber. Autoregulation of

choroidal blood flow keeps IOP stable [3]. However,

this process is slow, so that sudden increases in sys-

temic blood pressure or central venous pressure

(coughing, bucking) will cause a transient increase

in choroidal blood volume and thus IOP. Addition-

ally, there is a linear relationship between choroidal

blood volume and hyper- and hypoventilation, so that

an increase in carbon dioxide tension will raise IOP.

A sudden drop in IOP to atmospheric pressure (open

eye) can cause rupture of choroidal vessels.

Extraocular muscles (EOM) have a unique mor-

phologic structure that enables rapid and precise

control with resistance to fatigue. Whereas skeletal

muscles have a single nerve axon connected to an

endplate at the mid-belly of each fiber, EOM are

both singly innervated and multiply innervated. With

firing of synapses, the action potential of multiply

innervated fibers is not an all-or-none phenomenon;

instead, there are tonic focal contractions and the

force generated is directly proportional to the mem-

brane depolarization [4]. This may explain differ-

ences in the response of EOM to succinylcholine; in

the EOM of cats, multiply innervated fibers are more

sensitive to succinylcholine than singly innervated fi-

bers [5].

Am 19 (2006) 279 – 285

reserved.

ophthalmology.theclinics.com

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chidiac & raiskin280

Succinylcholine and IOP

When first introduced, succinylcholine was seen

as an ideal muscle relaxant [6]. Soon thereafter, it was

reported that succinylcholine increased IOP [7] and

with personal communications from surgeons, con-

cerns were raised regarding possible vitreous extru-

sion [8]. Others studied intraocular physiology and

described loss of vitreous after succinylcholine ad-

ministration under light anesthesia, suggesting that

the use of succinylcholine in intraocular surgeries

was ‘‘hazardous’’ [9]. Anesthesiologists at the Wills

Eye Hospital in Philadelphia performed a retrospec-

tive review of 100 of 228 open eye trauma cases from

1982. Of those 100 cases, 81 had general anesthesia:

11 had an inhalational induction (all were children)

and 70 had an intravenous induction. Of those 70,

there were 63 who received succinylcholine, at 60 to

160 mg. Based on the description of the eye on the

operative report and in the preoperative progress

notes, there was no extrusion of vitreous in any of the

cases where succinylcholine had been used. They

added that they had no anecdotal reports of loss of

ocular content using succinylcholine for eye injury

patients in more than 10 years at their institution [10].

This article generated two Letters to the Editor, one

with a case report of extrusion of vitreous necessitat-

ing an enucleation [11] and the other from the

anesthesiologists at the Massachusetts Eye and Ear

Infirmary in Boston, MA, citing more than 10 years

of using succinylcholine at induction in open globe

injuries without vitreous expulsion [12].

IOP increases within 1 minute and peaks at an

increase of 9 mm Hg within 6 minutes after suc-

cinylcholine administration [13]. The exact mecha-

nism of this increase is unknown. Some feel that tonic

contractions of the extraocular muscles may explain

this IOP increase. However, in a feline model of an-

terior and posterior ocular trauma, there was no ex-

trusion of ocular contents after succinylcholine. The

only effect was forward displacement of the lens and

iris [13]. In a study of 15 patients undergoing elective

enucleation, succinylcholine was given after all the

extraocular muscles to the diseased eye had been

detached. There was no difference in IOP increase

between the detached and intact eyes [14]. It is now

thought that succinylcholine-induced IOP increase is

a vascular event, with choroidal vascular dilatation or

a decrease in drainage secondary to elevated central

venous pressure, temporarily inhibiting the flow of

aqueous humor through the canal of Schlemm [15].

Therefore, it is clear that succinylcholine raises

IOP. However, at induction of general anesthesia

there are many activities that raise IOP with a much

larger increase than that with succinylcholine, includ-

ing crying, Valsalva, forceful blinking, and rubbing

of the eyes [16] as well as coughing or bucking during

poor intubating technique [1]. Therefore, the increase

in IOP owing to succinylcholine may be inconse-

quential if optimal intubating conditions are not pro-

vided [17].

Nondepolarizing muscle relaxants

There are many nondepolarizing muscle relaxants

that can be used to facilitate rapid-sequence induction

for open eye injuries. In general, onset time is slower

than succinylcholine. Various methods have been

proposed to speed this onset: priming, administering

the neuromuscular agent before the induction agent,

and using high-dose regimens.

The priming principle suggests that a small dose

of a nondepolarizing muscle relaxant be given 3 min-

utes before rapid sequence induction, when the induc-

tion agent and the rest of the nondepolarizing drug

are given. This runs the risk of partial paralysis from

the priming dose itself as well as the risk of loss of

airway control [18].

Some have proposed administering the neuro-

muscular agent before the induction agent. With that

technique, the concern is a poorly timed disconnec-

tion at the site of the intravenous catheter and a longer

interval between induction and intubation [19].

Some have proposed using high-dose regimens

of nondepolarizing muscle relaxant. High doses of

vecuronium, 0.2 to 0.3 mg/kg, can provide good in-

tubating conditions in 90 seconds [20]. Rocuronium

0.6 mg/kg can be a good substitute for rapid se-

quence induction and intubation [21,22]. When

comparing succinylcholine 1.5 mg/kg versus rocu-

ronium 0.6 mg/kg, the intubating conditions were

excellent after 60 seconds and the IOP rise with

succinylcholine was 21.6 mm Hg as opposed to

13.3 mm Hg with rocuronium [23]. However, others

have suggested that as much as 0.9 to 1.2 mg/kg of

rocuronium is needed to provide equivalent intubat-

ing conditions to succinylcholine, at the expense of

prolonged duration of action [24–26].

Therefore, despite various methods to optimize

their use, nondepolarizing muscle relaxants can result

in nonideal intubating conditions at 60 seconds, a

delay in intubation, a prolonged effect, increases in

intraocular pressure from mask application, and a

longer time with an unprotected airway. Some feel

that depolarizing agents will always be faster be-

cause, compared with succinylcholine molecules,

more receptors have to be occupied by nondepolariz-

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succinylcholine & the open eye 281

ing muscle relaxant molecules to produce an equiv-

alent degree of paralysis [27].

Regional anesthesia for open globe injuries

Regional anesthesia can be a safe, albeit non-

routine anesthesia technique for repair of open eye

injuries. It is a reasonable alternative for the manage-

ment of trauma patients where general anesthesia

may expose patients to excessive risk for complica-

tions, or for patients with less traumatic globe injuries

that pose a lower threat of loss of the eye.

There are many techniques for ocular conduction

anesthesia: cannula-based sub-Tenon block tech-

niques, topical anesthesia, intracameral injection,

and peribulbar and retrobulbar anesthesia. Selection

of the appropriate anesthesia technique should con-

sider many factors that pertain to the patient, surgery,

surgeon, anesthesia provider, and operative venue.

The risks of all ocular block techniques are inversely

proportional to education and experience. This is af-

firmed by several reports of complications by in-

adequately trained personnel [28–31].

Regional anesthesia has traditionally been consid-

ered contraindicated in patients with penetrating eye

injuries because of the concerns with potential extru-

sion of intraocular contents from the force generated

by local anesthetics, from needle instrumentation of

the orbit, from squeezing of the eyelids because of

pain on injection, or from a potential hemorrhage

after injection. Nonetheless, there are some anecdotal

case reports of successful use of ophthalmic blocks in

this setting [32,33].

There is a spectrum of eye injuries based on type

(defined by the mechanism of the injury), grade

(based on visual acuity), pupillary defect, and zone of

injury [34]. This spectrum has been validated in a

subsequent study, with a prognostic correlation be-

tween initial evaluation and eventual visual out-

come [35].

Regional anesthesia can be a reasonable alter-

native to general anesthesia for selected patients with

open globe injuries. Two retrospective studies inves-

tigated clinical features and visual acuity outcomes

associated with regional anesthesia versus general

anesthesia for open globe injuries in adult reparable

eyes. With a total of 458 patients with open globe

injuries, those who underwent surgery without gen-

eral anesthesia were more likely to have an intra-

ocular foreign body, better presenting visual acuity,

more anterior wound location, shorter wound length,

and dehiscence of previous surgical wound, and were

less likely to have a pupillary defect. There were no

anesthesia-related complications. The general anes-

thesia groups had longer operating times. Change

in visual acuity between the presenting and final

examinations was similar in the general anesthesia

and regional anesthesia groups [36,37]. A similar

prospective study showed that patients with small

anterior penetrating globe injuries may be operated

with a combined peri- and retrobulbar anesthetic,

with operative conditions as good as those with gen-

eral anesthesia [38].

Topical anesthesia has been used for an open

globe injury in a situation where cardiopulmonary

disease prevented the use of general anesthesia and

the extensive extrusion of eye contents made peri-

and retrobulbar blocks contraindicated [39]. A pro-

spective study of 10 open globe injuries repaired

under topical anesthesia showed that, for less severe

eye injuries, surgeons have adequate operative con-

ditions (slight difficulty in 9, moderate difficulty in

1 case) and most patients have minimal pain and

discomfort [40].

Blunting the effect of succinylcholine on IOP

Various methods have been used to attenuate the

effects of succinylcholine on IOP. They include self-

taming and pretreatment with lidocaine, narcotics,

nifedipine, nondepolarizing muscle relaxants, nitro-

glycerin, and propranolol.

Self-taming is a technique where a small dose

of succinylcholine is initially given, before rapid-

sequence induction. This has been found to be inef-

fective in reducing the rise in IOP and can, by itself,

cause an increase in IOP [41,42].

Pretreatment with lidocaine partially blunts the

IOP increase from succinycholine and blunts the

further increase from intubation [43].

Pretreatment with narcotics decreases the IOP rise

from succinylcholine. After fentanyl or alfentanil, IOP

increased significantly following suxamethonium, but

mean IOP remained significantly less than control

values. Tracheal intubation caused a further significant

increase in IOP, and both opioids reduced, but did not

abolish the hemodynamic responses to tracheal intu-

bation [44]. The IOP rise from succinylcholine can be

obtunded with remifentanil [45,46], sufentanil [47],

and alfentanil [48]. This decrease may be related to the

effects of opioids on systemic vascular resistance [49].

Pretreatment with nifedipine can blunt the IOP

increase from succinylcholine: the IOP increased

7.82 mm Hg in the placebo group and 0.15 mm Hg

Page 125: Anestesia Ocular

chidiac & raiskin282

in those who received 10 mg sublingual nifedi-

pine [50].

Pretreatment with a small defasciculating dose of

nondepolarizing muscle relaxant has shown mixed

results. Some have suggested that mivacurium at-

tenuates the IOP increase from succinylcholine [51].

D-tubocurarine has been shown to be beneficial by

some authors [52], while others have shown no sig-

nificant difference between the IOP increase after

succinylcholine alone or after succinylcholine when

given 3 minutes after d-tubocurarine [53–55].

Pretreatment with nitroglycerin will cause signifi-

cantly less increases in IOP after succinylcholine and

after tracheal intubation [56].

Pretreatment with propranolol has been shown to

prevent significant increases in IOP after succinyl-

choline, but there was significant cardiovascular

depression [57].

The practice at the Kresge Eye Institute

At our institution, we feel that succinylcholine

may be used to facilitate endotracheal intubation

during rapid sequence induction, despite its effects

on IOP, because it allows intubation within 30 to

60 seconds. Its short half-life also allows fast recov-

ery of muscle power if the airway conditions are

difficult. In a ‘‘full stomach-open eye injury’’ situa-

tion, with the need for a rapid-sequence induction

with avoidance of IOP increase, there is a balancing

act: preventing aspiration and preventing IOP in-

crease. When succinylcholine is chosen, we use vari-

ous medications to blunt its effect on IOP, such as

opioids, lidocaine, nifedipine, and defasciculating

doses of nondepolarizing drugs.

Is this an easy airway?

YES NO

Short- orintermediate-

actingnondepolarizing

musclerelaxants.

Is the eye viable?

YES NO

Fiberopticlaryngoscopy

Succinylcholine(after pre-treatments)

Fig. 1. Intubation algorithm for open eye injuries.

After approval by our Institutional Review Board,

we retrospectively reviewed all open globe surgeries

performed at the Kresge Eye Institute in a 24-month

period. There were 59 cases and all were adults re-

ceiving general endotracheal anesthesia. One was a

planned fiberoptic intubation because of facial inju-

ries. Eight were judged to be possibly difficult intu-

bations (see algorithm, Fig. 1) and therefore received

succinylcholine. Five of them were indeed difficult

intubations, requiring more than one attempt (one of

these five patients required fiberoptic intubation). In

all 59 cases, comparing ophthalmologists’ comments

in the preoperative assessment and after induction,

similar to the process used by Libonati et al [10],

there were no increases in vitreous loss, no lens or

uvea extrusion, and no excessive intraocular bleeding

causing further extrusion.

