regional anesthesia for pediatric orthopaedic...

CHAPTER 31

Regional Anesthesia for PediatricOrthopaedic Surgery

SANTHANAM SURESH/ADRIAN T. BÖSENBERG

� INTRODUCTION

Regional anesthesia is commonly used as an adjunct togeneral anesthesia and plays a key role in the multimodalapproach to perioperative pain management in children.Its use in pediatric orthopaedic surgery is gaining in popu-larity1,2 despite concerns from some orthopaedic surgeonsthat the profound analgesia offered may mask ischemicpain of compartment syndromes.

The worldwide trend toward more day-case surgeryand the associated advantages offered has increased theuse of regional anesthetic techniques. Furthermore, theadvent of more complex and innovative surgical proce-dures in children has improved outcome but also led tomore invasive surgery and consequently more pain inthe postoperative period. These factors have providedthe impetus for the development of continuous periph-eral nerve block techniques that target the site of surgeryin both children1 and adolescents.

The practice of peripheral nerve blockade continuesto improve with the development of age-appropriateequipment and the introduction of safer long-acting localanesthetic agents such as ropivacaine and levobupiva-caine. Although caudal blockade remains the most popularand frequently used block in infants and small children,the safety of peripheral nerve blocks has been establishedin large-scale prospective studies in children.3 Peripheralnerve blocks have consequently been recommended,rather than central neuraxial techniques, where appropri-ate.3 The majority of peripheral nerve blocks are performedin the operating room by experienced anesthesiologists,

but there are several blocks, such as femoral nerve or dig-ital block, that may be done in the emergency room oreven the intensive care unit.

The purpose of this chapter is to outline some meth-ods used to identify and block individual nerves and toconsider regional anesthetic techniques that can be usedfor surgical procedures of the upper and lower limbs inchildren. The choice of technique may be dictated by thepathology, the extent of surgery, the child’s body habi-tus, and the presence of contractures. The differencesbetween adults and children are highlighted, togetherwith techniques to improve the success of blocks.

� METHODS TO IMPROVE THEACCURACY OF PERIPHERALNERVE BLOCKS

Peripheral nerve blocks, particularly in young children,can be difficult. Anatomic landmarks are poorly definedand vary according to the stage of the child’s develop-ment, particularly in those with limb defects. The suc-cessful placement of peripheral nerve blocks requires anawareness of these differences, knowledge of develop-mental anatomy, and an understanding of the equipmentused. For most of the blocks presented in this chapter,the use of an insulated needle and peripheral nerve stim-ulator is recommended although successful blocks mayalso be achieved with noninsulated needles.4

Given the difficulty in obtaining cooperation, particu-larly in young infants, most children are sedated or under

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general anesthesia when nerve blocks are performed.Caution must therefore be exercised while placing theblocks, since paresthesias and pain cannot be elicited.

Nerve Stimulator

A number of basic principles need to be emphasizedregarding the use of a nerve stimulator (see Chap. 19). Inorder to locate a peripheral nerve or plexus accurately,neuromuscular blocking agents should be withheld untilafter completion of the nerve block. The proper function-ing of the nerve stimulator, according to the manufac-turer’s recommendations, should be understood before itis used.5 With the many peripheral nerve stimulators cur-rently on the market, it is best to familiarize oneself thor-oughly with one particular model and to stick with it.5

The negative electrode should be attached to theneedle and the positive electrode attached to the patientwith a standard electrocardiographic (ECG) skin attach-ment. Once the appropriate landmarks have been deter-mined or “surface mapped” and the peripheral nerve stim-ulator initially set at 1 to 1.5 mA, 100 to 300 µs. and 1 to 2 Hz,the needle should be advanced through the skin andunderlying tissue planes until appropriate distal musclecontractions are elicited. The current output should thenbe decreased and the needle moved until a brisk motorresponse is elicited with the least amount of current; i.e.,0.3 to 0.5 mA. The appropriate dose of local anestheticshould be injected at this point. If the needle is correctlyplaced, the muscle contractions will immediately cease,indicating that a successful block is likely. Failure to elicitthis response requires the needle to be repositionedbefore repeating the process. At this stage of our knowl-edge we believe that the local anesthetic should notbe injected if intense muscle contractions are elicited at<0.2 mA or if there is resistance to injection. Both eventssuggest that the tip of the needle may be intraneural andthat the nerve may be damaged by further injection.

Newer techniques for improving the success ofperipheral nerve blocks include surface nerve mapping6

and ultrasonography,7,8 because both techniques areparticularly useful in small children, who are consideredto be a group at greater risk for complications or failure.

Surface Nerve Mapping

This is a modification of the standard nerve stimulatortechnique.6 The path of a superficial peripheral nerve orplexus can be traced before skin penetration by stimu-lating the motor component of the nerve transcuta-neously. The nerve stimulator’s output is set at 2 to 5 mAat 1 to 2 Hz and the negative electrode is used as themapping electrode. The current required varies anddepends on the depth of the nerve and the moistness ofthe overlying skin. The point at which the appropriatemuscle responses are strongest is marked and used asthe landmark for that specific nerve block.

Direct muscle stimulation is finer and more local-ized and should be recognized as a “false positive”response. Excessive pressure applied over the nervemay inhibit the response. The nerve-mapping techniquemay be used for various approaches to the brachialplexus as well as for axillary, musculocutaneous, ulnar,median, and radial nerve blocks of the upper limb andfemoral, sciatic, and popliteal nerve blocks in the lowerlimb. Surface nerve mapping is particularly useful whenclassic anatomic landmarks are absent or difficult todefine; for example, in children with arthrogryposis orthose with major congenital limb defects.

Ultrasound Imaging

Ultrasound is becoming an important adjunct to regionalanesthesia.8 Ultrasonography is noninvasive, relativelyinexpensive, being used to improve the accuracy of localanesthetic placement. Technological advances haveallowed the development of small portable ultrasoundequipment that can be taken into the operating theater.Finally, the technique is easily taught.

There are a number of reasons why ultrasonographymay be of greater value in pediatric regional anesthesia. Inthe sedated or anesthetized child, direct visualization ofthe nerve or neuraxial structures, vessels, tendons, andbones and placement of the local anesthetic is possible.Since, in children, most peripheral nerves lie within rangeof portable ultrasound probes, good definition can beachieved. Using real-time imaging, ultrasound can verifycorrect needle and local anesthetic placement around thenerve and reduce the risk of intraneural or intravascularinjection. The position of continuous catheters can also beconfirmed.

Proponents of ultrasound guidance claim earlieronset times, improved quality and duration of block withsmaller volumes of local anesthetic, and fewer complica-tions in children.8 To date the use of ultrasound in pedi-atric regional anesthesia is limited but gaining in popu-larity, particularly in Europe.8

� REGIONAL ANESTHESIA FOR THEUPPER EXTREMITY

The motor and sensory innervation of the whole upperextremity is supplied by the brachial plexus with theexception of part of the shoulder, which is innervated bythe cervical plexus, and the sensory innervation to themedial aspect of the upper arm, which is supplied by theintercostobrachial nerve, a branch of the second intercostalnerve.

Anatomy of the Brachial Plexus

The anterior primary rami of C5-8 and the bulk of T1 formthe brachial plexus (Fig. 23-1). These five roots emerge

386 PART III REGIONAL ANESTHESIA FOR ORTHOPAEDIC SURGERY


from the intervertebral foramina to lie between thescalenus anterior and scalenus medius muscles (whichattach to the anterior and posterior tubercles of the trans-verse process of the cervical vertebrae, respectively).

The fascia from these muscles encloses the plexus ina sheath that extends laterally into the axilla. A single injec-tion of local anesthetic within this sheath produces com-plete plexus blockade by blocking the trunks (supraclavic-ular approaches) or the cords (infraclavicular approaches).As the five spinal roots pass between the scalene muscles,they unite to form three trunks: upper C5-6, middle C7,and lower C8-T1 (Fig. 23-4). Emerging from the intersca-lene groove, the three trunks pass downward and laterallyto lie posterolaterally to the subclavian artery as it cross theupper surface of the first rib. The subclavian artery is not aseasily palpable above the clavicle in children as it is inadults. At the lateral border of the first rib, each trunkdivides into anterior and posterior divisions, which thenjoin to form the three cords, named according to their rela-tionship to the axillary artery: lateral, medial, and posterior.These cords then divide into the nerves of the brachialplexus: musculocutaneous, ulnar, median, and radial (seeChaps. 23 and 24).

