beyondpvalue.com Draft... · Web viewWith the development of safer drugs, sterile equipment, and aseptic techniques, spinal anesthesia would earn a place in the armamentarium of most

RESPECTED SIR, FOLLOWING OBSERVATION HAS BEEN GIVEN BY THE GUIDE-:(HIGHLIGHTED IN RED)

- USG 3 D PROBE DETAILS NOT REQUIRED (PLEASE REMOVE THAT TABLE)

- REFENCES 18,19 IN RED ARE RELATED TO ASSOCIATION BETWEEN OBESITY AND SOCIOECONOMIC STATUS WHICH IS NOT RELATED TO SPINE ANAESTHESIA (SIR I COULD NOT UNDERSTAND ITS RELEVENCE,IF POSSIBLE PLEASE DELETE).

- IN DICUSSION PLS DON,T MENTION ABOUT REALTIME ULTRASOUND TECHNIQUE ITS TOTALLY DIFFERENT TOPIC

- SPACING NEED TO BE DONE PROPERLY.

- REST ALL OK SIR

THANKS AND REGARDSDR SEEMA SINGH

INTRODUCTION:

Spinal anaesthesia is widely performed using a surface landmark-based “blind” technique.

Multiple passes and attempts while administering spinal anaesthesia are associated with a

greater incidence of postdural puncture headache, paraesthesia, and spinal hematoma 1, 2.

Real-time and preprocedural neuraxial ultrasound techniques have been used to improve the

success rate of spinal anaesthesia. Information on the use of real-time ultrasound- guided

spinal anaesthesia has, to date, been limited to case series and case reports 3-5. Its use may be

limited by the requirement for wide-bore needles and the technical difficulties associated with

simultaneous ultrasound scanning and needle advancement 6. The use of preprocedural

ultrasound has been shown to increase the first-pass success rate for spinal anaesthesia only

in patients with difficult surface anatomic landmarks 7.

Studies on preprocedural ultrasound-guided spinal techniques have focused on a midline

approach using a transverse median (TM) view. The parasagittal oblique (PSO) view

consistently offers a better ultrasound view of the neuraxis compared with TM views 8, 9.

However, very few studies have been conducted to assess whether these superior PSO views

translate into easier paramedian needle insertion.

The use of ultrasound imaging techniques in regional anaesthesia is rapidly becoming an area

of increasing interest. It represents one of the largest changes that the field of regional

anaesthesia has seen. For the first time, the operator is able to view an image of the target

nerve directly, guide the needle under real-time observation, navigate away from sensitive

anatomy, and monitor the spread of local anaesthetic (LA). This comes at a time when an

ageing population presents with an increasing range of comorbidities, thereby demanding a

wider choice of surgical and anaesthetic options to ensure optimal clinical care and a

decreased risk of complications. The key to successful regional anaesthesia is deposition of

LA accurately around the nerve structures. In the past, electrical stimulation or paraesthesia,

both of which relied on surface landmark identification, was used for this. However,

landmark techniques have limitations; variations in anatomy and nerve physiology 4, as well

as equipment accuracy have had an effect on success rates and complications. The

introduction of ultrasound may go some way towards changing this.

If the use of ultrasound is to become more widespread amongst anaesthetists, then it must be

shown to be clinically effective, practical and cost-effective 10. The use of ultrasound

guidance in daily clinical practice requires a degree of training and an understanding of the

equipment and technology.

US-guided Central Neuraxial block is a promising alternative to traditional landmark-based

techniques 6. It is non-invasive, safe, simple to use, can be quickly performed, does not

involve exposure to radiation, provides real-time images, and is free from adverse effects. US

guidance may also allow the use of central neuraxial block in patients who in the past may

have been considered unsuitable for such procedures due to abnormal spinal anatomy.

Spinal anaesthesia may be challenging in patients with poorly palpable surface landmarks or

abnormal spinal anatomy. Pre-procedural ultrasound imaging of the lumbar spine can help by

providing additional anatomical information, thus permitting a more accurate estimation of

the appropriate needle insertion site and trajectory.

We hypothesized that the routine use of a preprocedural ultrasound-guided technique for

spinal anaesthesia would reduce the number of passes required to achieve entry into the

subarachnoid space when compared with the conventional landmark-guided midline

approach.

REVIEW OF LITERATURE:

ANATOMY of SPINE11

The vertebral column consists of 33 vertebrae: 7 cervical, 12 thoracic, 5 lumbar, 5 sacral, and

4 coccygeal segments. The vertebral column usually contains three curves. The cervical and

lumbar curves are convex anteriorly, and the thoracic curve is convex posteriorly.

Fig 1. Anatomy of spine

VERTEBRA The typical vertebra consist of two parts

(1) Body: placed anteriorly and bear weight

(2) Arch: It consist of 2 pedicles, 2 superior and 2 inferior articular process, 2 transverse

process, 2 laminae, 1 spinous process . It surround the cord laterally and posteriorly

Fig 2. The vertebral arch (green) forms the spinal canal (blue) through which the spinal cord

runs. Seven bony processes arise from the vertebral arch to form the facet joints and

processes for muscle attachment.

The vertebral arch, spinous process, pedicles, and laminae form the posterior elements of the

vertebra, and the vertebral body forms the anterior element. The vertebrae are joined together

anteriorly by the fibrocartilaginous joints with the central disks containing the nucleus

pulposus, and posteriorly by the zygapophyseal (facet) joints. The thoracic spinous process is

angulated steeply caudal as opposed to the almost horizontal angulation of the lumbar

spinous process This is a clinically important distinction for needle insertion and

advancement in the thoracic versus lumbar levels. The sacral canal contains the terminal

portion of the dural sac, which typically ends at S2.

SPINAL CORD

The spinal cord is continuous with the brainstem proximally and terminates distally in the

conus medullaris as the filum terminale (fibrous extension) and the cauda equina (neural

extension). This distal termination varies from L3 in infants to the lower border of L1 in

adults because of differential growth rates between the bony vertebral canal and the central

nervous system. It is about 40 cm long and 1-1.5 cm in diameter. Surrounding the spinal cord

in the bony vertebral column are three membranes (from innermost to outermost): the pia

mater, the arachnoid mater, and the dura mater (Fig. 56-1). The cerebrospinal fluid (CSF)

resides in the space between the pia mater and the arachnoid mater, termed the subarachnoid

(or intrathecal) space. The pia mater is a highly vascular membrane that closely invests the

spinal cord and brain. Approximately 500 mL of CSF is formed daily by the choroid plexuses

of the cerebral ventricles, with 30 to 80 mL occupying the subarachnoid space from T11-T12

downward. The arachnoid matter is a delicate, nonvascular membrane that functions as the

principal barrier to drugs crossing into (and out of) the CSF and is estimated to account for

90% of the resistance to drug migration.12

Fig 3. The ventral (motor) and dorsal (sensory) roots join to form the spinal nerve.

Spinal cord is composed of white and grey matter and is divided into spinal segments each

segment forms a pair of spinal nerves. The spinal nerves are numbered according to the

vertebrae above which it exits the spinal canal. The 8 cervical spinal nerves are C1 through

C8, the 12 thoracic spinal nerves are T1 through T12, the 5 lumbar spinal nerves are L1

through L5, and the 5 sacral spinal nerves are S1 through S5. There is 1 coccygeal nerve.

Thirty-one pairs of spinal nerves branch off the spinal cord. Each spinal nerve has two roots.

The ventral (motor) and the dorsal (sensory). (Fig. 9). Once the nerve passes through the

intervertebral foramen, it branches; each branch has both motor and sensory fibers. The

smaller branch (called the posterior primary ramus) turns posteriorly to supply the skin and

muscles of the back of the body. The larger branch (called the anterior primary ramus) turns

anteriorly to supply the skin and muscles of the front of the body and forms most of the major

nerves.

Fig 4. The spinal nerves exit the spinal canal through the intervertebral foramen below each

pedicle.

LIGAMENTS

The ligaments are strong fibrous bands that hold the vertebrae together, stabilize the spine,

and protect the discs. The three major ligaments of the spine are the ligamentum flavum,

anterior longitudinal ligament (ALL), and posterior longitudinal ligament (PLL) (Fig. 7). The

ALL and PLL are continuous bands that run from the top to the bottom of the spinal column

along the vertebral bodies. They prevent excessive movement of the vertebral bones. The

ligamentum flavum attaches between the lamina of each vertebra. ligamentum flavum (the

so-called yellow ligament) extends from the foramen magnum to the sacral hiatus. Although

classically portrayed as a single ligament, it is actually comprised of two ligamenta flava—

the right and the left—which join in the middle and form an acute angle with a ventral

opening13 The ligamentum flavum is not uniform from skull to sacrum, nor even within an

intervertebral space. Ligament thickness, distance to the dura, and skin-to-dura distance vary

with the area of the vertebral canal. The vertebral canal is triangular and largest in area at the

lumbar levels, and it is circular and smallest in area at the thoracic levels. The two ligamenta

flava are variably joined (fused) in the midline, and this fusion or lack of fusion of the

ligamenta flava even occurs at different vertebral levels in individual patients. Immediately

posterior to the ligamentum flavum are the lamina and spinous processes of vertebral bodies

or the interspinous ligaments. Extending from the external occipital protuberance to the

coccyx posterior to these structures is the supraspinous ligament, which joins the vertebral

spines.

Fig 5. The ligamentum flavum, anterior longitudinal ligament (ALL), and posterior

longitudinal ligament (PLL) allow the flexion and extension of the spine while keeping the

vertebrae in alignment.

EPIDURAL SPACE: It is also called as peridural or extradural space .It is circular space

extending from foramen magnum to sacral hiatus and surround the duramater anteriorly,

laterally and posteriorly

Boundaries of epidural space:

Anteriorly : Posterior longitudinal ligaments,

Laterally : Pedicles and intervertebral foramina

Posteriorly : Ligamentum flavum.

Contents: nerve roots and fat, areolar tissue, lymphatics, and blood vessels including the well-

organized Batson venous plexus.

BLOOD SUPPLY14

Blood is supplied to the spinal cord

Arterial Supply

1) One anterior spinal artery (originating from the vertebral artery),

2) Two posterior spinal arteries (originating from the inferior cerebellar artery)

3) Segmental spinal arteries (originating from the intercostal and lumbar arteries).

Venous drainage

Venous drainage of the spinal cord follows a similar distribution as the spinal arteries. There

are three longitudinal anterior spinal veins and three posterior spinal veins that communicate

with the segmental anterior and posterior radicular veins before draining into the internal

vertebral venous plexus in the medial and lateral components of the epidural space. There are

no veins in the posterior epidural space except those caudal to the L5-S1

CEREBROSPINAL FLUID

Lumbosacral CSF has a constant pressure of approximately 15 cm H2O, but its volume

varies by patient, in part because of differences in body habitus and weight.15 It is estimated

that CSF volume accounts for 80% of the variability in peak block height and regression of

sensory and motor blockade. Nevertheless, except for body weight (less CSF in subjects with

high body mass index [BMI]), the volume of CSF does not correlate with other

anthropomorphic measurements available clinically.16

PHYSIOLOGY AND MECHANISM OF SPINAL ANAESTHESIA

Local anaesthetic binding to nerve tissue disrupts nerve transmission, resulting in neural

blockade. For spinal and epidural anaesthesia, the target binding sites are located within the

spinal cord (superficial and deep portions) and on the spinal nerve roots in the subarachnoid

and epidural spaces. The spinal nerve roots and dorsal root ganglia are considered the most

important sites of action. Nerves in the subarachnoid space are highly accessible and easily

anesthetized, even with a small dose of local anaesthetic, as compared to the extradural

nerves, which are often ensheathed by duramater (the “dural sleeve”).17

The speed of neural blockade depends on-:

- Size of nerve fibre

- Surface area of the nerve fibres exposed to the local anaesthetic

- degree of myelination of the nerve fibres exposed to the local anaesthetic.