A proposed algorithm

We feel that two questions need to be asked before

the decision about the use or the avoidance of suc-

cinylcholine in open globe surgeries: Is this an easy

airway? and Is the eye viable? (see Fig. 1).

If the airway assessment shows that intubation

should be easy, then regardless of the patient’s aspi-

ration risk and regardless of the viability of the eye,

we feel that succinylcholine can be avoided and re-

placed with the currently available short- or inter-

mediate-acting nondepolarizing muscle relaxants.

If the airway assessment, using whatever tools the

anesthesiologist prefers, shows that this could be a

difficult intubation, regardless of the patient’s aspira-

tion risk, then a second question becomes important:

Is the eye viable? In that setting, the anesthetic in-

duction plan may need to change.

If, during the preoperative ophthalmologic exami-

nation, it is felt that the eye is not salvageable, and

the surgery is to assess the damage and create a cos-

metic closure, we prefer to use fiberoptic laryn-

goscopy. This, we realize, may increase intraocular

pressure (gagging from local anesthetic spray, retch-

ing from local anesthetic nebulized breathing treat-

ments, bucking from transtracheal injection,

hypercarbia from sedation), but this increase should

be similar to that from blinking, crying, or rubbing

the eye.

If the ophthalmologist feels that the eye is via-

ble, then we prefer using succinylcholine over any

other modality. In this setting, we start with other

drugs that attenuate the intraocular pressure effect

of succinylcholine.

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succinylcholine & the open eye 283

Summary

There is still no real case report of extrusion. The

witnessed extrusions of the 1950s and 1980s spoke

of ‘‘light anesthesia.’’ Although it is inevitable that the

use of succinylcholine will decline with the availabil-

ity of new drugs [58], the currently available shorter-

acting nondepolarizing muscle relaxants have yet to

replace the fast onset and short duration profile of

succinylcholine [59]. A new ideal replacement must

work as fast as succinylcholine, wear off as quickly as

succinylcholine, and not cause an IOP increase.

Choosing or avoiding succinylcholine is a matter

of balance of risk. To control IOP at induction, there

must be adequate dosing of drugs and adequate

timing to coincide with the three potent stimuli: the

administration of succinylcholine, the laryngoscopy,

and the endotracheal intubation. We know that

succinylcholine increases IOP, but this increase can

be attenuated with various pretreatments, is less than

the increases seen with inadequate paralysis at the

time of laryngoscopy and intubation, and is unim-

portant when weighed against the risk of loss of

the airway. Therefore, we feel that in the situation

of ‘‘difficult airway, eye viable,’’ one should

use succinylcholine.

Acknowledgments

Many thanks to Dr. Steven Gayer, Associate

Professor of Anesthesiology and Ophthalmology at

the University of Miami and Director of Anesthesia

Services at the Bascom Palmer Eye Institute, for his

advice and guidance, particularly in the area of re-

gional anesthesia for open eye injuries.

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Ophthalmol Clin N

Management of a Blind Painful Eye

Shannath L. Merbs, MD, PhD

Wilmer Eye Institute, 600 North Wolfe Street, Maumenee 505, Baltimore, MD 21287, USA

Ophthalmologists are often asked to treat patients

who have eye pain from a variety of ocular diseases.

Topical steroids, cycloplegics, ocular hypotensives,

and bandage contact lenses can be effective in many

cases. However, when the pain is intractable and the

eye has very poor vision and is disfigured, surgical

removal of the eye has traditionally been the

definitive treatment of choice. In several situations,

an alternative to enucleation is warranted, and in-

jection of a neurolytic substance can often induce

long-lasting anesthesia for a blind painful eye.

One of the most common causes of a blind pain-

ful eye is trauma [1,2], but many other ocular condi-

tions, such as retinal detachment, chronic open-angle

glaucoma, phthisis, intraocular inflammation, and

corneal decompensation can lead to loss of vision

and pain.

A blind eye can be associated with several types

of pain or discomfort. Most common is an aching or

sharp pain of the eye or orbit, but the pain may also

be referred to the forehead or temple. Photophobia

of the contralateral eye is not uncommon, even in

patients who have lost all sight in the affected eye [2].

Retrobulbar injection

Ethyl alcohol

Retrobulbar alcohol injections have been used as

an alternative to enucleation since the early 1900s to

treat blind painful eyes. Retrobulbar injections may

be preferred in cases where the blind painful eye is

cosmetically normal and not disfigured, as is often

0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights

doi:10.1016/j.ohc.2006.02.010

E-mail address: [email protected]

the case in refractory, or end-stage glaucoma [3,4].

Patients, who cannot proceed with enucleation for

medical reasons or who are reluctant to proceed with

enucleation for psychological, cultural, or religious

reasons, can be temporarily relieved of their eye pain

by a retrobulbar alcohol injection in about 85% of

cases for at least 1 month [4]. However, the discom-

fort often returns an average of 6 months after injec-

tion [3,4]. The pain is believed to recur because the

alcohol, that infiltrates the area surrounding the sen-

sory nerve fibers, damages but does not destroy the

nerve fibers. After a few months, the peripheral por-

tion of the nerve fibers regenerate and the pain recurs.

Typically, 1 mL of 95% ethyl alcohol is injected

after a standard retrobulbar block (see later discus-

sion). Immediately after a retrobulbar alcohol injec-

tion, the patient may experience a sharp pain in the

orbit or a dull occipital headache [4]. This discom-

fort can last for several minutes. Other transient com-

plications include eyelid swelling, ptosis, chemosis of

the conjunctiva, slight proptosis of the globe, and

temporary paralysis of one or more extraocular

muscles. In general, these complications last for a

few days to two months [4,5]. Neurotrophic kera-

titis is a rare complication of retrobulbar alcohol in-

jection [4].

Phenol

Chemical neurolysis by phenol is frequently used

by disciplines other than ophthalmology to provide

relief of pain and spasticity. Phenol has several

advantages over alcohol, including a less painful

injection and a more rapid onset [6]. In the treatment

of blind painful eyes, the effectiveness of phenol

(80%) is similar to alcohol, although the duration

may be longer (mean 15 months) [7]. Using the stan-

Am 19 (2006) 287 – 292

reserved.

ophthalmology.theclinics.com

Page 130: Anestesia Ocular

merbs288

dard technique described below, injection of local

anesthetic is followed by 1.5 mL of a 1:15 (6.7%)

aqueous phenol solution [7]. Complications, which

include ptosis, ophthalmopelgia, and neurotrophic

keratitis, are also similar to retrobulbar alcohol and

typically resolve after a few weeks [7].

Chlorpromazine

Chlorpromazine is another chemical that has been

injected into the retrobulbar space to treat blind pain-

ful eyes [8]. The effectiveness of phenol for elimi-

nating pain with one injection (80%–83%) is similar

to retrobulbar alcohol and phenol [8,9]. Like phenol,

the duration of pain control after a retrobulbar in-

jection of chlorpromazine can exceed that of alcohol

and normally lasts more than a year. Mild to moder-

ate chemosis, lid edema, and ptosis can occur but

usually resolve within a few weeks [9]. Typically,

1 mL of 25 mg/mL chlorpromazine is injected after

retrobulbar anesthesia.

Technique

Retrobulbar injection of neurolytic agents, espe-

cially alcohol, is painful. To minimize discomfort, the

injection is preceded by a retrobulbar block which is

administered using standard technique [4]. The

patient is asked to look up and nasally. A 3.5-cm,

22-gauge needle is inserted into the lateral third of the

lower lid just above the rim of the orbit. The needle is

passed through Tenon’s capsule between the lateral

and inferior rectus muscles into the muscle cone. The

plunger of the syringe is withdrawn slightly to insure

that the needle has not entered a blood vessel. An

initial injection of 1-2 cc of 2% lidocaine is given into

the retrobulbar space. The syringe is removed, and

the needle is held in place with a clamp. A second

syringe, containing 1–1.5 mL of either 95% ethanol,

6.7% aqueous phenol, or 25 mg/mL chlorpromazine,

is attached to the needle, and the solution is injected

into the orbit. A patch is applied.

A variation on the injection technique uses

95% ethanol and 2% lidocaine in the same syringe

[10]. Because the specific gravity of ethanol is less

than lidocaine, ethanol drawn first into a syringe

remains above the lidocaine if the syringe is held

perpendicular to the floor while the lidocaine is

drawn into the syringe slowly to avoid turbulence and

inadvertent mixture. Use of a single syringe sim-

plifies the procedure. Alternatively, two syringes can

be attached to the same retrobulbar needle with a

three-way stopcock.

Intravitreal injection

Phthisis bulbi is a progressive process in which

intraocular fibrosis leads to ciliochoroidal detach-

ment, hypotony, and a blind painful eye. In one report,

intravitreal corticosteroid injection into a phthisical

eye alleviated pain for at least 2 months [11], and this

treatment may be a viable alternative to retrobulbar

alcohol injection. The corticosteroid also appeared to

reduce ocular inflammation, with decreased conjunc-

tival congestion after injection [11]. After standard

retrobulbar anesthesia, 0.3 mL (12 mg) of triamcino-

lone acetonide (40 mg/mL) is injected intravitreally

and the eye is patched. Most patients reported pain

relief within 24 hours [11].

Cyclodestruction

Cyclodestruction destroys a portion of the ciliary

body and reduces aqueous production which de-

creases intraocular pressure. This form of therapy can

be used to relieve pain in patients who have a blind

hypertensive eye. Cyclodestruction by transcleral

cryotherapy effectively reduces intraocular pressure

and pain, but this technique is usually reserved for

cases of end-stage glaucoma because of an increased

risk of complications such as visual loss and phthisis

bulbi [12]. Cyclophotocoagulation by diode laser is

more commonly used and also effectively provides

pain relief in blind hypertensive eyes and results

in fewer complications [12,13]. Under retrobulbar

or peribulbar anesthesia, a quartz fiberoptic probe

(600 mm diameter) is used to apply the diode laser

over the ciliary body. One-half to three-quarters of

the ciliary body is treated with 20–40 applications

of 1.5–2 seconds duration. Complications of cyclo-

destruction include post-operative uveitis and hyphema,

and persistent hypotony [12,13].

Enucleation

One of the leading causes of enucleation, or re-

moval of the eye from the orbit, is a blind painful

eye [1,14]. When topical medications or retrobulbar

injections fail to control the pain, enucleation can

usually provide complete pain relief within 3 months

[15]. Painful, and severely traumatized or phthisical

blind eyes are usually best treated by enucleation

or evisceration (see later discussion). The decision

to recommend enucleation must take into account a

patient’s psychological state and general medical

condition, the etiology of the pain, the cosmesis of

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blind painful eye management 289

the eye, and the potential for complications. Patients

who have blind painful eyes that are disfigured from

trauma, may more readily agree to enucleation [2].

Enucleation provides pain relief for over 90% of

patients [2]. Some patients experience phantom

eye pain or visual hallucinations after enucleation

[16,17].

Technique

Standard enucleation techniques are detailed in a

number of oculoplastic surgical textbooks [18–21].

Enucleation is usually performed under general anes-

thesia [18–20], although it can be performed with

a retrobulbar or peribulbar block [22–24]. After an

eyelid retractor is placed, a 360� conjunctival peri-

tomy is performed around the corneoscleral limbus.

Tenon’s capsule is opened in all 4 quadrants between

the rectus muscles with blunt dissection. Each rectus

muscle is isolated, secured with a locking suture, and

severed from the globe at its insertion. The superior

oblique tendon is isolated and divided. The muscular

insertion of the inferior rectus muscle is clamped or

cauterized to minimize bleeding and then divided.

Remaining fibrous attachments to the globe are di-

vided. The optic nerve is clamped behind the eye

and enucleation scissors are used to cut the optic

nerve between the clamp and the back of the eye.

Alternatively, a snare can be used to isolate and cut

the optic nerve. Hemostasis is achieved with digital

pressure for several minutes.

In most cases, the orbital volume lost by removing

the eye is replaced with an alloplastic orbital implant.

Many implant materials have been advocated in the

past, but integrated implants that allow for fibrovas-

cular tissue ingrowth into the inorganic material are

currently favored. Two of the most commonly used

materials are hydroxyapatite and high-density porous

polyethylene [25–27]. The hydroxyapatite implant is

usually wrapped in a material such as donor sclera,

pericardium, or synthetic mesh to decrease the rate

of extrusion of the implant and to facilitate the at-

tachment of the extraocular muscles to the implant

[28–30]]. The porous polyethylene implant, in con-

trast to hydroxyapatite, is less expensive and does not

require wrapping because of its smoother surface.

Greater malleability of the porous polyethylene im-

plant makes it possible to suture the extraocular

muscles directly to the implant [26].

