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MILITARY ADVANCED REGIONAL ANESTHESIA ANDANALGESIA HANDBOOK


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Published by the

Office of The Surgeon GeneralDepartment of the Army, United States of America

US Army Medical Center and School

Fort Sam Houston, Texas

John P. Murtha Neuroscience and Pain Institute

Johnstown, Pennsylvania

Telemedicine and Advanced Technology Research Center

US Army Medical Research and Materiel Command, Fort Detrick, Maryland


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MILITARY ADVANCED REGIONAL ANESTHESIA ANDANALGESIA

HANDBOOK

Chester Buckenmaier III, MDColonel, Medical Corps, US ArmyWalter Reed Army Medical Center

Associate Professor of Anesthesiology, Uniformed Services University of the Health SciencesMilitary Advanced Regional Anesthesia and Analgesia Initiative

Lisa Bleckner, MDWalter Reed Army Medical Center

Assistant Professor of Anesthesiology, Uniformed Services University of the Health SciencesMilitary Advanced Regional Anesthesia and Analgesia Initiative

With original illustrations by

Lieutenant Michael K. Sracic, MD, MC, US Navy

Borden InstituteWalter Reed Army Medical Center, Washington, DC

2008


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v

CONTENTSContributors vii

Preface ix

Prologue xi 1. The Military Advanced Regional Anesthesia and Analgesia Initiative: A Brief History 1

2. Peripheral Nerve Block Equipment 5

3. Local Anesthetics 11

4. Nerve Stimulation and Ultrasound Theory 17

5. Upper Extremity Neuroanatomy 21

6. Cervical Plexus Block 237. Interscalene Block 25

8. Supraclavicular Block 29

9. Infraclavicular Block 33

10. Axillary Block 37

11. Peripheral Nerve Blocks of the Arm 41

12. Paravertebral Nerve Block 4513. Lower Extremity Neuroanatomy 49

14. Lumbar Plexus Block 51

15. Femoral Nerve Block 53

16. Individual Nerve Blocks of the Lumbar Plexus 57

17. Sciatic Nerve Block: Posterior and Alternative Approaches 61

18. Sciatic Nerve Block: Anterior Approach 6719. Sciatic Nerve Block: Lateral Approach 69

20. Popliteal Nerve Block 73

21. Saphenous Nerve Block 77

22. Ankle Block 79

23. Bier Block 81

24. Continuous Peripheral Nerve Block 83

25. Regional Anesthesia Complications 91


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vi

26. Acute Pain Management in the Field 95

27. Improving Surgical Pain Management With Multidisciplinary Care 103

28. Interventional Chronic Pain Treatment in Mature Theaters of Operation 10729. Air Transport of the Critically Injured Patient: Controlling Pain During Transport and Flight 113

30. Basic Pediatric Regional Anesthesia 119

31. Acute Pain Nursing in the Field 125

32. Novel Medical Acupuncture Treatments for Active Combat Units on the Battlefield 129

Further Reading xiii

Abbreviations and Acronyms xvii


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vii

CONTRIBUTORSTODD CARTER, MDLieutenant Colonel, Medical Corps, US Air Force

JOHN CHILES, MD

Colonel (Retired), Medical Corps, US ArmyJAMES E. COX, MDColonel (Retired), Medical Corps, US Air Force

SCOTT CROLL, MDLieutenant Colonel, Medical Corps, US Army

STEVE COHEN, MDColonel, Medical Corps, US Army

JOHN DUNFORD, MD

Assistant Professor of Anesthesiology, UniformedServices University of the Health Sciences

ERIC ELSTER, MDCommander, Medical Corps, US Navy

CARLO FRANCO, MDAssociate Professor of Anesthesiology and Anatomy,Rush University Medical Center

BILL FRITZ, MD

Conemaugh Health SystemKURT GRATHWOHL, MDLieutenant Colonel, Medical Corps, US Army

SCOTT GRIFFITH, MDMajor, Medical Corps, US Army

STEPHEN M. KLEIN, MDAssociate Professor of Anesthesiology, DukeUniversity Medical Center

ROBERT S. LENNON, DOBrigadier General (Retired), Medical Corps, USArmy; Associate Professor, Mayo Clinic MedicalSchool

COURTNEY LENNONEnsign, Medical Corps, US Navy

ROBERT LENNON, JD

Ensign, Medical Corps, US NavyRANDALL MALCHOW, MDColonel, Medical Corps, US Army

GREG MALONE, MDCaptain, Medical Corps, US Air Force

GESELLE MCKNIGHT, CRNA, MSNWalter Reed Army Medical Center

BRIAN MCMILLAN, MD

Major, Medical Corps, US ArmyJONATHON ROGERS, MDCaptain, Medical Corps, US Air Force

CHRISTINE RUPPRECHT, RN, MSNWalter Reed Army Medical Center

CYNTHIA SHIELDS, MDColonel, Medical Corps, US Army

SEAN SHOCKEY, MD

Major, Medical Corps, US ArmyKENNETH SON, MDLieutenant Commander, Medical Corps, US Navy

ALEX STOJADINOVIC, MDColonel, Medical Corps, US Army

ANN VIRTIS, MDColonel (Retired), Medical Corps, US Air Force

RONALD WHITE, MD

Major, Medical Corps, US ArmyALON P. WINNIE, MDProfessor of Anesthesiology, NorthwesternUniversity Medical Center

MODELSMICHAEL ADAMS, MD

BRIAN MCLEAN, MD

AIDAN SHIELDS

MICHAEL SHIGEMASA

NECIA WILLIAMS, MD


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held at the Uniformed Services University of theHealth Sciences in Bethesda, Maryland. This yearmarks the 7th year of the workshop, directed by DrBuckenmaier and taught by senior anesthesiolo-gists from around the nation. This years faculty

included doctors Alon P Winnie, NorthwesternUniversity; Andre P Boezaart, University of Florida;John H Chiles, former anesthesiology consultant tothe Army surgeon general and currently at INOVAMount Vernon Hospital; Laura Lowrey Clark,University of Louisville; Steven Clendenen, MayoClinic; Scott M Croll, Uniformed Services Univer-sity and Walter Reed Army Medical Center; John MDunford, Walter Reed Army Medical Center; Carlo

D Franco, Rush University; Ralf E Gebhard, Uni-versity of Miami; Roy A Greengrass, Mayo Clinic;Randall J Malchow, Brooke Army Medical Center;Karen C Neilsen, Duke University; Thomas C Stan,Far Hills Surgery Center; and Gale E Thompson,Virginia Mason Medical Center.

Although the recognition of MARAAs successhas so far been directed to its immediate achieve-mentsimproved and systematic pain control forwounded soldiersits ultimate contribution maybe broader in scope. Patient care is a multispecialty

team effort that MARAA recognizes. Therefore,MARAA solicits, evaluates, and appreciates inputfrom other physician subspecialists and from nurs-ing providers; much of the spring 2006 meetingwas devoted to astute flight nurse observationscollected by Lieutenant Colonel Dedecker, a USAir Force nurse in charge of the Patient MovementSafety Program. MARAA meetings remain open toany person interested in attending, and all meeting

notes, data, and recommendations are freely avail-able. As impressive as MARAAs contributions topatient care have been, history may view its greatercontribution as a modern model of how a smallgroup of persons with vision and energy can dra-matically improve an entire field of care.

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9

Figure 2-5. Casualty evacuation acute pain management pump (AmbIT PCA pump [Sorenson Medical Inc, West Jordan, Utah; used with permission]) in current use, with operating instruction quick reference card

PERIPHERAL NERVE BLOCK EQUIPMENT 2


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26 LOCAL ANESTHETICS3

14

mechanism, has been shown to be effective inprolonging analgesia in spinal, epidural, andperipheral nerve blocks. Clonidine 100 g is fre-

quently added to local anesthetic for PNBs at WalterReed Army Medical Center to prolong analgesia.Dexamethasone 8 mg added to local anestheticshas also been reported to enhance the duration ofsensory and motor blockade.

The list of medications used to improve regionalanesthesia continues to grow, including drugs suchas midazolam, tramadol, magnesium, neostigmine,and ketamine, as well as others that have had

varying success. Expanding the list of local anesthet-ic drugs has the potential to improve patient safety,enhance analgesia, and expand the role of regionalanesthesia in perioperative management.

TABLE 3-2

RECOMMENDED TECHNIQUES AND CONDITIONS TO MINIMIZE THE RISK OF LOCALANESTHETIC INTRAVASCULAR INJECTION

Standard monitoring with audible oxygen saturation tone.

Oxygen supplementation.

Slow, incremental injection (5 mL every 1015 seconds).

Gentle aspiration for blood before injection and every 5 mL thereafter.

Initial injection of local anesthetic test dose containing at least 515 g epinephrine with observation for heart ratechange > 10 beats/min, blood pressure changes > 15 mmHg, or lead II T-wave amplitude decrease of 25%.

Pretreatment with benzodiazepines to increase the seizure threshold to local anesthetic toxicity.

Patient either awake or sedated, but still able to maintain meaningful communication with the physician.

Resuscitation equipment and medications readily available at all times.

If seizures occur, patient care includes airway maintenance, supplemental oxygen, and termination of the seizure withpropofol (2550 mg) or thiopental (50 mg).

Local anesthetic toxicity that leads to cardiovascular collapse should immediately be managed with prompt institutionof advanced cardiac life support (ACLS) protocols.

Intralipid (KabiVitrum Inc, Alameda, Calif) 20% 1 mL/kg every 35 minutes, up to 3 mL/kg, administered during

ACLS for local anesthetic toxicity can be life saving. Follow this bolus with an Intralipid 20% infusion of 0.25 mL/kg/min for 2.5 hours.