Injection of local anaesthetics into the spinal CSF allows access to sites of action both within

the spinal cord and the peripheral nerve roots 18. The traditional concept of spinal anaesthesia

causing complete conduction block is simplistic, as studies with somatosensory evoked

potentials demonstrate little change in amplitudes or latencies after induction of dense spinal

or epidural anaesthesia. There are multiple potential actions of local anaesthetics within the

spinal cord at different sites. For example, within the dorsal and ventral horns, local

anaesthetics can exert sodium channel block and inhibit generation and propagation of

electrical activity. Other spinal cord neuronal ion channels, such as calcium channels, are also

important for afferent and efferent neural activity. Spinal administration of N-type calcium

channel blockers results in hyperpolarization of cell membranes, resistance to electrical

stimulation from nociceptive afferents, and intense analgesia. Local anaesthetics may have

similar actions on neural calcium channels, which may contribute to analgesic actions of

central neuraxially administered local anaesthetics 19. 

Multiple neurotransmitters are involved in nociceptive transmission in the dorsal horn of

the spinal cord 20. Substance P is an important neurotransmitter that modulates nociception

from C fibers and is released from presynaptic terminals of dorsal root ganglion cells.

Administration of local anaesthetics in concentrations that occur after spinal and epidural

anaesthesia inhibits the release of substance P and inhibits the binding of substance P to its

receptor in the central neuraxis in a non-competitive fashion 21. Other inhibitory

neurotransmitters that may be important for nociceptive processing in the spinal cord, such as

γ-aminobutyric acid, are also affected by local anaesthetics. Local anaesthetics can potentiate

the effects of γ-aminobutyric acid by preventing uptake and clearance 22. These studies

suggest spinal anaesthesia may be partially mediated via  complex interactions at neural

synapses in addition to ion channel blockade and may explain the ability of spinal anaesthesia

to reduce central temporal summation in humans. 

Although spinal local anaesthetics can block sodium channels and electrical conduction in

spinal nerve roots, other mechanisms may also come into play. It is theorized that a large part

of the sensory information transmitted via  peripheral nerves is carried via  coding of

electrical signals in after-potentials and after-oscillations 23. Evidence for this theory is found

in studies demonstrating loss of sensory nerve function after incomplete local anaesthetic

blockade. For example, sensation of temperature of the skin can be lost despite unimpeded

conduction of small fibres 24. Furthermore, a surgical depth of epidural and spinal anaesthesia

can be obtained with only minor changes in somatosensory evoked potentials from the

anesthetized area 23. Previous studies have demonstrated that application of sub-blocking

concentrations of local anaesthetic will suppress normally occurring after-potentials and

after-oscillations without significantly affecting action potential conduction 24. Thus,

disruption of coding of electrical information by local anaesthetics may be a primary

mechanism for block of spinal nerve roots during spinal anaesthesia.

DRUG UPTAKE

When local anaesthetic is injected directly into the subarachnoid space during spinal

anaesthesia, it diffuses through the pia mater and penetrates through the spaces of Virchow-

Robin (extensions of the subarachnoid space accompanying the blood vessels that invaginate

the spinal cord from the pia mater) to reach the deeper dorsal root ganglia. Furthermore, a

portion of the subarachnoid drug diffuses outward through the arachnoid and dura mater to

enter the epidural space, whereas some is taken up by the blood vessels of the pia and dura

maters.25

Drug penetration and uptake is directly proportional to

- the drug mass

- CSF drug concentration

- contact surface area

- lipid content (high in spinal cord and myelinated nerves)

- local tissue vascular supply

Drug penetration is inversely related to nerve root size.

The concentration of local anaesthetic in the CSF is highest at the site of subarachnoid

injection in the case of spinal anaesthesia (generally L2-L4 levels).

DRUG DISTRIBUTION

Diffusion is the primary mechanism of local anaesthetic distribution in the CSF from areas of

high concentration (i.e., at the site of injection) toward other segments of the spinal cord with

low drug concentration.26 Rostral spread after the administration of a small local anaesthetic

dose, often evident within 10 to 20 minutes, is related to the CSF circulation time.

Longitudinal oscillations generated by the pulsations of the arteries in the skull are believed

to be responsible for CSF bulk flow.

DRUG ELIMINATION

Regression of neural blockade results from a decline in the CSF drug concentration, which in

turn is caused by nonneural tissue uptake and, most importantly, vascular absorption. Time

for block regression is also inversely correlated with CSF volume. Drug is absorbed by the

vessels in the pia mater or the epidural vessels through back diffusion before entering the

systemic circulation. No drug metabolism takes place in the CSF. The rate of elimination is

also dependent on the distribution of local anaesthetic; greater spread will expose the drug to

a larger area for vascular absorption and thus a shorter duration of action. 27

INDICATIONS

When considering spinal anaesthesia, the nature and duration of surgery, patient

comorbidities, the ease of spinal insertion (i.e., positioning and spinal pathology), and the

relative benefits and risks to the individual are important. Spinal anaesthesia is most

commonly used for patients who require surgical anaesthesia for procedures of known

duration that involve the lower extremities, perineum, pelvic girdle, or lower abdomen.

Spinal anaesthesia may be useful when patients wish to remain conscious or when

comorbidities such as severe respiratory disease or a difficult airway increase the risks of

using general anaesthesia.28

CONTRAINDICATIONS

ABSOLUTE

Patient refusal

Localized sepsis

Allergy to any of the drugs planned for administration.

A patient’s inability to maintain stillness during needle puncture, which can expose the neural

structures to traumatic injury. Raised intracranial pressure which may theoretically

predispose to brainstem herniation.29

RELATIVE

1) Neurologic Myelopathy or peripheral Neuropathy. The proof that neuraxial

anaesthesia or analgesia in the setting of pre-existing neurologic deficit can worsen

the extent of injury (so-called double-crush phenomenon) is absent.

2) Spinal Stenosis. Patients with spinal stenosis may be at increased risk of neurologic

complications after neuraxial blockade.

3) Previous spine surgery

4) Multiple Sclerosis.

5) Spina Bifida.

6) Aortic Stenosis or fixed cardiac output.

7) Hypovolemia.

8) Hematologic Thromboprophylaxis.

9) Inherited coagulopathy.

10) Infection

TECHNIQUE

Technique should be classified into a series of steps (i.e., the four Ps):

preparation

position

projection

puncture

Preparation

Informed consent must be obtained, with adequate documentation of the discussion of risk.

Resuscitation equipment must always be readily available whenever a spinal anaesthetic

procedure is performed.

The patient should have adequate intravenous access and be monitored with pulse oximetry,

non-invasive arterial blood pressure, and electrocardiogram. Record an initial set of vital

signs. Preload the patient with 1-1.5 litres of crystalloid intravenous solution.

Pre-prepared packs are now commonly used which contain fenestrated drapes, swabs and

towels, syringes, needles, filters, spinal needles, sterilizing solution, and local anaesthetic for

skin infiltration. Single use preservative free local anaesthetic ampoule should be used. Local

anaesthetics from multi dose vials or those that contain preservatives should NEVER be used

for spinal anaesthesia. Ensure that the local anaesthetic preparation is made specifically for

spinal anaesthesia.

When the local anaesthetic for subarachnoid injection is chosen, the duration of block should

be matched with both the surgical procedure and patient variables.

The most important characteristics of a spinal needle are the shape of the tip and the needle

diameter. Needle tip shapes fall into two main categories:

Cutting that cut the dura- Pitkin and Quincke-Babcock needle

Conical, pencil-point tip - Whitacre and Sprotte needles.

Spinal needles are available in a variety of sizes (from 16-30 gauge) and lengths. Commonly,

a 22 gauge needle is used in patients that are 50 years and older. A 25-27 gauge needle is

used in patients that are less than 50 years of age. A smaller needle is used in the younger

patient to decrease the incidence of post dural puncture headache. The removable stylet

occludes the lumen and avoids tracking tissue into the subarachnoid space. Blunt tipped

needles (pencil point) decrease the incidence of postdural puncture headaches compared to

cutting needle Sterility is an issue of utmost importance. One of the most common organisms

responsible for post-spinal bacterial meningitis is Streptococcus viridans, which is an oral

commensal, emphasizing the purpose of wearing a mask as part of a full aseptic technique.

Hands and forearms must be washed and all jewellery removed. A variety of solutions may

be used to clean the back, such as chlorhexidine or alcohol (alone or in combination), or

iodine solutions. Chlorhexidine and alcohol together have been concluded to be most

effective. If chlorhexidine is used, it is important that the solution is allowed to dry

completely before skin puncture because chlorhexidine is neurotoxic.

Position

The three primary patient positions include the lateral decubitus, sitting, and prone positions,

each of which has advantages in specific situations. Proper positioning is essential for a

successful block.

1. Place the patient in the position in which the neuraxial block will be performed:

sitting or lateral, with forward flexion of the lumbar spine.

2. Attempt to identify the midline and lumbar spine by

- Palpation of standard anatomical landmarks.

- Using ultrasound low-frequency (2–5 MHz), curved-array probe.

There are three positions used for the administration of spinal anaesthesia: lateral decubitus,

sitting, and prone.

Lateral Decubitus

Allows the anaesthetist to administer more sedation-less dependence on an assistant for

positioning (Never over sedate a patient)

The patient is positioned with their back parallel with the side of the OR table. Thighs are

flexed up, and the neck is flexed forward (fetal position).

Patient should be positioned to take advantage of the baricity of the spinal local anaesthetic.

Fig 6. Posture of the patient

Sitting

Used for anaesthesia of the lumbar and sacral levels (urological, perineal). Higher levels of

anaesthesia can be obtained if an appropriate dose of local anaesthetic is administered, and

the patient is quickly positioned to maximize the spread of local anaesthetic.

Identify anatomical landmarks. This may be a challenge in the obese or those with abnormal

anatomical curvatures of the spine.

Position- a stool can be provided as a footrest and a pillow placed in the lap. The assistant

helps to maintain the patient in a vertical plane while flexing the patient’s neck and arms over

the pillow, relaxing the shoulders, and asking the patient to “push out” the lower back to open

up the lumbar vertebral spaces. Care must be taken not to oversedate a patient in this position.

This will maximize the “opening” of the vertebral interspaces.

Fig 7. For a lower lumbar/sacral block (i.e. saddle block), leave the patient sitting for 5

minutes before assuming a supine position.

Prone

The prone position is used when the patient will be in this position for the surgical procedure

(i.e. rectal, perineal, lumbar procedures).

Hypobaric local anaesthetics are administered. Patient positions self, lumbar lordosis should

be minimized, a paramedian approach is often used.

Projection and Puncture

Midline approach

It relies on the ability of patients and assistants to minimize lumbar lordosis and allow access

to the subarachnoid space between adjacent spinous processes, usually at the L2-L3, L3-L4,

or the L4-L5 space. The spinal cord ends at the level of L1-L2 and so needle insertion above

this level should be avoided. The inter-crestal line is the line drawn between the two iliac

crests which corresponds to the level of the L4 vertebral body or the L4-L5 interspace.30 Once

the appropriate space has been selected, a subcutaneous skin wheal of local anaesthetic is

developed over this space, and the introducer is inserted at a slight cephalad angle of 10 to 15

degrees through skin, subcutaneous tissue, supraspinous ligament and interspinous ligament.

The introducer is grasped with the palpating fingers and steadied while the other hand is used

to hold the spinal needle like a dart, and the fifth finger is used as a tripod against the

patient’s back to prevent patient movement and unintentional insertion to a level deeper than

intended. The needle, with its bevel parallel to the midline, is advanced slowly to heighten the

sense of tissue planes traversed and to prevent skewing of nerve roots, until the characteristic

change in resistance is noted as the needle passes through the ligamentum flavum and dura.