Because of the fibrovascular ingrowth into an

integrated implant, a titanium peg can be placed into

the implant, which couples to the posterior surface of

the prosthesis for increased motility of the prosthesis.

Placement of the peg is usually performed at least

6 months after enucleation to allow for sufficient

vascularization of the implant. Although motility peg

placement can improve patient satisfaction after

enucleation [31], a significant proportion of patients

suffer from minor, peg-associated complications [32].

Therefore, most surgeons in the United States choose

not to place a motility peg [27].

After the orbital implant material has been se-

lected and the implant has been placed into the

muscle cone [33], the rectus muscles are sutured

to the implant, to the wrapping material, or to one

another anterior to the implant. Tenon’s capsule is

closed, with care not to incarcerate conjunctiva in the

closure. The conjunctiva is closed in a separate layer

to avoid conjunctival cyst formation. A conformer is

placed to occupy the fornices while the wound is

healing, and this is replaced by an ocular prosthesis in

about 6 weeks.

Enucleation can result in significant immediate

postoperative pain that requires outpatient oral

narcotics or inpatient analgesia [34,35]. Inadequate

postoperative pain relief can result in crying and

restlessness, which leads to hematoma formation, in-

creased pain, delayed wound healing, and prolonged

recovery. To reduce acute postoperative pain and

bleeding, 3–5 mL of a long-acting anesthetic with

epinephrine can be injected into the retrobulbar space

at the end of the surgical procedure. However, the

relief is only temporary. As an alternative, or in

combination with oral narcotics, an orbital catheter

can be placed for repeated delivery of a local anes-

thetic on an outpatient basis [36,37]. Although the

death of a patient who had a connective tissue ab-

normality has been attributed to the use of a par-

ticularly long indwelling orbital catheter [38], in

general, these catheters safely provide superior post-

operative pain control and allow a patient to recover

in a comfortable environment surrounded by a fa-

miliar support structure [37].

Perioperative complications of enucleation in-

clude orbital hemorrhage and edema, orbital infec-

tion, and conformer extrusion. These risks can be

minimized by preoperatively discontinuing antico-

agulants, leaving the clamp around the optic nerve

for several minutes after transaction of the optic

nerve, and administering systemic and topical anti-

biotics for 7 days postoperatively. A temporary su-

ture tarsorrhaphy can aid in the retention of the

conformer in cases of more severe postoperative

edema. Other complications, including implant migra-

tion, exposure, and extrusion, can be minimized by

the use of an integrated implant. Long-term compli-

cations after enucleation affecting cosmesis and fit-

ting of the ocular prosthesis include ptosis, lower

Page 132: Anestesia Ocular

merbs290

eyelid retraction, superior sulcus deformity, and rela-

tive enophthalmos of the prosthesis because of re-

duced orbital volume [39].

Evisceration

Evisceration is the complete removal of the con-

tents of the eye while the scleral shell attached to

the extraocular muscles remains intact. Evisceration

is another surgical procedure that can effectively

eliminate intractable ocular pain [15]. When com-

pared with enucleation, evisceration is a simpler pro-

cedure, recovery is faster, and there is less trauma

to the orbital tissues [40]. This leads to superior

cosmesis and prosthesis movement because of the

preservation of the muscular attachments to the sclera

and their relationship to the orbital implant [41–43].

Evisceration, because it removes only a portion of the

eye, may be more acceptable to patients who are

having difficulty psychologically with enucleation. In

the pre-antibiotic era, evisceration was the treatment

of choice for a blind painful eye in the setting of

endophthalmitis, because it minimized the chance of

orbit and central nervous system contamination with

infectious organisms [44]. Many surgeons still prefer

evisceration in the setting of endophthalmitis.

Although evisceration has many advantages over

enucleation, significant controversy surrounds the

evisceration procedure because of the very small risk

of sympathetic ophthalmia. Sympathetic ophthalmia

is a bilateral granulomatous panuveitis that occurs

after penetrating ocular surgery or injury that involves

the uvea of one eye. The exact pathogenesis of sym-

pathetic ophthalmia is unknown, but it is thought

that the ocular penetration may release a uveal an-

tigen that stimulates an immunologic response [45].

Although an increased risk of sympathetic ophthal-

mia theoretically exists after evisceration because of

the inability to completely remove the uveal tissue

from the sclera [41,43,44,46], the true incidence of

sympathetic ophthalmia after evisceration is

unknown [44,47]. Even though anecdotal reports of

sympathetic ophthalmia exist in the older literature,

many surgeons believe that evisceration is a safe

and effective procedure with little risk of sympa-

thetic ophthalmia and better cosmesis and motility

[27,47,48].

A disadvantage of evisceration when compared

with enucleation is increased pain in the immediate

postoperative period [41,44,49]. However, eviscera-

tion ultimately results in pain relief equivalent to that

of enucleation; most patients achieve pain relief

within 6 weeks and the rest within 15 months [15].

Evisceration can unsuspectingly disseminate an intra-

ocular tumor, and therefore, when evisceration is

being considered, ophthalmic ultrasound should be

performed to eliminate the possibility of intraocular

malignancy [50].

Technique

Like enucleation, the surgical technique of evis-

ceration is well described in textbooks [21,51]. The

technique usually involves removing the cornea if it

is thin or severely traumatized. Also, some patients

may complain of postoperative corneal sensitivity if

the cornea is left intact [43]. After a 360� conjunctivalperitomy, the conjunctiva and Tenon’s capsule are

undermined for several millimeters, the anterior

chamber is entered at the limbus, and the cornea is

removed with scissors. Anterior relaxing incisions are

made in the sclera to facilitate entry of a larger

implant into the scleral cavity. An evisceration spoon

is used to remove the intraocular contents from the

sclera. The interior surface of the scleral shell is

wiped with absolute alcohol to remove any residual

uveal pigment and then rinsed with saline. The sites

of the four vortex veins and the optic nerve head

should be cauterized to minimize bleeding. Poste-

rior meridional and equatorial sclerotomies make it

possible to place an 18- or 20-mm implant and still

maintain effective closure without tension [52]. It is

important to avoid incising the sclera through a rectus

muscle insertion when performing the sclerotomies

to minimize the chance for intraoperative hemor-

rhage. After placement of a non-porous or porous

implant, the scleral edges are overlapped and secured

with mattress sutures. It is usually necessary to trim

the scleral corners to avoid redundancy and allow for

a smooth closure. Interrupted absorbable sutures are

used to close Tenon’s capsule and the conjunctiva is

closed by using a running absorbable suture. In cases

of endophthalmitis, placement of an orbital implant

is usually performed as a secondary procedure after

evisceration, to minimize the risk of implant infection

[19,21], although some believe it is safe to place the

implant during the primary procedure [53].

Complications after evisceration with an implant

are similar to enucleation: possible implant exposure,

infection, or extrusion as well as periorbital changes

such as superior sulcus defect [54].

Summary

Debilitating ocular pain poses a significant chal-

lenge to the ophthalmologist. Enucleation or eviscera-

Page 133: Anestesia Ocular

blind painful eye management 291

tion of a blind painful eye is usually recommended

because of its ability to permanently eliminate the

eye pain. However, many people are uncomfortable

psychologically with removal of their eye, however

painful, and other patients are not good surgical can-

didates. For both of these situations, retrobulbar

injection provides an excellent alternative for tempo-

rary pain relief.

References

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[2] Custer PL, Reistad CE. Enucleation of blind, painful

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[10] Maza CE. A safer technique for retrobulbar alcohol

injections. Ophthalmic Surg 1989;20(11):823.

[11] Rodriguez ML, Juarez CP, Luna JD. Intravitreal

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Ophthalmol Clin N

Complications of Anesthesia for Ocular Surgery

Marc Goldberg, MDT

Wills Eye Hospital, 840 Walnut Street, Philadelphia, PA 19107, USA

Ophthalmic anesthesia is unique because ophthal-

mic surgery itself rarely causes unanticipated hemo-

dynamic instability. Unlike more invasive surgery,

intravascular fluid shifts, blood loss, and changes

in cardiac, respiratory, hepatic, and renal function are

almost never caused by the surgical procedure. Com-

plications of anesthetic management stand alone;

patients are subject to every known complication of

anesthesia, magnified at times by ophthalmologic

or patient demographic factors, but not caused by

those factors. Ocular anesthesia complications can be

divided into three categories: complications of moni-

tored anesthesia care (MAC), complications of gen-

eral anesthesia, and a small set of complications

unique to ophthalmic surgery.

Systematic study of anesthesia complications be-

gan in 1984 when the American Society of Anesthe-

siologists (ASA) initiated a review of closed medical

malpractice claims, the ASA Closed Claims Project.

Malpractice insurers voluntarily reported details of

5,475 claims against anesthesiologists that were

finally adjudicated between 1970 and 1999 [1]. It

was quickly evident that respiratory misadventures,

particularly inability to ventilate patients by mask

or intubate patients’ tracheas, were the cause of the

worst outcomes and highest dollar payouts for mal-

practice claims. Analysis of the types of claims al-

lowed classification by root causes and prompted

specific anesthesia practice guidelines that have

significantly improved patient safety and reduced

the number of claims and their severity (Fig. 1) [2].

Malpractice costs for anesthesiologists have reflected

0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights

doi:10.1016/j.ohc.2006.02.018

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NJ 08077.

E-mail address: [email protected]

this emphasis on safety. Average cost for malpractice

insurance for anesthesiologists is $21,000 per year,

less than 20 years ago in constant dollars [3].

The Closed Claims Project allowed analysis of

clusters of complications, showing systemic issues

or common root causes and suggesting methods of

prevention not evident via analysis of any one par-

ticular claim. Closed claims results show that the

frequency of hypoxic episodes resulting in brain

death or damage has decreased, although these claim

payouts are still in the hundreds of thousands of

dollars [4]. As Cheney [4] noted, in the 1970 to 1979

period, 41% of closed claims were for death and 15%

were for brain damage. By 1990 to 1994, only 22%

of closed claims were for death and only 9% were for

brain damage. This correlates with the universal in-

troduction of pulse oximetry and capnometry in first-

world countries. At the other end of the frequency/

payout spectrum, dental damage during airway

manipulation is now the most frequent minor claim.

Warner found an incidence of dental injury in 1 in

2,805 patients who had endotracheal intubation [5].

The mean repair cost was $782, with a range of $88

to $8,200. Closed claims analysis is used in this

article to elaborate the complications of MAC and

general anesthesia.

Complications of monitored anesthesia care

Postoperative nausea and vomiting

The most frequent complication of MAC is post-

operative nausea or vomiting (PONV). Awide variety

of afferent pathways, including vagal, sympathetic,

and vestibular nerves, activated by visceral distention

or traction, activate the chemoreceptor trigger zone

Am 19 (2006) 293 – 307

reserved.

ophthalmology.theclinics.com

Page 136: Anestesia Ocular

Fig. 1. American Society of Anesthesiologists Difficult Airway Algorithm. As a practice parameter and standard of care, the

difficult airway algorithm provides guidance for management of suspected and unsuspected airways. The conceptualization

behind its adoption has significantly decreased anesthesia morbidity and mortality from hypoxia. (Adapted from American

Society of Anesthesiologists Task Force on Management of the Difficult Airway. Practice guidelines for management of the

difficult airway. A report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway.

Anesthesiology 1993;78(3):597–602.)

goldberg294

Page 137: Anestesia Ocular

Fig. 2. Cumulative risk of PONV. Risk factors include female gender, nonsmoking, history of motion sickness or PONV, and the

use of postoperative narcotics. (Data from Apfel CC, Laara E, Koivuranta M. A simplified risk score for predicting post-

operative nausea and vomiting: conclusions from cross-validations between two centers. Anesthesiology 1999;91:693–700.)

complications of anesthesia for ocular surgery 295

(CTZ), located on the floor of the fourth ventricle.

Higher cortical pathways triggered by pain, hypoxia,

increased intracranial pressure, and odors also acti-

vate the CTZ. All narcotics act directly on the CTZ to

cause PONV, but reversal of narcotic action by nal-

oxone may paradoxically increase PONV because of

the resulting increased perception of pain.

Different studies estimate the incidence of PONV

to be between 10% and 80%. Risk factors include

female gender, particularly in premenopausal women,

nonsmoking, use of narcotics and nitrous oxide, a

past history of PONV or motion sickness, younger

age, and gynecologic and certain ophthalmic surger-

ies. Apfel and colleagues [6] developed a risk score

for prediction of PONV, demonstrating that the risks

were cumulative (Fig. 2).

PONV is the complication most feared by

patients. In addition to patient discomfort, PONV

contributes to increased nursing costs, delays in post-

operative discharge from the operative facility, and

readmissions to hospital. Prevention of PONV is

more effective than treatment, but antiemetics have

independent adverse side effects and increase the cost

of surgery. Identification of at-risk patients allows

targeting of prophylactic treatment. Prophylaxis is

more cost-effective for the high-risk pediatric patient

having strabismus surgery than for the elderly patient

having cataract removal. Narcotic treatment, a major

trigger of PONV, should be avoided whenever pos-

sible for ocular patients.