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LOCAL ANESTHETICS 3

15

TABLE 3-3

STANDARD ADULT ROPIVACAINE DOSAGES FOR SINGLE INJECTION AND CONTINUOUS REGIONAL ANESTHESIA AT WALTER REED ARMYMEDICAL CENTER

Regional Anesthesia Technique Adult Single Injection* Continuous Infusion of0.2% Ropivacaine(mL/h)

Patient-Controlled Bolus Rateof 0.2% Ropivacaine

(mL bolus/20 min lockout)

Notes

Interscalene 3040 mL of 0.5% ropivacaine 810 23 Often supplemented with an intercostal brachialnerve block

Supraclavicular 3040 mL of 0.5% ropivacaine 810 23 Shortest latency block of the brachial plexus

Infraclavicular 3540 mL of 0.5% ropivacaine 1012 23 Catheter techniques less effective compared tosupraclavicular catheters

Axillary 40 mL of 0.5% ropivacaine 1012 23 Catheter techniques less common

Paravertebral 35 mL of 0.5% ropivacaine perlevel blocked

810 23 Catheters effective in thoracic region only

Lumbar plexus (posteriorapproach)

3040 mL of 0.5% ropivacaine 810 23 Epidural spread is a concern

Femoral 2030 mL of 0.5% ropivacaine 810 23 Catheter techniques may miss the obturator or

lateral femoral cutaneous nervesSciatic (anterior or posteriorapproach)

2030 mL of 0.5% ropivacaine 810 23 Proximal approaches to the sciatic nervepreferable for catheters

Sciatic (lateral or poplitealapproach)

3540 mL of 0.5% ropivacaine 1012 23 Often the only approach available to the sciaticnerve following polytrauma

Lumbar plexus or femoral + sciatic 5060 mL of 0.5% ropivacainebetween both sites

510 for both catheters 23 on one catheter Infusion rates divided between catheters basedon distribution of patients pain

Epidural 2025 mL of 0.5% ropivacaine 610 thoracic1020 lumbar

23 Opioids often added to infusions

Spinal 515 mg of 1.0% ropivacaine NA NA Opioids often added to injections

*Mepivacaine 1.5% can be used in place of ropivacaine at the volumes noted when a shorter duration block is desirable.Occasionally, a 5 mL bolus per 30-minute lockout is used in selected patients. Generally, total infusion (continuous plus bolus) > 20 mL/h are avoided.NA: not applicable.


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cord, innervates all of the muscles of the posteriorcompartments of the arm and forearm and mostof the posterior skin of the upper extremity.Although there are numerous other namedbranches of the brachial plexus, familiarizationwith the plexus as outlined above is adequatefor most upper extremity regional anesthesiaprocedures.

Considerable controversy has arisen about theexistence of a nerve sheath surrounding thebrachial plexus and including the artery, vein, andinvesting connective tissue. Anatomical dissectionof the brachial plexus consistently reveals a distin-guishable sheath of fibrous tissue surrounding thebrachial plexus, vasculature, and loose investingconnective tissue. In Figure 5-3, the platysma mus-cle has been reflected, exposing the brachial plexus

sheath just posterior to the omohyoid muscle andlateral to the sternocleidomastoid muscle. In Figure

5-4, the omohyoid muscle has beenretracted, and the sheath has beenfilled with normal saline. The nervesof the brachial plexus can now be seenthrough the window created by thefluid-filled sheath.

The existence of nerve sheathsis not unique to the brachial plexusand can be demonstrated on

neurovascular structures throughoutthe human body. The practice ofregional anesthesia depends on theanatomical fact of the sheath. Thesheath improves the success of singleinjection blocks and continuousperipheral nerve catheters bycontaining the local anesthetic nearnervous tissue targets and allowing

the anesthetic to surround and bathethe nerves.

Figure 5-4. Sheath injected with normal saline. Note the nerve tissue

visible within the sheath.

Figure 5-3. Sheath prior to injection with salineFigure 5-2

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5 UPPER EXTREMITY NEUROANATOMY

6 CERVICAL PLEXUS BLOCK h h ( ) hfi i l i f h h d d k


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6. CERVICAL PLEXUS BLOCK

INTRODUCTION

The cervical plexus block provides anesthe-sia and analgesia to the head and neck region.

Depending on the type of surgery, the plexus canbe blocked either at a superficial or a deep level.The superficial branches (Figure 6-1) of the plexusinnervate the skin and superficial structures ofthe head, neck, and shoulder. The deep branches(Figure 6-2) innervate the muscles of the deepanterior neck and the diaphragm. The deep cervicalplexus block is used for deeper surgeries of theneck, such as carotid artery or thyroid surgery, and

the superficial cervical plexus block is used for su-

ANATOMY

The cervical plexus is formed from the anteriorrami of the C1 through C4 nerve roots; it liesanterior to the cervical vertebrae and posterior tothe sternocleidomastoid muscle. There are five maincomponents of the cervical plexus: (1) the cutaneousbranches, which supply the lesser occipital, greaterauricular, transverse cervical, and supraclavicularnerves; (2) the ansa cervicalis, which innervates theinfrahyoid and geniohyoid muscles; (3) the phrenic

nerve, which is the only motor nerve to innervate

Figure 6-1. Superficial cervical plexus Figure 6-2. Deep cervical plexus

the diaphragm; (4) contributions to the accessorynerve (CN XI), which innervates the sternocleido-mastoid and trapezius muscles; and (5) directmuscular branches, which supply prevertebralmuscles of the neck.

Bilateral deep cervical plexus blocks, whichwould result in total diaphragmatic paresis, shouldnot be performed. Also, patients with chronic respi-ratory conditions may not be suitable candidates foran ipsilateral deep cervical plexus block. Cautionmust be taken when placing a deep cervical plexusblock because of the close proximity of the vertebralartery and the dural sleeve. Placing the block tooclose to the vertebral artery may result in an intra-vascular injection; placing it too close to the duralsleeve may result in a subarachnoid injection.

perficial cutaneous surgeries of the head and neck.This block is also useful as a supplement to otherregional techniques of the upper torso.

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6 i t t d ithd th dl 1


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24

6 CERVICAL PLEXUS BLOCK

PROCEDURE

Landmarks

Superficial Cervical Plexus(Figure 6-3). Identify

and mark the posterior border of the sterno-cleidomastoid, as well as the midpoint of themuscle.

Deep Cervical Plexus(Figure 6-4). Position thepatient supine with the head turned toward thenonoperative side. Palpate the transverse processof C6 (Chassaignacs tubercle) at the level of thecricoid cartilage. Palpate the mastoid process

behind the ear. Draw a line between the mastoidprocess and Chassaignacs tubercle. The trans-verse processes of the other cervical vertebraewill lie on or near this line. The first palpabletransverse process below the mastoid process isC2. Palpate and mark the transverse processes ofC2 to C4 (the C4 transverse process lies approxi-mately at the level of the mandible). Insert theneedle medially and caudally so that the needle

tip is resting on the transverse process.

Needles

22-gauge, 5-cm, short bevel needle.

Injection

Superficial Cervical Plexus.Insert the needle at the

midpoint of the posterior border of the sternocleido-mastoid muscle to approximately half the depth ofthe muscle, and inject 3 to 4 mL of local anesthetic.Also perform a subcutaneous injection of additionallocal anesthetic cephalad and caudad along thelength of the sternocleidomastoid muscle posteriorborder.

Deep Cervical Plexus.Attach a 10-mL controlsyringe to the needle. Once the transverse process

Figure 6-3

Figure 6-4

is contacted, withdraw the needle 1to 2 mm. Injectthe local anestheticslowly with frequent aspirations.After completing the injection,remove the needleand repeat theblock at the next level. (Many in-stitutions perform only a superfi-cial cervical plexus block, and thesurgeon infiltrates deeper struc-tures as required.)

Local Anesthetic

Superficial Cervical Plexus.510mL.

Deep Cervical Plexus.35 mL ateach level or 15 mL at C3 only.

Teaching Points. Cautionshould be exercised in patientsreceiving a deep cervical plexusblock for carotid endarterec-tomy surgery. These patients

will likely have atheromatousplaques that could be dislodgedwith excessive head hyper-extension or cause cerebralischemia with head rotation.For carotid endarterectomies,the surgeon must infiltratethe carotid body with localanesthetic because the cervical

plexus does not innervate thisstructure.

7 INTERSCALENE BLOCK between the anterior and middle scalene


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Figure 7-2

7. INTERSCALENE BLOCK between the anterior and middle scalenemuscles; C6 corresponds to the level of thecricoid cartilage. By blocking the plexus at thislevel, the local anesthetic is deposited aroundthe upper roots (C5, C6) that innervate themuscles of the shoulder, specifically the deltoid,

supraspinatus, infraspinatus, and teres major(Figure 7-1 through 7-3). Occasionally, theremay be proximal spread to the cervical plexus(C3, C4) and cervical sympathetic chain, whichcan result in Horners syndrome and hoarsenesspost block; this is not considered a complica-tion, but the patient should be made aware ofthese possible side effects before the procedureis performed.

The interscalene block always results inhemidiaphragm paresis because of the closeproximity of the phrenic nerve (C3C5) to the in-

Figure 7-3. Dermatomes anesthetized with the interscalene block (dark blue)

INTRODUCTION

The interscalene approach to the brachial plexusis particularly well suited for operations on the

shoulder, clavicle, or upper arm. The approachpreferentially blocks nerves of the brachial plexus(C5C7), with variable proximal spread to the cervi-cal plexus (C3C4), while usually sparing the ulnarnerve (C8T1). The nerves of the brachial plexusemerge from their respective intervertebral foram-ina and course posterior to the vertebral artery. Theythen pass between the anterior and middle scalenemuscles as the trunks (superior C5C6, middle C7,

inferior C8T1) of the brachial plexus.