On passing through the dura, there is often a slight “click” or “pop” sensation. The stylet is

then removed, and CSF should appear at the needle hub. The smaller the needle diameter, the

longer the wait for CSF flow, particularly if the patient is not in the sitting position. If the

CSF does not flow, the needle might be obstructed and rotation in 90-degree increments can

be undertaken until CSF appears. If CSF does not appear in any quadrant, the needle should

be advanced a few millimetres and rechecked in all four quadrants. If CSF still has not

appeared and the needle is at a depth appropriate for the patient, the needle and introducer

should be withdrawn and the insertion steps should be repeated. A common reason for failure

is insertion of the needle off the midline. After CSF is freely obtained, the dorsum of the

anaesthesiologist’s nondominant hand steadies the spinal needle against the patient’s back

while the syringe containing the therapeutic dose is attached to the needle. CSF is again

freely aspirated into the syringe, and the anaesthetic dose is injected at a rate of

approximately 0.2 mL/sec. After completion of the injection, 0.2 mL of CSF can be aspirated

into the syringe and reinjected into the subarachnoid space to reconfirm location and clear the

needle of the remaining local anaesthetic.

Paramedian approach

It exploits the larger “subarachnoid target” that exists if a needle is inserted slightly lateral to

the midline. The paramedian approach may be especially useful in the setting of diffuse

calcification of the interspinous ligament. In this approach the spinal needle traverse the skin,

subcutaneous fat, ligamentum flavum, dura mater, subdural space, arachnoid mater, and then

passes into the subarachnoid space The most common error when using the paramedian

technique is that the needle entry site is placed too far off the midline, which makes the

vertebral laminae barriers to insertion of the needle. In the paramedian approach, a skin wheal

is raised 1 cm lateral and 1 cm caudal to the corresponding spinous process. A longer needle

(e.g., 3 to 5 cm) is then used to infiltrate deeper tissues in a cephalomedial plane. The spinal

introducer and needle are next inserted 10 to 15 degrees off the sagittal plane in a

cephalomedial plane. Similar to the midline approach, the most common error is to angle the

needle too far cephalad on initial insertion. Nevertheless, if the needle contacts bone, it is

redirected slightly in a cephalad direction. If bone is again contacted, but at a deeper level,

the slight cephalad angulation is continued because it is likely that the needle is being

“walked up” the lamina. After CSF is obtained, the block is carried out in a manner similar to

that described for the midline approach.

OBESITY PREVALENCE AND PROBLEMS

Over the last three to four decades, over nutrition and obesity have been transformed from

relatively minor public health issues that primarily affected the most affluent societies to a

major threat to public health that is being increasingly seen throughout the world. The plight

of the most affected populations, like those in high-income countries in North America,

Australasia and Europe, has been well publicized. However, the more recent increases in

population obesity in low- and middle-income countries that are now increasingly being

observed have been less recognized.

Two relatively recent papers documented the global prevalence of obesity 31, 32. The Global

Burden of Metabolic Risk Factors of Chronic Diseases Collaborating Group analyzed data

from 199 countries and territories and 9.1 million adults with respect to the prevalence of

overweight and obesity between 1980 and 2008 31. During that 28-year period, the prevalence

of obesity nearly doubled worldwide. In 2008, about 1.5 billion adults were estimated to have

a body mass index (BMI) of 25 or more (about 34%). Of these, 500 million were considered

obese (about 10% in men and 14% in women).

In 2008, the highest rates of obesity in women were observed, in descending order of

magnitude, in Southern Africa, North Africa and the Middle East, Central Latin America,

North America (US and Canada) and Southern Latin America. In men, the top 5 regions were

North America (US and Canada), Southern Latin America, Australasia, Central Europe and

Central Latin America. Note that many of these regions comprise low- or middle-income

countries.

More recently, the analyses for the Global Burden of Disease Study 2013 32 further

documented that worldwide, the proportion of adults with a BMI of 25 or greater increased

between 1980 and 2013 from about 29 to 37% in men and from about 30 to 38% in women.

These estimates are slightly higher than those calculated by Finucane et al. 31. The estimates

by Ng et al. 32 may reflect further increases between 2008 and 2013, but this may also be due

to methodological differences between the two studies. In adults, the estimated prevalence of

obesity exceeded 50% in men in Tonga (Polynesia) and in women in some countries in the

Middle East, Polynesia and Micronesia. Since 2006, the increase in adult obesity seems to

have leveled off in several high-income countries, but the incidence generally remains higher

than in most low- and middle-income countries.

In the analyses for the Global Burden of Disease Study, estimates were also made of the

global prevalence of overweight and obesity in children and adolescents. Ng et al. 32 showed

that among children and adolescents in developed countries, the prevalence in 2013 was high;

about 24% of boys and 23% of girls were either overweight or obese. In general, the

prevalence of overweight and obesity had increased considerably since 1980. There were,

however, large differences in the prevalence of obesity and secular trends. The prevalence of

overweight and obesity had also increased in children and adolescents in developing

countries, from about 8% in 1980 to 13% in 2013 for boys and girls. Ng et al. 32 estimated

that in 2013, more than 2 billion people in the world were overweight or obese and about 671

million of them were obese.

About 25 years ago, obesity was considered to be particularly a problem of high-income

countries. In those high-income countries, as illustrated by Molarius et al. 33, an inverse

association was seen between obesity and socioeconomic status, particularly in women. In

contrast, in low- and middle-income countries, the prevalence of obesity tended to be low and

was confined to those with relatively high socioeconomic status 34. Monteiro et al. 34 were

among the first to show that this was no longer true in 2003 and that obesity had also become

a problem of lower socioeconomic groups, particularly of women in middle-income

countries. More recently, Dinsa et al. 35 observed that by 2012, the association between

socioeconomic status and obesity remained positive for both men and women in low-income

countries. However, in middle-income countries, the association varied greatly in men and

was generally negative in women. In children and adolescents, however, obesity remained

predominantly a problem of those with relatively high socioeconomic status in low- and

middle-income countries.

The epidemiology of obesity has for many years been difficult to study because many

countries had their own specific criteria for the classification of different degrees of

overweight. Gradually, during the 1990s, however, the BMI (weight/height2) became a

universally accepted measure of the degree of overweight, and now, identical cutoff points

are generally recommended. This most recent classification of overweight in adults by the

World Health Organization (WHO) is given in table 1[6]. In many community studies in

affluent societies, this scheme has been simplified and cutoff points of 25 and 30 are used for

descriptive purposes. Both the prevalence of a very low BMI (<18.5) and of a very high BMI

(40 or higher) is usually low, in the order of 1-2% or less.

HISTORY OF SPINAL ANAESTHESIA AND ITS EVOLUTION TO USG GUIDED

SPINAL ANAESTHESIA

Spinal anesthesia was first performed by August Bier in Germany in 1889. However, its

earliest roots can be traced to J. Leonard Corning, a New York neurologist who conceived of

the idea of spinal anesthesia by administering cocaine in the central nervous system. Rudolf

Matas first published a case report on spinal anesthesia in the United States in 1899, followed

shortly thereafter by the publication of Tate and Caglieri's study of the subarachnoid space

and their experience with spinal anesthesia. In the 2 years after Bier's report was published,

over 1000 articles on spinal anesthesia appeared in the literature 36. As in other developments

in regional anesthesia, spinal anesthesia appeared in many areas of the world at about the

same time. Six months after Bier's work was published (October 1899), Dr. J.B. Seldowitsch,

in St. Petersburg, Russia, reported four cases of spinal anesthesia for lower extremity surgery

37. Tuffier, in France, published his studies in November 1899 38, 39. These studies were little

more than case reports, offering no solutions for the troubling side effects associated with the

technique. With the development of safer drugs, sterile equipment, and aseptic techniques,

spinal anesthesia would earn a place in the armamentarium of most practicing

anesthesiologists. These early pioneers led the way, and others would follow and improve the

technique.

Spinal anaesthesia became more popular as new developments occurred, including the

introduction in 1946 of saddle block anaesthesia by Adriani and Roman-Vega 40. However, in

1947 the well-publicized case of Woolley and Roe (United Kingdom) resulted in two patients

becoming paraplegic in one day 41.

The classical method for spinal anaesthesia relies on the use of bony landmarks to identify

the level and point of entry of the spinal needle. Over the years, in experienced hands, this

method has proved to be successful and safe. The introduction of ultrasound to guide

neuraxial anaesthesia has been relatively slow compared to its use in peripheral nerve blocks

or central venous catheterization. This could be due to the technical difficulties as the bony

structures surrounding the spinal cord and dura block the path of the ultrasound beam. Many

anaesthetists are reluctant to change from the conventional landmark technique, particularly

with studies showing minimal change in the success rate between ultrasound-guided and

landmark techniques.

PRINCIPLE OF ULTRASOUND, EQUIPMENT, PROBES

Medical ultrasound (also known as diagnostic sonography or ultrasonography) is based on the

use of high-frequency sound to aid in the diagnosis and treatment of patients. Ultrasound

frequencies range from 2 to approximately 15 MHz, although even higher frequencies may be

used in some situations.

Principle of Ultrasound

Two basic principles need to be understood regarding how ultrasound is generated and an

image is formed. The first is the piezoelectric effect, which explains how ultrasound is

generated from ceramic crystals in the transducer 42, 43. An electric current passes through a

cable to the transducer and is applied to the crystals, causing them to deform and vibrate. This

vibration produces the ultrasound beam. The frequency of the ultrasound waves produced is

predetermined by the crystals in the transducer.

The second key principle is the pulse-echo principle, which explains how the image is

generated. Ultrasound waves are produced in pulses, not continuously, because the same

crystals are used to generate and receive sound waves, and they cannot do both at the same

time. In the time between the pulses, the ultrasound beam enters the patient and is bounced or

reflected back to the transducer. These reflected sound waves, or echoes, cause the crystals in

the transducer to deform again and produce an electrical signal that is then converted into an

image displayed on the monitor. The transducer generally emits ultrasound only 1% of the

time; the rest of the time is spent receiving the returning echoes 43.

Ultrasound transducers contain a range of ultrasound frequencies, termed bandwidth. For

example, 2.5-3.5 MHz for general abdominal imaging and 5.0-7.5 MHz for superficial

imaging 44.

Ultrasound waves are reflected at the surfaces between the tissues of different density, the

reflection being proportional to the difference in impedance. If the difference in density is

increased, the proportion of reflected sound is increased, and the proportion of transmitted

sound is proportionately decreased 44.

If the difference in tissue density is very different, then the sound is completely reflected,

resulting in total acoustic shadowing. Acoustic shadowing is present behind bones, calculi

(stones in kidneys, gallbladder, etc.) and air (intestinal gas) (See Fig. 1 with acoustic

shadowing).

Echoes are not produced if there is no difference in a tissue or between tissues. Homogenous

fluids like blood, bile, urine, contents of simple cysts, ascites and pleural effusion are seen as

echo-free structures.

Fig 8: A model of an ultrasonograph

CURVILINEAR PROBE

Fig 9: Curvilinear probe

PROBE MARKER

Fig 10. Probe marker

ULTRASOUND PROBES

FOR 2D IMAGING

Probe type Feature Application Centralfrequency Element

Linear typewide footprint and keep same field of view at deep part.

Vascular applicationArteria carotisarterial sclerosisvenipuncture,blood vessel visualizationBreast,ThyroidTendon,arthrogenousntraoperative,laparoscopy

2.5MHz|12MHz

64ch|256ch

Convex(Curved)Type

wide footprint, field of view will be spreaded at deep part.

Abdominal application.Transvaginal and Transrectal application.Diagnoses organs.

2.5MHz|7.5MHz

64ch|192ch

Phased(Sector)Type

small footprint, field of view will be spreaded widely at deep part.

Cardiac application.Transesophageal

application.Abdominalapplication.

Brain diagnosis

2MHz|7.5MHz

32ch|128ch

Single type

OphthalmologyTransesophageal application.Transvaginal and Transrectal application.Transurethral application.The blood flow

2MHz|22MHz

-

measurement with Doppler.

Frequency and Resolution

High frequency probe can get the fine imaging with good resolution.

However the imaging of deep part will be smudgy due to wave length is short.

Meanwhile the imaging resolution of low frequency probe is low but ultrasonic wave can

reach deep part. The scanning depth and resolution are mainly determined by the frequency

of probe.