Thousands of papers in the anesthesiology litera-

ture have assessed different antiemetic regimens, with

no clear consensus as to which regimen is most ef-

fective. Avoidance of triggering agents, particularly

narcotics and nitrous oxide, has been shown in mul-

tiple studies to decrease the incidence of PONV.

Some studies find a benefit to high inspired oxygen

concentrations; other studies do not [7,8]. Acetamino-

phen and ketorolac may substitute for narcotics for

relief of postoperative pain. Nonnarcotic analgesics

are more effective if administered before the onset

of surgical stimulation. The modern use of propofol,

which itself has an antiemetic effect, and midazolam

for sedation has decreased the incidence of PONV

compared with barbiturates and diazepam [9].

The most common agents used prophylactically

or for treatment of PONV are the antiserotonin drugs

ondansetron, dolasetron, and granisetron. These drugs

have no effect on dopaminergic, cholinergic, adren-

ergic, or histaminic receptors and have a remarkably

low incidence of adverse side effects. Ondansetron

may be associated with headaches (9%), and dolase-

tron may cause symptomatic electrocardiographic

changes, including increases in PR and QRS intervals

[10,11]. Depending on type of surgery and patient

population considered, 5-HT3 receptor blockers have

been found to significantly decrease the incidence

of PONVor to decrease it no more than supplemental

oxygen [12,13].

The corticosteroid dexamethasone has prophylac-

tic PONV and antiemetic effects, demonstrated in

many studies. Bhatia and colleagues [14] found a

much lower incidence of PONV in pediatric strabis-

mus patients prophylactically treated with dexametha-

sone 0.25mg/kg (P = .001) between 0 and 24 hours

after surgery than in the control group. Fifty-one

percent of children who received dexamethasone had

no PONV compared with only 15% of children in the

Page 138: Anestesia Ocular

Box 1. General anesthesia complications

Airway difficultiesCardiac compromise and arrestRespiratory depression and aspirationUnexpected awareness during anesthesiaFailure to regain consciousnessComplications of monitoringPeripheral nerve damageAllergic reactionsHepatic and renal compromiseEquipment malfunctions, mechanical

misadventures, and syringe swapMortalityDental damageAirway management

goldberg296

control group. Hyperglycemia and impaired wound

healing were not seen.

Droperidol, a centrally acting butyrophenone, is

extremely effective in low doses for PONV prophy-

laxis and treatment by itself and in combination with

other drugs [15]. After several incidents of prolonged

QT intervals leading to the ventricular dysrhythmia

torsades de pointes, the American Food and Drug

Administration issued a ‘‘black box’’ warning against

the use of droperidol for PONV. A review of the

cases, particularly considering the many millions of

previous uses of droperidol for PONV, suggests that

the warning was unnecessary [16].

Metaclopramide acts on central domaminergic re-

ceptors and has long been used as an adjunct, rather

than as a primary anti-PONV drug. By itself, it has

little efficacy and probably has no role in nonrescue

PONV treatment [17,18]. Extrapyramidal side effects,

although rare, are extremely disturbing.

PONV is the most common complaint after MAC

anesthesia. Adequate (pre-) treatment of pain with

nonnarcotic analgesics and avoidance of narcotics

whenever possible, and prophylactic pretreatment of

high-risk patients with use of serotonin antagonists

and dexamethasone, are the most reliable means to

avoid PONV.

Oversedation and undersedation

Another frequent complication of MAC for oph-

thalmic surgery is over- or undersedation of patients.

Adequate topical or nerve block anesthesia is critical

to use of MAC because using intravenous sedatives

(propofol, midazolam, narcotics) to compensate for

inadequate local anesthetic will result in oversedation

and airway obstruction. Careful attention to the pa-

tient’s level of consciousness and comfort is critical

to avoid the extremes of either patient discomfort or

hypoxia and respiratory compromise during surgery.

During ocular surgery, the anesthesia provider has

impaired access to the patient’s airway and less abil-

ity to assess patient response because the patient’s

head position is oriented away from the anesthetist.

There is an unfortunate tendency to be less ‘‘in

contact’’ with the patient and to lower the level of

vigilance; MAC is sometimes considered less of an

anesthetic than general anesthesia. The same level of

vigilance is required for MAC as for general anes-

thesia. For certain patients, MAC is more difficult

to provide than general anesthesia. Though the use

of the pulse oximeter has decreased the incidence

of unrecognized hypoxia, electronic monitoring

should not substitute for visual and tactile contact

with the patient.

Inadvertent local anesthetic injection

Intravascular and subarachnoid injection of local

anesthetic agents is an infrequent but serious com-

plication of MAC [19]. Undoubtedly an under-

reported complication, unexpected subarachnoid

local anesthetic injection has decreased with replace-

ment of retrobulbar blocks by topical, peribulbar, or

subtenon’s injection of local anesthetic. Newer topi-

calization techniques have also decreased the inci-

dence of accidental intraorbital injection of local

anesthetics. Intravenous injection of ophthalmic

volumes of local anesthetics (eg, 5 to 10 mL of

bupivicaine or carbocaine 0.5%) may cause transient

CNS effects but rarely cause cardiovascular collapse,

as would larger volumes of local anesthetics. Intra-

arterial injection of these volumes of local anesthetics

may cause a grand-mal seizure or respiratory arrest.

Although the incidence of intravascular and sub-

arachnoid local anesthetic injection has decreased,

anesthesia providers must be ready immediately to

secure the patient’s airway and to administer ad-

vanced cardiac life support if needed.

Complications of general anesthesia

Ophthalmic anesthesia is subject to all of the po-

tential complications of general anesthesia even

though the level of surgical stimulation and fluid

shifts are smaller than for other operations. A list of

general anesthesia complications appears in Box 1.

As noted, skillful airway management is critical to

avoid hypoxia upon induction of anesthesia. Evalua-

tion begins with the history of previous anesthetics,

particularly whether patients have been told that their

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complications of anesthesia for ocular surgery 297

tracheas are difficult to intubate. After difficulty in

either ventilating by mask or intubating, the anes-

thesiologist must inform the patient or family of the

difficulty. This is best done via a letter that explains

the problems encountered and how the airway was

ultimately established (or not). Patients with known

difficult airways should be advised to share such a

letter with future anesthesiologists and to consider ob-

taining a MedicAlert bracelet for difficult intubation.

The anesthesiologist observes the airway, looking

for the visibility of the epiglottis, tonsil pillars, uvula,

and soft palate as the airway class advances from 0 to

4, as described by Mallampati [20]. A class 0 airway,

wherein the epiglottis itself is visible, should present

little intubation difficulty. A class 4 airway, with a

large tongue, small oral opening, protruding teeth,

and only hard palate visible, correlates with 84%

sensitivity and 71% specificity for inadequate view

on laryngoscopy [21]. The anesthesiologist’s goal is

to detect potentially difficult airways before induction

of general anesthesia, however, Mallampati classi-

fication and other screening systems imperfectly

predict intubating difficulty [22]. Morbid obesity,

pregnancy, cervical spine disease, thyroid nodules,

Down’s syndrome, and congenital or acquired tra-

cheal stenosis may also increase the potential for air-

way management problems. Patients with anticipated

difficult intubations, or a history of difficult intuba-

tion, may require awake (sedated) fiberoptic intuba-

tion to prevent loss of the airway and inability to

ventilate the lungs. Laryngeal mask airways (LMA)

are commonly used either to avoid endotracheal intu-

bation or as rescue airways after difficult intubation

or ventilation. LMAs can provide an airway seal up to

20 cmH20 pressure, giving some assurance against

aspiration. However, many anesthesiologists are

reluctant to rely on LMAs for positive pressure ven-

tilation in paralyzed patients because of the risk of

regurgitation of stomach contents and pulmonary as-

piration. If an ophthalmology patient needs paralysis

or the guarantee of minimal eye movement, and has a

difficult airway, the anesthesiologist may prefer to

secure the airway via awake fiberoptic intubation—

an intervention considerably more invasive than

many ocular surgeries. The ASA Difficult Airway

Algorithm (see Fig. 1) gives best practice parameters

for the anticipated and unanticipated difficult airway.

Peterson recently reviewed ASA closed claims

data for difficult airway management between 1985

and 1999 [23]. Since promulgation of the ASA

difficult airway algorithm, the likelihood of death or

brain damage for an airway claim during induction

decreased almost 50%, whereas the odds of death

or brain damage during the other phases of the

anesthetic remained the same. The fear that practice

guidelines may be used legally against physicians did

not materialize. The airway algorithm was used in

only 8% of claims to defend the care given; it was

cited in only 3% of claims to criticize the care given.

A related airway compromise at the end of the

general anesthetic may result in life-threatening pul-

monary edema. Obstruction of the airway, most

commonly by laryngospasm, may result in markedly

negative intrapleural pressures (up to �100 cmH20)

and draws transcapillary fluid into the alveoli. Risk

factors include young age, male gender, sleep apnea,

hypertrophied adenoids or tonsils, hypoxia, and

hyperadrenergic states. If early airway obstruction

during emergence is suspected, mechanical airway

opening (oral airways) or administration of small

amounts of succinylcholine (5 to 10 mg) may relieve

obstruction or laryngospasm and prevent develop-

ment of negative-pressure pulmonary edema. If these

measures fail, most patients require reintubation,

positive-pressure ventilation, and postincident moni-

toring. Episodes resolve quickly without diuresis and

without permanent sequellae, unlike other causes of

postoperative pulmonary edema, such as aspiration

pneumonia, acute respiratory distress syndrome, co-

existing cardiac anomalies or myocardial infarction,

and anaphylaxis.

Aspiration of gastric contents

Passive or active aspiration of gastric contents can

cause aspiration pneumonia, which has a high rate

of morbidity and mortality. Traditional practice has

called for an 8-hour fast before elective surgical

procedures for adults. Recent studies have indicated

that a total fast can decrease gastric pH and make

aspiration-induced pulmonary damage worse. Fasting

guidelines for children reflect this change [24]. Chil-

dren under 6 months of age should have a 2-hour

clear-liquid fast before elective surgery. Children be-

tween 6 and 36 months should fast for 3 hours; older

children should fast for 8 hours. Formula and breast

milk are considered solids and should occasion a

4-hour fast. Particulate aspiration is probably more

harmful than acid aspiration.

Patients at risk for aspiration include those who

require emergency surgeries, morbidly obese or preg-

nant patients, and diabetics with gastric motility dis-

orders. These patients are always considered to have

‘‘full stomachs.’’ Patients with difficult airways are

also at risk due to gastric gas insufflation during air-

way manipulation.

Page 140: Anestesia Ocular

Table 1

American Society of Anesthesiologists Physical Status

Classification

ASA

class Description

I Healthy patient

II Mild systemic diseases—no functional limitation

III Severe systemic disease—definite functional

limitation

IV Severe systemic disease that is a constant threat

to life

V Moribund patient unlikely to survive 24 hours

with or without surgery

VI Organ donor

goldberg298

Warner and colleagues [25] found the incidence

of aspiration in general anesthetics was 1 in 3,216;

aspiration was 4.3 times more likely during emer-

gency surgery. Most (64%) of patients who aspirated

did not develop coughing, wheezing, or decreased

arterial oxygen saturation within 2 hours of aspira-

tion. This patient group did not develop respiratory

sequellae. One half of the remaining patients needed

respiratory support for longer than 6 hours after

aspiration, and 5% of these patients died of respira-

tory insufficiency.

Prophylaxis against aspiration includes delaying

emergency surgery if possible, administration of non-

particulate antacids, use of cricoid pressure to prevent

regurgitation during endotracheal intubation, and

postintubation emptying of gastric contents by way

of a nasogastric tube.

Cardiac complications

All of the currently used potent inhalation anes-

thetics (isoflurane, sevoflurane, and desflurane) have

negative inotropic effects and may affect heart

rhythm and atrial-ventricular conduction.Cardiac con-

cerns for young patients are primarily avoidance of

severe bradycardia or asystole from the occulocardiac

reflex and recognition of rare congenital or acquired

valvular or cardiac structural anomalies, such as atrial

or ventricular septal defects. Elderly patients present

issues of myocardial ischemia, cardiomyopathy, and

valvular stenosis or insufficiency.