ANATOMY

The interscalene block is performed at the levelof the C6 vertebral body (Chassaignacs tubercle)

terscalene groove. Any patient who cannot tolerate a reduction in pulmonary function greater than 30% shouldnot receive this block. Even healthy patients may need reassurance that their feeling of dyspnea is transient.

The inter-scalene blockis not ap-propriate forsurgery ofthe hand andforearm, spe-cifically in theulnar distribu-tion of C8, T1.Because it isperformed atthe upper rootsof the plexus,the block typi-cally spares theulnar aspectof the hand.Additionally,C3, C4 nerveroots (capearea) are notconsistentlyblocked.

Figure 7-1

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7 INTERSCALENE BLOCK


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PROCEDURE

Landmarks.Place the patient supine with the headturned toward the nonoperative side. Identify the

cricoid cartilage, which indicates the C6 level. Palpatethe lateral border of the sternocleidomastoid muscle(SCM), and move your fingers laterally into the in-terscalene groove (between the anterior and middlescalene muscles). Ensure that the clavicular head ofthe SCM, rather than the more medial sternal head,is being palpated. The external jugular vein oftencrosses the border of the SCM muscle at this point.If this is the case, the initial needle insertion should

be posterior to the vessel (Figure 7-4). Initial needleinsertion (at the level of C6) is indicated by an X(Figure 7-5).

Needles

22-gauge, 5-cm, insulated needle. 18-gauge, 5-cm insulated Tuohy needle for catheter

placement. Catheters introduced 3 cm beyondneedle tip.

Stimulation. The nerve stimulator is initially set at1.0 to 1.2 mA. Muscle twitch in the shoulder, biceps,or triceps at 0.5 mA or less indicates adequateproximity to the brachial plexus for local anestheticinjection. Stimulation below the elbow suggests aneedle position that is too caudal in the brachialplexus for shoulder surgery. In most adults, thebrachial plexus is rarely deeper than 1 to 2 cm

below the skin. Stimulation of the trapezoid musclesuggests that the needle tip is too posterior to theplexus. Conversely, stimulation of the diaphragmindicates phrenic nerve stimulation, and the needletip is anterior to the plexus.

Local Anesthetic. In most adults, 30 to 40 mL oflocal anesthetic is sufficient to block the plexus.

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26 Figure 7-5

Figure 7-4

INTERSCALENE BLOCK

Additional Procedures.An intercostobrachial nerveblock (subcutaneous injectionof local anesthetic from theaxilla to the midpoint of theclavicle on the anterior chest)should be performed formajor shoulder procedures.Paravertebral nerve blocks ofT1T2 may supplement theinterscalene block for proce-dures involving significantposterior dissections.

Teaching Points. Injectionof local anesthetic intothe neighboring vertebralartery can result in a dev-astating complication ofthis block. Proper injectiontechnique with frequent,

gentle aspiration for bloodis critical for safe blockplacement.

7INTERSCALENE BLOCK


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Figure 7-7

Figure 7-6

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7

Figure 7-8

BLOCK WITH ULTRASOUND PROBE

Probe.High frequency (5-12 MHz), linear.

Probe Position.The oblique plane gives the besttransverse view of the brachial plexus; a cross-sectional (axial) view displays the nerves as hy-poechoic circles with hyperechoic rings. Position theprobe on the neck at the level of C6 (Figure 7-6).

Approach.The plexus can be approached fromeither a posterior or anterior position. To use theposterior approach, begin the needle insertionat the lateral aspect of the probe; the needle will

traverse the middle scalene muscle as the plexusis reached. For the anterior approach, insert theneedle at the medial aspect of the probe, takingcare to avoid the carotid artery and internal jugularvein; the needle will traverse the anterior scalenemuscle on the way to the plexus (Figure 7-7).

Injection.Once the needle is adjacent to the nervetrunks, injection of local anesthetic may begin. The

donut sign (created by the local anesthetic sur-rounding the nerves) is a positive indicator thatthe anesthetic is being properly distributed. Properneedle positioning should ensure local anestheticspread around the superior and middle trunks.

INTERSCALENE BLOCK

Teaching Points.For ease of anatomic identifi-cation, locate the plexus at the level of a supra-

clavicular block (identify the subclavian artery,and the plexus will be just lateral to it). Oncethe plexus is located, slowly move the probecephalad to observe the bundled nerve structurescoalescing into the three major trunks, alignedsuperior to inferior. This is the transition fromthe more caudad divisions to the more cephaladtrunks (Figure 7-8). Injection of local anestheticshould be directed toward the superior trunk of

the plexus.

8. SUPRACLAVICULAR BLOCK anesthesia easily


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Figure 8-2

INTRODUCTION

The supraclavicular nerve block is ideal for pro-cedures of the upper arm, from the midhumeral

level down to the hand (Figure 8-1). The brachialplexus is most compact at the level of the trunksformed by the C5T1 nerve roots, so blockade herehas the greatest likelihood of blocking all of thebranches of the brachial plexus. This results in rapidonset times and, ultimately, high success rates forsurgery and analgesia of the upper extremity (ex-cluding the shoulder).

ANATOMY

At the trunk level of the brachial plexus, the C5and C6 nerve roots join to form the superior trunk,the C7 nerve root forms the middle trunk, and theC8, T1 nerve roots join to form the inferior trunk(the C4 and T2 nerve roots may also contribute sig-nificantly at these points) (Figure 8-2). Because theplexus is compactly arranged at this location, local

Figure 8-3

Figure 8-1. Dermatomes anesthetized with the supraclavicular block

(dark blue)

The complication most often associatedwith this block is pneumothorax. Whenmanipulating the needle in this region,remember that the apex of the lung isjust medial and posterior to the brachial

plexus as well as deep to the first rib.Using a shorter needle (5 cm) can decreasethe incidence of pneumothorax. Unlikean interscalene block, the supraclavicularblock causes diaphragmatic hemiparesisin approximately 50% of patients, withminimal accompanying reduction inforced vital capacity (FVC). Signs andsymptoms of a large pneumothorax

include sudden cough and shortness ofbreath.

ycovers all the plexusnerves, which resultsin a rapid, denseblock.

To locate the bra-

chial plexus at thesupraclavicular level,gently palpate theinterscalene groovedown to the mid-point of the clavicle(Figure 8-3). Notethat the groove canoccasionally be ob-

scured near the clav-icle by the omohyoidmuscle. Palpation orultrasound visualiza-tion of the subclavianartery just superior tothe clavicle providesa useful anatomiclandmark for locating

the brachial plexus,which is lateral to theartery at this level.

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PROCEDURE

Landmarks.Place the patient in a supine positionwith the head turned toward the non-operative side.

Palpate the posterior border of the sternocleido-mastoid muscle at the C6 level and roll your fingerslaterally over the anterior scalene muscle until theylie in the interscalene groove (the groove may beharder to identify below the C6 level because ofthe overlying omohyoid muscle). Then move yourfingers laterally down the interscalene groove untilthey are approximately one centimeter from themid-clavicle. This location is the initial insertion site

for the needle (Figure 8-4). Standing at the patientshead, direct the needle toward the axilla, as demon-strated in Figure 8-5.

Needles

22-gauge, 5-cm, insulated needle. 18-gauge, 5-cm, insulated Tuohy needle for catheter

placement. Catheters introduced 3 to 5 cm beyondneedle tip.

Stimulation. The nerve stimulator is initiallyset at 1.0 to 1.2 mA. Proper needle placement isindicated by flexion or extension of the digits at 0.5mA or less. The brachial plexus can be deep at thislocation, but is often reached at 2 to 4 cm. Aspirationof bright red blood suggests subclavian arterypenetration, indicating the needle is too medial.Stimulation of the musculocutaneous nerve (bicepscontractions) usually indicates the needle is too

lateral. Pectoralis muscle contraction indicates theneedle is anterior, and scapular movement indicatesthe needle is posterior to the plexus.

Local Anesthetic. In most adults, 30 to 40 mL oflocal anesthetic is sufficient to block the plexus.

Additional Procedures.The intercostobrachialnerve lies anterior and slightly superior to theaxillary artery; it innervates the skin along the

upper medial border of the arm. To block this

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nerve, place a subcutaneouswheal of local anestheticfrom the border of the pec-toralis muscle insertion on

the humerus to the inferiorborder of the axilla. Theskin wheel should be placedas proximal on the arm aspossible.

Teaching Points. Becauseof the close proximity ofthe lung, the needle shouldnever be directed medially.If a tourniquet is beingused for surgery, considerintercostobrachial blockade.

Figure 8-4

Figure 8-5

8SUPRACLAVICULAR BLOCK


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Figure 8-7

Figure 8-6

31Figure 8-8


Probe.High frequency (5-12 MHz), linear.

Probe Position.The coronal oblique plane gives the best transverseview of the brachial plexus; again, a cross-sectional (axial) viewdisplays the nerves as hypoechoic circles with hyperechoic rings(bundle of grapes). Position the probe on the neck directly abovethe clavicle in the supraclavicular fossa. At this level, the plexus willbe configured as trunks or divisions and is typically located lateraland slightly superior to the subclavian artery at a depth of 2 to 4 cm(Figure 8-6).

Approach.Insert the needle at the lateral end of the ultrasoundprobe and advance it parallel to the ultrasound beam until it ap-proaches the plexus. Take care to maintain the needle within theultrasound beam plane; this maneuver helps ensure that you canconstantly visualize the entire needle shaft to the tip. If the imageof the needle is lost during the block procedure, cease advancingthe needle until it can be re-visualized through probe manipulation(Figure 8-7).