Frequency ResolutionPenetratio

n

Possible

scanning depth

High Fine Weak Shallow

Low Rough Strong Deep

Ultrasound Imaging of the spine (various planes of US guided spinal anaesthesia)

Basic considerations

Because the spine is located at a depth, US imaging of the spine typically requires the use of

low-frequency ultrasound (2-5 MHz) and curved array transducers. Low-frequency US

provides good penetration but unfortunately, it lacks the spatial resolution at the depth (5-7

cm) at which the neuraxial structures are located. The osseous framework of the spine, which

envelops the neuraxial structures, reflects much of the incident US signal before it reaches the

spinal canal, presenting additional challenges in obtaining good quality images. Recent

improvements in US technology, the greater image processing capabilities of US machines,

the availability of compound imaging, and the development of new scanning protocols have

improved the ability to image the neuraxial space significantly. As a result, today it is

possible to reasonably accurately delineate the neuraxial anatomy relevant for CNB.

Ultrasound Scan Planes

Figure 11. Anatomic planes of the body

Gross anatomy of the lumbar spine 45

The lumbar spine comprises five vertebrae (L1–L5).Each vertebra has two functional parts: a

vertebral body and a vertebral arch. Each vertebral arch is composed of a spinous process,

pedicles laminae, transverse processes, and superior and inferior articular processes. The

lumbar spinous processes are broad (in the superior–inferior dimension), flat, oblong-shaped

structures that project posteriorly from the union of the laminae. The superior and inferior

articular processes extend posteriorly in a cranial and caudad direction, respectively, from the

point at which the pedicles and laminae fuse. Long, slim transverse processes protrude

laterally from the vertebral arch at the junction of the laminaeandpedicles. The laminae slope

from posterior to anteriorin acaudad – to –cephalad direction. In contrast to the thoracic

spine, the laminae and spinous processes of adjacent lumbar vertebrae do not overlap. This

gives rise to distinct gaps—the interlaminar and interspinous spaces—through which the

vertebral canal can be accessed. These spaces can be enlarged by forward flexion of the

lumbar spine.

The anterior wall of the vertebral canal is formed by the posterior longitudinal ligament and

the posterior surface of the vertebral bodies and intervertebral discs.

The posterior wall of the vertebral canal comprises the laminae and the ligamentum flavum,

which forms a thick, fibrous bridge over the interlaminar spaces

Pre procedural USG scanning45

The patient is placed in a sitting or lateral decubitus position for the block, with forward

flexion at the lumbar spine. This eliminates lumbar lordosis, opens up the lumbar interspinous

spaces, and generally improves the acoustic window. The use of a curved, low-frequency (2–

5 MHz) probe is recommended to provide enhanced beam penetration, and wide field of

view, both of which improve identification of anatomy.

Sonoanatomy of the spine and ultrasonographic views for neuraxial block

Bone is not penetrated by ultrasound and casts a dense acoustic shadow. The contours of the

posterior bony surfaces of the lumbar vertebra thus have characteristic patterns of acoustic

shadowing that are key to interpretation of the sonoanatomy of the lumbar spine.

Visualization of the vertebral canal is only possible through the soft-tissue acoustic windows

of the interlaminar and interspinous spaces. There are five basic ultrasonographic views of the

spine that can be systematically obtained:

(i) parasagittal transverse process view,

(ii) parasagittal articular process view,

(iii) parasagittal oblique (interlaminar) view,

(iv) transverse spinous process view,

(v) transverse interlaminar (interspinous) view.

The parasagittal oblique (interlaminar) view (PSO view) and the transverse

interlaminar/interspinous view (TI view) are the most important views in clinical practice

since they provide a view of the neuraxial structures through acoustic windows. These

structures include: ligamentum flavum, posterior dura, spinal canal, anterior dura, and

posterior longitudinal ligament.45

Parasagittal transverse process view

The ultrasound probe is placed over the lower lumbar spine in a parasagittal orientation, a 3-4

cm lateral to the midline. The transverse processes appear as finger-like acoustic shadows,

separated by the striated psoas major muscle, which lies deep to the transverse processes. The

erector spinae muscle lies superficial (posterior) to the transverse processes

Fig 12. Parasagittal transverse process view

FIG Parasagittal transverse process view (A) with corresponding anatomical section(B) and

ultrasound probe orientation(c)TP; transverse processes ESM, erector spinae muscle; Pm,

Psoas major muscle; L, Lamina; SP, spinous process

Parasagittal articular process view 45

Maintaining a strictly sagittal orientation, the ultrasound probe is now moved medially until

the acoustic shadows of the transverse processes give way to a pattern of continuous hump-

like shadows, formed by the overlapping superior and inferior articular processes. Observe

the transition from the discontinuous pattern of the transverse process view to the continuous,

hyperechoic line formed by the articular processes The articular process view is also

distinguished from the transverse process view by the more superficial depth of the acoustic

shadows

Fig 13. Parasagittal articular process view (A) with corresponding anatomical section (B)

and ultrasound probe orientation(C) AP; articular processes TP; transverse processes ESM,

erector spinae muscle; Pm, Psoas major muscle; L, Lamina; SP, spinous process

Parasagittal oblique (interlaminar) view (PSO view) 45

Starting from the parasagittal articular process view, the ultrasound probe is now slowly tilted

to direct the beam in a lateral to-medial direction until the humped pattern of the articular

processes changes into a ‘sawtooth’ pattern of acoustic shadows. The ‘teeth’ correspond to

the down sloping laminae and the gaps between represent the interlaminar spaces. The PSO

view therefore gives us an acoustic window into the vertebral canal. Structures that are

penetrated by the ultrasound beam are (from posterior to anterior): ligamentum flavum,

epidural space, dura (posterior), intrathecal space, dura (anterior), and posterior longitudinal

ligament. The ligamentum flavum, epidural space, and posterior dura appear as a hyperechoic

linear structure and are collectively referred to as the posterior complex; while the anterior

dura, posterior longitudinal ligament and posterior border of the vertebral body and discs

constitute a deeper hyperechoic linear structure called the anterior complex. In the PSO view,

slide the probe caudad until the sacrum is identified as a long horizontal hyperechoic line.

This is an important and easily recognizable ultrasonographic landmark. The gap between the

hyperechoic line of the sacrum and the ‘sawtooth’ of the adjacent L5lamina represents the

L5–S1 interspace. Starting at this point, each interspace is centered on the ultrasound screen

and a corresponding skin mark made at the midpoint of the long edge of the probe to indicate

its location.

Fig 14. Parasagittal oblique (interlaminar) view (PSO view) (A) with corresponding

anatomical section(B) and ultrasound probe orientation(c) ESM; erector spinae muscle; L,

Lamina; AC, anterior complex; PC, posterior complex

Transverse spinous process view

In order to obtain a transverse spinous process view, the ultrasound probe is placed in a

horizontal orientation with the centre of the probe placed over the midline. If the ultrasound

beam is placed over a spinous process, the tip of the spinous process appears as a superficial

hyperechoic ‘cap’ surmounting at all dense acoustic shadow. Lateral to the spinous process,

the erector spinae muscle can be visualized, with the lamina of the vertebral body casting its

own dense acoustic shadow at the level of the anterior border of the erector spinae muscle.

Fig 15. Transverse spinous process view(A) with corresponding anatomical section(B) and

ultrasound probe orientation(c) ESM; erector spinae muscle; L, Lamina; SP, spinous process

Transverse interlaminar/interspinous view (TI view)45

Starting from the transverse spinous process view, the TI view is obtained by sliding the

probe in a cephalad or caudad direction as needed until the beam enters the acoustic window

between the spinous processes. A slight cephalad tilt in the horizontal plane may have to be

applied to compensate for the angulation of the spinous processes. The interspinous ligament

appears as a hypoechoic midline stripe. The hypoechoic intrathecal space is bounded

anteriorly and posteriorly by the parallel hyperechoic lines of the anterior and posterior

complexes, respectively

Centre the neuraxial midline on the screen. – Make skin marks at the:

(i) midpoint of the probe’s long edge(corresponding to the neuraxial midline);

(ii) midpoint of the probe’s short edge (corresponding to the interspinous

/interlaminar space).

The intersection of these two marks gives the needle insertion point for a midline

approach. – Estimate needle insertion depth by measuring the distance from skin to the

deep aspect of the posterior complex. – If a satisfactory TI view (i.e.one in which the

posterior complex is visible)cannot be obtained, the location of the interlaminar space

may be instead determined from the PSO view, which usually offers a larger and better

window into the vertebral canal. This is the same skin marking used to indicate the

identity of the intervertebral levels (see point 5). The intersection of this mark with the

skin mark of the neuraxial midline obtained in the TI view is a suitable alternative needle

insertion point for a midline approach

Fig 16. Transverse interlaminar/interspinous view (TI view) (A) with corresponding

anatomical section(B) and ultrasound probe orientation(c)TP, transeverse process;AP,

articular process L, Lamina; AC, anterior complex; PC, posterior complex ESM; erector

spinae muscle; ITS, intrathecal space

Needle insertion – 45

Insert the needle at the marked site in the midline. Maintain the same cephalad angle with

respect to the horizontal plane that was applied to the probe to obtain the optimal TI view. –

Needle insertion and re-direction should be guided by tactile feedback(contact with bone,

‘feel’ of the ligamentum flavum, loss of resistance, etc.) in a similar manner to the

conventional landmark-based technique of neuraxial block. – Ensure that needle redirections

are not inappropriately large, and that there is no deflection from its intended trajectory,

particularly when using smaller-gauge spinal needles.

Fig 17. Needle insertion for a midline needle approach at the intersection point between

the skin markings of the neuraxial midline and the interspinous and interlaminar space

MOST RELEVANT STUDIES:

1. Furness G et al. 46 intended to know the accuracy of ultrasound imaging to identify

lumbar intervertebral level in 50 patients undergoing X-ray of the lumbar spine. Using an

ultraviolet marker, an anaesthetist attempted to mark the L2/3, L3/4 and L4/5

intervertebral spaces. A radiologist unaware of these marks attempted to mark the same

spaces with the aid of ultrasound imaging. X-ray-visible pellets were taped to the back at

the various marks prior to lateral lumbar X-ray. Ultrasound imaging identified the correct

level in up to 71% of cases, but palpation was successful in only 30% (p < 0.001). Up to

27% of marks using the palpation method were more than one spinal level above or

below the assumed level using palpation, but none were more than one level high or low

using ultrasound guidance.

2. Nomura JT et al. 47 wanted to know whether ultrasound-assisted LP would increase the

success rate and ease of performing LP with a greater benefit in obese patients through

randomized, prospective, double-blind study conducted at the emergency department of a

teaching institution. Patients were randomized to undergo LP using palpation landmarks

(PLs) or ultrasound landmarks (ULs). Data collected included age, body mass index,

number of attempts, ease of performance and patient comfort on a 10-cm. A total of 46

patients were enrolled, 22 randomized to PLs and 24 to ULs. There were no differences

between the groups in mean age or body mass index. Six of 22 attempts failed with PLs

versus 1 of 24 with ULs (RR, 1.32; 95% confidence interval, 1.01-1.72). In 12 obese

patients, 4 of 7 PL attempts failed versus 0 of 5 UL attempts (RR, 2.33; 95% confidence

interval, 0.99-5.49). The ease of the procedure was better with ULs versus PLs. There

were no statistical differences in the number of attempts, traumatic LPs, patient comfort,

or procedure length. They concluded that the use of ultrasound for LP significantly

reduced the number of failures in all patients and improved the ease of the procedure in

obese patients.

3. Chin KJ et al. 48 assessed real-time ultrasound-guided spinal anesthesia in patients with

a challenging spinal anatomy. They described two patients with an abnormal spinal

anatomy in whom ultrasound-assisted spinal anaesthesia was unsuccessful. Successful

dural puncture was subsequently achieved using a technique of real-time ultrasound-

guided spinal anaesthesia. This may be a useful option in patients in whom landmark-

guided and ultrasound-assisted techniques have failed.