The preanesthetic history includes a functional

assessment of the patient’s cardiac status using a

standardized guideline, such as the American College

of Cardiology/American Heart Association scale of

cardiac risk factors, including exercise capability,

recent history of myocardial infarction, dysrhythmias,

congestive heart failure, and presence of a pacemaker

or automatic implanted defibrillator [26]. These

assessment systems are used to determine the extent

of preoperative cardiac function investigation needed

to reduce risk of intraoperative or postoperative myo-

cardial ischemia. Patients with multiple risk factors

who have not had a reasonable cardiologic evaluation

may require consultation, a stress test or echocardio-

gram, or, rarely, cardiac catheterization before elec-

tive ophthalmic surgery.

The incidence of myocardial infarction or ische-

mia after ocular surgery is small. McCannel and col-

leagues [27] followed 418 patients for 4 weeks who

had received general anesthesia for vitreoretinal or

ocular oncologic surgery. The incidence of myocar-

dial infarction was 0.24% (one case). However, the

average American Society of Anesthesiology physi-

cal status of his patients was 2.1; elderly patients

frequently have multiple medical conditions and a

physical status of III or IV, indicating greater like-

lihood of postoperative complications (Table 1). Mor-

tality and morbidity estimation based on ASA

physical status must be qualified by the limited inva-

siveness of ocular surgery.

General anesthesia permits alleviation of anxiety

and pain with provision of high levels of arterial

oxygenation and decreased myocardial demand for

oxygen (from the negative inotropic effect of inhaled

anesthetics). For patients and procedures not amena-

ble to local anesthesia, general anesthesia is safe as

long as the patient’s cardiac risk factors are assessed

and optimized, symptoms and signs of ischemia are

monitored and recognized, and airway obstruction

and hypoxia throughout the perianesthetic period are

avoided. Anesthesia personnel should be prepared

to provide initial treatment of myocardial ischemia

and should be advance cardiac life-support certified

(or its equivalent) to treat dysrhythmias during or af-

ter surgery.

Awareness during anesthesia

Unintended patient consciousness during general

anesthesia has received increased recognition in the

past 10 years [28]. The ASA Closed Claims Project

disclosed 79 (1.9%) of 4,183 claims were for intra-

operative awareness [29]. Estimates of awareness

during anesthesia with use of neuromuscular blocking

drugs (NMBs) are as high as 1 in 556 general anes-

thetics [30]. Potent inhalation anesthetics generally

provide amnesia at 20% of the dose required to pre-

vent movement upon surgical stimulation. Anesthetic

adjuncts, such as midazolam, have excellent amnesic

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complications of anesthesia for ocular surgery 299

properties in small doses. However, patient variation,

use of NMBs, and lack of definitive clinical signs of

awareness make it difficult to detect. During general

anesthesia with an LMA, spontaneous ventilation and

avoidance of NMBs require deep enough levels of

anesthesia to prevent movement so that conscious-

ness rarely occurs. Patient paralysis may mask

inadequate anesthesia. Emergency (eg, trauma, Cae-

sarian section) and cardiac surgery patients, who

receive more NMB than inhalation agent, are more at

risk of awareness than ocular patients.

Patientsmay remember a combination of conscious-

ness, conversations, or pain during general anesthesia.

Self-doubt, anger, nightmares, and fear of future op-

erations may result, as a form of posttraumatic stress

syndrome [31]. Treatment involves frank discussion

with the patient acknowledging that awareness has

occurred. Fear of legally admitting liability should not

dissuade the anesthesiologist from discussing the

problem with the patient. The best legal defense against

a claim for awareness during anesthesia is that the

anesthesiologist has informed a patient of the risk be-

fore the operation; (2) talked to her after the surgery

about her experience; and (3) provided her with an

explanation or an apology [32].

Some of the increased concern about awareness

during general anesthesia may coincide with the in-

troduction of a monitor that purports to detect it [33].

The BIS monitor uses a proprietary algorithm to pro-

cess an electroencephalographic signal. It produces

an absolute number from 0 (isoelectric EEG) to 100

(fully awake); awareness and recall supposedly do

not occur when the BIS score is between 50 and 60.

O’Connor and colleagues [34] performed a power

analysis to determine the cost of preventing aware-

ness using BIS monitoring. If the incidence of aware-

ness is 1 in 20,000, the cost to detect one case is

$400,000; if the incidence is 1 in 100, the cost to

detect one case is $2,000. Because there are reported

cases of awareness using BIS monitoring, O’Connor

[35] concludes that BIS monitoring is not cost-

effective for prevention of awareness.

The ASA is currently in heated discussion about

adopting some type of EEG monitoring to detect and

prevent intraoperative awareness. Until BIS or some

equivalent monitor becomes a standard of care by

way of a practice guideline, its use is at the discretion

of the individual anesthesiologist. Ophthalmologic

patients are rarely at high risk for awareness. Judi-

cious use of NMBs and administration of low doses

of potent inhalation agents along with pre- and

postoperative patient consultation is the most cost-

effective way to prevent the consequences of aware-

ness during general anesthesia.

Failure to regain consciousness after general

anesthesia

Unanticipated failure to regain consciousness after

general anesthesia is fortunately a rare complication.

The most common reason is probably anesthetic

overdose. This is usually as a result of inadvertently

continuing to administer inhalation anesthetics by

failing to turn off the vaporizer, overuse of narcotics

or NMBs, or syringe swap (eg, giving an NMB in-

stead of a NMB reversal agent). Use of capnometry

with analysis of inhalation agents is useful to detect

their accidental continued administration. Peripheral

nerve monitoring (‘‘twitch monitoring’’) allows as-

sessment of the degree of neuromuscular blockade

and the effectiveness of NMB reversal drugs. Recog-

nizing the potential for reactive hypertension and

tachycardia, naloxone, physostigmine, and flumazenil

may be used to reverse sedation from, respectively,

narcotics, centrally acting anticholinergic agents

(scopolamine and rarely ophthalmic atropine), and

benzodiazepines. Hyperventilation, used to quickly

eliminate inhalation anesthetics, frequently decreases

arterial carbon dioxide levels below the level required

(PaCO2 of 45 mmHg). This eliminates the sponta-

neous hypercarbic ventilatory drive needed to acti-

vate the respiratory centers. Respiratory drive is also

blunted by small residual doses of inhalation anes-

thetics. Because the patient (hopefully) lacks a hyp-

oxic ventilatory drive, relative hypocarbia leaves the

patient apneic until carbon dioxide levels rise with

metabolism. Hypocarbic apnea combined with mini-

mal stimulation and use of ocular local anesthetics

can make the patient appear unresponsive for 10 to

20 minutes after cessation of a general anesthetic.

After unexpected unresponsiveness persists and

anesthetic overdose has been eliminated as a cause,

less frequent and more serious causes must be con-

sidered. Metabolic causes of persistent unconscious-

ness include hypoglycemia, particularly in diabetic

patients, hyperglycemia and hyperosmolar syn-

dromes, hepatic and renal dysfunction, electrolyte

imbalance (particularly hyponatremia), hypothermia

and hyperthermia, and acidosis. Intraoperative neuro-

logic injury may occur from hypoxemia or cerebral

hypoxia and hypoperfusion, intracranial hemorrhage,

and cerebral embolism. Though some operations are

associated with cerebral impairment (heart surgery

with cardiopulmonary bypass, major joint replace-

ment), ocular surgery normally lacks this association.

Failure to regain consciousness after general anes-

thesia requires maintenance of oxygenation and

ventilation with mechanical ventilatory support; veri-

fication of arterial oxygen, carbon dioxide, pH, elec-

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goldberg300

trolyte, glucose, and serum osmolarity levels; and, if

not tested preoperatively, determination of hepatic

and renal function. CT or MRI scans may detect intra-

cranial hemorrhage, mass lesions, or anoxic enceph-

alopathy. If due to anesthetic overdose of some kind,

patients will regain consciousness to some de-

gree within hours of anesthetic cessation. If uncon-

sciousness persists longer, neurologic or neurosurgical

consultation should be obtained.

Monitoring complications

Ophthalmic patients frequently have significant co-

morbidity, including coronary artery disease, chronic

obstructive pulmonary disease, diabetes, and cerebral,

renal, or hepatic insufficiency. Use of electrocardio-

gram, noninvasive blood pressure, capnometry, pulse

oximetry, and temperature during general anesthesia is

the standard of care [36]. Complications from these

monitors are extremely rare.

Invasive monitors, such as peripheral arterial,

central venous, and pulmonary artery catheters, have

a significantly higher risk of complications, including

vessel thrombosis, arterial dissection, ventricular dys-

rhythmias, and infection [37]. A more subtle com-

plication of invasive monitoring is lack of usefulness

or misinterpretation of the information provided [38].

Considering the risks of invasive hemodynamic

monitoring and its marginal benefits to the ocular

patient who does not undergo massively stimulating

surgery or suffer large fluid shifts, few of these pa-

tients need invasive monitoring for purely ocular sur-

gery. The patient whose preoperative evaluation

suggests a need for invasive monitoring is probably

not in optimal medical condition for elective surgery.

Peripheral nerve damage

Peripheral nerve damage is a surprisingly fre-

quent complication after general anesthesia. The ASA

Closed Claims study reviewed 670 claims for pe-

ripheral nerve damage (16% of 4,183 claims); most

claims associated with general anesthesia were for

injury to the ulnar nerve [39]. Warner and colleagues

[40] found a rate of development of unilateral (91%)

or bilateral (9%) ulnar neuropathy in 1 in 2,729 pa-

tients undergoing general anesthesia at the Mayo

Clinic. Predisposing factors include male gender, thin

or obese body habitus, and preexisting neuropathy

and diabetes. Although proper padding and patient

positioning during general anesthesia are critical to

preventing ulnar nerve injury, postoperative deficits

may still occur despite these precautions. Neurop-

athies may not become manifest until days after

surgery; the anesthesiologist will only discover them

if the patient complains to the surgeon [41]. The

ultimate outcome is not good; only 53% of Warner’s

patients regained complete motor function and sen-

sation a year after anesthesia and surgery [40]. Be-

cause good anesthesia practice (proper positioning

and padding) does not reliably prevent postanesthetic

neuropathy development, it may be useful to include

this complication when obtaining informed consent

for general anesthesia.

Allergic reactions during general anesthesia

Most intravenous anesthetic agents have been re-

ported to cause allergic reactions. However, reactions

range from the expected (nausea from narcotics,

reddish facial flushing from atropine) to the catas-

trophic (anaphylactic/anaphylactoid), requiring car-

diopulmonary resuscitation. Preoperative evaluation

involves careful questioning of the circumstances of a

reaction to medication. For example, patients com-

monly claim to be allergic to local anesthetics, but

true anaphylaxis is exceedingly rare, even reportable

[42]. Much more likely, the circumstances will reveal

an expected cerebral reaction to rapid injection of

local anesthetic or cardiovascular reaction to rapid

injection of adjuvant epinephrine (eg, during den-

tal injections).

Anaphylactic reactions are immune mediated;

some previous exposure to a related antigen is neces-

sary for antibody formation and reaction to occur.

Anaphylactoid reactions are not immune related and

may occur on first exposure to a triggering agent.

Like most emergencies in anesthesia, recognition and

immediate treatment is more important than definitive

diagnosis of which agent has caused the reaction and

why [43,44].

Anaphylactic reactions under general anesthesia

produce any of the following symptoms and signs:

wheezing, hypoxia, increased peak airway pressures,

acute pulmonary edema, bronchospasm, tachycardia,

dysrhythmia, severe hypotension or cardiovascular

collapse, urticaria, or periorbital and perioral edema

[45]. Treatment requires removal of the triggering

agent if identified and discontinuation of anesthetic

agents, early use of epinephrine and corticosteroids,

fluid resuscitation, protection of the airway by way of

endotracheal intubation, administration of 100%

oxygen, and rapid termination of the surgical proce-

dure. Even in the operating room context with instant

observation, full monitoring and resuscitative mea-

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complications of anesthesia for ocular surgery 301

sures available, severe outcomes, such as cardiac

arrest, renal failure, coma, persistent vegetative state,

hemiplegia, or other neurologic sequellae, may re-

sult [46].

A recent French study reviewed 789 episodes of

anaphylactic reactions during anesthesia. Most (58%)

were caused by NMBs, particularly the newer non-

depolarizing NMB rocuronium, with the rest caused

by latex (17%), antibiotics (15%), and other various

medications (10%) [47]. Rocuronium and succinyl-

choline were the NMBs most likely to cause these

reactions; after allergy testing, cross-reactivity be-

tween NMBs was observed in 75% of cases [47].

Although the French study may have overestimated

the incidence of anaphylaxis as a result of their

method of skin testing, American and Norwegian

studies also found NMBs to be the most common

cause of perioperative anaphylactic reactions [48,49].