Many anatomic landmarks used in adults may bedifficult to find in children of different ages, particularlyif they are sedated or under anesthesia.6 The younger thechild is, the poorer the definition of the muscular land-marks. The interscalene groove is difficult to delineatebecause the scalenus muscles are poorly developed. Thesubclavian artery is seldom palpable in the supraclavicu-lar region in infants and preadolescent children.

The brachial plexus can be blocked at variouslevels.9 The choice of a particular technique is based onthe planned surgical procedure, the experience of the anes-thesiologist, the presence of contractures, and the poten-tial benefits for the patient, which may include placing acatheter for continuous infusions.

The infraclavicular and the axillary approaches areconsidered safer and easier for the placement and fixa-tion of an indwelling catheter for continuous peripheralnerve blocks. Although the use of the interscaleneapproach has been reported for shoulder surgery and forelbow surgery in children,9 it should be used with cautionin children because of the increased risk of intravascularor intrathecal injection or temporary phrenic nerve palsy.

Axillary Approach to theBrachial Plexus

The axillary block is the most popular approach in chil-dren.9–12 It is relatively safe and provides good analgesiafor surgery of the forearm and hand. The primary advan-tages of this block are its easy placement and low risk ofcomplications. Its main limitations are incomplete blockof the shoulder and lateral aspect of the forearm onto thethenar eminence (sensory distribution of the musculocu-

taneous nerve). It may be used for a variety of proce-dures on the forearm (particularly on the medial aspect)and hand, such as open reduction with internal fixationof a forearm fracture or the repair of congenital anom-alies (syndactyly) of the hand (see Chap. 15),12 vascularinsufficiency, finger reimplantation, or closed reductionof forearm fractures (see Chap. 16).11

Axillary Perivascular ApproachThe patient is positioned supine with the arm abducted90 degrees, elbow flexed, and hand behind the head.The landmarks are the pectoralis major and coraco-brachialis muscles and the axillary artery. Surface nervemapping, ultrasound, or a nerve stimulator may be usedto aid in the correct placement of the block. The dose oflocal anesthetic is 0.2 to 0.3 mL/kg 0.25 to 0.5% bupiva-caine, ropivacaine, or levobupivacaine. Lower concentra-tions will reduce the degree of motor block if required.

TECHNIQUE

Palpate the axillary artery in the tissues overlying thehumerus at the junction of the lower border of pectoralismajor and coracobrachialis muscles or as high as possi-ble in the axilla. The nerve stimulator output is set at 1 mA.An insulated needle should be introduced immediatelysuperior to the axillary arterial pulsation at a 45- to60-degree angle to the skin and directed parallel to theartery13 or toward the midpoint of the clavicle. Muscletwitches are usually elicited in the areas of median orradial nerve distribution (rarely in the ulnar nerve) as theplexus sheath is penetrated. The output of the nervestimulator should then be gradually reduced to approxi-mately 0.3 to 0.4 mA while the muscle twitch is main-tained by adjusting the position of the needle as needed.Local anesthetic solution can then be injected.

Alternatively, a nerve stimulator set at 3 to 5 mA canbe used to map the median, radial, and or musculocuta-neous nerve transcutaneously in the axilla on either sideof the arterial pulsation. An insulated needle should beinserted at the point where the stimulator causes maxi-mum muscle twitches.

Multiple injection techniques have been describedin both adults and children. There is little advantage tomultiple injections in children10 because the loose fascialattachments allow the even spread of the anesthetic. Asingle-injection can provide adequate blockade of thebrachial plexus.

As the local anesthetic solution fills the sheath, alongitudinal swelling may become visible beneath theskin, but it should disappear quickly as the solutionspreads proximally. Distal pressure may be applied dur-ing and immediately following injection, while the armshould be adducted to release the pressure from thehead of the humerus from the fossa in order to facilitatethe proximal spread of the solution and facilitate block-ade of the musculocutaneous nerve.

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The musculocutaneous nerve may be blocked sep-arately to provide reliable analgesia for procedures thatinvolve the lateral forearm (lateral cutaneous nerve offorearm). This should be done by advancing a needleintroduced perpendicularly to the skin, just above theaxillary artery pulsation, into the coracobrachialis muscleuntil forearm flexion is elicited by using a nerve stimula-tor. Then 0.5 to 1 mL of local anesthetic solution shouldbe injected just deep to the fascia.

When long-term pain relief or relief of chronic pain isrequired, a catheter can be introduced into the axilla forthe continuous infusion of a local anesthetic. The immobi-lization, fixation, and dressing of these catheters are ratherdifficult in the axilla, but this may be overcome by tunnel-ing the catheter medially onto the chest or laterally overthe deltoid area. After the initial block dose, an infusionrate of 0.2 to 0.4 mg/kg/h should be adequate.

COMPLICATIONS

Complications of axillary block are rare but includehematoma from accidental vascular puncture. If the arteryis inadvertently punctured, pressure should be applied forat least 5 min to avoid possible vascular insufficiency dueto compressive hematoma formation.

Transarterial ApproachThe transarterial approach, traditionally used in adults,14–16

is not popular for children but is included here for com-pleteness. Proponents of this approach claim greater suc-cess with posterior cord (musculocutaneous) blockade.Among the reasons for avoiding the transarterial approachin children is the fact that most soft tissue surgery of theupper extremity (e.g., syndactyly, reimplants) is vascular innature; hence it is important to avoid vascular insufficiencycaused by vessel spasm or hematoma formation.

The risk of toxicity is also high in children, and evenrelatively small volumes may produce toxic effects. Thedetection of intravascular injection and toxicity undergeneral anesthesia is difficult but may be detected bytransient changes in the heart rate or ECG.17 Theseinclude changes in the amplitude of T waves or ST seg-ments when using a local anesthetic solution containingepinephrine (usually 1:200,000).

Infraclavicular Approach The patient’s position is supine with a pillow under theshoulder, the head turned to the opposite side, and theupper arm abducted alongside the body. The elbow isflexed to 90 degrees with the forearm placed on theabdomen. The landmarks are the lower border of the clav-icle, coracoid process of the scapula, and axillary artery asit emerges beneath the clavicle. A nerve stimulator, surfacemapping, and ultrasound can aid correct placing.

The dose of local anesthetic can be 0.2 to 0.3 mL/kg0.5% bupivacaine, 0.5% ropivacaine, or 0.5% levobupi-

vacaine. Lower concentrations may reduce the degree ofmotor block.

TECHNIQUE

Safety considerations have steered practitioners awayfrom the supraclavicular approach in order to reduce therisk of pneumothorax. A number of infraclavicularapproaches have been described.18–20 With the child cor-rectly positioned, the clavicle is divided visually intothree parts. A mark should be made at the point wherethe arterial pulsation is felt as it emerges below the clav-icle or where any distal flexion or pronation is “mapped”with a nerve stimulator. An insulated needle should beinserted infraclavicularly at the junction of the middleand lateral thirds of the clavicle and directed toward thismark. The needle passes lateral to the cupola of the lungand has little chance of encountering the lung along itscourse. Pronation or flexion at the elbow should besought. Once the nerve is located, the nerve stimulator’scurrent should be reduced to 0.2 to 0.3 mA.

Alternatively, the needle can be inserted at themidpoint of the lower border of the clavicle at a 45- to60-degree angle and directed toward the axilla in thesame manner until distal muscle twitches are elicited.

A vertical infraclavicular approach using the cora-coid process as a landmark has been described in chil-dren.18,20 The site of puncture is 1 to 2 cm caudal and 0.5to 1 cm medial to the coracoid process in the lower partof the deltopectoral groove. An insulated needle shouldbe inserted perpendicular to the skin until distal muscletwitches are elicited. The brachial plexus may be difficultto locate in some patients, and an ultrasound-guidedapproach has been recommended.21 Proponents of thistechnique claim more effective sensory and motor blockthan with the axillary approach.20,21

When long-term pain relief or relief of chronic painis necessary, a catheter for continuous infusion of a localanesthetic solution can be used. Immobilization and fix-ation of these catheters to the chest is easier than in theaxilla, and tunneling is seldom required.