4. Arzola C et al. 49 did a randomized controlled trial to assess spinal ultrasound versus

palpation for epidural catheter insertion in labour by a group of trainees. A group of 17

second-year anaesthesia residents and five anaesthesia fellows underwent a training

programme in ultrasound assessment of the spine. Parturients with easily palpable

lumbar spines were randomized to either ultrasound or palpation group. Residents and

fellows performed both the assessment (ultrasound or palpation) and the epidural

procedure. On the whole, they analysed 128 epidural catheter insertions (residents 84,

fellows 44). There was no difference in median (interquartile range, IQR) epidural

insertion time between the ultrasound and palpation groups [174 (120 to 241) versus 180

(130 to 322.5) s, respectively; P = 0.14]. The number of interspace levels attempted and

needle passes were also similar in both groups. The total procedural time was longer in

the ultrasound group. They concluded that the use of preprocedural spinal ultrasound by

a cohort of anaesthesia trainees did not improve the ease of insertion of labour epidural

catheters in patients with easily palpable lumbar spines, as compared with the traditional

palpation technique based on anatomical landmarks.

5. Srinivasan KK et al. 50 compared Conventional Landmark-Guided Midline and

Preprocedure Ultrasound-Guided Paramedian Techniques in Spinal Anesthesia among

100 patients scheduled for elective total joint replacements (hip and knee). They were

randomized into group C (conventional) and group P (preprocedural ultrasound-guided

paramedian technique) with 50 in each group. In group C, spinal anesthetic was done via

the midline approach using clinically palpated landmarks. In group P, a preprocedural

ultrasound scan was used to mark the paramedian insertion site, and spinal anesthetic

was performed via the paramedian approach. The average number of passes in group P

was approximately 0.34 times that in group C, a difference that was statistically

significant (P = 0.01). Similarly, the average number of attempts in group P was

approximately 0.25 times that of group C (P = 0.0021). In group P, on an average, it took

81.5 (99% confidence interval, 68.4-97 seconds) seconds longer to identify the

landmarks than in group C (P = 0.0002). It was opined that routine use of paramedian

spinal anesthesia in the orthopedic patient population undergoing joint replacement

surgery, guided by preprocedure ultrasound examination, significantly decreases the

number of passes and attempts needed to enter the subarachnoid space.

6. Grau T et al. studied the real-time ultrasound control of the procedure for puncture

among thirty parturients scheduled for Caesarean section who were randomized to three

equal groups. Ten control patients received conventional combined spinal-epidural

anaesthesia. Ten of the remaining patients received ultrasonic scans by an offline scan

technique, and 10 received online imaging of the lumbar region during epidural puncture.

The number of attempts to advance the needle to achieve a successful puncture was

measured and compared, as well as the number of vertebral interspaces punctured before

successful entry into the epidural space. Results showed that in the ultrasound group, the

reduction in the number of attempts at puncture was significant (P < 0.036). The number

of interspaces necessary for puncture was reduced (P < 0.036) in the ultrasound online

group compared with controls. The number of spinal needle manipulations was

significantly reduced (P < 0.036). The authors noted the real-time ultrasonic scanning of

the lumbar spine is an easy procedure and it provides an accurate reading of the location

of the needle tip and facilitates the performance of combined spinal-epidural anaesthesia.

7. Srinivasan KK et al. 51 did a randomized controlled trial on the superiority of pre-

procedure ultrasound-guided paramedian spinal anaesthesia at L5-S1 over landmark-

guided midline approach among120 consenting patients scheduled for elective total joint

replacements (Hip and Knee). They were randomized into either Group C where

conventional midline approach with palpated landmarks was used or Group P where pre-

procedural ultrasound was used to perform subarachnoid block by paramedian approach

at L5-S1 interspace (real time ultrasound guidance was not used). There was no

difference in primary outcome (difference in number of passes) between the two groups.

Similarly there was no difference in the number of attempts (i.e., the number of times the

spinal needle was withdrawn from the skin and reinserted). The first pass success rates (1

attempt and 1 pass) was significantly greater in Group C compared to Group P [43% vs.

22%, P = 0.02]. They concluded that routine use of paramedian spinal anaesthesia at L5-

S1 interspace, guided by pre-procedure ultrasound, in patients undergoing lower limb

joint arthroplasties did not reduce the number of passes or attempts needed to achieve

successful dural puncture.

8. Niazi AU et al. 52 investigated whether SonixGPS(R), a new needle tracking system that

displays needle tip position on the ultrasound screen might aid performance of real-time

ultrasound-guided spinal anesthesia. Twenty patients with body mass index < 35 kg/m(2)

undergoing elective total joint arthroplasty under spinal anesthesia were recruited.

Following a pre-procedural ultrasound scan, a 17G proprietary needle-sensor assembly

was inserted in-plane to the transducer in four patients and out-of-plane in 16 patients.

Then a 25G 120 mm Whitacre spinal needle was inserted through the 17G SonixGPS(R)

needle. The findings revealed an overall success rate of 14/20 (70%) was with two

failures (50%) and four failures (25%) in the in-plane and out-of-plane groups

respectively. Dural puncture was successful on the first skin puncture in 71% of patients

and in a single needle pass in 57% of patients. The median total procedure time was 16.4

and 11.1 min in the in-plane and out-of-plane groups respectively. The SonixGPS(R)

system simplifies real-time ultrasound-guided spinal anesthesia to a large extent,

especially the out-of-plane approach. Nevertheless, it remains a complex multi-step

procedure that requires time, specialized equipment, and a working knowledge of spinal

sonoanatomy.

9. Wong SW et al. 53 elaborated on a case report on a patient with difficult spinal anatomy

about the use of the SonixGPS system for successful performance of real-time

ultrasound-guided spinal anesthesia. The patient was a 67-yr-old male was admitted to

our hospital to undergo revision of total right hip arthroplasty. A 19G 80-mm proprietary

needle (Ultrasonix Medical Corp, Richmond, BC, Canada) was inserted and directed

through the paraspinal muscles to the ligamentum flavum in plane to the ultrasound

beam. Successful dural puncture was achieved on the second attempt, as indicated by a

flow of clear cerebrospinal fluid. The patient tolerated the procedure well, and the spinal

anesthetic was adequate for the duration of the surgery. The SonixGPS is a novel

technology that can reduce the technical difficulty of real-time ultrasound-guided

neuraxial blockade.

10. Weed JT et al. 54 performed a pre-procedure ultrasound examination of the spine on 60

patients undergoing lower extremity orthopaedic surgery under spinal anaesthesia to test

whether the posterior longitudinal ligament or vertebral body easily with ultrasound

would be associated with difficulty placing a spinal anaesthetic. The procedure difficulty

was defined by total procedure time (> 400 s) and number of needle passes (>/= 10)

required to achieve return of cerebrospinal fluid, or abandonment of the procedure due to

unsuccessful dural puncture. When images of the posterior longitudinal ligament were

poor (low score group), the mean (SD) number of passes was 21.2 (30.6), compared with

4.8 (7.5) with good ultrasound images (high score group) (p < 0.01). The mean (SD) time

for placement was 420 (300) s in the low score group vs 176 (176) s in the high score

group (p < 0.01).

11. Creaney M et al. compared the pre-procedural lumbar ultrasonography with landmark

palpation to locate the needle insertion point in women with impalpable lumbar spinous

processes presenting for caesarean delivery. Twenty patients were randomized to

palpation or ultrasound. There were significantly fewer needle passes in the ultrasound

group (median 3 [IQR 1.8-3.2]) compared to the palpation group (median 5.5 [IQR 3.2-

7.2] (P=0.03)). More time was required to locate the needle insertion point in the

ultrasound group (ultrasound 91.8+/-30.8s vs. palpation 32.6+/-11.4s, P<0.001). There

was no difference in the total procedural time between groups (ultrasound 191.8+/-49.4s

vs. palpation 192+/-110.9s, P=0.99). The use of ultrasonography to locate the needle

insertion point reduced the number of needle passes in women with impalpable lumbar

spinous processes undergoing elective caesarean delivery under spinal anaesthesia. Its

use did not prolong overall procedural time.

12. Chin KJ et al. 55 studied how far ultrasound-assisted approach facilitates spinal

anesthesia among fifty patients undergoing elective total joint arthroplasty. Using a

curved-array 2-5 MHz transducer, the lumbar spine was imaged in two views, i.e.,

longitudinal parasagittal (LP) and transverse midline (TM). The findings showed that the

surface landmarks were difficult or impossible to palpate in 38% of the patients. Dural

puncture was achieved with one needle insertion attempt and within two needle insertion

attempts in 84% and 98% of the patients, respectively. The ultrasound-measured depth to

the intrathecal space correlated well with the actual needle insertion depth (concordance

correlation coefficient = 0.82, accuracy 0.95, precision 0.86), with a tendency to

overestimate the depth by just 2.1 +/- 5.4 mm. They concluded that ultrasound imaging

of the lumbar spine provides clinically useful information that can facilitate spinal

anesthesia in the older orthopedic patient population.

13. Chin KJ et al. 56 assessed if ultrasound imaging facilitates spinal anesthesia in adults

with difficult surface anatomic landmarks. They recruited 120 orthopedic patients with

one of the following: body mass index more than 35 kg/m(2) and poorly palpable

spinous processes; moderate to severe lumbar scoliosis; or previous lumbar spine

surgery. Patients were randomized to receive spinal anesthetic by the conventional

surface landmark-guided technique (group LM) or by an ultrasound-guided technique

(group US). The first-attempt success rate was twice as high in group US than in group

LM (65% vs. 32%; P < 0.001). There was a two-fold difference between groups in the

number of needle insertion attempts (group US, 1 [1-2] vs. group LM, 2 [1-4]; P < 0.001)

and number of needle passes (group US, 6 [1-10] vs. group LM, 13 [5-21]; P = 0.003).

More time was required to establish landmarks in group US (6.7 +/- 3.1; group LM, 0.6

+/- 0.5 min; P < 0.001). Preprocedural ultrasound imaging facilitates the performance of

spinal anesthesia in the nonobstetric patient population with difficult anatomic

landmarks.

14. Ansari T et al. 57 pregnant patients are in exclusion criteria compared the use of

ultrasound to the landmark method in patients with no anticipated technical difficulty,

presenting for caesarean delivery under spinal anaesthesia among total of 150 pregnant

women for the randomized, controlled study. Patients were randomized to either the

Ultrasound Group (n=75) or the Landmark Group (n=75). In both groups the level of L3-

4 or L4-5 was identified by ultrasound (transverse and longitudinal approach) or

palpation. Findings revealed that average procedure time, number of skin punctures and

needle passes, were similar in both groups. When performed by anaesthetists experienced

in both ultrasound and landmark techniques, the use of ultrasound does not appear to

increase the success rate of spinal anaesthesia, or reduce the procedure time or number of

attempts in obstetric patients with easily palpable spines.

15. Brinkmann S et al. 58 in their case series reported performance of the SonixGPS system

for real-time ultrasound-guided spinal anesthesia in 20 American Society of

Anesthesiologists' class I-II patients scheduled for lower limb joint arthroplasty.

Successful spinal anesthesia for joint arthroplasty was achieved in 18/20 patients, and 17

of these required only a single skin puncture. In 7/20 (35%) patients, dural puncture was

achieved on the first needle pass, and in 11/20 (55%) patients, dural puncture was

achieved with two or three needle redirections. Median (range) time taken to perform the

block was 8 (5-14) min. All patients with successful spinal anesthesia found the

technique acceptable and were willing to undergo a repeat procedure if deemed

necessary. This case series showed that real-time ultrasound-guided spinal anesthesia

with the SonixGPS system is possible within an acceptable time frame. It proved

effective with a low rate of failure and a low rate of complications.

16. Soni NJ et al. 59 reviewed the literature and describe techniques to use ultrasound to

guide performance of lumbar puncture (LP). They noted that Ultrasound mapping of the

lumbar spine reveals anatomical information that is not obtainable by physical

examination, including depth of the ligamentum flavum, width of the interspinous

spaces, and spinal bone abnormalities, including scoliosis. Using static ultrasound, the

lumbar spine anatomy is visualized in transverse and longitudinal planes and the needle

insertion site is marked. Using real-time ultrasound guidance, the needle tip is tracked in

a paramedian plane as it traverses toward the ligamentum flavum. Future research should

focus on efficient methods to train providers, cost-effectiveness of ultrasound-guided LP,

and the role of new needle-tracking technologies to facilitate the procedure.