Inhalation agents do not cause anaphylactic reac-

tions. The only instance of allergic reaction to inhala-

tion anesthetics is rare, reportable cases of hepatitis

after repeated exposure. Sufficient doubt has been

cast on the existence of ‘‘halothane hepatitis’’ to con-

sider it an exceedingly rare reaction [50]. However,

prolonged exposure to inhalation anesthetics that pro-

duce trifluroacetyl (halothane, isoflurane, and des-

flurane) results in antibodies to the molecule in

anesthesia personnel [51]. Inhalation agent related

hepatitis remains a diagnosis of exclusion.

Renal and hepatic complications of general

anesthesia

Various metabolites of inhalation anesthetics have

been theorized to cause renal function impairment.

Fluoride ion from halothane, isoflurane, and sevo-

flurane can be measured, after long exposure, in

micron concentrations associated with nephrotoxicity

in animals [52]. However, Kharasch and colleagues

[53] measured serum creatinine, blood urea nitrogen,

creatinine clearance, urinary protein, and glucose

excretion for 24 and 72 hours after 9 hour mean

exposure to sevoflurane and isoflurane and found no

evidence of renal function impairment. Sevoflurane

metabolism under particular conditions (low fresh gas

flows, particularly desiccated carbon dioxide absor-

bent) produces a haloalkane called ‘‘compound A,’’

which causes nephrotoxicity in rats [54]. Kharasch

[53] and others who have reviewed this issue have

concluded that the incidence of renal function

abnormalities produced by sevoflurane must be ex-

ceedingly small given the large number of sevoflur-

ane anesthetics given since its introduction [55]. For

ophthalmic patients with compromised renal function

(eg, diabetics), sevoflurane may be used safely as

long as systemic hypotension and low fresh gas flows

(allowing washout of any compound A generated)

are avoided.

All potent inhalation anesthetics undergo hepatic

metabolism. Up to 15% to 20% of halothane is

metabolized, but the newer inhalation agents, sevo-

flurane and desflurane, undergo only 0.5% to 1%

metabolism [56]. There are case reports of fulminant

postoperative liver damage associated with all cur-

rently used inhalation anesthetics [57–59]. Proving a

causal association between hepatic dysfunction and

either a single or repeated exposure to an inhalation

anesthetic is exceptionally difficult. Patients who

present with hepatic dysfunction after anesthesia

most often have other comorbidities or surgeries that

predispose them to hepatic damage. Many studies

have closely measured hepatic function and found

minimal alterations after anesthesia. For example,

Suttner and colleagues [60] found that though

hepatocyte oxygenation levels slightly decreased dur-

ing general anesthesia with desflurane and sevoflur-

ane, overall hepatic function was unchanged.

Various mechanisms have been proposed for he-

patic injury after general anesthesia. Concurrent viral

hepatitis may be unmasked by the stress of surgery

and anesthesia, and most likely accounts for most

anesthesia-related hepatic dysfunction. Oxidative and

reductive metabolism of inhalation anesthetics results

in compounds hepatotoxic in some species (rats, cats)

but not others (dogs, mice) [61]. Metabolites of halo-

thane have been found to bind to liver proteins and

act as haptenes to produce hepatocyte-specific anti-

bodies, which in certain families and patient popu-

lations reliably cause postexposure hepatitis [62].

Risk factors for inhalation agent-related hepatitis

include obesity, middle age, female gender, and

Mexican-American ethnicity. Obesity allows extended

duration of storage and slow release and further

metabolism of lipid-soluble agents. Repeated ex-

posure, except in patients previously suspected of

inhalation-related hepatitis, does not predispose to

hepatic dysfunction.

The entire subject of inhalation-related hepatic

dysfunction has been compared with ‘‘a sea of mys-

tery, with some islands of knowledge, but generally

pervaded by clouds of speculation, misinformation,

and ignorance’’ [63]. The diagnosis of postinhalation

agent hepatitis is a diagnosis of exclusion, and cases

are rare enough to be reportable. Proper attention to

preexisting liver function via history and laboratory

examination, avoidance of (repeated) exposure in the

face of a family history of anesthesia-related hepatitis,

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goldberg302

and avoidance of liver hypoxia and hypoperfusion

should make postocular surgery hepatitis an ex-

tremely rare complication of general anesthesia.

Equipment malfunctions and mechanical

misadventures

Anesthesia gas delivery systems and monitors

are highly reliable but are subject to human error

(common) and mechanical or electronic failure (rare)

[64]. The standard of care is that anesthesia machine

and monitor readiness are checked extensively at the

beginning of the day and briefly before each sub-

sequent case against a US Food and Drug Adminis-

tration functionality checklist, much as a commercial

airline pilot goes through a checklist before takeoff

[65]. Unfortunately, compliance with the checklist

requirement has been less than optimal. Armstrong-

Brown and colleagues [66] reported that academic

attending anesthesiologists checked, on average, only

10 of 20 items on a standardized checklist. Intensive

training may improve machine checkout performance

[67]. Simulations with intentionally created machine

faults have also been disappointing. In a machine

with five intentional faults, 7% of anesthesiologists

found no faults and only 3% found all five faults. The

average number found was 2.2 faults [68]. Anesthesi-

ologists have reported some incredible human errors

(eg, complete anesthesia circuit obstruction due to

failure to remove shrink-wrap from carbon dioxide

absorber canisters) [69]. However, candor in report-

ing mechanical problems has led to improvements in

safety. For example, now carbon dioxide canisters

are packaged in corrugated plastic, which cannot

be ignored.

Modern anesthesia machines do not allow admin-

istration of hypoxic gas mixtures; ophthalmic office

practices should ensure that they do not use older

machines without this failsafe. Devices to indepen-

dently measure inspired oxygen concentration are par-

ticularly important in isolated or office facilities.

Anesthesia machines also have alarms that detect low

oxygen supply pressure, to alert to the need to switch

to new oxygen supply tanks or emergency oxygen

tanks mounted on the machine.

Initial and continuous measurement of end-tidal

carbon dioxide during general anesthesia is a firm

standard of care [70]. If a functioning capnometer is

not available, general anesthesia should not be pro-

vided. Introduction of capnometry has eliminated

otherwise undetected esophageal intubation, which

was previously a major source of anesthetic morbid-

ity and mortality, particularly in obese patients with

difficult airways and distant breath sounds. Analysis

of inspired and exhaled inhalation anesthetics, now

commonly and economically available on capnome-

ters, assists in not only decreasing unexpected

awareness during anesthesia but also in facilitating

anesthesia emergence.

An exhaustive list of equipment-related problems

with general anesthesia cannot be repeated here. En-

tire monographs have been dedicated to mechanical

misadventures in anesthesiology (including an amus-

ing photograph of a large ‘H’ oxygen cylinder’s mis-

sile trajectory when its yoke was broken and it flew

out of an operating room onto the sidewalk below)

and understanding anesthesia equipment [71,72].

New equipment malfunctions are reported continu-

ously and corrective actions are taken accordingly.

Compliance with machine checkout procedures, scru-

pulous adherence to monitoring standards, and avoid-

ance of personnel fatigue will increase detection and

prevention of mechanical problems with general

anesthesia [73].

Another common source of human error frequent

enough to mention is syringe swap [74]. Anesthesia

drugs are drawn from vials into labeled syringes in

advance of usage. Care must be taken to avoid mis-

taking look-alike vials or labels. Meticulous identifi-

cation of syringes immediately before injection can

prevent mistakes such as giving more NMB or nar-

cotic when an NMB reversal agent is intended. Mod-

ern inhalation vaporizers are agent specific and have

a key-lock system to prevent accidental introduction

of incorrect agents. Unfortunately, anesthesia person-

nel can be resourceful at bypassing safety systems.

Malignant hyperthermia

Malignant hyperthermia (MH) deserves mention

in a compendium of general anesthesia complications

because it has received attention disproportionate to

its incidence and is not likely to be encountered by an

ophthalmologist not specializing in pediatrics. MH is

an autosomal-dominant variable-penetrance genetic

defect of calcium reuptake. The incidence is reported

to be 1 in 15,000 children and may be more common

in pediatric strabismus patients [75]. The adult inci-

dence is less than 1 in 50,000 anesthetics. Succinyl-

choline and inhalation anesthetic agents trigger MH

and result in skeletal muscle hypermetabolism.

Before capnometry, the first indication of MH sus-

ceptibility was often high body temperature, para-

doxical masseter muscle rigidity, or oliguria and

myoglobinuria. By the time these signs appeared,

survival from an untreated episode was less than

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complications of anesthesia for ocular surgery 303

30%. Routine use of capnometry allows early de-

tection of MH episodes, as the first sign of an episode

is hypercapnia despite seemingly adequate minute

ventilation. A Web site (www.mhaus.org) and an

expert-assisted hotline (United States and Canada,

1-800-644-9737, outside North America, 0011 315

464 7079), as well as a registry of known patients in

North America, is maintained by theMalignant Hyper-

thermia Association of the United States (MHAUS).

Family history of high temperature or fatality after

anesthesia is suggestive of susceptibility, but non-

diagnostic. Although several animal models, human

blood tests, and DNA mapping have been studied,

definitive diagnosis of MH is still made either after

a well-documented episode or by way of muscle bi-

opsy with in-vitro characteristic reactivity to trigger-

ing agents. Patients with a suggestive family history

need not undergo muscle biopsy; a nontriggering

anesthetic with propofol, midazolam, fentanyl, and a

nondepolarizing NMB can be safely given [76].

The skeletal muscle relaxant dantrolene is a spe-

cific inhibitor of MH-induced hypermetabolism.

Although expensive, it is a standard of care that dan-

trolene be readily available wherever inhalation anes-

thesia is provided. If geographically feasible, several

facilities may share parts of the supply of dantrolene

to decrease the per-facility cost.

Anesthetic mortality

Older patients often fear general anesthesia. Be-

fore modern monitoring techniques and anesthetic

agents, mortality from general anesthesia was as high

as 1 in 1,216 anesthetics [77]. By 1989, Eichhorn

[78] was able to report a mortality rate solely at-

tributable to general anesthesia of 1 in 200,000. The

reduction in mortality closely followed introduction

of standardized monitoring protocols despite some

caviling about the introduction of mandatory moni-

toring standards without double blind study verifica-

tion of efficacy [36,79].

The American Society of Anesthesiologists devel-

oped a clinical classification of patient preoperative

physical status in 1941, and although attempts have

been made to supplant it, it remains in use today (see

Table 1). Anesthetic mortality is roughly correlated

with physical status. Wolters found a mortality rate of

0.1% for ASA physical status I patients and 18% for

ASA physical status IV patients [80]. Type of surgery

(major vascular) and emergency surgery also increase

anesthetic mortality. Patient tolerance of critical in-

cidents (‘‘near misses’’) decreases as ASA physical

status increases.

Whether a particular type of anesthetic (MAC

versus general, or one agent versus another) can

prospectively affect mortality has been an extremely

controversial subject. Thousands of studies and meta-

analyses have not provided a clear answer. In the

ocular surgery setting, the common-sense thought

that general anesthesia is a more invasive intervention

than MAC is often, but not always, correct. MAC

anesthesia affects cardiovascular and respiratory

function less than general anesthesia and usually pro-

vides faster return to preoperative functionality. How-

ever, patients with extreme anxiety, claustrophobia,

chronic obstructive pulmonary disease, motion dis-

orders, compromised airways, and those who need

long (greater than 1.5 hours) surgery may have less

physiological stress with general anesthesia than with

MAC. General anesthesia with a secure airway, lack

of tachycardia and hypertension, and an immobile

surgical field is less stressful (for everyone) than ‘‘big

MAC’’ anesthesia with sedation, resulting in airway

obstruction and patient head or body movement.

Choice of MAC versus general anesthesia depends in

part on the patient’s ASA physical classification but

also on type and duration of surgical procedure and

patient, anesthesiologist, and surgeon emotional

characteristics. Perioperative mortality is influenced

more by skill in selection and administration of the

anesthetic than by choice of MAC versus general

anesthesia or the particular agent chosen.

Dental damage

Damage to teeth during either anesthetic induction

or emergence is one of the most frequent but minor

complications of general anesthesia [81]. As major

morbidities and mortalities decrease, the incidence of

dental claims in the ASA Closed Claims database has

increased; dental injuries may account for as many as

33% of anesthesia-related malpractice claims [82].

Warner and colleagues [5] found an incidence of

dental injuries requiring repair or extraction in 1 in

4,537 general anesthetics. Risk factors include poor

dentition, preexisting crowns or caps, and various

indices of difficult intubation. The level of resident

training did not affect the likelihood of dental in-

jury [83].

Anesthesia complications specific to the eye and

ocular surgery

Several ophthalmic complications of general anes-

thesia should not be of concern during ocular surgery.

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goldberg304

Corneal abrasions account for 3% of ASA closed

claims; these cause pain, but permanent corneal dam-

age is rare. Malpractice payouts are low, and the

median payout is $3,000 [84]. Despite ophthalmo-

logic control of the surgical area, anesthesiologists

should be careful to prevent corneal abrasions of the

nonoperative eye.