Injection.It is important to observe the spread of the local anes-thetic during the injection, allowing real-time readjustment of theneedle tip position if the spread is not appropriate. The donut

sign (created by the local anesthetic surrounding thenerves) is a positive indicator that the anesthetic is beingproperly distributed (see section on interscalene ultra-sound injection). Precise application of the local anestheticcan be achieved by injecting small aliquots (5 mL) and ob-serving the local anesthetic spread (Figure 8-8).

Teaching Points.Be aware that this block is performedwith the needle passing from a lateral to medialdirection. It is very important to always keep thetip and shaft of the needle in clear view to ensurethat the needle is not penetrating too deep into thesupraclavicular fossa; deep penetration can result in aninadvertent pneumothorax or vascular puncture. If the

needle image is maintained above the level of the firstrib and pleura, the risk of pneumothorax is minimal.

9. INFRACLAVICULAR BLOCK ANATOMY


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INTRODUCTION

The infraclavicular brachial plexus block is idealfor operations distal to the elbow. Adequate time

(approximately 20 minutes) should be allowed afterthe block placement to achieve a surgical level of an-esthesia. Although there are multiple approaches tothe infraclavicular block, success depends on wherethe needle tip stimulates the plexus. Caution mustbe taken to ensure that the needle tip is maintainedwithin the infraclavicular fossa at the level of thecords and not directed distally toward the terminalbranches located in the axilla. The latter erroneous

position usually results from excessive angulationof the needle toward the axilla and may result ininadequate blockade of the musculocutaneous andaxillary nerves.

The infraclavicular block is performed at thelevel of the cords of the brachial plexus. The cordsare named according to their relation to the axillaryartery: lateral, medial, and posterior. The lateral

cord is formed from the anterior divisions of thesuperior and middle trunks, the medial cord isformed from the anterior division of the inferiortrunk, and the posterior cord is formed from theposterior divisions of all three trunks. The plexus,which begins to spread around the axillary arteryat this level, is not as compact as the more proximaltrunks (Figures 9-1 through 9-3). Therefore, thisblock typically has a longer latency, and may not be

as dense, as a supraclavicular nerve block.Compared to the supraclavicular block,an advantage of the infraclavicular block isthe reduced possibility of pneumothorax andavoidance of cervical vascular structures. Thisblock does not produce a reduction in respiratoryfunction. Additionally, the infraclavicular block

has been shown to besuperior to the axillary

nerve block for anesthe-tizing the axillary andmusculocutaneous nerves,making a supplementalmusculocutaneous nerveblock unnecessary.

Acceptable musclestimulation patterns areeither extension (radial

nerve) or flexion (mediannerve) of the digits. Abiceps twitch (musculocu-taneous nerve), suggeststhat the needle placementis too lateral. The axillaryvessels can be puncturedusing this approach, andvessel compression in this

area is difficult.

Figure 9-1

Figure 9-2

Figure 9-3. Dermatomes anesthetized with the infraclavicular block

(dark blue)

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9 INFRACLAVICULAR BLOCK


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34

PROCEDURE

Landmarks.Externally rotate and abduct the op-erative arm. Palpate the coracoid process. Make

a mark 2 cm medial and 2 cm caudad from thecoracoid process (Figure 9-4). This is the inser-tion point. Palpate the axillary artery as proximalas possible in the axilla. This is the direction ofinitial insertion. Insert the needle at an approxi-mately 60 angle from the horizontal (Figure9-5).

Needles

21-gauge, 10-cm, insulated needle.

Figure 9-4 Figure 9-5

ALTERNATIVE APPROACH

A simple alternative to the coracoid approachis the deltopectoral groove approach (see Figure

9-5). With the patients arm at his or her side, markthe base of the clavicle and palpate the deltopec-toral groove from the axilla up to the clavicle. Atapproximately 1 cm below the clavicle, place theneedle in the deltopectoral groove (perpendicular tothe bed), and then redirect it 10 toward the axilla.Advance the needle until the plexus is encountered.Compared to the coracoid approach, this approachwill block the plexus at a more proximal loca-

tion, which is desirable because the plexus is morecompact and easier to block proximal.

18-gauge, 10-cm, insulated Tuohy needle for cath-eter placement. Catheters inserted 3 cm.

Stimulation. The nerve stimulator is initially setbetween 1.0 and 1.2 mA. Finger and/or thumbflexion at 0.5 mA or less indicates adequate needleplacement for local anesthetic injection. Fingerextension with stimulation is also acceptable.Stimulation of the musculocutaneous nerve indi-cates that the needle is too lateral.

Local Anesthetic. In most adults, 30 to 40 mL oflocal anesthetic will block the plexus at this level.

INFRACLAVICULAR BLOCK 9


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26


Probe. High frequency (512 MHz), linear.

Probe Position.The parasagittal plane gives thebest transverse view of the brachial plexus; belowthe level of the clavicle, the nerves appear hyper-echoic. Position the probe beneath the clavicle andmedial to the coracoid process (Figure 9-6).

Approach.The needle is typically insertedin-plane at the cephalad (lateral) aspect of theprobe, and will be visualized at the lateral border

of the axillary artery. The hyperechoic structurelateral to the artery is the lateral cord; the needleshould pass lateral to this cord and progressfarther to the posterior cord. The posterior cordis the hyperechoic structure located at the base ofthe axillary artery (Figure 9-7). Recent evidencesuggests that deposition of local anestheticaround the posterior cord will result in improvedblock success.

Another approach to the posterior cord is via theinferior aspect of the probe (still in the parasagittalplane). With this technique, the needle is visual-ized at the medial border of the axillary artery, andbetween the axillary artery and vein. The needlemust travel along the lateral aspect of the medialcord to reach the posterior cord. This approachis technically more difficult because of the closeproximity of the axillary artery to the needle path;

however, it allows catheters to be threaded with lessdifficulty.

Injection. It is important to observe the spreadof the local anesthetic during the injection, whichallows readjustment of the needle position if thespread is not appropriate. Spread should appeararound the posterior cord; any spread above theartery in the area of the pectoralis muscles will

likely result in block failure (Figure 9-8).

Figure 9-6


Teaching Points.As with thenerve stimulator

technique, caremust be taken toavoid vascularpuncture becausecompressionfor bleeding inthis area can bedifficult. Alwayskeep the axillary

artery and veinin view duringneedle guidance,and always ensurethat the full lengthof the needle to thetip in the longitudi-nal (in-plane) viewis clear.

10. AXILLARY BLOCK lateral portion ofthe median nerve


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Figure 10-1. Dermatomes anesthetized with the axillary block (dark

blue)

Figure 10-2

Figure 10-3

INTRODUCTION

Except for single nerve blocks in the arm andforearm, the axillary block is the most distal block

performed on the brachial plexus. Because of thedistal location (in contrast to other brachial plexusapproaches), the axillary block has negligiblerisks of the respiratory compromise secondaryto pneumothorax or phrenic nerve blockade. Inaddition, the peripheral location permits adequatearterial tamponade to be applied if an inadvertentpuncture occurs.

ANATOMY

At this level, the plexus has divided into itsterminal nerve branches, with two major nervesoriginating from each cord. The lateral corddivides into the musculocutaneous nerve and the

the median nerve,the medial corddivides into theulnar nerve and themedial portion of

the median nerve,and the posteriorcord divides intothe radial nerveand axillary nerve(Figures 10-1 and10-2). The median,ulnar, and radialnerves all travel

with the axillaryartery within theaxillary sheath;however, themusculocutaneousnerve travelsseparately withinthe belly of the coraco-brachial is muscle. For this

reason, the musculocutaneousnerve must be blockedseparately during an axillarynerve block.

This block should onlybe performed for surgeriesinvolving the hand or forearm(Figure 10-3). A supraclavicularor infraclavicular nerve blockshould be used for surgeriesinvolving the upper arm orelbow to obtain more completecoverage of the upper extremity.Any patient who is unable toabduct their arm more than45 at the shoulder is not anappropriate candidate for theaxillary block.

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10AXILLARY BLOCK


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Figure 10-6

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Probe.High frequency (512 MHz), linear.

Probe Position.The transverse plane gives the bestview of the brachial plexus at this level; nerves willappear as hypoechoic roundish structures withhyperechoic borders.

Approach.The patient is supine, with the armabducted 90 and externally rotated so the dorsumof the hand rests on the bed. The probe should beplaced high in the axilla, at the intersection of thepectoralis major muscle with the biceps muscle(Figure 10-6). At this level, the axillary artery andall three main nerves to be blocked (median, ulnar,radial) should be in view (Figure 10-7). Typicalanatomic relations of the nerve to the artery areas follows: the median nerve is located superficialand slightly cephalad to the artery, the radial nerveis located deep to the artery, and the ulnar nerve

is located caudad to the artery. If all three nervesare not visualized at the same time, sliding theprobe from a medial to lateral direction shouldhelp identify the missing nerve. Individual nervescan be confirmed by stimulation. Once each nerveis identified, 10 mL of local anesthetic should beinjected around each nerve (Figure 10-8). (Note:axillary veins are often not seen while performingthis block under ultrasound guidance because they

are easily compressed by the ultrasound probe.)

is slowly brought toward the biceps muscle,the musculocutaneous nerve should comeinto view, either between the biceps andcoracobrachialis muscles or within the body ofthe coracobrachialis muscle (Figure 10-9). Localanesthetic should be injected when the needletip is visualized near the nerve or stimulation ofthe biceps muscle is noted.