17. Lim YC et al. 8 studied whether pre-procedural ultrasound scanning improved first-

attempt success rate and decreased time taken for the procedure in the general adult

population. Patients were randomised into two groups, ultrasound-guided identification

of landmarks (Ultrasound Group) and manual palpation of landmarks (Manual Palpation

Group). Finding showed that the first-attempt success rate was 64% in the Ultrasound

Group and 52% in the Manual Palpation Group (P=0.16). Time taken for procedure was

shorter in the Ultrasound Group compared to the Manual Palpation Group (2.9±3.6

minutes versus 3.9±3.7 min, P= 0.007). Patient satisfaction was higher in the Ultrasound

Group. There were no differences in complications. The current use of pre-procedural

ultrasound scanning will probably be limited to selected patients where spinal

anaesthesia may be technically challenging with conventional methods.

MATERIALS AND METHODS

STATISTICAL METHODS:

Number of attempts, number of passes time taken for identifying landmark (sec), time for

successful lumbar puncture (sec), were considered as outcome variable.

Procedure (Land Mark (LM), Ultra Sound Guided (US)) was considered as primary

explanatory variable.

Normality test for quantitative variables:

A Shapiro- Wilk’s test (p>0.05) and a visual inspection of their histograms, normal Q-Q plots

and box plots showed that age, BMI, number of passes, number of attempts, time taken for

identifying space (sec), time for successful lumber puncture(sec) were non-normally

distributed for study group.

The comparison between procedure (LM, US) and age, BMI number of passes, number of

attempts, time taken for identifying space (sec) and time for successful lumber puncture (sec)

parameters was assessed by comparing the median values. Mann Whitney U test was used to

assess statistical significance. Data was also represented using appropriate diagrams like

comparative box plots and bar chart.

Comparison of categorical variable:

The association between procedure and gender, success was assessed by cross tabulation and

comparison of percentages. Chi square test was used to test statistical significance. Data was

also represented using appropriate diagram like clustered bar chart.

P value < 0.05 was considered statistically significant. IBM SPSS version 22 was used for

statistical analysis60.

RESULTS:A total of 80 subjects were included in the final analysis Table 1: Descriptive analysis of group in study population (N=80)Group Frequency PercentagesLand Mark ( LM) 40 50.00%Ultra Sound Guided (US) 40 50.00%

Among the study population, 40 (50%) were land mark (LM) and remaining 40 (50%) were

ultra sound guided (US). (Table 1)

Table 2: Comparison of median value in age between study group (N=80)

Group AgeMedian (IQR)

Mann Whitney U test (P value)

Land mark ( LM) 59.50 (52.25, 65.75) 0.965Ultra sound guided (US) 58.50 (50.25, 65.75)

Among the people with, land mark (LM), the median age was 59.50 (IQR 52.25 to 65.75) and

it was 58.50 (IQR 50.25 to 65.75) in people with ultra sound guided (US). The difference in

the age between group was statistically not significant (P Value 0.965). (Table 2 & Figure 1)

Figure 1: Box plots of comparison of median value in age between study group (N=80)

Table 3: Comparison of group with gender of study population (N=80)

GenderGroup

Chi square P-valueLM(N=40) US (N=40)

Male 15 (37.5%) 12 (30%)0.503 0.478

Female 25 (62.5%) 28 (70%)

In land mark (LM) group 15 (37.5%) were in male, and remaining 25 (62.5%) were in

female. In ultra sound guided (US) group 12 (30%) were in male, and remaining 28 (70%)

were female. The difference in the proportion of group between gender was statistically not

significant (P value 0.478). (Table 3 & figure 2)

Figure 2: Cluster bar chart of comparison of group with gender of study population (N=80)

Land Mark (LM) Ultra Sound Guided (US )0.00%

10.00%20.00%30.00%40.00%50.00%60.00%70.00%80.00%

38%30%

63%70%

Male Female

Group

Perc

enta

ge

Table 4: Comparison of median value in BMI between study group (N=80)

Group BMIMedian (IQR)

Mann Whitney U test (P value)

Land mark ( LM) 34.9 (33.1, 36.40) 0.958Ultra sound guided (US) 34.9 (33.1, 36.35)

Among the people with, land mark (LM), the median BMI was 34.9 (IQR 33.1 to 36.40) and

it was 34.9 (IQR 33.1 to 36.35) in people with ultra sound guided (US). The difference in the

BMI between group was statistically not significant (P Value 0.958). (Table 4 & Figure 3)

Figure 3: Box plots of comparison of median value in BMI between study group (N=80)

Table 5: Comparison of median value in number of attempts between study group (N=80)

Group Number of AttemptsMedian (IQR)

Mann Whitney U test (P value)

Land mark ( LM) 3 (2,4)<0.001

Ultra sound guided (US) 2 (1,2)

Among the people with, land mark (LM), the median number of attempts was 3 (IQR 2 to 4)

and it was 2 (IQR 1 to 2) in people with ultra sound guided (US). The difference in the

number of attempts between group was statistically significant (P Value <0.001) (Table 5 &

Figure 4)

Figure 4: Bar chart of comparison of median value in number of attempts between study group (N=80)

Land mark ( LM) Ultra sound guided (US)0

0.5

1

1.5

2

2.5

3

3.53

2

Group

Num

ber

of A

ttem

pts (

Med

ian)

Table 6: Comparison of median value in number of passes between study group

Group Number of PassesMedian (IQR)

Mann Whitney U test (P value)

Land mark ( LM) (N=40) 5.50 (4, 6.75) <0.001Ultra sound guided (US) (N=40) 4 (3,4)

Among the people with, land mark (LM), the median number of passes was 5.50 (IQR 4 to

6.75) and it was 4 (IQR 3 to 4) in people with ultra sound guided (US). The difference in the

number of passes between group was statistically significant (P Value <0.001). (Table 6 &

Figure 5)

Figure 5: Bar chart of Comparison of median value in number of passes between study group

Land mark ( LM) (N=38) Ultra sound guided (US) (N=37)0

1

2

3

4

5

6 5.5

4

Group

Num

ber

of P

asse

s Med

ian

Table 7: Comparison of median value in time taken for identifying space (sec) between study group

GroupTime taken for

Identifying Space (sec)Median (IQR)

Mann Whitney U test (P value)

Land mark ( LM) (N=38) 38.19 (25.05, 57.95)<0.001Ultra sound guided (US)

(N=37) 78.35 (60.20, 90.67)

Among the people with, land mark (LM), the median identifying space was 38.19 sec (IQR

25.05 to 57.95) and it was 78.35 sec (IQR 60.20, 90.67) in people with ultra sound guided

(US). The difference in the identifying space (sec) between group was statistically significant

(P Value <0.001). (Table 7 & Figure 6)

Figure 6: Box plots of comparison of median value in time taken for identifying space (sec) between study group

Table 8: Comparison of median value in time for successful lumber puncture (sec)between study group

GroupTime for successful lumber

puncture (sec)Median (IQR)

Mann Whitney U test (P value)

Land mark ( LM) (N=38) 88.31 (51.74, 120.19)0.048Ultra sound guided (US)

(N=37) 64.32 (51.46, 88.31)

Among the people with, land mark (LM), the median spinal injection was 88.31 sec (IQR

51.74 to 120.19) and it was 64.32 sec (IQR 51.46 to 88.31) in people with ultra sound guided

(US). The difference in the time for successful lumber puncture (sec) between group was

statistically significant (P Value 0.048). (Table 8 & Figure 7)

Figure 7: Box plots of comparison of median value in time for successful lumber puncture between study group

Table 9: Comparison of group with success (N=80)

SuccessGroup

Chi square P-valueLand Mark (LM) Ultra Sound Guided

(US)Success 38 (95%) 37 (92.5%)

0.213 0.644Converted to GA 2 (5%) 3 (7.5%)

Among land mark (LM) group, 2 (5%) people were converted to GA. Among ultra sound

guided (US) group, 3 (7.5%) people were converted to GA. Hence these patients were

excluded from subsequent analysis.

Note: 38 patients in land mark (LM) group and 37 patients in ultra sound guided (US) group

were analysed.

DISCUSSION

Since the first description of spinal anaesthesia in humans by Bier in 189861, the identification

of the subarachnoid space has traditionally been achieved by an anatomical landmark guided

approach. While surface anatomical landmarks are useful, they are nevertheless surrogate

markers. They may be difficult to palpate in obese patients as well as those with edema.

Landmark-based approaches do not take into account all anatomical variations or

abnormalities, and frequently lead to incorrect identification of a given lumbar interspace 62.

Accurate identification of the subarachnoid space is paramount as multiple attempts at needle

placement may cause patient discomfort, higher incidence of spinal hematoma, postdural

puncture headache 62, and trauma to neural structures 63. Having alternative approaches may

help improve success and mitigate the limitations of the current techniques.

For the identification of a safe lumbar interspace, clinicians often rely on three beliefs.

Firstly, an imaginary line (described by Tuffier) joining the iliac crests is assumed to be close

to the fourth lumbar spine, but it may cross higher or lower64. Secondly, classical teaching is

that the spinal cord ends at L1–2, but it has been known for over half a century4that this is the

mean position of a normal distribution. Several series describe the spinal cord extending to

the body of L3 in 1–3% of cases, and to L2 or lower in almost 50% of cases, with increased

variability in women65. Thirdly, reliance may be placed on a lack of paraesthesia, but this

confidence may be misplaced if the latter does not occur during cordotomy with a 22 G

needle until electrical stimulation is applied66. A technique to improve the localization of a

lumbar interspace would be an advantage.

Neuraxial ultrasound is a recent development in the field of regional anesthesia. This

technique allows the operator to preview spinal anatomy, identify midline, and determine the

inter- space for needle insertion. A “pre-procedural” ultrasound examination of the spine

accurately delineates the underlying relevant anatomy, thus aiding in successful insertion of a

spinal or epidural needle; this has also been termed “ultrasound-assisted ” neuraxial blockade.

Since 2011, Only five randomized controlled trials and one cohort study have been published

on use pre-procedural ultrasound to guide spinal anaesthesia in non-obstetric patients8, 50, 56, 67-

69. Among these, four studies looked at the routine use of US approach8, 50, 67, 69 and two

others were performed in patients in whom the procedure was presumed to be difficult. While

the use of US method in patients with difficult anatomy has been largely positive, the data on

its routine use are equivocal8, 50, 67, 69.

Of the total 80 patients included in the study, equal proportion of (40 each) belonged to

landmark (LM) guided and US-guided spinal anaesthesia groups. Comparatively all studies

have included more patients. In their randomized controlled trial, Abdelhamid et al.67 studied

90 patients, it was 10050 and 12069 in two separate studies by Srinivasan et al. while Lim et

al.8 studied 170 patients. However, Chin et al.56 in their clinical trial studied lesser (60)

patients undergoing lower limb orthopedic surgery.

Regarding age of the patients, the median age of those receiving LM guided (59.50 years)

was similar to that of US-guided group (58.50 years). In comparison the age of the subjects

was higher (68 years in LM group and 65.3 years in US-guided group) in the study by

Srinivasan et al.69 and Srinivasan et al.50 (65.2 years in the former and 63.4 years in the latter

group), in that of Chin et al. 56 (61.2 years in LM group, 62.5 years in US group) and in the

study by Lim et al.8 (62.2 years). However, Abdelhamid et al.67 study had younger patients

(34.7 years).

Gender wise females were higher in both the groups as compared to males (62.5% females vs

37.5% males in LM group) (70% females vs 30% males in US guided group). This is similar

to that of Chin et al. 56 who had 63.3% females in the former group and 66.6% in the latter.

Contrastingly Srinivasan et al. 50 had equal proportion of either sex in the LM group (52%

males and 48% females), however, in the US group, proportion of females was higher (60%

vs 40%), which was similar to our findings.

The median BMI of patients in both the groups was same (34.9), indicating that most of them

were obese. Contrastingly Srinivasan et al.69 observed a lesser average BMI in both LM

group (30.6) and US-guided group (30.1). Also in their earlier study, Srinivasan et al. 50 noted

the overall BMI of subjects in LM group (30.14) and US group (28.57) being lower.