Catastrophic visual loss after nonophthalmologic

surgery is rare. Ischemic optic neuropathy and reti-

nal arterial or venous occlusion are the most likely

mechanisms of injury [85]. Predisposing factors in-

clude preexisting hypertension, diabetes, sickle cell

anemia, renal failure, gastrointestinal ulcer, narrow-

angle glaucoma, vascular occlusive disease, cardiac

disease, arteriosclerosis, polycythemia vera, and col-

lagen vascular disorders. Precipitating factors for

ischemic optic neuropathy include prolonged hypo-

tension, anemia, surgery trauma, gastrointestinal

bleeding, hemorrhage, shock, prone position, direct

pressure on the globe, and long operative times.

Prone and Trendelenburg positions and increased in-

tracranial pressure are additional risk factors. Unex-

pected vision loss in the nonoperative eye after ocular

surgery is extremely rare.

Certain specific complications of general anes-

thesia occur during ocular surgery. Thirty percent of

ASA closed claims for ocular injury were due to

unexpected patient movement during ocular surgery;

blindness resulted in every case [84]. Inadequate

muscle relaxation by NMBs during inadequately

deep general anesthesia, or coughing from endotra-

cheal intubation, may cause retinal detachment,

corneal laceration, lens subluxation, or expulsion of

intraocular contents during corneal grafting. Preven-

tion requires use of neuromuscular blockade moni-

toring, assurance of adequate levels of anesthesia, and

acceptance of delayed NMB reversal upon com-

pletion of surgery as the price of assuring unexpected

movement during surgery.

The hoary debate about the effect of succinylcho-

line on intraocular pressure during ruptured globe

surgery has been obviated by use of nondepolarizing

NMBs [86]. Increased intraocular pressure from

succinylcholine may be associated with small corneal

lacerations or globe puncture wounds that have main-

tained overall globe integrity. If the globe is ruptured

or the laceration is large enough that the intraocular

pressure is near 0 mmHg, succinylcholine will not

increase the intraocular pressure. Use of a large dose

of nondepolarizing NMB provides emergency muscle

relaxation for intubation quickly compared with

succinylcholine [87].

A rare but avoidable complication of general

anesthesia after retinal surgery is blindness caused by

nitrous oxide-induced expansion of perflurocarbon or

sulfur hexafluoride bubbles. Nitrous oxide will dif-

fuse into gas-filled spaces faster than nitrogen; oxy-

gen or ophthalmic gases diffuse out and cause retinal

ischemia. Yang and colleagues [88] first reported a

case of blindness after nonocular general anesthesia

in 2002, and seven cases have been reported since

then. Patients who have retinal surgery with use of

intraocular gas bubbles should wear warning brace-

lets until the bubble has likely dissipated. The anes-

thesia history should disclose recent ocular surgery

for past retinal surgery or current retinal surgery, and

nitrous oxide is easily avoided.

Summary

Complications of MAC and general anesthesia are

increasingly rare, and severe morbidity and mortality

have decreased as techniques for prevention and

treatment have become widespread. Ocular anesthe-

sia involves population subsets (geriatric, pediatric,

vascular, and diabetic) that have known propensities

to have certain complications, and ophthalmic sur-

gery requires certain routine precautions to avoid

the most common complications. Vigilance in patient

evaluation, equipment and drug preparation, and

monitoring during surgery, despite production pres-

sure of modern anesthetic practice, is the best way to

prevent avoidable anesthesia complications [89].

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Ophthalmol Clin N

Economic Evaluation of Different Systems for Cataract

Surgery and Anesthesia

Kevin D. Frick, PhD

Johns Hopkins Bloomberg School of Public Health, Department of Health Policy and Management,

Health Services Research and Development Center, 624 North Broadway, Room 606, Baltimore, MD 21205, USA

Economic evaluation is an increasingly important

component of health and medical care policy making

although it continues to be met with some resistance—

in part because of misgivings about the methods that

are used [1,2]. Many fields of medical care services

and public health have extensive economic evalua-

tion literature. In ophthalmology, the literature is

less well developed and there is an ongoing dis-

cussion of the most appropriate methods [3–5]. This

article (1) outlines different types of economic eval-

uations providing examples on their potential use

in ophthalmic care decision making, (2) reviews

three articles in the brief recent literature on the

cost-effectiveness of ophthalmic anesthesia and cata-

ract surgery in the United States with a focus on

explaining methods that were used, and (3) dis-

cusses ways in which research in this area might be

moved forward.

Types of economic evaluations

High-quality economic evaluations provide a

logically consistent and methodologically rigorous

way of describing the costs associated with a

condition or comparing costs of a treatment to effects

of the treatment. Evaluations include information on

costs, clinical effectiveness measures, quality of life,

or other aspects of the value that individuals place on

care and the effects of care.

0896-1549/06/$ – see front matter D 2006 Elsevier Inc. All rights

doi:10.1016/j.ohc.2006.02.013

This work was supported by the National Eye Institute’s

grant no. 5R01EY012045.

E-mail address: [email protected]

In most evaluations, all spending is given equal

weight in the cost analysis and the clinical and quality

of life changes for all patients are given equal weight

in the assessment of effectiveness [6]. Treating

everyone equally is fair, but it does not capture other

values that may be of interest. For example, there is

no explicit consideration of whether the treatment is

more likely to be administered to those of higher or

lower socioeconomic status. An intervention may be

aimed at one socioeconomic group so that the results

will obviously be interpreted with a focus on a

specific socioeconomic group, or subgroup analyses

may be conducted to help policy makers understand

the effects on different groups. However, general

cost-effectiveness analysis of a treatment affecting

multiple socioeconomic groups does not dictate or

even use relative values for different individuals. All

analyses must be interpreted with an understanding of

how the analysis treats different individuals and

whether this is consistent with the values of the

policy maker or the affected population.

The following six types of economic evaluations

are discussed in this section [6–8].

� Cost of illness/burden of disease� Cost minimization� Cost consequence� Cost effectiveness� Cost utility� Cost benefit

The types of studies are listed in order of in-

creasing ability to provide policy makers with infor-

mation that can be directly used to set policy. The

Am 19 (2006) 309 – 315

reserved.

ophthalmology.theclinics.com

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frick310

reasons that the studies at the bottom of the list pro-

vide information that can be used more directly will

become clear as each is described. Along with each

definition, the use of the type of study for health de-

cisions about cataract surgery or ophthalmic anes-

thesia will be illustrated.

Cost of illness and burden of disease studies pro-

vide the least information for policy makers as both

types of studies only describe the costs experienced

and do not compare costs with effects. Cost of ill-

ness studies can take either an incidence cost ap-

proach or a prevalence cost approach [9]. Incidence

costs are lifetime costs associated with a new case of

the condition being studied. Prevalence costs are all

costs of treating everyone with the condition in a

given year. We will refer to cost of illness studies

taking an incidence cost approach as cost of illness

studies and those that take a prevalence approach

as burden of disease studies.

To illustrate the implications of these definitions,

consider studies related to cataract surgery. A cost of

illness study focusing on cataracts will enumerate

the expected lifetime costs of an incident case of cat-

aract. In contrast, a cataract burden of disease study

will enumerate the amount of money that is spent

to treat all cataract patients in a year. This includes

treatment for both cases prevalent at the start of the

year and cases incident during a year.

If cataract prevention were the objective, a cost

of illness study would provide information on the

lifetime costs that could be avoided by preventing a

cataract. If cataract surgery for an individual who is

otherwise legally blind were the objective, a cost of

illness study focusing on blindness would provide

information on the lifetime costs that could be

avoided by a successful surgery. In neither case does

the cost of illness alone provide an economic reason

for prioritizing cataract surgery. In both cases the cost

of illness that could be avoided must be compared

with the cost of treatment to make an economic

recommendation. Burden of disease provides infor-

mation on the impact of a condition on the economy

in a year but can only be used to describe the total

costs that can be avoided if all cases of the condition

are eliminated. This type of study is useful for

directing the public’s attention to the importance of a

condition but is not particularly useful in making

policy recommendations.

Cost minimization studies can be used to facilitate

policy recommendations when two interventions or

treatments have similar effects. Similar effects could

mean literally the same effect. However, similar

effects could also mean two treatments for which

the effects are not statistically different. Finally, two

treatments might both meet a threshold criterion, and

the policy maker may not be concerned with the

degree to which the effects exceed the threshold.

Healthy People 2010 provides an example of thresh-

olds of interest [10], although many of the vision

care objectives are developmental and the only ob-

jective for cataract is to reduce visual impairment as

a result of a cataract. If each of two interventions

reduced visual impairment and a policy maker was

not interested in the magnitude of reduction, then

the two alternatives could be compared to determine

which has the lower costs. Cost minimization based

on two alternatives meeting a threshold would be

more useful if the objective were stated in the form

of ‘‘reduce the proportion of the population with

visual impairment due to cataract to less than 1% of

the population aged 65 or older.’’

Another important aspect of cost minimization

analyses is an understanding of the perspective from

which costs are being considered. The perspective

refers to whose costs are considered. The objective

may be to minimize costs to the government, costs to

a private insurer, costs to the patient, or costs to all of

society. A single intervention may not minimize costs

from all perspectives.

Cost consequence studies are useful when there

are multiple impacts of a treatment or intervention but

it is difficult or impossible to find a suitable summary

measure for the outcomes. This type of analysis may

be more palatable to a policy maker; in spite of the

lack of a summary measure, the outcomes are more

transparent as the policy maker does not need to

understand how dollar values are placed on clinical

outcomes or how quality adjusted life years are

calculated [7]. This type of analysis is not likely to

be necessary for ophthalmology interventions or

treatments. Ophthalmology care is usually aimed at

avoiding or overcoming visual impairment or blind-

ness—and cases of these conditions are often the

primary outcomes of interest. These can affect quality

of life and mortality, which can also be considered in

cost outcome studies.

When cost consequence studies are performed,

they are less directly informative than cost minimi-

zation studies. Cost minimization studies can be used

to make a clear case for one intervention based on

having a lower cost when multiple interventions have

similar effects. In contrast, cost consequence studies

essentially provide a list of pros and cons. The policy

maker must then make a comparison of the pros and

cons in a relatively unstructured way.

The result of a cost-effectiveness analysis is the

amount of money spent per clinical outcome. In

the context of cataract, the simplest clinical outcome

Page 152: Anestesia Ocular

economic evaluation 311

is cases of visual impairment prevented. Obviously,

there could be more specific measures of visual

acuity or visual function as well. The key is that there

is a clear primary outcome. These studies are useful

when making a decision about a new treatment or

intervention used for a specific condition or to avoid

a specific clinical outcome.

If there were an improvement in cataract surgical

technique, a cost-effectiveness study could address

the following question: using the new surgery rather

than the old, how much extra money is spent and how

many more cases of visual impairment are avoided?

Taking the ratio of these two figures, the result can be

expressed as the extra cost per extra case of visual

impairment avoided. A limitation with this type of

study is that there is no explicit way to compare cost-

effectiveness analyses done for different conditions or

treatments. For example, there is no explicit way to

determine whether spending $2000 to avoid a case of

visual impairment is worth more or less than

spending $10,000 to avoid a stroke. This limitation

may not be severe, as health policy makers rarely

make decisions on whether to treat visual impairment

or stroke but most often seem to make decisions on

the best way to treat a particular condition.

Cost-utility analyses use a standard outcome that

summarizes multiple types of morbidity and mortal-

ity. This summary measure is referred to as a quality

adjusted life year. Ophthalmology patients can gain

quality adjusted life years by increasing their quality

of life (by maintaining visual functional) during the

years they would have been alive anyway or by ex-

tending the length of their lives. The final result in cost

utility analyses is not the extra dollars spent per extra

case of visual impairment avoided, but the extra

dollars spent per extra quality adjusted life year gained.

The use of cost-utility results requires policy

makers to decide whether it is worth spending a cer-

tain amount of money to gain a quality adjusted life

year (QALY). The advantage over cost-effectiveness

is that only a single figure is needed, because the

theory underlying cost-utility analysis suggests that

the reason for improvements in QALYs should not

affect the value of the QALYs.

Cost-benefit analyses require the analyst to ex-

press the benefits in dollars. Some effects of changes

in health at the individual or population level are

difficult to express in monetary terms and can only

appear alongside the main result in a cost-benefit

analysis. The primary result is the calculation of the

difference between the dollar value of benefits and the

costs, and the primary criterion for implementation is

that the net benefit is positive, that is, benefits are

larger than costs. Thus, the policy interpretation is

much more direct with cost-benefit analyses than

with other cost outcome analyses.