Teaching Points.As opposed to a field blockor stimulation technique, blockade of themusculocutaneous nerve under ultrasoundguidance is more precise. The patients armremains abducted and externally rotated whilethe probe is positioned at the junction betweenthe pectoralis major and biceps muscles withthe axillary artery in view. While the probe

Figure 10-7

Figure 10-8

Figure 10-9


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11 PERIPHERAL NERVE BLOCKS OF THE ARM

PROCEDURE At th W i t


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42

PROCEDURE

Landmarks. Pertinent landmarks at the level ofthe elbow consist of the ulnar groove, median andlateral condyles of the humerus, brachial artery

pulsation (median nerve), and tendon of the bicepsmuscle (radial nerve). At the level of the wrist,key landmarks include the tendons of the flexorpalmaris longus and flexor carpi radialis (mediannerve), anatomic snuffbox (radial nerve), and ulnarstyloid (ulnar nerve).

At the Elbow

Radial nerve. Identify the biceps tendon. Insertthe needle lateral to the tendon and above the ante-cubital crease (the line bisecting medial and lateralepicondyles). The nerve lies within the groovebetween the tendon and the brachioradialis muscle(Figure 11-2). Two excellent localization cues areparesthesia and motor response (finger/wristextension) elicited by a nerve stimulator. Inject 5 to 7mL of local anesthetic.

Figure 11-3

Figure 11-4

Figure 11-2

Median nerve. Insert the

needle at the antecubital crease,just medial to the palpatedbrachial pulse (see Figure11-2). When a paresthesia ormotor response (finger/wristflexion or hand pronation) iselicited, usually at 1- to 2-cmdepth, inject 5 to 7 mL of localanesthetic.

Ulnar nerve. With the elbowflexed at mid-range, insert theneedle into the ulnar groove 1to 3 cm proximal to the medialepicondyle. Take care to avoidexcessive injection pressure orintraneural injection in this rela-tively tight space. Limit localanesthetic injection to 4 or 5 mL(Figure 11-3).

At the Wrist

Radial nerve. To block the branchesof the radial nerve, make an injection

along the radial arterys lateral border 2cm proximal to the wrist (Figure 11-4).Then extend the injection dorsally overthe border of the wrist, covering theanatomic snuffbox. Injection of 5 to 7 mLof local anesthetic is usually sufficient.

PERIPHERAL NERVE BLOCKS OF THE ARM11

Median nerve Identify the tendons of the flexor Local Anesthetic In most adults 3 to 5 mL


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Teaching Points. As with all regionalanesthesia techniques, proper injectiontechnique should be followed. Thisincludes frequent aspiration for blood,incremental injection, consideration ofinjection pressure, and avoidance ofpinning nerves against underlying bonewith the injection needle.

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Median nerve. Identify the tendons of the flexorpalmaris longus and flexor carpi radialis by flexingthe wrist during palpation. Insert the needle betweenthe tendons 2 cm proximal to the wrist flexor crease,

posteriorly towards the deep fascia (Figure 11-5).Inject 3 to 5 mL of local anesthetic while withdrawingthe needle.

Ulnar nerve. Many texts describe the ulnar arterypulsation as a landmark for the ulnar nerve blockat the wrist; however, the ulnar pulse is difficult toappreciate in many patients. A practical approach isto insert the block needle just proximal to the ulnarstyloid process (Figure 11-6). After aspiration to

confirm that the needle is not within the ulnar artery,inject 3 to 5 mL of local anesthetic.

Figure 11-6

Needles

22-gauge, 5-cm, insulated needle fornerve stimulation techniques.

22-gauge, 5-cm regional needle or 25-gauge, 1- to 1.5-inch b-bevel needle.

Stimulation. Set the nerve stimula-tor initially at 1.0 to 1.2 mA. Muscletwitches for radial, median, and ulnardistributions should be sought at 0.5 mAor less, indicating adequate proximity tothe peripheral nerve prior to injection.Stimulation at the level of the elbowis useful for defining peripheral nervebranches. Peripheral nerve blockadeat the wrist is essentially a field blocktechnique, with minimal utility gainedfrom stimulation.

Local Anesthetic. In most adults, 3 to 5 mLof local anesthetic for each desired branchis sufficient. At the level of the elbow, 5 to7 mL may be used for median and radial

nerve blocks. The choice of local anestheticis determined by user preference; usuallymepivacaine, bupivacaine, or ropivacaine isselected. The use of epinephrine 1:400,000 asan adjuvant to local anesthetic is advisable forblocks at the level of the elbow but not recom-mended for distal blocks such as wrist blocksor digit blocks.

Additional Procedures. When performingan elbow block, an additional 5 mL of sub-cutaneous local anesthetic injected laterallyfrom the biceps tendon to the brachioradialismuscle will provide anesthesia for the lateralcutaneous nerve of the forearm.Figure 11-5


11 PERIPHERAL NERVE BLOCKS OF THE ARM


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Probe.High-frequency (512 MHz), linear.

Approach.Because of the proximity to vascularstructures and the smaller size of nerves at thislevel, the in-plane approach is recommended.Ultrasound views of various nerves at the elbow arepresented in Figures 11-7 through 11-9.

Injection.As above, 5 to 7 mL at each injection site.

Teaching Points.Use caution when injectinglocal anesthetic into the olecranon fossafor selective blockade of the ulnar nerve.As shown in Figure 11-9, the ulnar nerve istrapped in a confined space at this location.

Ensure that injection pressure is not too high,use less than 5 mL of anesthetic, and avoidover-flexing the elbow during the block so theulnar nerve does not become pinned in thefossa and therefore more prone to intraneuralinjection or damage.

The radial nerve is easily traced from thecubital fossa more proximally to the mid-humeral level. Although the radial nerve may

be more superficial proximally, the chance ofvascular injury is decreased when the injectionis done at the cubital fossa.

Figure 11-7. Brachial artery and median nerve of the right arm at elbow

levelFigure 11-8. Radial nerve of the right arm at elbow level

Figure 11-9. Ulnar nerve within the olecranon fossa, right arm

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12 PARAVERTEBRAL NERVE BLOCK

PROCEDUREh h h h

12


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46

PROCEDURE

Landmarks.The patient is placed sitting uprightwith the neck and back flexed and the shouldersrelaxed forward. The spinous process of each levelplanned for the block is palpated and marked at itssuperior aspect. In thoracic paravertebral blocks,the numbered spinous process corresponds to thenext numbered nerve root caudally because of

Figure 12-2

Figure 12-3

the cephalad angulation of the thoracic transverseprocesses. For example, a paravertebral block per-formed at the C7 spinous process actually blocksthe T1 nerve root if the needle is passed caudally(Figure 12-2). From the midpoint of each spinousprocess, the needle entry site is marked 2.5 cm later-ally (Figure 12-3). In the thoracic area these markswill overlie the transverse process of the next verte-

bral body, as noted above. In the lumbar areathe transverse process is usually at the samelevel as the spinous process.

For mastectomy surgery with axillarydissection, T1T6 is routinely blocked. Forsentinel node biopsy with possible axil-

Needles

21-gauge, 10-cm Tuohy needle with extensiontubing.

21-gauge, 10-cm insulated needle for stimulationtechnique.

18-gauge, 10-cm Tuohy needle with hemostasisvalve/sideport assembly and extension tubing.Catheters placed 2 cm into paravertebral space.

lary dissection, block-ing T1T3 is sufficient.For breast biopsy, oneinjection is made at thedermatome correspond-ing to the lesion locationplus additional injec-

tions one dermatomeabove and below thissite. For inguinal herni-orrhaphy, levels T11L2are blocked. For umbili-cal hernia, levels T9T11are blocked bilaterally.Ventral hernia repair andother applications of PVB

require determining thedermatomes involvedand then blocking theselevels, as well as onedermatome above andbelow.

Block Without Stimulation Employing aseptic transverse process is successfully contacted

PARAVERTEBRAL NERVE BLOCK 12

until the resistance lessens (the tip has passed beyond


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26

Figure 12-4. Finding the transverse process

Figure 12-5. Finger backstop

Block Without Stimulation.Employing aseptictechnique, place a skin wheal of lidocaine localanesthetic at each level to be blocked. The Tuohyneedle is attached via extension tubing to a syringe

of local anesthetic. Grasp the shaft of the needlein your dominant hand, insert the needle throughthe skin wheal, and advance it anteriorly in theparasagital plane (perpendicular to the back) untilit contacts the transverse process (25 cm deep,depending on the body habitus of the patient). Ifyou cannot identify the transverse process at anappropriate depth, assume that the needle tip liesbetween adjacent transverse processes, and redirect

the needle cephalad and then caudad until the

transverse process is successfully contacted(Figure 12-4). This depth should be noted asthe estimated distance to subsequent trans-verse processes. With the needle contacting the

transverse process, grasp the needle shaft withyour fingers 1 cm from the skin surface (Figure12-5). The fingers now serve as a backstop toprevent the needle passing beyond 1 cm intothe paravertebral space and possibly into thepleura of the lung. Then withdraw the needletip to the subcutaneous tissue and angle it towalk off the caudad edge of the transverse

12

until the resistance lessens (the tip has passed beyondthe ligament) or bone is contacted (necessitating reposi-tion of the needle). The reason for the caudal directionof needle placement is that if initial bone contact is in-

advertently with the rib (too deep to the paravertebralspace), walking off caudally will lead to needle contactwith the transverse process at a more superficial point(stepping up), thus minimizing unintended deepneedle insertion (Figure 12-6).

process, advancing no more than 1 cm into

the space. Often, a loss of resistance or popis appreciated,indicating thatthe needle tiphas penetratedthe superiorcostotransverseligament. Aftergentle aspiration

of the syringe forblood and air,inject 3 to 5 mLof local anesthet-ic into the space.