However, Chin et al. 56 reported a higher BMI (obese patients) in both groups (41.2 in the

former group, 38.5 in the latter).

Regarding the number of attempts for successful anaesthesia, Srinivasan et al.69 noted equal

attempts in both groups (2 in LM group and 2.07 in US-guided group. In comparison, the

number of attempts was similar in the study among the US-guided group (2), which was

however, significantly (P Value <0.001) lesser when compared to the LM group (3).

However, in their previous study Srinivasan et al. 50 reported US method required

significantly (P=0.0021) lesser attempts (1.28) compared to the LM method (1.98). Chin et

al. 56 also found the US guided method requiring significantly (P Value <0.001) lesser

attempts (1) compared to LM method (2).

The number of passes were significantly (P Value <0.001) more in LM group (5.50)

compared to the US-guided group (4). A similar finding of 4 passes was observed in the

study by Srinivasan et al. 50 for the latter method, however, the former required considerably

more passes (8.2) and the difference was statistically significant (P=0.01) indicating the

inaccuracies in locating the landmarks. Chin et al. in their study on orthopaedic patients also

found US guided method requiring significantly (P Value <0.001) lesser passes (6) than the

LM method (13).Though, the average number of passes similar in both groups reported by

Srinivasan et al.69 (6.13 in LM group and 6.95 in US-guided group), the latter method

required more number of passes in relation to the present study.

The number of passes was being more in the LM group could be due to many reasons. First,

the patient population was different. Mean age and body mass index in our study were 59

years and 34.9 kg/m2, respectively, versus 63-68 years and 28.5-30.5 kg/m2 in the referenced

studies50, 69. Second, in the study by Kim et al.70 , the number of passes was self-reported,

whereas in our study, it was recorded by an independent observer. This is important, because

it has been shown that the self-reported number of passes is always lower than the actual

number of passes50.

We note a reduction in number of passes required to enter the subarachnoid space because of

the following probable reasons. First, the age of our population group was, on average, 64.3

years (SD = 12.8), and spinal anesthesia has been shown to be more difficult in an older

population compared with a general adult population.16 Second, we used a paramedian

approach to the neuraxis (guided by ultrasound), which has not been studied so far. In the

presence of interspinous ligament calcification and an inability to achieve adequate flexion

(both of which are common in the elderly), this paramedian approach might be valuable. It

has also been shown that both the length and the width of the lumbar spinous process increase

significantly with aging, which further narrows the interspinous space available for a midline

approach71. The interlaminar space is least affected by changes attributable to aging and

offers a potential window for spinal anesthesia.

When the median time taken for identifying space for each group was compared, it was 38.

19 seconds for LM group, while it was twice as high (78.35 seconds) for US-guided group

which was statistically significant (P Value <0.001). The average time taken in the study by

Srinivasan et al.69 was very less (12.3 seconds) for LM group than that of US-guided group

(105.1 seconds), which were in turn were in line with their earlier study findings (14.6

seconds for the former method, 96.1 seconds for the latter) and this finding was statistically

significant (P=0.0002) 50. In a study by Chin et al.56 , using similar endpoints, this process in

the ultra- sound group took 240 seconds longer. The difference might be because of the fact

that in their study, scanning was done in patients with difficult surface landmarks, and it

involved marking 3 interspinous spaces.

The technical difficulty of neuraxial blockade is measured using two main parameters: the

number of needle manipulations required for success and the time taken to perform the block.

Of the two, the former is more important because multiple needle insertions are an

independent predictor of complications, such as inadvertent dural puncture, vascular

puncture, and paresthesia1. Elicitation of paresthesia, in turn, is a significant risk factor for

persistent neurologic deficit after spinal anesthesia72, 73.

Regarding the time taken for successful lumbar puncture between the groups, the US-guided

method took significantly (P Value =0.048) less time (64.32 seconds) compared to LM

method (88.31 seconds). A similar finding was seen the study by Srinivasan et al. 50 with the

former method requiring less time (97.8 seconds) for successful procedure compared to the

latter method (169.9 seconds). However, the overall time taken by both the procedures was

higher in the study of Srinivasan et al.69 [US-guided procedure took more time (137.2

seconds) than LM group (127.4 seconds)], which was contrasting to our study findings.

The successfulness of the both the methods were comparable (95% in LM group; 92.5% in

US-guided group) with only 2 (5%) cases converted to GA in the LM group and 3 (7.5%) of

them needed the same in US-guided group. Similarly, Srinivasan et al.69 noted slightly more

cases in the US-guided group (3) requiring GA in relation to LM group (2). Also using

midline approach of US-guided spinal anaesthesia Abdelhamid et al. 67 reported significantly

improved success rate (the subjects were younger), however, Lim et al.8 who studied elderly

subjects like the present study, found no difference between the LM group and US-guided

paramedian approach.

As suspected by many clinicians, precise lumbar interspace identification by palpation is

prone to error. Broadbent and colleagues74 confirmed this, showing that anaesthetists were

29% accurate, as determined by MRI. Ultrasonography was not investigated in this study.

The inaccuracy was corroborated by Furness et al.46, who showed that clinical identification

by anaesthetists using palpation was 30% accurate, determined by lumbar spine x ray. Both

previous studies also showed that clinical identification by anaesthetists was often inaccurate

by two, three or four interspaces. Using ultrasound, markers were always within one

interspace of the intended position.

There are consistent data to suggest that neuraxial ultrasound identifies lumbar intervertebral

levels, with greater accuracy than palpation of surface anatomical landmarks75. Using plain

X-ray of the lumbar spine as a reference standard, Furness et al.46 demonstrated that

ultrasound correctly identified individual inter- spaces (from L2-3 to L4-5) 71% of the time,

whereas palpation was only correct 29% of the time. Furthermore, the margin of error never

exceeded one level with ultrasound, but was up to 2 spaces higher or lower in 27% of

palpation assessments. These findings are consistent with those reported by Watson et al.76

who, using MRI as their reference standard, found that ultrasound accurately identified the

L3-4 interspace in 76% of cases with a margin of error that did not exceed one level.

In a learning curve study that used CT as a reference standard, Halpern et al. 77 reported an

overall identification accuracy rate for ultrasound of 68%. However, analysis of the learning

curve showed that the 2 anesthesiologists in the study with no previous experience with

neuraxial ultrasound achieved accuracy rates of 90% or greater after 22 and 36 procedures,

respectively.

It is possible to use ultrasound scanning to accurately identify the lumbar spinous processes

in unselected patients. This result suggests that, with appropriate training, this tool can be

used to enhance the accuracy of needle placement during neuraxial techniques77. Watson et

al.76 concluded that ultrasonography may be a useful adjunct to safe subarachnoid

anaesthesia. Also Chin et al.56 inferred that preprocedural ultrasound imaging facilitates the

performance of spinal anesthesia in the non-obstetric patient population with difficult

anatomic landmarks.

The study does have limitations. First, neither the observer nor the attending anesthesiologists

were blinded to either of the group. The fact that the ultrasound group would have skin

markings and the difference in the direction of needle insertion would have made blinding

very difficult but still a potential for bias cannot be excluded. Second, the procedure is

heterogeneous with multiple factors affecting the number of passes, including individual

anesthesiologist preference and style of practice and the number of attempts and/or time

taken before using alternate methods. This may reflect daily clinical practice. Having a

single anesthesiologist perform all procedures might limit the differences because of the

aforementioned reasons, but it might also be more appropriate to reflect individual bias and

lack of validation. Third, neuraxial ultrasound has limitations. TM views for a midline

approach to dural puncture have a positive predictive value of up to 85% but a negative

predictive value of just 30%9. Also, ultrasound views are generally more difficult to acquire

in the elderly because of anatomical changes (facet hypertrophy, interspinous, and

supraspinous ligament calcification)78. In addition, the necessity to remember the angle of

approach of the needle and the inaccuracies of skin markings can further decrease the utility

of ultrasound views in patients with a longer distance between skin and duramater.

CONCLUSIONS

Pre-procedural Ultrasound-guided method of needle insertion needed significantly

lesser number of attempts compared to the landmark guided method for successful

spinal anaesthesia.

The US-guided method needed significantly less number of passes in relation to the

LM methods.

The landmark guided method took needed significantly less time of identifying space,

while the US-guided method took twice of the time.

The US-guided method took significantly less time for successful lumbar puncture

compared to LM method.

Ultrasonography can be a useful adjunct to safe spinal anaesthesia and also it

facilitates the performance of spinal anesthesia in the non-obstetric patient population

with difficult anatomic landmarks, like obese patients.

RECOMMENDATIONS:

REFERENCES:

1. de Filho GR GH, da Fonseca MH, Hoffman JC, Pederneiras SG, Garcia JH. Predictors of successful neuraxial block: a prospective study. Eur J Anaesthesiol. 2002;19:447–51.2. de Seze MP SF, Janvier G, Joseph PA. Severe and long-lasting complications of the nerve root and spinal cord after central neuraxial blockade. Anesth Analg. 2007;104:975–9.3. Conroy PH LC, McCartney CJ, McHardy PG. Real-time ultrasound-guided spinal anaesthesia: a prospective observational study of a new approach. Anesthesiol Res Pract. 2013;2013:525818.4. Wong SW NA, Chin KJ, Chan VW. Real-time ultrasound-guided spinal anesthesia using the SonixGPS® needle tracking system: a case report. Can J Anaesth. 2013;60:50–3.5. Lee PJ TR, Sawka A, Krebs C, Vaghadia H. Brief report: real-time ultrasound-guided spinal anesthesia using Taylor’s approach. Anesth Analg. 2011;112:1236–8.6. Chin KJ KM, Peng P. Ultrasonography of the adult thoracic and lumbar spine for central neuraxial blockade. Anesthesiology. 2011;114:1459–85.7. Chin KJ PA, Chan V, Brown-Shreves D, Koshkin A, Vaishnav V. Ultrasound imaging facilitates spinal anesthesia in adults with difficult surface anatomic landmarks. Anesthesiology. 2011;115:94–101.8. Lim YC CC, Tan KT. A randomised controlled trial of ultrasound-assisted spinal anaesthesia. Anaesth Intensive Care. 2014;42:191–8.9. Chin KJ RR, Arzola C, Singh M, Chan V. The utility of ultrasound imaging in predicting ease of performance of spinal anesthesia in an orthopedic patient population. Reg Anesth Pain Med. 2013;38:34–8.10. Ansari T YA, El Gamassy A, Fayez M. Ultrasound-guided spinal anaesthesia in obstetrics: is there an advantage over the landmark technique in patients with easily palpable spines? Int J Obstet Anesth. 2014;23:213–6.11. Ronald Miller, Lars Eriksson, Lee Fleisher, Jeanine Wiener-Kronish, Neal Cohen, Young W. Miller's Anesthesia. 8th ed: Elsevier Health Sciences; 2009.12. Bernards CM, Hill HF. Morphine and alfentanil permeability through the spinal dura, arachnoid, and pia mater of dogs and monkeys. Anesthesiology. 1990;73(6):1214-9.13. Hogan QH. Lumbar epidural anatomy. A new look by cryomicrotome section. Anesthesiology. 1991;75(5):767-75.14. Nikolay L. Martirosyan, Jeanne S. Feuerstein, Nicholas Theodore, Daniel D. Cavalcanti, Robert F. Spetzler, Mark C. Preul. Blood supply and vascular reactivity of the spinal cord under normal and pathological conditions. Journal of Neurosurgery: Spine. 2011;15(3):238-51.15. Hogan QH, Prost R, Kulier A, Taylor ML, Liu S, Mark L. Magnetic resonance imaging of cerebrospinal fluid volume and the influence of body habitus and abdominal pressure. Anesthesiology. 1996;84(6):1341-9.16. Carpenter RL, Hogan QH, Liu SS, Crane B, Moore J. Lumbosacral cerebrospinal fluid volume is the primary determinant of sensory block extent and duration during spinal anesthesia. Anesthesiology. 1998;89(1):24-9.17. Hogan Q. Size of human lower thoracic and lumbosacral nerve roots. Anesthesiology. 1996;85(1):37-42.18. J B. Physiology of spinal anesthesia: What are the implications for management? Reg Anesth Pain Med. 1998;23:370–3.