A simple cost-benefit analysis from the limited

perspective of an insurer would ask whether there is a

business case for a new treatment, or ‘‘Does care

under a new treatment regimen cost less than an older

treatment regimen?’’ From a broader societal per-

spective, there could be an interest in the amount of

productivity gained by patients, the amount of de-

creased informal care provided by family and friends,

and other results of morbidity and mortality that

can be expressed in monetary terms.

From a payer’s perspective, a new development in

ophthalmic anesthesia could lead to higher costs in

the operating room but lower total costs including

recovery time. From society’s perspective, a cost-

benefit analysis focusing on cataract surgery could

define all economic changes related to cataract sur-

gery and ask whether the dollar value of the ben-

eficial changes is higher than the dollar value of the

changes that increase costs.

Cataract surgery and anesthesia

One recent study used a decision analytic model

to evaluate different anesthesia management strat-

egies [11]. This article demonstrates many methods

common to economic evaluations. These methods in-

clude modeling, the need for transparent parameters,

preference elicitation, sensitivity analysis, and appro-

priate incremental analysis.

Decision trees and modeling

Reeves and colleagues [11] used a decision tree to

model the costs and effects of six anesthesia manage-

ment strategies. A decision tree represents a sequence

of decisions, random events, and outcomes. The out-

comes usually include costs and either clinical or

quality of life outcomes. The tree allows for the cal-

culation of the probability of each outcome that is

used to define expected costs and expected outcomes.

The costs and clinical or quality of life outcomes are

compared to determine which alternative yields the

most preferred combination of costs and outcomes or

which alternative yields the best outcome but is not

excessively costly per unit of outcome. The authors

provide a useful and understandable description of

decision trees.

Many economic evaluations rely on models be-

cause randomized trials would be unethical, or cost

prohibitive, or require too much time relative to the

time frame for policy making. In some cases, a model

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frick312

can be used as a precursor to a randomized trial.

Models can be simple, for example, a screening

model in which individuals are true positive, true nega-

tive, false positive, or false negative and the results

do not vary once a patient is in one of these groups.

Alternatively, models can be complex with multiple

levels of random events necessary to represent events

like annual diabetic retinopathy screenings over time.

Transparent model parameters

A key feature of the article by Reeves and

colleagues [11] is a table that lists all the parame-

ters in the model including probabilities of events,

the costs associated with the choice of anesthesia

management methods and the consequences of the

methods, and the preferences for each method. The

combination of a figure showing the decision tree and

a table showing the parameters in the tree helps to

make the model that is being used transparent so that

readers can evaluate validity of the model. At one

level of validation, a model must include appropriate

outcomes that are linked to choices and random

events in ways that make clinical sense. A model can

also be externally validated if there is an outside data

source that includes longitudinal data on individuals

who begin at a point at which they would enter the

model. The observed probability of various outcomes

can then be compared with the results obtained when

individuals are modeled to assess how well the model

predicts the distribution of outcomes.

The table in the Reeves and coworkers’ article

[11] not only lists the parameters but also the sources

of data for the parameters. In general, there are

multiple sources of data for nearly every model-based

cost-effectiveness or decision analysis—past reports

of randomized trials, administrative claims data,

Medicare reimbursement rates for prices, average

wholesale prices, survey data, and expert panel data.

Expert panel data are generally the least preferred and

should be used sparingly, but these data are some-

times the only data available. In this study, only the

three probabilities of converting between types of

anesthesia and preferences for management strategies

were provided by the expert panel.

Obtaining probabilities from an expert panel is

less problematic than obtaining preferences. Stein

[12] suggests that providers have a different percep-

tion of the utility of various treatments and health

conditions than their patients have. The standard

recommendation for preference measurement is that a

cost-effectiveness or decision analysis should use

preferences of a cross-section of individuals from

society at large [6]. Societal preferences are thought

to be best to use when allocating societal resources.

However, at least some authors focus on patient

preferences [3]. Societal preferences can be difficult

to obtain if the condition or treatment has not been

studied before and if the condition or treatment is

difficult to describe to a group of respondents who

have not experienced the condition.

Preference elicitation

The research [11] used a visual analog scale ap-

proach for preference elicitation. This is the least cog-

nitively demanding and least preferred method from

a theoretical perspective, although for an assessment

of the preferences for a temporary condition like

anesthesia management rather than a chronic condi-

tion like blindness, it was completely appropriate. The

visual analog scale approach to preference elicita-

tion has two important limitations. First, given the

historical definition of health utility measures, they

are supposed to reflect tradeoffs and forced choices

between alternatives [6]. The visual analog scale does

not do this. Second, the visual analog scale described

in the article used anchor points representing the ideal

experience and the worst experience imaginable. Not

everyone imagines the same worst experience. The

scale used in most preference elicitation methods that

involve a specific tradeoff is anchored by perfect

health and death.

Given the limitations of visual analog scale

methods generally and the relatively narrow topic

for which preferences were measured in this study,

the preference scale can only be used to compare

anesthesia management methods for cataract surgery.

Preferences measured in this study lack comparability

with preferences assessed in other studies. Compara-

bility across studies is a goal of cost-utility analyses.

Other preference elicitation measures include the

time tradeoff and standard gamble [6]. These methods

force respondents to make a choice between an al-

ternative involving living the remainder of one’s life

in a less than optimal health state and a second al-

ternative involving either living in perfect health a

shorter amount of time for certain or a probability of

perfect health or immediate death. These are more

cognitively demanding and many respondents refuse

to make this type of tradeoff, but they are based more

clearly in economic theory. There is not a single

preference value for blindness. One study found a

value of 0.70 for monocular blindness and 0.35 for

binocular blindness [13]. A second study demon-

strated that among a legally blind sample there is a

wide range of utilities that patients report for their

own condition: those with no light perception have the

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economic evaluation 313

lowest utility; those with light perception have higher

utility; and those with visual acuity of 20/200-20/400

in the better seeing eye have the highest utility [14].

The utility weight for blindness in a community

sample was 0.75 [15].

Sensitivity analysis

Sensitivity analysis is a term for assessing changes

in the cost-effectiveness results with changes in the

values of parameters—particularly those that are

assumed. Reeves and colleagues [11] conduct sensi-

tivity analysis by varying one parameter or two para-

meters at a time. While this type of analysis indicates

whether the results change when a parameter

changes, this type of analysis does not give a clear

indication of the likelihood of a change in the quali-

tative nature of the cost-effectiveness results. State of

the art analyses at present use probabilistic sensitivity

analyses in which parameters are drawn repeatedly

from distributions and the results are reevaluated with

each draw to describe the probability of the quali-

tative cost-effectiveness results holding.

Incremental analysis

Finally, the authors performed a proper incremen-

tal analysis. Sometimes authors simply ask how much

it would cost per QALYor improved clinical outcome

under each alternative. A true incremental analysis

considers all the alternatives (six in this case) simul-

taneously. The alternatives are arranged in order by

cost. Alternatives that are equally expensive but pro-

duce less positive outcome and alternatives that pro-

duce a similar positive outcome but cost more are

eliminated from consideration. Among those that re-

main, the extra cost per extra unit of outcome is

assessed as the policy choice changes from the least

expensive to the most expensive alterative that

has not been eliminated. This allows the policy

maker to ask repeatedly, ‘‘How much would more

of the outcome cost?’’ Based on economic criteria

alone, resources should be allocated to the alterna-

tive with the maximum positive outcome for which

the policy maker is willing to pay the cost per im-

proved outcome.

Conclusion

The authors concluded that alternatives including

topical anesthesia yielded a lower utility at approxi-

mately the same costs as alternatives without topi-

cal anesthesia. Among the three alternatives without

topical anesthesia, having an anesthesiologist on call

cost only a small amount more than not having

an anesthesiologist available but that the preference

for the on-call scenario was much higher. In con-

trast, while having an anesthesiologist present in-

creased the preference weight relative to having an

anesthesiologist on call, the cost was over six times

higher per patient.

Cataract surgery

Two relatively recent US studies characterize the

cost-effectiveness of cataract surgery separately in

the first eye and the second eye [16,17]. Both used

similar methods that will be described together.

Modeling and parameters

Similar to the work by Reeves and colleagues

[11], both articles used modeling. An article on care

for age-related macular degeneration patients still

used a model but built more directly on a randomized

trial [18]. The decisions modeled in the two articles

on cataract surgery were ‘‘surgery in the first eye or

not’’ and ‘‘surgery in the second eye or in one eye

only.’’ In each model, the decision on surgery is

followed by the possibility of one of four compli-

cations within the first 4 months. One of the com-

plications (retinal detachment) is given a single

preference value and each of the other three com-

plications will result in one of two outcomes. A key

implication of the model is that the preference weight

improvement is the same no matter how old the

patient is. When there are no complications, a gain of

0.15 units on a scale that ranges from 0 to 1 for

surgery in the first eye is assumed to apply for the

remainder of the person’s life. A gain of 0.11 units on

the same scale is assumed to apply for the remainder

of the person’s life after surgery in the second eye.

The gains in utility from improved vision may di-

minish over time as a patient experiences other co-

morbidities that limit utility.

Present value

In the article analyzing the management of

anesthesia, the analysis included preferences for the

management strategy during the short surgery rather

than for the chronic health state being addressed. In

the cost-effectiveness analyses related to cataract

surgery, the time period to which the preference

applies is the remainder of the patient’s life. For most

patients, the life expectancy is more than 1 year. The

analysis applies relative weights to benefits and costs

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that occur in the future in comparison with those that

occur immediately. This is the process of calculating

a present value or discounting.

Under the standard approach the relative weight

for future events is smaller than for immediate events.

For costs, the reasoning is straightforward. If a patient

will need to spend $100 for eye care next year, the

patient could put less than $100 in the bank now, earn

interest, and have the $100 next year. This generalizes

so that the present value of any dollars used a year

from now is lower than number of dollars considered.

Health benefits are treated the same—so a year with

better vision that happens in the future is worth less

than the current year with better vision. A commonly

recommended discount rate is 3% [6,19]. This

implies that the value of events that occur 1 year

later is 97% of the value this year. One year later, the

value is 97% of the 97%. This continues indefinitely

and the value of a future benefit 24 years in the future

is approximately one half of the value of the same

benefit that occurs today. This can make the lifetime

value of a health improvement considerably smaller

than the 1-year gain multiplied by the remaining life

expectancy. The authors of the two articles [16,17] use

a 3% discount rate and it diminishes the QALYs gained

from 1.78 without discounting to 1.25 in present va-

lue terms—in effect decreasing the gains by one third.

Sensitivity analyses

Both articles [16,17] used one-way sensitivity ana-

lyses and analyses that changed all utility values si-

multaneously. The reason for changing all utility

values simultaneously is not entirely clear. The effect

of changing all values simultaneously is essentially

that the differences in utilities will increase or

decrease by the percentage of increase or decrease.

The differences are critical to incremental cost-

effectiveness analysis. By way of example, increasing

the utility of both no surgery and no complications by

10% would change the utilities from 0.71 and 0.86

(a difference of 0.15) [16] to 0.78 and 0.95 (a differ-

ence of 0.17). The increase in the difference is

approximately 10%. One difficulty with a scale that is

bounded at 1 is that increasing the utility of some of

the states by a substantial amount makes the health

state appear to be much less negative or much less

worse than a perfectly healthy status.

Conclusions

Both studies demonstrate that cataract surgery

costs a small amount for each QALY gained in the

analysis using all the base assumptions and in all

sensitivity analyses. A key consideration is the

interpretation of ‘‘a small amount per quality adjusted

life year gained.’’ In the United States, a threshold

of $50,000 per QALY gained is often used to separate

treatments and interventions that are deemed to be

relatively cost-effective from those that are not. How-

ever, there is not complete agreement on the appro-

priate threshold value [20].

Future of economic evaluation in ophthalmic

anesthesia and cataract studies

If economic studies continue to gain traction in

health care priority setting, the number of economic

evaluations of anesthesia management practices

associated with ophthalmology procedures and eco-

nomic evaluations of the procedures themselves is

likely to grow. Economic evaluation can be an im-

portant input to policy making and treatment recom-

mendations but should never be the only input. The

studies reviewed are instructive; they provide a tem-

plate and set a high standard for future studies. Addi-

tional assessment of patients’ and the general public’s

preferences for health states associated with vision

problems and the incidence costs of visual impair-

ment will make future studies more informative.

Following methods recommendations, particularly

making models and their parameters transparent will

increase future studies’ impact.

Summary

This article (1) outlines different types of eco-

nomic evaluations, (2) reviews three recent articles on

the cost-effectiveness of ophthalmic anesthesia and

cataract surgery, and (3) discusses ways in which

research in this area might be moved forward. Cost-

utility analyses using decision trees, societal pref-

erences, and probabilistic sensitivity analyses would

represent the state-of-the-art in all respects. The three

articles reviewed do not meet all three criteria. Read-

ing, interpreting, and conducting such analyses in

the future will be facilitated by understanding

methods recommendations.

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