Supraclavicular ApproachThe patient’s position is supine, with a pillow under theshoulders, the arm extended alongside the body, and thehead turned to the opposite side.

The landmarks are the midpoint of the clavicle, thetransverse process of C6 (Chassaignac’s tubercle), theposterior border of the sternocleidomastoid muscle, andthe cricoid cartilage.

Surface nerve mapping, nerve stimulator, or ultra-sound will aid placement.

The dose of local anesthetic may be 0.2 to 0.3 mL/kgof 0.5% bupivacaine, 0.5% ropivacaine, or 0.5% levobupi-vacaine; lower concentrations may reduce the degree ofmotor block.



TECHNIQUE

Although the reported incidence of pneumothorax inchildren is low,22 the fear of this complication remainshigh among most pediatric practitioners. The supraclav-icular approach is indicated for all upper extremity sur-gery, but particularly so if the shoulder is involved. Withthe patient correctly positioned, the components of thebrachial plexus become more superficial and are easilypalpable in most children. The site of puncture shouldbe at the junction of the middle third and the lower thirdof a line joining Chassaignac’s tubercle to the midpointof the clavicle22 (if Chassaignac’s tubercle cannot be pal-pated, a line extending from the cricoid cartilage to pos-terior border of sternocleidomastoid should suffice).

Alternatively, an insulated needle can be insertedperpendicular to the skin at the stimulation site wherethe strongest distal muscle contractions (usually flexionor extension at the elbow) can be evoked or simply overthe point where the brachial plexus can be palpated sub-cutaneously with the patient in the supine position.

The success rate is high, but complications causedby faulty technique include pneumothorax, vascular punc-ture, Horner’s syndrome, and phrenic nerve palsy.9 Nervedamage is possible with injudicious injection against resist-ance, but the possibility of surgical damage should alwaysbe excluded.

When long-term pain relief or relief of chronic pain isnecessary, a catheter for the continuous infusion of a localanesthetic solution can be inserted.23 Immobilization andfixation of the catheter can be achieved by tunneling sub-cutaneously to the chest or shoulder.

Blocks at the Elbow

A single nerve or combination of nerves can be blocked atthe elbow to provide analgesia distally. These blocks areparticularly useful for pain relief after operations on theforearm or hand without the risks associated with brachialplexus blocks. Four nerves—the median, radial, ulnar, andmusculocutaneous nerves—can be located at the elbow.These can be found by surface mapping, using a nervestimulator capable of generating about 5 mA, as describedpreviously. Once the surface landmark has been mapped,the nerve can be located and blocked using a nerve stimu-lator and a sheathed needle, thus avoiding multiple skinpunctures and reducing the risk of nerve injury.

Median NerveThe patient’s position is supine with the arm extendedand the elbow slightly flexed to accentuate the tendonsof the biceps and the brachioradialis. The landmarks arethe cubital fossa, brachial artery, and biceps tendon.Surface nerve mapping, ultrasound, or a nerve stimulatorcan aid placement of the block. The median nerve in thecubital fossa is located medial to the brachial artery andthe biceps tendon beneath the deep fascia.

After the median nerve has been located, an insu-lated needle should be inserted medial to the pulsationof the brachial artery. Pronation of the arm with opposi-tion of the fingers is noted when the median nerve isstimulated. The anesthetic dose is 1 to 2 mL of 0.25 to0.5% bupivacaine, ropivacaine, or levobupivacaine. Theindications for this block are surgery on the volar aspectof the forearm and the palmar portion of the hand.Potential complications include hematoma, paresthesias,and intravascular injection.

Ulnar NerveThe patient’s position is supine, with the elbow flexed90 degrees, the arm on the chest, and the hand on theopposite shoulder. The landmark is the olecranon groove,and surface mapping, ultrasound, or nerve stimulator aidsplacement.

The ulnar nerve lies in the groove posterior to themedial condyle of the humerus midway between theolecranon and the medial epicondyle. The anestheticdose is 1 to 2 mL of 0.25 to 0.5% bupivacaine, ropiva-caine, or levobupivacaine. Indications for this block aresurgery in the ulnar distribution of the hand, includingthe medial aspect of the hand and fingers. The ulnarnerve can easily be blocked at the olecranon groove. Asmall volume of 0.25% bupivacaine with 1:200,000 epi-nephrine is injected into the area. Complications arenerve injury and compression of the nerve if an exces-sive volume of local anesthesia solution is used. Notethat the nerve is in a confined space here, and thisapproach should be used with caution.

Radial Nerve The patient’s position is supine with the elbow slightlyflexed. Landmarks are the biceps tendon and lateralcondyle of the humerus. Surface nerve mapping, ultra-sound, and the use of a nerve stimulator can aid correctplacement. The anesthetic dose is 1 to 2 mL of 0.25 to 0.5%bupivacaine, ropivacaine, or levobupivacaine. The lateralcondyle of the humerus and the tendon of the biceps mus-cle should be identified. The radial nerve lies adjacent tothe condyle, lateral to the biceps tendon. With the armslightly flexed at the elbow, the radial nerve can be stimu-lated with a mapping probe. Movement of the thumb con-firms the location of the radial nerve, and a small volumeof local anesthetic can be injected at that point.

Musculocutaneous NerveThe patient’s arm is either extended or on the abdomenand the landmark is the lateral condyle of the humerus.Surface nerve mapping, ultrasound, or a nerve stimulatorcan confirm this. The anesthetic dose is 1 to 2 mL of 0.25to 0.5% bupivacaine, ropivacaine, or levobupivacaine.The musculocutaneous nerve courses superficially alongthe lateral aspect of the forearm and can easily be



blocked in this location. A superficial ring of local anes-thetic injections (0.1 mL/kg) at the distal end of the lat-eral condyle of the humerus, along the pronator teresmuscle, should block the musculocutaneous nerve. Thenerve can be mapped along most of its course.

Wrist Blocks

Analgesia for children undergoing minor surgical proce-dures of the hand or fingers can be provided by anappropriate nerve block at the wrist. The nerves that canbe blocked at this level are the median, ulnar, and radialnerves. Small volumes of local anesthetic (1 to 2 mL) canprovide good analgesia for several hours.

Median NerveThe hand is pronated and the palmaris longus tendonand the volar aspect of the wrist are used as landmarks.Surface nerve mapping aids placement of the block.

An anesthetic dose of 0.5 to 1 mL of 0.25 to 0.5%bupivacaine, ropivacaine, or levobupivacaine is used.

The median nerve is the major nerve supplying thehand; most surgical operations of the hand will thereforerequire a median nerve block at least.

The median nerve is located in a fascial sheathbetween the palmaris longus tendon and the flexor carpiradialis. Surface nerve mapping with a nerve-stimulatingelectrode at this point will elicit opposition of the thumb.A bursa that communicates with the neurovascular bun-dle is located at the ulnar aspect of the palmaris longustendon. The median nerve can be blocked by injectinglocal anesthetic into this bursa.

Complications such as carpal tunnel syndrome orinjury to the median nerve are rare and can be avoidedby using the above technique or restricting the volumeof local anesthetic used.

Radial NerveThe hand is supinated. The landmarks are the anatomic“snuffbox,” styloid process, and radial artery. The anes-thetic dose is 1 to 2 mL of 0.25 to 0.5% bupivacaine, ropi-vacaine, or levobupivacaine.

The radial nerve at the wrist is purely sensory; thusnerve mapping is not possible here. Just above the sty-loid process, the radial nerve divides into two branches,one supplying the dorsum of the hand and the othersupplying the thenar eminence and 1.5 fingers.

The nerve is superficial proximal to the anatomicsnuffbox. A wheal of local anesthetic solution should beinjected subcutaneously, starting lateral to the radialartery on the lateral aspect of the wrist, using a fine(27-gauge) needle.

Ulnar NerveThe hand is supinated. The landmarks are the flexor carpiulnaris tendon and the ulnar artery. Surface nerve map-ping and the use of a nerve stimulator aid placement.

The anesthetic dose is 1 to 2 mL of 0.25 to 0.5%bupivacaine, ropivacaine, or levobupivacaine.

The ulnar nerve is located in the palmar sheathimmediately lateral to the flexor carpi ulnaris tendon butmedial to the ulnar artery. Surface nerve mapping with astimulator at this point will elicit flexion of the little finger.Using a fine needle, 1 to 2 mL of local anesthetic can beinjected into the area to provide analgesia for surgery onthe ulnar aspect of the hand and the medial 1.5 fingers.