19. Sugiyama K MT. Local anesthetics depress the calcium current of rat sensory neurons in culture. Anesthesiology. 1994;80:1369–78.20. Hodgson PS NJ, Pollock JE, Liu SS. The neurotoxicity of drugs given intrathecally (spinal). Anesth Analg 1999;88:797–809.21. Li YM WD, Too HP, Marnerakis M, Stimson ER, Strichartz GR et al. Local anesthetics inhibit substance P binding and evoked increases in intracellular Ca2+. Anesthesiology. 1995;82:166–73.22. Curatolo M P-FS, Arendt-Nielsen L, Zbinden AM. Spinal anaesthesia inhibits central temporal summation. Br J Anaesth. 1997;78:88-9.23. Thalhammer JG RS, Popitz-Bergez FA, Strichartz GR. Modality-dependent modulation of conduction by impulse activity in functionally characterized single cutaneous afferents in the rat. Somatosensory Motor Res 1994;11:243–57.24. SA R. Subblocking concentrations of local anesthetics: Effects on impulse generation and conduction in single myelinated sciatic nerve axons in frog. Anesth Analg 1992;75: 906–21.25. Greene NM. Uptake and elimination of local anesthetics during spinal anesthesia. Anesth Analg. 1983;62(11):1013-24.26. Greene NM. Distribution of local anesthetic solutions within the subarachnoid space. Anesth Analg. 1985;64(7):715-30.27. Higuchi H, Hirata J, Adachi Y, Kazama T. Influence of lumbosacral cerebrospinal fluid density, velocity, and volume on extent and duration of plain bupivacaine spinal anesthesia. Anesthesiology. 2004;100(1):106-14.28. Denny N, Selander D. Continuous spinal anaesthesia. British journal of anaesthesia. 1998;81(4):590-7.29. Neal JM, Bernards CM, Hadzic A, Hebl JR, Hogan QH, Horlocker TT, et al. ASRA Practice Advisory on Neurologic Complications in Regional Anesthesia and Pain Medicine. Reg Anesth Pain Med. 2008;33(5):404-15.30. Chin KJ, Karmakar MK, Peng P. Ultrasonography of the adult thoracic and lumbar spine for central neuraxial blockade. Anesthesiology. 2011;114(6):1459-85.31. Finucane MM SG, Cowan MJ, Da- naei G, Lin JK, Paciorek CJ, et al. National, regional, and global trends in body-mass index since 1980: systematic analysis of health examination surveys and epidemiological studies with 960 country-years and 9.1 million participants. Lancet. 2011;377:557–67.32. Ng M FT, Robinson M, Thomson B, Graetz N, Margono C, et al. Global, regional, and national prevalence of overweight and obesity in children and adults during 1980– 2013: a systematic analysis for the Global Burden of Disease Study 2013. Lancet. 2014;384:766–81.33. Molarius A SJ, Sans S, Tuomilehto J, Kuulasmaa K. Educational level, relative body weight, and changes in their associa- tion over 10 years: an international perspec- tive from the WHO MONICA project. Am J Public Health 2000;90:1260–8.34. Monteiro CA ME, Conde WL, Popkin BM. Socioeconomic status and obesity in adult populations of developing countries: a review. Bull World Health Organ. 2004;82(2):940-6.35. Dinsa GD GY, Fumagalli E, Suhrcke M. Obesity and socioeconomic status in developing countries: a systematic review. Obes Rev. 2012;13:1067–79.36. Larsen MD. Tait and Caglieri the first spinal anesthetic in America. Anesthesiology. 1996;85(4):913-9.37. JB S. Über cocainisirung des Rüchenmartks nach Bier. Centralblatt Chir. 1899;26:1110-3.

38. T T. Analgésie Chirurgicale par l'injection sousarachno dienne lombaire de coca ne. ı ı Soc Biol 1899:882-4.39. T T. Analgesie Chirurgicale par l'injection de coca ne sous l'arachnoide lombaire. ı Presse Med. 1899;91:294-5.40. Adriani J R-VD. Saddle block anesthesia. Am J Surg 1946:71:12.41. Maltby JR HC, Clayton KC. The Woolley and Roe case. Br J Anaesth 2000;84(1):121–6.42. Curry TS III DJ, Murry RC. Ultrasound. Christensen's Physics Of Diagnostic Radiology. 4 ed. Philadelphia: Lea & Febiger; 1990. p. 323-71.43. FW K. Diagnostic Ultrasound: Principles And Instruments. 5 ed. Philadephia: WB Saunders; 1998.44. Nyland TG M, JS, Herrgesell EJ, Wisner ER. Physical Principles, Instrumentation, And Safety Of Diagnostic Ultrasound. In: Nyland TG MJ, editor. Small Animal Diagnostic Ultrasound. 2 ed. Philadelphia: WB Saunders; 2002. p. 1-18.45. Ghosh SM, Madjdpour C, Chin KJ. Ultrasound-guided lumbar central neuraxial block. BJA Education. 2016;16(7):213-20.46. Furness G RM, Kuchi S. An evaluation of ultrasound imaging for identification of lumbar intervertebral level. Anaesthesia. 2002;57:277–80.47. Nomura JT LS, Shenbagamurthi S, Sierzenski PR, O'Connor RE, Bollinger M et al. A randomized controlled trial of ultrasound-assisted lumbar puncture. J Ultrasound Med. 2007;26(10):1341-8.48. Chin KJ, Chan VW, Ramlogan R, Perlas A. Real-time ultrasound-guided spinal anesthesia in patients with a challenging spinal anatomy: two case reports. Acta Anaesthesiol Scand. 2010;54(2):252-5.49. Arzola C, Mikhael R, Margarido C, Carvalho JC. Spinal ultrasound versus palpation for epidural catheter insertion in labour: A randomised controlled trial. Eur J Anaesthesiol. 2015;32(7):499-505.50. Srinivasan KK IG, Loughnane F, Lee PJ. Conventional Landmark-Guided Midline Versus Preprocedure Ultrasound-Guided Paramedian Techniques in Spinal Anesthesia. Anesth Analg. 2015;121(4):1089-96.51. Kallidaikurichi Srinivasan K, Iohom G, Loughnane F, Lee PJ. Conventional Landmark-Guided Midline Versus Preprocedure Ultrasound-Guided Paramedian Techniques in Spinal Anesthesia. Anesth Analg. 2015;121(4):1089-96.52. Niazi AU, Chin KJ, Jin R, Chan VW. Real-time ultrasound-guided spinal anesthesia using the SonixGPS ultrasound guidance system: a feasibility study. Acta Anaesthesiol Scand. 2014;58(7):875-81.53. Wong SW, Niazi AU, Chin KJ, Chan VW. Real-time ultrasound-guided spinal anesthesia using the SonixGPS(R) needle tracking system: a case report. Can J Anaesth. 2013;60(1):50-3.54. Weed JT, Taenzer AH, Finkel KJ, Sites BD. Evaluation of pre-procedure ultrasound examination as a screening tool for difficult spinal anaesthesia*. Anaesthesia. 2011;66(10):925-30.55. Chin KJ, Perlas A, Singh M, Arzola C, Prasad A, Chan V, et al. An ultrasound-assisted approach facilitates spinal anesthesia for total joint arthroplasty. Can J Anaesth. 2009;56(9):643-50.56. Chin KJ, Perlas A, Chan V, Brown-Shreves D, Koshkin A, Vaishnav V. Ultrasound imaging facilitates spinal anesthesia in adults with difficult surface anatomic landmarks. Anesthesiology. 2011;115(1):94-101.

57. Ansari T, Yousef A, El Gamassy A, Fayez M. Ultrasound-guided spinal anaesthesia in obstetrics: is there an advantage over the landmark technique in patients with easily palpable spines? Int J Obstet Anesth. 2014;23(3):213-6.58. Brinkmann S, Tang R, Sawka A, Vaghadia H. Single-operator real-time ultrasound-guided spinal injection using SonixGPS: a case series. Can J Anaesth. 2013;60(9):896-901.59. Soni NJ F-SR, Schnobrich D, Dancel R, Tierney DM, Salame G et al. Ultrasound guidance for lumbar puncture. Neurol Clin Pract. 2016;6(4):358-68.60. Corp I. IBM SPSS statistics for windows, version 22.0. Armonk, NY: IBM Corp. 2013.61. A B. “Versuche über cocainisirung des rückenmarkes,” Deutsch Zeitschrfti für Chirurgie. 1899;51(3):352–8.62. Broadbent CR MW, Ferrie R, Wilson DJ, Gawne-Cain M, Russell R. Ability of anaesthetists to identify a marked lumbar interspace. Anaesthesia. 2000;55(11):1122–6.63. Puolakka R HJ, Pitkanen MT, Kallio M, Rosenberg PH. Technical aspects and postoperative sequelae of spinal and epidural anesthesia: a prospective study of 3,230 orthopedic patients. Regional Anesthesia and Pain Medicine. 2000;25(5):488–97.64. Render C. The reproducibility of the iliac crest as a marker of lumbar spine level. Anaesthesia. 1996;51(11):1070-1.65. Reimann AF, Anson BJ. Vertebral level of termination of the spinal cord with report of a case of sacral cord. The Anatomical Record. 1944;88(1):127-38.66. Pounder D, Elliott S. An awake patient may not detect spinal cord puncture. Anaesthesia. 2000;55(2):194-.67. Abdelhamid SA, Mansour MA. Ultrasound-guided intrathecal anesthesia: Does scanning help? Egyptian Journal of Anaesthesia. 2013;29(4):389-94.68. Gnaho A, Nguyen V, Villevielle T, Frota M, Marret E, Gentili ME. Assessing the depth of the subarachnoid space by ultrasound. Revista brasileira de anestesiologia. 2012;62(4):525-30.69. Srinivasan KK, Leo AM, Iohom G, Loughnane F, Lee PJ. Pre-procedure ultrasound-guided paramedian spinal anaesthesia at L5-S1: Is this better than landmark-guided midline approach? A randomised controlled trial. Indian J Anaesth. 2018;62(1):53-60.70. Kim JH, Song SY, Kim BJ. Predicting the difficulty in performing a neuraxial blockade. Korean J Anesthesiol. 2011;61(5):377-81.71. Aylott CEW, Puna R, Robertson PA, Walker C. Spinous process morphology: the effect of ageing through adulthood on spinous process size and relationship to sagittal alignment. European Spine Journal. 2012;21(5):1007-12.72. Auroy Y, Narchi P, Messiah A, Litt L, Rouvier B, Samii K. Serious complications related to regional anesthesia: results of a prospective survey in France. Anesthesiology. 1997;87(3):479-86.73. Horlocker TT, McGregor DG, Matsushige DK, Schroeder DR, Besse JA. A retrospective review of 4767 consecutive spinal anesthetics: central nervous system complications. Anesthesia & Analgesia. 1997;84(3):578-84.74. Broadbent C, Maxwell W, Ferrie R, Wilson D, Gawne Cain M, Russell R. Ability of ‐anaesthetists to identify a marked lumbar interspace. Anaesthesia. 2000;55(11):1122-6.75. Perlas A, Chaparro LE, Chin KJ. Lumbar neuraxial ultrasound for spinal and epidural anesthesia: a systematic review and meta-analysis. Regional anesthesia and pain medicine. 2016;41(2):251-60.

76. Watson M, Evans S, Thorp J. Could ultrasonography be used by an anaesthetist to identify a specified lumbar interspace before spinal anaesthesia? British journal of anaesthesia. 2003;90(4):509-11.77. Halpern SH, Banerjee A, Stocche R, Glanc P. The use of ultrasound for lumbar spinous process identification: a pilot study. Canadian Journal of Anesthesia/Journal canadien d'anesthésie. 2010;57(9):817-22.78. Scapinelli R. Morphological and functional changes of the lumbar spinous processes in the elderly. Surgical and Radiologic Anatomy. 1989;11(2):129-33.