Resistanceto local anes-thetic injectionindicates that

the needle tipis not in theparavertebralspace or has notpenetrated theligament. If thisoccurs, advancethe needle nomore than 0.5 cm


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13. LOWER EXTREMITY NEUROANATOMY

INTRODUCTION

LUMBAR PLEXUS

The lumbar spinal nerves exit caudad to theirnumbered vertebrae and divide into posterior

Ilioinguinal and iliohypogastric nerves(L1): passesanterior to the quadratus lumborum andemerges near the anterior superior iliac spine to


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Regional anesthesia of the lower extremity in-volves two major nerve plexuses, the lumbar plexus

and the sacral plexus. The safe practice of lowerextremity regional anesthesia depends on a com-prehensive understanding of neuroanatomy in thisregion of the body.

numbered vertebrae and divide into posteriorand anterior rami. The posterior rami of L1through L5 supply the muscles and skin of theback. The lumbar plexus (Figure 13-1) consistsof the anterior rami of L1 through L4. It formsanterior to the lumbar transverse processeswithin the proximal body of the psoas muscle.The major nerves of the lumbar plexus includethe following (Figure 13-2):

Figure 13-2. Lumbar plexus and sacral plexus

Figure 13-1. Dissected right lumbar plexus. The exposed nerves have been dissectedfrom the substance of the psoas muscle, which has been removed.

innervate the abdominal muscles and skin of theinguinal and pubic area.

Lateral femoral cutaneous nerve (L2, L3): emergesmedial to the anterior superior iliac spine,passing deep to the inguinal ligament, to supplysensation to the anterolateral surface of thethigh.

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PROCEDURE

L d k Pl th ti t i id tif th

12

NeedlesTeaching Points. Studies have demonstrated

15 FEMORAL NERVE BLOCK


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54

Landmarks.Place the patient supine, identify theanterior superior iliac spine and the pubic symphy-sis, and draw a line between these two landmarks.

This line represents the inguinal ligament. Thefemoral nerve passes through the center of the line,which makes this landmark useful for positioningthe needle in the inguinal crease, particularly in anobese patient. Then palpate the femoral pulse andmark it at the inguinal crease. Studies have dem-onstrated that the most successful point of needleentry is directly lateral (11.5 cm) to the artery in theinguinal crease. At this location the femoral nerve is

wide and superficial, and the needle does not passthrough significant muscle mass. Direct the needlecephalad toward the center of the inguinal ligamentline (Figure 15-5).

Figure 15-5

Figure 15-6

22-gauge, 5-cm insulated needle. 18-gauge, 5-cm insulated Tuohy needle for

catheter placement. The catheter is inserted 3 to 5cm for the femoral block.

Stimulation. The nerve stimulator is initially setat 1.0 to 1.2 mA. The needle is directed cephalad atapproximately a 30 to 45 angle. A brisk patellarsnap with the current at 0.5 mA or less is indica-tive of successful localization of the needle nearthe femoral nerve. The nerve is usually superficial,rarely beyond 3 cm from the skin (Figure 15-6).

Local Anesthetic. In most adults, 20 to 40 mL oflocal anesthetic will produce a successful femoralblock.

that the anterior branch of the femoral nerve isusually encountered with the first needle pass,which results in stimulation of the sartoriusmuscle, often seen as contraction of the lowermedial thigh. If this occurs, advance the needletip until either the sartorius twitch is extin-guished or a patellar snap is elicited before redi-recting the needle. If the sartorious twitch is ex-tinguished without the patellar snap, withdrawthe needle toward the skin (without exitingthe skin), and redirect it slightly lateral andslightly deeper than the original needle pass.The posterior branch of the femoral nerve istypically lateral and deep to the anterior branch.

The anesthetist should resist the urge to usethe patients thigh as a hand rest while directingthe needle. Stimulation of the femoral nerve canresult in brisk vastus muscle twitching that candisrupt needle positioning.

Figure 15-8

FEMORAL NERVE BLOCK15


Probe. High frequency (512 MHz), linear.

the needle to the nerve from a short-axis view(visualizing the needle as a dot) as opposed to thelong-axis view Both approaches are acceptable


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55

26

Figure 15-7

12

obe. g eque cy (5 M ), ea

Probe Position.Place the probe in the inguinal

crease, parallel to the inguinal ligament. The nervewill be visualized as a hyperechoic, triangular-shaped structure immediately lateral to the femoralartery.

Approach. Insert the needle at the lateral endof the ultrasound probe and advance it parallelto the ultrasound beam, in full view, until it ap-proaches the femoral nerve (Figure 15-7). This

is the preferred approach at Walter Reed ArmyMedical Center because it allows visualization ofthe entire needle. Some providers opt to advance

long-axis view. Both approaches are acceptable.The femoral nerve is easily visualized near thefemoral artery in most patients (Figure 15-8). The

relatively superficial depth of the femoral nerve atthe inguinal crease enhances visualization of theneedle under ultrasound. A medial approach tothe femoral nerve should be avoided because thefemoral artery can obstruct the needle approach tothe femoral nerve.

Injection. Ensure that the needle has penetratedthrough the fascia lata (which divides the subcu-

taneous tissues of the thigh from the underlyingmuscles and vessels) as well as the fascia iliaca(which surrounds the iliopsoas and femoral

Teaching Point. Studies have demonstrated thatuse of the ultrasound can improve the femoralnerve block by decreasing the block latency byas much as 10 minutes, improving the sensorycomponent of the block, and reducing theamount of local anesthetic needed to achieveblock success.

nerve). To ensurea successful block,the local anes-thetic must eithersurround thefemoral nerve com-

pletely or surroundthe medial, lateral,and inferioraspects of thenerve (Figure 15-9).If the local anes-thetic is distributedonly at the superioraspect of the nerve,

the needle maynot have crossedthe fascia iliaca,the local anestheticwill be unable toproperly penetratethe nerve, andthe block may bedelayedor fail.

Figure 15-9

16. INDIVIDUAL NERVE BLOCKS OF THE

LUMBAR PLEXUS

LATERAL FEMORAL CUTANEOUS NERVE

B OCK


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Figure 16-1. Dermatomes anesthetized with the LFC block (dark blue)

Figure 16-2Figure 16-3

Figure 16-4

BLOCK

Introduction. The lateral femoral cutaneous (LFC)

nerve is a purely sensory nerve derived from theL2L3 nerve roots. It supplies sensory innervation tothe lateral aspect of the thigh (Figure 16-1). Becauseit is one of six nerves that comprise the lumbarplexus, the LFC can be blocked as part of the lumbarplexus block. Most of the time, but not always, it canalso be simultaneously anesthetized via a femoralnerve block. An occasional need arises to performan individual LFC nerve block for surgery such as a

thigh skin graft harvest or for the diagnosis of myal-gia paresthetica (a neuralgia of the LFC nerve).

Anatomy. The LFC nerve emerges from the lumbarplexus, travels along the lateral aspect of the psoasmuscle, and then crosses diagonally over the iliacusmuscle. After traversing beneath the inguinal liga-ment, it enters the thigh and passes medially to theanterior superior iliac spine (ASIS). It is the rela-

tionship of the nerve to the ASIS that anatomicallydefines this block (Figure 16-2).

Procedure.Because the LFC nerve is purely sensory,

nerve stimulation is not typically used. Insert theneedle perpendicular to all planes at a point 2 cmcaudal and 2 cm medial to the ASIS. Advance theneedle until a loss-of-resistance is felt; this signifiesthe penetration of the fascia lata. Inject 5 mL of localanesthetic at this location, then redirect the needlefirst medially and then laterally, injecting an addi-tional 5 mL at each of these points (Figure 16-3).

Teaching Point.A useful procedure in both thepediatric and adult populations is a variation ofthe LFC nerve block, the fascia iliaca block. Likethe femoral 3-in-1 block, the fascia iliaca blockoften fails to anesthetize the obturator nerve. Toperform this procedure, draw a line from the

dicating the fascia lata and the fascia iliaca. After thesecond pop, drop the needle to a 30 angle, and ad-vance it 1 cm. Slowly inject 30 mL of local anesthetic(Figure 16-4).

ASIS to the pubic tubercle, and divide it into thirds.At the point where the lateral and middle thirdsmeet, draw a line 1 cm caudally, and insert the nee-dle at this point. Two fascial pops will be felt, in-

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Alternative Approach to the Obturator Nerve Block.The anterior obturator branch supplies an articular

h h h h

present (71%92% of cases), the posterior branch ofthe obturator nerve also sends a branch to the knee

16INDIVIDUAL NERVE BLOCKS OF THE LUMBAR PLEXUS

(Figures 16-8 and 16-9). Insert a 21-gauge, 100-mminsulated needle slightly lateral and posterior, with

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branch to the hip and the anterior adductor muscles,and it provides cutaneous innervations to the lower

medial aspect of the thigh. The posterior branchsupplies the deep adductor muscles and often anarticular branch to the knee joint. The accessory ob-turator nerve (L3 and L4) is present in a third of cases(8%29% of human bodies) and sends a branch to thehip joint. When the accessory obturator nerve is not

joint.The inguinal interadductor obturator nerve block

approach landmarks are the inguinal ligament, thefemoral artery, and the long adductor muscle tendon.Draw a line immediately below the inguinal liga-ment from the medial edge of the femoral pulse tothe medial border of the tendon of the long adductormuscle. Insert the needle at the midpoint of this line

a superior inclination. Carefully advance the needleuntil twitches of the anterior adductor muscles (an-

terior obturator branch) occur, and inject 5 to 7 mLof local anesthetic solution. Then advance the needleslowly a few millimeters in a slightly lateral directionuntil the posterior (major) adductor muscles twitch(posterior obturator branch), and inject another 5 to 7mL of local anesthetic at this location.