� REGIONAL ANESTHESIA FOR THELOWER EXTREMITY

Most lower extremity operations can be performed witha caudal block, the most common block used in chil-dren. Some children, particular those of school age, findthe altered sensation and bilateral weakness associatedwith neuraxial blocks disturbing. Peripheral nerveblocks are more specific, can be confined to the site ofsurgery, and have a longer duration of analgesia.24–26

They also avoid the side effects of neuraxial blockade(bilateral motor weakness, urinary retention). For quickdischarge, peripheral nerve blocks are therefore betterthan caudal or other neuraxial blocks.

Anatomy of the Lumbarand Sacral Plexus

The motor and sensory innervation of the lower extremityis supplied by the lumbar plexus and the sacral plexus andis more complex than that of the upper extremity (see alsoChap. 29). The lumbar plexus is derived from the anteriorprimary rami of the lumbar nerves from L1 to L4 with avariable contribution from T12 and L5. It is located anteriorto the transverse processes of the lumbar vertebrae withinthe psoas major muscle. The psoas compartment is bor-dered posteriorly by quadratus lumborum and anteriorlyby psoas major muscles. The femoral nerve, lateral cuta-neous nerve of the thigh, and obturator nerve are branchesof the lumbar plexus and supply the majority of the upperleg, including the thigh and its lateral aspect (Fig. 31-1).The saphenous nerve, the largest sensory branch of thefemoral nerve, provides sensory innervation to the medialaspect of the leg below the knee and to the foot.

The sacral plexus is derived from the anterior pri-mary rami of L5, and S1 to S3 with contributions from L4and S4. The plexus lies anterior to the piriformis musclebehind the pelvic fascia on the posterior wall of the pelviccavity. The sciatic nerve, the largest nerve of the body, isderived from the sacral plexus and supplies the knee, theleg, and most of the foot except for the medial aspectsupplied by the saphenous nerve. A proximal branch ofthe sciatic nerve, the posterior cutaneous nerve of thethigh, supplies the posterior aspect of the thigh and thehamstring muscles.



Psoas Compartment BlockThe patient is placed in the lateral position with the hipsand knees flexed. The landmarks are the posterosupe-rior iliac spine, intercristal (Touffier’s) line, and spinousprocess L4.

A nerve stimulator and ultrasound aid placement ofthe block.

The anesthetic dose is 0.5 mL/kg of 0.25 to 0.5%bupivacaine, ropivacaine, or levobupivacaine.

The lumbar plexus can be blocked in the psoascompartment within the psoas muscle at the level of thetransverse process of L4. It provides a unilateral block ofthe thigh or hip for congenital dislocation of hip, thighfor open reduction and internal fixation of femoral frac-tures, or knee surgery.

TECHNIQUE

Several approaches that rely on bone contact with thetransverse process of L4 have been described in adults.In children, the transverse process is not fully devel-oped, and using it as a guide places the needle far toomedially and increases the risk of spinal anesthesia sec-

ondary to puncture of the dural cuff on the spinal rootsor retrograde epidural spread to the opposite side.

The approach that should be used in children is a mod-ification of Winnie’s approach.27 With the child in a lateralposition, an insulated needle should be inserted perpendic-ularly to the skin, where a line drawn from the posteriorsuperior iliac spine parallel to the spinous processes of thevertebrae crosses the intercristal (Touffier’s) line. The needleshould be advanced through the posterior lumbar fascia,paraspinous muscles, anterior lumbar fascia, quadratus lum-borum, and into the psoas muscle. Passage through thesefascial layers may be detected by distinct “pops” when ashort-beveled needle is used. With a nerve stimulator,quadriceps muscle twitches in the ipsilateral thigh will con-firm stimulation of the lumbar plexus. If hamstring contrac-tions are observed, the needle should be directed more lat-erally; if hamstring and quadriceps contractions are observedsimultaneously, the needle should be directed more cepha-lad to isolate the lumbar plexus rather than the sacral plexus.

The depth from the skin to the lumbar plexus isapproximately the same distance as the posterior supe-rior iliac spine is to the intercristal line.28 The depth of


FIGURE 31-1. Lower extremity dermatomes of the peripheral nerves in the infant.


the needle is emphasized because of the serious compli-cations associated with wayward needle advancementinto the peritoneum or retropritoneum, which may resultin renal hematoma, vascular puncture (retroperitonealhematoma), or even bowel puncture.

Ultrasound-guided psoas compartment blockade ispossible8 but is limited to younger children. In older chil-dren, the definition obtained with portable ultrasoundunits is inadequate for accurate placement.

If long-term pain relief is required, a catheter can beinserted for continuous infusion of a local anestheticsolution. After the initial block, an infusion rate of 0.2 to0.4 mg/kg/h should be adequate. Immobilization andfixation of these catheters on the back is simple and sub-cutaneous tunneling is not usually necessary because thelarge muscle mass anchors the catheter.

Femoral Nerve Block

The position is supine with the foot rotated outward. Thelandmarks are the femoral pulse and the inguinal ligament.Surface nerve mapping, ultrasound, and a nerve stimulatoraid placement. The anesthetic dose is 0.2 to 0.3 mL/kg of0.25 to 0.5% bupivacaine, ropivacaine, or levobupivacaine.

The femoral nerve blocks is probably the most com-mon peripheral nerve block performed in children, its mostuseful application being for fractured femurs,24,29,30 where itprovides for painless transport, radiographic examination,and application of splints. There are several large studies onthe use of femoral nerve blocks, alone or in combinationwith sciatic nerve or lateral cutaneous nerve of thigh block,for postoperative analgesia in lower limb surgery. For surgi-cal procedures on the knee, the femoral nerve block is bestused in combination with a sciatic nerve block.24,31

TECHNIQUE

The femoral nerve may be blocked where it emerges frombelow the inguinal ligament in the femoral canal lateral tothe femoral artery in the femoral triangle. The use of anerve stimulator can make femoral nerve block more suc-cessful, but the block can be done without it; e.g., for anunsedated child with a femoral fracture, so that paincaused by muscle contraction can be avoided.

With the child supine and the foot rotated outward, ashort-bevel or insulated needle should be insertedapproximately 0.5 to 1 cm lateral to the femoral artery pul-sation and approximately 0.5 to 1 cm below the inguinalligament. This distance will vary according to the size ofthe child; it is therefore better to map the course of thefemoral nerve before inserting the needle.6

The nerve lies beneath the fascia lata and fascia iliaca,and often two distinct “pops” are felt when a needlepierces these layers. Contraction of the quadriceps, a“patellar kick,” confirms femoral nerve stimulation andshould not be confused with direct stimulation of the sar-

torius muscle. Local anesthetic should be easy to inject intothe femoral canal. Resistance to injection suggests intra-neural injection; in such an instance the position of theneedle should be adjusted until the resistance is lost.Because of the close proximity of femoral vessels, inter-mittent aspiration for blood is obligatory before and duringfemoral nerve blockade. In the event of a femoral arterialpuncture, pressure should be applied for at least 5 min toprevent hematoma formation.

An appropriate catheter can be inserted into thefemoral canal for continuous infusion. After the initialblock, an infusion rate of 0.2 to 0.4 mg/kg/h should beadequate. The degree of analgesia obtained is depend-ent on the final position of the catheter. Immobilizationand fixation of these catheters on the thigh is relativelysimple, but subcutaneous tunneling may be necessary toreduce the risk of infection when long-term pain relief isrequired. Psoas abscess is a rare but serious complica-tion associated with femoral nerve catheters that to datehas been described only in adults.32

A “3 in 1” block is essentially a femoral nerve blockthat attempts to anesthetize the femoral nerve, lateralcutaneous nerve of the thigh, and obturator nerves withone injection. This is done by promoting retrogradespread of the local anesthetic within the femoral sheathup to the lumbar plexus by applying digital pressure dis-tal to the injection site and increasing the volume of thelocal anesthetic. The 3-in-1 block has been shown toanesthetize the femoral nerve 100 percent of the time,but it is only 20 percent effective in blocking all threenerves.33 To do this more reliably, a fascia iliaca or lum-bar plexus block should be employed.