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17. SCIATIC NERVE BLOCK:

POSTERIOR AND ALTERNATIVE APPROACHES

INTRODUCTION

ANATOMY

This anatomy description applies to all approach-es of the sciatic nerve block (through Chapter 19).The sciatic nerve arises from the ventral rami of L4

(fibular) nerves. These nerves usually do notseparate until the mid-thigh, although separationas proximal as the pelvis occurs in about 12% of


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The sciatic nerve supplies motor and sensoryinnervation to the posterior aspect of the thigh aswell as the entire lower leg, except for the medialleg, which is supplied by the saphenous nerve (theterminal branch of the femoral nerve). The sciaticnerve, formed from the anterior rami of spinalnerves L4S3, is the largest nerve in the body.Because the sciatic nerve is so large, it can be blockedfrom several different locations along the lowerextremity. Labats sciatic nerve block is the classicapproach, targeting the nerve in the gluteal region.Other sciatic nerve blocks include the anterior(Chapter 18) and lateral (Chapter 19) approaches,which allow the patient to remain in the supine posi-tion, as well as the parasacral and prone approaches.Rajs subgluteal approach is performed in the supineposition with the hip flexed.

Sciatic nerve blocks require adequate set-up be-cause this large nerve resists local anesthetic penetra-tion, leading to longer block onset times. For com-plete anesthesia of the leg below the knee the saphe-nous nerve must also be blocked, either directly orvia a femoral nerve block.

Figure 17-1. Dissected proximal sciatic nerve

through S3, which forms most of the sacral plexus(L4S4). The sciatic nerve is actually two nerves in

close apposition, the tibial and common peroneal

as proximal as the pelvis occurs in about 12% ofpatients. The sciatic nerve leaves the pelvis via thegreater sciatic foramen, travels under the gluteus

maximus (Figure 17-1), and continues distally

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toward the posterior thigh between the greater tro-chanter and ischial tuberosity (Figure 17-2). Althoughthe sciatic nerve does not innervate any muscles inthe gluteal region, it does supply motor innervation

Teaching Point.Of the various approaches tothe sciatic nerve, Labats posterior technique(first described in 1924) has the advantage of alsoblocking the posterior femoral cutaneous nerve.

This nerve provides sensory innervation to thegluteus and uppermost medial and posteriorthigh, and blocking it is important when thightourniquets are used for lower extremity proce-dures of long duration.

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Figure 17-3. Dermatomes anesthetized with a proximal block of the sciatic nerve (dark blue)

Figure 17-2

to the posterior thigh muscles as well as all musclesof the leg and foot. It also provides sensory innerva-tion to the skin of most of the leg and foot (Figure17-3).


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SCIATIC NERVE BLOCK: POSTERIOR17

ALTERNATIVE APPROACHES TO THE SCIATIC NERVE BLOCK

Raj Technique. This posterior approach is unique Midline Technique. Franco has described twoParasacral Technique. This technique is the most


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Raj Technique. This posterior approach is uniquebecause the patient remains in the supine position.

The hip and knee are both flexed at a 90 angle, withthe foot resting on a Mayo stand or held up by anassistant. By flexing the hip in this way, the glutealmuscles are flattened and the sciatic nerve becomesmore superficial. Palpate the greater trochanter andischial tuberosity, and draw a line connecting them.Insert a 10-cm needle at the midpoint of this line, at aperpendicular angle to the skin (Figure 17-9).

Midline Technique. Franco has described twotechniques that target the sciatic nerve 10 cm lateral

to the midline of the pelvis. The first, a midglutealapproach, is performed with the patient in the proneposition. Insert a 10-cm needle at the midpoint ofthe intergluteal sulcus 10 cm lateral to the midline.Advance the needle parallel to midline and perpen-dicular to the table. If no response is elicited, adjustthe needle slightly medial or lateral.

The second technique is a subgluteal approachwith the patient in the lateral decubitus position,

flexed at the hips and knees (as if performing alateral neuraxial technique). Insert the needle in thesubgluteal fold 10 cm from the intergluteal sulcus,directing it parallel to the bed (Figure 17-11).

Parasacral Technique. This technique is the mostproximal approach to the sciatic nerve, targeting

the nerve in the greater sciatic foramen. Patientsare placed in the lateral decubitus position. Thistechnique typically blocks the obturator nerve,enabling the entire lower extremity to be anesthe-tized with a sciatic and femoral nerve block (withouta lumbar plexus block). Landmarks are the PSIS andthe ischial tuberosity. Draw a line connecting thesetwo points, and insert a 10-cm needle 6 cm caudalto the PSIS. If bone is contacted, walk off the

needle caudally until it advances through the sciaticforamen. The nerve is usually found at a depth of 6to 7cm (Figure 17-10).

Figure 17-9

Figure 17-10

Figure 17-11


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ANTERIOR APPROACH

INTRODUCTION

The anterior approach to the sciatic nerve block


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The anterior approach to the sciatic nerve blockis particularly useful in patients needing lower

extremity anesthesia who are unable to assumethe lateral decubitus position (Figure 18-1). Thistechnique is a deep block that requires a 15-cmneedle in adults. It can be associated with morepatient discomfort than other approaches, and thelocation of the femoral artery anterior to the sciaticnerve in this position increases the risk of inadver-tent arterial puncture. Continuous peripheral nervecatheters, although possible, are typically avoided

using this approach.

Figure 18-1. Dermatomes anesthetized with the anterior sciatic nerve block (dark blue)

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18 SCIATIC NERVE BLOCK: ANTERIOR

PROCEDURE

Landmarks.With the patient positioned supine,draw a line from the anterior superior iliac spine to


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Figure 18-4

Teaching Points. These blocks depend on localanesthetic volume for success. This approachdoes not block the posterior cutaneous nerveof the thigh, which may be a problem if a thightourniquet is used. A complete block of thelower leg requires the addition of a saphenousnerve block.

Needles


catheter placement. Because of the depth of the

block, catheters are not recommended; if used,they should be inserted 5 cm beyond the needletip.

Stimulation. Set the nerve stimulator initially at 1.5mA, and advance the needle perpendicular to allplanes. If bone is contacted, withdraw the needleslightly and rotate the leg internally. Then advancethe needle in the same plane as before until a twitch

is elicited. If the needle again contacts bone, theinitial insertion site may be distal to the lesser tro-chanter. In this case, slightly withdraw the needle,externally rotate the leg 45, and then readvance theneedle; this should allow a stimulation response tobe elicited. Plantar flexion/inversion or dorsiflex-ion/eversion is sought at a current of 0.5 mA or less.Stimulation of the hamstring muscle suggests theneedle is deep to the nerve (Figure 18-4).

Figure 18-2. Landmarks for anterior sciatic nerve block

Figure 18-3

p pthe pubic tubercle, and divide the line into thirds.

Draw a second line, parallel to the first, medial fromthe cephalad aspect of the greater trochanter. Then,draw a third line perpendicular from the medialthird of the first line to intersect the second line.The intersection, which will be located over thelesser trochanter of the femur, represents the pointof initial needle insertion (Figures 18-2 and 18-3).Recent studies have suggested that the lesser tro-chanter obstructs the route to the sciatic nerve when

the leg and foot are in neutral position; however,internal rotation of the leg by 45 exposes the nerveand allows the needle to pass through unobstructed.

Local Anesthetic. In most adults, 30 to 40 mL oflocal anesthetic is sufficient.


LATERAL APPROACH

INTRODUCTION

Like the anterior approach the lateral approach


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Like the anterior approach, the lateral approachto the sciatic nerve has the advantage of being

performed with the patient in the supine position.Both approaches anesthetize the same dermatomes(see Figure 18-1). The lateral approach may betechnically easier than the anterior block, and theneedle depth is shallower, making it more comfort-able for the patient. This block is typically doneat a more distal location immediately cephaladto the popliteal fossa (Figure 19-1). Because thisblock is more distal than the posterior or anterior

approaches to the sciatic nerve, the anesthetistmust take care to ensure adequate anesthesia andanalgesia of both components of the sciatic nerve(tibial and common peroneal). For this reason,larger volumes of local anesthetic are used toensure adequate distribution.

Figure 19-1

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12

19 SCIATIC NERVE BLOCK: LATERAL

PROCEDURE

Landmarks.Palpate the popliteal crease andmeasure a distance of 10 cm cephalad in the grooveb t th t l t li d th bi f i

Stimulation. Set the nervestimulator at 1.2 to 1.5 mA.After sterile preparation ofthe area, introduce needle and

Figure 19-5


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Local Anesthetic. In most adults, 40 mL of local an-esthetic is sufficient.

Figure 19-5Teaching Points. For the needle to gain

proximity to the sciatic nerve from thisapproach, it must pass through the bicepsfemoris muscle. Local stimulation of this muscleis often seen, and advancing the needle tipfurther will cause this twitch to stop and footor toe twitching to start. If stimulation of thevastus lateralis muscle is observed, the needletip is too anterior and should be withdrawntoward skin and repositioned in a more

posterior plane.

between the vastus lateralis and the biceps femoris

muscles of the thigh (Figure 19-2). If these land-marks are difficult to identify, flex the patients legat the knee to further delineate the anatomy.

Needles


catheter placement. Catheters introduced 5 cmbeyond the needle tip.

Figure 19-2


,advance it in a horizontal plane

until the femur is contacted(Figure 19-3). Upon contact,withdraw the needle backtoward the skin and redirectit approximately 30 posteriorto the original insertion site,advancing slowly until a stimu-lation pattern appears (Figures19-4 and 19-5). The nerve is

typically 1 to 2 cm beyond thepoint of initial femur contact.Studies have demonstratedthat plantar flexion, as opposedto dorsiflexion, of the foot is amore desirable twitch to obtainwith the lateral approach to thesciatic nerve, resulting in a morecomplete sensory block. Once

plantar flexion is established,turn the stimulator currentdown to 0.5 mA and inject thelocal anesthetic.