Lateral Femoral Cutaneous Nerveof the Thigh

The patient is in the supine position. The landmarks arethe anterosuperior iliac spine and the inguinal ligament.Ultrasound aids the placement of the block. The anes-thetic dose is 1 to 3 mL of 0.25 to 0.5% bupivacaine, ropi-vacaine, or levobupivacaine.

The lateral cutaneous nerve of the thigh is derivedfrom the lumbar plexus (L2-L3) and is purely sensory,supplying the anterolateral aspect of the thigh for a vari-able distance down to the knee. The nerve descendsover the iliacus muscle just below the pelvic rim in anaponeurotic canal formed in the fascia lata and enters thethigh close to the anterosuperior iliac spine behind theinguinal ligament. In the thigh, it crosses or passesthrough the tendinous origin of the sartorius muscle. Itdivides into anterior and posterior branches.

Blockade of this nerve provides analgesia for platingof the femur, plate removal, drainage of femoral osteitis,harvesting of skin grafts, or obtaining muscle biopsies.



TECHNIQUE

A point 1 to 2 cm below and medial to the origin of theinguinal ligament at the anterosuperior iliac spine isidentified. A blunt needle should be inserted perpendi-cular to the skin until a “pop” is felt as the fascia lata ispenetrated and a second “pop” is felt when the fascia ili-aca is entered. If bone contact is made, the needleshould be withdrawn and redirected. Correct placementof the needle can also be determined with loss of resist-ance, which is noted when the fascia iliaca compartmentis entered. Alternatively, withdraw and redirect the nee-dle laterally and advance deep to the fascia lata in a fan-like manner, or direct the needle laterally in order tomake bone contact and deposit the local anesthetic justmedial to the anterosuperior iliac spine.

Fascia Iliaca Compartment Block

The patient is in the supine position. The landmarks are theanterosuperior iliac spine, the inguinal ligament, and thepubic tubercle. Ultrasound aids placement of the block.

The anesthetic dose is 0.5 to 1 mL/kg of 0.25 to 0.5%bupivacaine, ropivacaine, or levobupivacaine.

A fascia iliaca compartment block in children wasoriginally described by Dalens.33 It is more effective inblocking the femoral nerve, lateral cutaneous nerve ofthe thigh, and the obturator nerves than the 3-in-1 block,with a reported success rate of 90 percent, compared to20 percent for the 3-in-1 block.33 It is particularly usefulfor any surgery on the lower extremity above the kneeand for femoral shaft fractures.

The aim of a fascia iliaca compartment block is todeliver local anesthetic deep to the fascia iliaca andsuperficial to the iliacus muscle, where the three nervesof the lumbar plexus emerge from the psoas muscle.

With the child in the supine position and the thighslightly abducted and externally rotated, a line should bedrawn from the pubic tubercle to the anterosuperior iliacspine along the inguinal ligament. A short beveledneedle should be inserted perpendicular to the skin 0.5to 1 cm below the junction of the lateral and middlethirds of this line. Two “pops” are felt as the needlepierces the fascia lata and then the fascia iliaca. A slightloss of resistance may be detected if light pressure is heldon the plunger of the syringe. After a negative aspirationtest for blood, local anesthetic (0.5 to 1 mL/kg) may beinjected. Because the aim is to block all three nerves withone injection, larger volumes of local anesthetic solutionare required with this block than with many others.Massaging the area in an upward direction facilitates theupward spread of local anesthetic. A nerve stimulator isof no benefit, since there is no motor nerve that can bedirectly stimulated at the point of entry.

No significant complications have been described inassociation with a fascia iliaca compartment block if the

needle remains inferior to the inguinal ligament and awayfrom the femoral vessels. Some investigators have shownparticularly high blood levels of local anesthetic after a fas-cia iliaca compartment block, which could be explained bythe large surface area available for absorption.

Continuous infusions have been used for femorallengthening procedures, internal fixation of femoral frac-tures, and amputations. The degree of analgesia obtainedis dependent on the final position of the catheter. After theinitial block, an infusion rate of 0.2 to 0.4 mg/kg/h shouldbe adequate. Immobilization and fixation of thesecatheters on the thigh is simple.

Obturator Nerve

An isolated obturator nerve block is seldom performedto provide analgesia for orthopaedic surgery in children.However, the obturator nerve may be included with thelateral femoral cutaneous nerve and the femoral nerve ina 3-in-1 nerve block.33 The obturator nerve (L2-L4) sup-plies the motor innervation to the adductors of the legand sensory innervation to the medial portion of thelower thigh and knee joint. Blockade of this nerve can beconsidered for pain management after adductor tendonreleases in children with spastic cerebral palsy.

Sciatic Nerve Block

The sciatic nerve leaves the posterior pelvis through thegreater sciatic foramen and the piriformis muscle into thebuttock and descends down the midline of the back ofthe leg to the apex of the popliteal fossa. The sciaticnerve lies midway between the greater trochanter andthe ischial tuberosity at the gluteal cleft, where it is pal-pable in most young children.4 It divides into the com-mon peroneal and tibial nerves within the popliteal fossain the majority of children.34

The sciatic nerve can be blocked using several differ-ent approaches at the hip35–37 (anterior, posterior andlateral) or in the popliteal fossa.34 In children, the posteriorapproach is more popular than in adults because theirsmaller limbs are easily lifted. The chosen approach ulti-mately determines the distribution of motor and sensoryblockade. Block of the sciatic nerve at the gluteal level pro-vides anesthesia of the posterior aspect of the thigh (pos-terior cutaneous nerve of thigh) and leg below the kneebut excludes the medial aspect of the lower half of the leg,the medial malleolus, and the medial aspect of the foot.

Sciatic nerve block is suitable for all surgical proce-dures involving the posterior aspect of the leg, especiallybelow the knee—for example, in lengthening of theAchilles’ tendon and clubfoot repair as well as major footarthrodesis.4 Sciatic nerve block may need to be supple-mented with other blocks, depending on the type ofsurgery; this would, for example, be the case with kneesurgery or tibial osteotomies.



The different approaches to the sciatic nerve in chil-dren are described below.

Posterior Approach to theSciatic Nerve

The patient’s position is laterally recumbent with the hipand knee flexed. Landmarks are the coccyx, greatertrochanter, and ischial tuberosity. A nerve stimulator aidsin placement of the block. The anesthetic dose is 0.2 to0.3 mL of 0.25 to 0.5% bupivacaine, ropivacaine, or lev-obupivacaine.

TECHNIQUE

A modified posterior approach to the sciatic nerve iseasy to use and poses a low risk of complications. Withthe child in the lateral position, the side to be blockedshould be uppermost, with the leg flexed at the hip andknee (modified Sims position); a line is then drawn fromthe tip of the coccyx to the greater trochanter of thefemur. An insulated needle is inserted at the midpoint ofthis line and directed toward the ischial tuberosity.Nerve mapping is not possible, but a nerve stimulator,set at 0.3 to 0.4 mA, will elicit distal motor responses inthe leg, foot, or both (plantar- or dorsiflexion, inversionor eversion) and will confirm stimulation of the sciaticnerve (which supplies all the muscles below the knee).Careful aspiration should be performed before injectionof local anesthetic to avoid the risk of intravascularinjection.

Infragluteal Approach to theSciatic Nerve

The patient is in the supine or lateral decubitus positionwith the hip flexed and the knee extended.

Landmarks are the greater trochanter, ischialtuberosity, gluteal crease, and biceps femoris muscle. Anerve stimulator and ultrasound aid in placement of theblock.

The anesthetic dose is 0.2 to 0.3 mL of 0.25 to 0.5%bupivacaine, ropivacaine, or levobupivacaine.

TECHNIQUE

Raj37 described an approach that is particularly useful inchildren.4 With the hip flexed and knee extended, thesciatic nerve can be approached posteriorly by insert-ing a needle perpendicular to the skin at a point mid-way between the ischial tuberosity and greatertrochanter on the gluteal crease. With exaggerated hipflexion, the glutei may be flattened, so that the sciaticnerve becomes relatively superficial even in someobese children. The greater trochanter is not easilydefined in non-weight-bearing children, but the sciaticnerve may be palpable in the groove lateral to thebiceps femoris muscle in children.

An alternative approach that can also be applied inchildren has recently been described.36 The surface land-marks are the gluteal crease and the lateral border of thebiceps femoris muscle. An insulated needle is inserted atan angle of 70 to 80 degrees 1 cm distal to the glutealcrease along the lateral border of the biceps femorismuscle. The needle should be directed cephalad with ananterior orientation in the parasagittal plane.36

Plantarflexion, inversion, or dorsiflexion at 0.3 to 0.4 mAconfirms sciatic nerve stimulation. If bone contact ismade before a motor response is elicited, the needleshould be withdrawn and redirected. The posterior cuta-neous nerve of the thigh can be missed, since it may sep-arate more proximally in the thigh.

Posterior Midthigh Approachto the Sciatic Nerve

The patient’s position is supine, with the hip flexed andthe knee flexed or extended.

Landmarks are the ischial tuberosity and the head ofthe fibula. Surface nerve mapping, ultrasound, and anerve stimulator aid in placement of the block.

The anesthetic dose is 0.2 to 0.3 mL/kg of 0.25 to0.5% bupivacaine, ropivacaine, or levobupivacaine.

TECHNIQUE

An insulated needle is inserted perpendicular to the skinat the midpoint of a line drawn from the head of thefibula to the ischial tuberosity in the posterior thigh. Thenerve is surrounded by the hamstring muscles at thispoint, and this compartment can be detected using aloss of resistance technique as the needle tip emergesfrom the deep surface of the biceps femoris.38 A moreaccurate location of the nerve may be obtained by adistal motor response in the ankle or foot or simply thebig toe (plantarflexion, inversion, eversion, or dorsiflexion).The posterior cutaneous nerve of the thigh is missed atthis level.

Lateral Approach to the SciaticNerve at the Thigh

The patient’s position is prone, lateral, or supine. A nervestimulator aids placement of the block. The anestheticdose is 0.2 mL/kg of 0.25 to 0.5% bupivacaine, ropiva-caine, or levobupivacaine.

TECHNIQUE

An insulated needle is inserted 0.5 to 1 cm below thegreater trochanter and advanced toward the posteriorborder of the femur. With this approach, the broadestaspect of the nerve is targeted. If bone contact is made,the needle can be “walked off” the femur posteriorly orwithdrawn and redirected until muscle twitches areelicited in the lower leg or foot. Continuous catheters



have been placed using this technique, but their fixationis difficult unless the leg is immobilized.

Sciatic Nerve Block at thePopliteal Fossa

The patient’s position is prone, lateral, or supine. Thelandmark is the apex of the popliteal fossa. Surface nervemapping, ultrasound, and a nerve stimulator aid in place-ment of the block. The anesthetic dose is 1 to 2 mL of 0.25to 0.5% bupivacaine, ropivacaine, or levobupivacaine.

The sciatic nerve may be blocked where it coursesthrough the popliteal fossa behind the knee for opera-tions on the distal lower extremity.38–40 The boundariesof the popliteal fossa are formed by the semimembra-nosus and semitendinosus tendons medially, the bicepsfemoris tendon laterally, and the popliteal creasebetween the femoral condyles inferiorly.

Near the popliteal fossa, the sciatic nerve dividesinto two branches: the common peroneal and the poste-rior tibial nerves. The exact location of this divisionvaries, but in the majority of children it is within thepopliteal fossa.34,41 The common peroneal nerve thenruns laterally medial to the biceps femoris tendon beforepassing over the lateral head of the gastrocnemius mus-cle and around the head of the fibula. The posterior tib-ial nerve extends down the midline of the posterioraspect of the lower leg in close proximity but superfi-cially to the popliteal artery within the popliteal fossa.

Although the nerves branch, there is a commonepineural sheath that envelops both the posterior tibial andthe common peroneal nerves.40 For this reason a high rateof success can be achieved even when the motor responseof only one branch is elicited. Stimulation of the commonperoneal nerve will cause dorsiflexion and eversion of thefoot, while stimulation of the posterior tibial nerve will elicitinversion and plantarflexion of the foot. (Internal nerve;i.e., posterior tibial nerve results in inversion of the foot;external nerve; i.e., common peroneal nerve results in ever-sion of the foot.) The nerves are superficial enough to be“surface mapped” individually, particularly in young infants.

Various landmarks have been described for theinsertion of the needle. Konrad and Johr base their pointof insertion on the weight of the child. For each 10 kgbody weight, the needle insertion is moved 1 cm furtherabove the popliteal crease just lateral to the midline.34

Alternatively, an insulated needle may be inserted mid-way between the intercondylar line and the apex of thepopliteal fossa to block the posterior tibial nerve andthen directed laterally at the same level to block the com-mon peroneal nerve. In small children, the block canalso be performed with the patient lying supine by ele-vating the limb; in older children, this can be done byresting the foot on the operator’s shoulders while access-ing the popliteal fossa.

More recently, ultrasonography has been utilized todetermine the exact location of the bifurcation.41 With thisinformation, the nerves can be blocked individuallybelow the bifurcation or simultaneously above the bifur-cation of the sciatic nerve.24 Surface mapping may be usedin thin children to achieve similar results. Complicationsare rare, but care should be taken to avoid intravascularinjection (the popliteal artery lies deep to the nerves in thepopliteal fossa).

Lateral Approach to Sciatic Nerveat the Knee

The patient’s position is supine. The landmark is thebiceps femoris tendon. A nerve stimulator aids in place-ment of the block.


TECHNIQUE

A lateral approach to the popliteal fossa, originallydescribed in adults,25 has recently been described in chil-dren.42 The advantage of this approach is that it can beperformed on a supine patient. The biceps femoris ten-don is identified on the posterolateral aspect of the knee.A point 4 to 6 cm above the crease of the popliteal fossais identified. An insulated needle is then inserted anteriorto the biceps femoris tendon until it contacts the shaft ofthe femur. At this point, the needle is gently walked offthe femur posteriorly and, using a nerve stimulator, isslowly inserted until a motor response is elicited with acurrent of 0.3 to 0.4 mA. Dorsiflexion or plantarflexionalong with eversion is desirable. Careful aspiration forblood should be carried out to avoid intravascularinjection.

Anterior Approach to theSciatic Nerve

The patient’s position is supine. The landmarks are theanterosuperior iliac spine, pubic tubercle, and greatertrochanter. A nerve stimulator aids in placement of theblock. The anesthetic dose is 0.1 to 0.2 mL of 0.25 to0.5% bupivacaine, ropivacaine, or levobupivacaine.

TECHNIQUE

The anterior approach is less commonly used but has theadvantage that the patient need not be turned.43 Theneed for only one sterile area is a further advantage whenthis approach is combined with a femoral or saphenousnerve block for lower limb surgery.

A line drawn from the pubic tubercle to the anterosu-perior iliac spine (inguinal ligament) is divided into thirds. Aperpendicular line is then drawn from the junction of theinner and middle thirds onto a line drawn parallel to theinguinal ligament through the greater trochanter. Using a



nerve stimulator, an insulated needle is inserted perpendi-cular to the skin until contact is made with the femur of thefemur. The needle is then “walked off” the lesser trochanterposteriorly and advanced about 1 cm or until distal motorresponses are elicited. A loss of resistance can also bedetected as the needle passes through the posterior aspectof the adductor magnus muscle.43

Saphenous Nerve Block

The patient is supine and the landmarks are the femoralartery, sartorius muscle, and inguinal ligament. A nervestimulator and ultrasound are used to aid in placement ofthe block.

The anesthetic dose is 0.1 to 0.2 mL/kg of 0.25 to0.5% bupivacaine, ropivacaine, or levobupivacaine.

TECHNIQUE

The saphenous nerve runs along the medial aspect of thethigh just lateral to and within the same fascial sheath asthe motor nerve supplying the vastus medialis. The mainindication for blocking this nerve is to complement a sci-atic nerve block for surgery on the medial aspect of thelower limb or foot.

The nerve to the vastus medialis muscle can belocated using a nerve stimulator. With the child in thesupine position, an insulated needle is inserted perpen-dicularly to the skin 0.5 cm lateral to the point where thefemoral artery crosses the medial border of the sartoriusmuscle in the anterior thigh. Muscle twitches of the sar-torius muscle confirm the close proximity to the saphe-nous nerve at this level. The distance from the inguinalligament (3 to 5 cm) varies with age, as does the depthof the nerve (0.5 to 3 cm). An advantage of this blockover a femoral block is that motor activity in the remain-der of the quadriceps is spared.