Probe.Mid-frequency (512 MHz), linear.

Probe Position. Place the patient in the supine po-

SCIATIC NERVE BLOCK: LATERAL19


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Probe Position. Place the patient in the supine position with the foot and ankle resting on a stack ofblankets; this will allow enough room to place theprobe directly beneath the leg. Position the probeapproximately 8 cm proximal and parallel to thepopliteal crease (with a transverse view; Figure 19-6). Scan in the cephalad and caudad directions untilthe sciatic nerve is identified. Often, the poplitealartery is identified and can be used as a landmarkfor sciatic nerve locationthe nerve is lateral to theartery. The sciatic nerve is seen as a round, hyper-echoic structure (Figure 19-7). If two smaller round,hyperechoic structures are viewed, the probe is distalto the split of the tibial and peroneal nerve compo-nents and must be moved to a more proximal loca-tion on the leg.

Figure 19-6

Approach.Insert the 21-gauge needle at the lateralaspect of the ultrasound probe, allowing visibility ofthe entire needle shaft. Note: needle adjustments seen

Figure 19-7

Figure 19-8

Figure 19-9

Teaching Points.To help identify the sciaticnerve, begin with probe placement just abovethe popliteal crease. Often, the tibial andperoneal components can be viewed as two

hyperechoic round structures (Figure 19-9).Continue sliding the probe in the cephaladdirection, and the two smaller structures willmerge into the single structure of the sciaticnerve. This technique ensures that probeplacement is proximal to the split of the nerve.

The low-frequency, curved probe is difficultto manipulate behind the leg. Usually, a linear,higher frequency probe is sufficient for adequate

visualization of the sciatic nerve.

71

on the ultrasound screen are the reverse of the operatorshand movement, which can be confusing.Injection.Inject 30 to 40 mL of local anesthetic, sothat the sciatic nerve is completely embedded ina hypoechoic ring (Figure 19-8). If circumferential

spread is incomplete, withdraw the needle and redi-rect it to contact any missed areas.

20. POPLITEAL NERVE BLOCK

INTRODUCTION

The popliteal nerve block is a block of the sciaticnerve in the popliteal fossa with the patient in the

ANATOMY

The popliteal fossa is bordered laterally bythe biceps femoris muscle and medially by thesemimembranosus muscle. It is the site wherethe sciatic nerve splits into its two major com-

The sciatic nerve supplies motor innervation tothe entire lower leg via the posterior tibial nerve,superficial and deep peroneal nerves, and the suralnerve. The sural nerve is sensory only. These majorbranches of the sciatic nerve also supply sensory


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prone position. The block is ideal for surgeries

of the lower leg, particularly the foot and ankle.It anesthetizes the same dermatomes as both theanterior and lateral approaches to the sciatic nerve(Figure 18-1). Unlike more proximal approachesto the sciatic nerve, the popliteal nerve blockpreserves hamstring function, allowing easierambulation of the postoperative patient. Evenso, patients should be cautioned against bearingweight on the blocked lower extremity for 24

hours, as with all blocks of the sciatic nerve.

Figure 20-1

ponents, the tibial and common peroneal nerves

(Figure 20-1). To avoid an incomplete nerveblock, the needle entry site must be proximal tothe splitting of these two nerves (Figure 20-2).Studies have demonstrated that the needleentry point should be 10 cm from the poplitealcrease to optimize needle placement. Because ofthe possibility of needle placement distal to thebifurcation of the two nerves, a larger volumeof local anesthetic is typically used with this

approach (4045 mL).

pp y yinnervation to the lower leg, except for the medial

inner strip, which is supplied by the saphenousnerve (a branch of the femoral nerve).

Teaching Points. Vascular puncture and in-travascular injection are rare with this blockbecause the nerve is superficial to the poplitealartery and vein at this location.

For a complete sensory blockade of the lower

extremity, the saphenous nerve must also beblocked, which can be done at the level of thepopliteal fossa (see Chapter 21).

Figure 20-2

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20 POPLITEAL NERVE BLOCK

PROCEDURE

Landmarks. Place the patient in the prone positionwith the operative leg supported below the knee.The knee should be slightly bent and the foot resting

Stimulation. Set the nerve stimulator initiallybetween 1.0 and 1.2 mA. Inversion of the footindicates stimulation of the tibial and deep peronealnerves, eversion of the foot indicates stimulation

Local Anesthetic. In most adults, 35 to 45 mL oflocal anesthetic is sufficient to block the nerves.


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Teaching Points.If no motor response isobtained with initial stimulation, subsequent

attempts should be made more lateral (ratherthan more medial, which causes a risk ofinadvertent vascular penetration). The anes-thetist should attempt to achieve stimulationin a position as cephalad in the poplitealfossa as possible, making it less likely that thesciatic nerve has divided at that point, and

improving block success.

Figure 20-4

Figure 20-3

The knee should be slightly bent and the foot restingfreely above the bed. The popliteal fossa can beaccentuated by having the patient bend the kneeagainst resistance. The popliteal triangle is formedmedially by the semitendinosus and semimem-branosus muscles, laterally by the biceps femorismuscle, and at the base by the popliteal crease.Needle insertion should be at least 7-cm superior tothe popliteal crease and approximately 1 cm lateralto the apex of the popliteal triangle (Figure 20-3).Insert the needle at a 45 to 60 angle to the skin in acephalad direction (Figure 20-4).

Needles


catheter placement. Catheters inserted aminimum of 3 to 5 cm beyond the needle tip.

nerves, eversion of the foot indicates stimulationof the superficial peroneal nerve, plantar flexionindicates stimulation of the posterior tibial nerve,and dorsiflexion indicates stimulation of the deepperoneal nerve. Studies have shown that inversionof the foot leads to the best sensory and motorblock, and dorsiflexion of the foot is second best(in contrast to more proximal sciatic nerve blocks,where the nerve components are in close proximity,allowing injection of local anesthetic on any twitchin the sciatic distribution).

Occasionally, a local twitch of the biceps femorismuscle is elicited after needle insertion, indicatingthat needle placement is too lateral and must beredirected slightly medial. Conversely, if localtwitching of the semitendinosus and semimem-branosus muscles occurs, needle placement istoo medial and must be redirected slightly morelateral.


Probe.High frequency (512 MHz), linear.

b l ( ll l h

Teaching Points.For block success, the localanesthetic must be deposited proximal to thesplitting of the sciatic nerve. By placing the

b h li l d i h

POPLITEAL NERVE BLOCK20

Approach.As with most ultrasound-guided blocks,an in-plane or out-of-plane approach is possible.Because the in-plane technique allows for completevisualization of the needle, it is the preferred ap-

h W l R d A M di l C Wi h


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Probe Position.A transverse plane (parallel to the

popliteal crease) gives the best image of the sciaticnerve (Figure 20-5). Depending upon the location ofthe split of the sciatic nerve into its tibial and perone-al components, either one large or two smaller roundhyperechoic structures will be seen. If the poplitealartery is visualized, the nerve will be lateral to theartery (Figure 20-6).


Figure 20-7

probe at the popliteal crease and scanning the

leg in the cephalad direction, both the tibial andperoneal components of the sciatic nerve can bevisualized separately as they coalesce to formthe sciatic nerve (Figure 20-7).

The popliteal block is performed in thesame area as the lateral sciatic block; however,the patient is in a prone rather than a supineposition. Scanning the nerve in the poplitealapproach may be easier, although positioning

the patient prone is more cumbersome.The common peroneal and tibial nerves can

be blocked distal to the sciatic nerve bifurcationusing two separate injections of local anestheticaround each nerve.

75

proach at Walter Reed Army Medical Center. With

the probe parallel to the popliteal crease and at alevel proximal to the nerve split, insert the needle atthe lateral aspect of the probe and advance it towardthe nerve. After the sciatic sheath is penetrated andthe nerve is stimulated, inject 40 mL of local anes-thetic. Repositioning the needle may be necessary toensure complete coverage of the nerve.

21. SAPHENOUS NERVE BLOCK

INTRODUCTION

The saphenous nerve is the only nerve belowthe knee that is not derived from the sciatic nerve.Rather it is a continuation of the femoral ner e (part

ANATOMY

The saphenous nerve is the largest sensorybranch of the femoral nerve, derived from theL34 nerve roots. Its cutaneous area of innerva-tion spans from the medial lower leg just distalto the knee down to the medial malleolus and in

rius muscle (Figure 21-3). Another technique is theparavenous approach, which takes advantage of thenerves proximity to the saphenous vein, and a thirdis the simple field block, in which local anesthetic isdeposited subcutaneously around the medial sur-face of the tibia. Recently, ultrasound-guided saphe-


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Rather, it is a continuation of the femoral nerve (part

of the lumbar plexus) extending the length of thelower extremity. It provides cutaneous innervationover the medial, anteromedial, and posteromedialareas of the lower leg; all other sensory and motorinnervation to the lower leg is supplied by the sciaticnerve. Because it is a terminal branch of the femoralnerve, the saphenous nerve can be anesthetized witha lumbar plexus nerve block, or more commonly,a femoral nerve block. This nerve can also be indi-

vidually blocked directly at the knee or the ankle(see Chapter 22, Ankle Block). The saphenous nerveblock is frequently combined with a sciatic nerveblock to anesthetize the entire lower leg.

Figure 21-1

Teaching Point. If a tourniquet will be usedfor the surgical procedure, its placementeither above or below the knee must first bedetermined. For above-knee placement, afemoral nerve block is more appropriate toprovide analgesia accommodating the tourni-

quet; for below-knee tourniquet placement, asaphenous nerve block is appropriate.

to the knee down to the medial malleolus, and in

some patients as far down as the great toe (Figure21-1). The nerve travels through the femoraltr

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