The saphenous nerve is a purely sensory nerve atthe knee. It is therefore difficult to identify it with a nervestimulator, making blockade at this level unreliable. Atthe level of the tibial plateau, the saphenous nerve per-forates the fascia lata between the sartorius and gracilismuscles, where it lies subcutaneously in close proximityto the long saphenous vein.

A deep linear subcutaneous infiltration below andbehind the insertion of the sartorius tendon (medial sur-face of tibia) is performed where the nerve lies in a shal-low gutter immediately in front of the upper part of themedial head of the gastrocnemius muscle. Intermittentaspiration tests for blood will reduce the risk of injectioninto the long saphenous vein.

Ankle Block

The patient’s position is supine or prone. The landmarksare the medial and lateral malleolus, extensor hallucislongus tendon, Achilles’ tendon, and dorsalis pedis pulse.


An ankle block can be used for procedures con-fined to the foot, including distal phalangeal amputa-tions, foreign-body removal, and simple reconstructivesurgery including syndactyly or polydactyly repair. Theperipheral nerves blocked at this level are the terminalbranches of both the sciatic (posterior tibial, superficialperoneal, deep peroneal, and sural nerves) and femoral(saphenous) nerves. There is considerable variationin the branching and sensory distribution of thesenerves, and for this reason block of all five nerves isadvocated.

An ankle block is relatively easy to perform byinjecting local anesthetic solution subcutaneously in aring-like fashion at the ankle. It is important to avoidusing local anesthetics that contain epinephrine, sincethe end arteries in the foot may be compromised. Eachnerve should be blocked separately for best results(Figs. 28-1 to 28-3 and Fig. 31-1).

1. The tibial nerve innervates the sole of the footand medial aspect of the heel and is locatedbetween the medial malleolus and the calcaneumdeep to the flexor retinaculum immediately pos-terior to the posterior tibial artery. Local anes-thetic injected through a needle inserted posteri-orly and medially to the Achilles’ tendon anddirected toward the pulsation of the artery shouldblock the tibial nerve.

2. The superficial peroneal nerve supplies the dor-sum of the foot. A subcutaneous injection acrossthe dorsum of the foot between the lateralmalleolus and the extensor hallucis longus ten-don will block the nerve. Sometimes it is useful toperform this block with a 25-gauge spinal needle,since the entire block can be achieved by usingone needle puncture.

3. The deep peroneal nerve innervates the first webspace between the first and the second toe. A nee-dle is passed medial to the extensor hallucislongus tendon along the pulsation of the anteriortibial artery until contact with the tibia is made.The needle should then be withdrawn a few mil-limeters and the local anesthetic solution injected.

4. The sural nerve innervates the lateral aspect ofthe foot. A needle is introduced posteriorly andlaterally to the Achilles’ tendon between the lat-eral malleolus and the calcaneum until contactwith the calcaneum is made. The needle is thenwithdrawn a few millimeters and the local anes-thetic solution injected.

5. The saphenous nerve innervates the medialaspect of the ankle and foot and lies in closeproximity to the saphenous vein. It is located onthe medial side of the dorsum of the foot anterior



to the medial malleolus. A subcutaneous injec-tion of local anesthetic from the medial malleolusalong the anterior aspect of the ankle toward thesaphenous vein using a fine needle will effec-tively block the nerve.

� METHODS FOR PROLONGINGDURATION OF NERVE BLOCKS

Continuous Peripheral Nerve Blocks

Catheters for continuous peripheral nerve blocks havenot been readily available for use in children untilrecently (see also Chap. 20). A variety of improvisedmethods, some of which formed the basis for the devel-opment of the modern “designer” catheters, were used.As the appropriate equipment has become available, anincreasing number of reports of their use for continuouspostoperative pain management or therapeutic care havebeen published.19,23,30,44–50

The main indications for continuous blocks havebeen for children who undergo procedures, or have pro-cedures that are associated with significant or prolongedpostoperative pain44; or to improve peripheral perfusionin microvascular surgery or in vasospastic disordersinvolving the limbs. In selected cases, patient-controlledanalgesia is also feasible. Continuous infusions have alsobeen used to provide analgesia and to allow physicaltherapy in chronic regional pain syndromes. Blood lev-els reached during continuous brachial plexus infusionsare less than those attained during continuous epiduralanalgesia.

For the lower extremity, the main indication hasbeen the management of femoral fracture30,45 or majortrauma. Catheters have also been placed in the lumbarplexus (psoas compartment)46 or fascia iliaca compart-ments47 to provide unilateral analgesia of the hip orthigh. The psoas compartment block provides a morereliable block of all three nerves of the lumbar plexus.Fixation of the catheters for continuous use is consideredeasier on the lower extremity, particularly for psoas com-partment blocks.

Ideally, a commercially available kit should be used,since it allows a nerve stimulator to identify the correctnerve sheath before placement of the catheter. Severalmanufacturers now provide insulated Tuohy needles of“child friendly” length through which an appropriatesized catheter can be passed. Research on the role ofstimulating versus nonstimulating catheters for continu-ous peripheral nerve blocks is continuing.

Instead of stimulating catheters, one could improvisewith a modification of the Seldinger technique. With thistechnique, the nerve to be blocked is stimulated via aguidewire passed through a needle or intravenous can-nula. The needle is then removed and a catheter placed

over the wire or threaded through the cannula. Theseimprovised methods are very reliable for accuratecatheter placement; radiographic confirmation may berequired.

The dosage recommended for continuous infusionsafter an initial bolus dose are 0.1 to 0.2 mL/kg/h of eitherbupivacaine or levobupivacaine (0.125 to 0.25%) orropivacaine (0.15 to 0.2%). The lower rates are generallyused for upper extremity catheters and the higher ratesfor lower extremity plexus analgesia. The infusion ratemay be adjusted as needed up to the maximum rec-ommended rates of 0.2 mg/kg/h for infants less than6 months of age and 0.4 mg/kg/h in children older than6 months.48 Disposable infusion pumps, which may beprogrammed to deliver local anesthetic based on achild’s weight, are currently available and may offer anoption for pain control in outpatients in the future.49

To date the reported incidence of complications hasbeen low. They include catheter-induced infection, par-ticularly in immunocompromised patients, as well ashematoma formation, catheter breakage, or knot forma-tion on removal.

Additives and Adjuvants

Additives are used to prolong the duration of analgesiaand improve safety by reducing the dose of local anes-thetic required. By reducing the concentration, some ofthe unwanted side effects, such as motor blockade, canbe eliminated.

A variety of additives has been studied in adults; theseinclude opiates (morphine, fentanyl, sufentanil, buprenor-phine) ketamine, neostigmine, ketorolac, hyaluronidase,and clonidine. One of the advantages of regional anesthe-sia is the low incidence of nausea and vomiting, but thisadvantage is lost with some additives without any convinc-ing evidence that they enhance analgesia in acute pain.

Clonidine (0.5 to 1 mL/kg) may have a peripherallymediated effect. It seems to be effective in prolongingthe duration of the shorter-acting agents (e.g., mepiva-caine after single-injection peripheral nerve blocks) butis less effective when used with bupivacaine or ropiva-caine. Research in this area is ongoing, as the clinicalefficacy of peripheral clonidine remains unresolved.Studies in children are limited.51

� CAUDAL BLOCK

Caudal anesthesia is the most useful technique in chil-dren for operations below the umbilicus.52–55 Its popu-larity stems from its simplicity, safety, and efficacy in allpediatric age groups, and it is extensively used in con-junction with light general anesthesia for postoperativepain relief for orthopaedic procedures on the lowerextremities.



Anatomy

The sacral hiatus is formed as a result of failure of fusionof the fifth sacral vertebral arches. The remnants of thearch are represented by two prominences, the sacral cor-nua, on either side of the hiatus. The sacral cornua areapproximately 0.5 to 1 cm apart, depending on the ageof the child. The sacral hiatus extends from the sacralcornu to the fused arch of the fourth sacral vertebra. Thesacrococcygeal membrane covers the sacral hiatus, sep-arating the caudal space from the subcutaneous tissue.In some individuals, the fourth and even the third sacralvertebral arch may not be fused.

The sacral bones are not completely ossified inneonates and infants. The cortex of the sacral bones iswafer-thin and the risk of interosseus injection is high,particularly in this age group. Ossification of the sacrumstarts in the teens and is complete by the end of the sec-ond decade. As a result, a sacrointervertebral block canbe performed in young children, and this is a usefulalternative when the caudal approach is not possible.

There is considerable variation in the sacral hiatalanatomy, mainly due to incomplete posterior fusion ofthe sacral vertebrae and ossification that starts at aboutage 7. However, a few important surface landmarks needto be identified to enhance the success of the block inboth normal and abnormal sacra. The sacral hiatus lies atthe apex of an equilateral triangle that has the line drawnbetween the posterior superior iliac spines as its base.Furthermore a line drawn from the patella through thegreater trochanter with the hips flexed will transect a linedrawn down the vertebral column at the sacral hiatus.This landmark is useful when the sacral cornua are cov-ered by adipose tissue and difficult to identify, particu-larly toddlers and prepubertal children.

The distance between dural sac and the sacral hia-tus is extremely variable. The dural sac ends at S3-S4 innewborns and is usually situated at S2 in adults.Individual variation occurs and the dural sac may evenextend down into the caudal canal in 1 to 2 percent ofthe population.

The caudal space contains the cauda equina (sacralnerves), blood vessels, lymphatics, fat, and connectivetissue. The consistency of the fat and connective tissuevaries with age; the connective tissue is loose and the fatless gelatinous in infants and small children.

Technique

Caudal block is performed in the lateral decubitus posi-tion with both knees drawn up. The prone or knee-chestposition has also been described but is usually reservedfor small infants and neonates. The sacral hiatus and cor-nua are identified by palpation and feel similar to ametacarpal interspace. Under sterile conditions, a shortbeveled needle held gently between the thumb and

index finger is introduced at approximately 30 to 45 degreesto the skin (i.e., with the bevel parallel to the skin) at thesacral hiatus and advanced until it pierces the sacrococ-cygeal ligament. This can be detected by a distinct “give”as it enters the caudal epidural space and may be con-firmed by loss of resistance. Changing the angle andadvancing the needle as described in adults is unneces-sary. This maneuver would simply increase the risk ofdural puncture or a bloody tap without improving thesuccess of the block.

Styletted needles are considered mandatory in someinstitutions to reduce the risk of an epidermal inclusioncyst, which may be caused by introducing a skin pluginto the epidural space. Others prefer to use an intra-venous cannula.

Penetration of the sacrococcygeal membrane justabove the sacral cornua is associated with a lower inci-dence of bloody tap. The caudal space at this point isdeeper than below the cornua, where it narrows signifi-cantly and makes identification of the narrower spacedifficult. An approach that is too low is one of the com-monest reasons for failure.

Failure to obtain loss of resistance after the sacro-coccygeal ligament has been penetrated may indicatethat the bevel is lying directly up against the anterior wallof the caudal space. This may be overcome by simplyrotating the needle through 180 degrees.

Once the needle position is confirmed and aspirationfor blood and CSF has been negative, the appropriate vol-ume of local anesthetic can be injected. Confirming thecorrect placement of the caudal needle with the “whooshtest,” whereby the injection of air into the epidural spaceis confirmed by auscultation, is potentially dangerous (airembolus) and should be avoided.

A test dose has been advocated to detect the possi-bility of intravascular injection. The standard test dosecontains 0.5 to 1 µg/kg epinephrine and is defined as anincrease in heart rate (10 to 20 beats per minute) or sys-tolic blood pressure (10 percent) following intravenousinjection in awake patients. The reliability of the testdose is reduced under general anesthesia and variesunder different anesthetic conditions.

The use of epinephrine-containing solutions as atest dose in children under anesthesia may, but does notalways, produce an increase in heart rate when injectedintravascularly.58–61 Atropine administered prior to thetest dose improves reliability.Halothane, sevoflurane, andisoflurane attenuate the tachycardic response to epi-nephrine. Atropine administered prior to test dose mayimprove the sensitivity under halothane anesthesia.

Careful observation of the electrocardiogram (ECG),particularly an increase in T-wave amplitude, ST-segmentelevation, or any other arrhythmia, is more sensitive indetecting an intravascular injection of bupivacaine withepinephrine.62



Dosage

The most commonly used drugs for caudal block are bupi-vacaine,52,53,55 lignocaine,56 and more recently ropiva-caine57 and levobupivacaine.63 The most practical formulais that suggested by Armitage: 0.5 mL/kg of local anestheticfor sacrolumbar dermatomes, 1 mL/kg for lumbar thoracicdermatomes (subumbilical), and 1.25 mL/kg for midtho-racic dermatomes (upper abdominal), respectively.64

The duration of analgesia is dependent on the drugand dose administered, the age of the patient, the site ofsurgery, and whether epinephrine is used. Bupivacaine0.125 to 0.25% and ropivacaine 0.2% are effective for 4 to6 h of analgesia. Increasing the concentration does notoffer any additional advantage but may increase the inci-dence of motor blockade and urinary retention.65,66

Adjuvants

Various agents have been added to prolong the analgesiceffect of the local anesthetics or to reduce the side effectsduring caudal block. Opiates (morphine, fentanyl, sufen-tanil) are effective but unwanted side effects (pruritus,nausea and vomiting, and respiratory depression)have limited their use in the day care setting and promptedthe search for alternatives. Clonidine, an alpha2-adrenoreceptor agonist, has been shown to be effective.67,68

No significant hypotension and minimal sedation isapparent when the dose is limited to 1 to 2 µg/kg.Ketamine, an NMDA receptor antagonist, is also effectivein prolonging the duration of analgesia; 0.5 to 1 mg/kghas been used with minimal side effects.

Continuous Caudal Block

Continuous caudal catheter techniques are also used toprolong the duration of analgesia.69 Several kits are nowmarketed for caudal catheter placement. Essentially allthat is required is an intravenous cannula, which is intro-duced through the sacrococcygeal ligament and into thecaudal space; an epidural catheter can pass through thiscannula to facilitate the continuous infusion of localanesthetic agents.9 The catheter need only be introduceda short distance for surgery on the lower extremities.Because of its proximity to the anus, care must be takento protect the catheter site from fecal contamination. Toreduce the risk of contamination or infection, thecatheter should be removed after 48 to 72 h or if thedressings become soiled.

Complications

These are uncommon but are usually caused by mis-placement of the needle. Systemic toxicity may manifestas arrhythmia, cardiovascular collapse, or convulsionsfollowing accidental intravascular or sacral interosseousinjections. The incidence of bloody tap (2 to 10 percent)

varies with experience, the age of the patient, and theequipment used.

Urinary retention and delayed micturition arerelated not only to the duration of preoperative starva-tion but also to the concentration of the local anestheticsolution. The incidence is negligible when 0.25% bupi-vacaine or 0.2% ropivacaine or lower concentrationsare used. Motor blockade and inability to walk is alsoconcentration-dependent.

Total spinal anesthesia may occur following anundetected dural puncture. Supportive managementuntil the return of diaphragmatic function and sponta-neous respiration should be instituted. Nerve injury andneurologic defects have been reported but are extremelyuncommon following caudal blockade. Intrapelvic injec-tions have also been reported but should not occur.

� CONCLUSION

There are a variety of reasons why regional anesthesia,particularly peripheral nerve blocks, is advantageous forchildren who undergo elective or emergency orthopaedicsurgery. Regional anesthesia provides good pain reliefwithout the need for additional analgesia in both healthychildren as well as those with compromised respiratoryfunction or increased sensitivity to opiates (muscle disor-ders, mucopolysaccharidoses, cerebral palsy, kyphoscolio-sis). The reduction of unwanted side effects such as nauseaand vomiting can aid in the “fast tracking” (early discharge)of day-stay patients and improve the quality of care of hos-pitalized patients.

As better techniques are developed, the utilizationof peripheral nerve blocks in children should graduallyincrease. Surface nerve mapping and more recentlyportable ultrasound are promising developments. Theseshould encourage skilled practitioners to improve theirsuccess rates and inexperienced practitioners to developtheir skills.

Further development of continuous peripheralnerve blocks will enhance patient comfort for longer intothe postoperative period. Their use in children to datehas been confined to special circumstances. It is tooearly to judge the risk-benefit ratio, but it seems likelythat they will find a place, particularly in children withassociated diseases.

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