Handbook of Clinical Anesthesia

Chapter 38

Peripheral Nerve Blockade

Introduction

Regional anesthesia enables site-specific, long-lasting, and effective anesthesia and analgesia (Tsui BCH, Rosenquist RW: Peripheral nerve blockade. In Clinical Anesthesia. Edited by Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC. Philadelphia: Lippincott Williams & Wilkins, 2009, pp 955–1002). Peripheral nerve blocks (PNBs) can be used as the only anesthetic, as a supplement to provide analgesia and muscle relaxation along with general anesthesia, or as the initial step in the provision of prolonged postoperative analgesia such as with intercostal blocks or continuous peripheral nerve catheters.

  1. General Principles and Equipment

An exciting advance in technology in relation to regional anesthesia in recent years has been the introduction of anatomically based ultrasound imaging to visualize the target nerve. In many situations, it is prudent to combine the two technologies of nerve stimulation and ultrasound imaging to achieve the goal of 100% success with all regional blocks.

  1. Set-up and Monitoring(Table 38-1)
  2. Common Techniques: Nerve Stimulation
  3. Basics of Technique and Equipment.A low-current electrical impulse applied to a peripheral nerve produces stimulation of motor fibers and theoretically identifies proximity to the nerve without actual needle contact of the nerve or related patient discomfort.
  4. Practical Guidelines.After a low threshold response is obtained, 2 to 3 mL of local anesthetic is injected, and the operator watches for disappearance of the motor twitch, which is a signal to inject the remainder of the proposed dose in divided aliquots. After nerve localization using a stimulating needle, introduction

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of a stimulating catheter with continuous stimulation of the nerve is suitable for provision of continuous analgesia.

Table 38-1 Set-up and Monitoring for Regional Blocks

Set-up All supplies located in this area must be readily identifiable andaccessible to the anesthesiologist.
The area should be of ample size to allow block performance, monitoring, and resuscitation of patients.
There should be equipment for oxygen delivery, emergency airwaymanagement, and suction, and the area should have sufficientlighting.
A practically organized equipment storage cart is desirable andshould contain all of the necessary equipment (includingequipment required for emergency procedures).
A selection of sedatives, hypnotics, and intravenous anestheticsshould be immediately available to prepare patients for regionalanesthesia.
Emergency drugs (atropine, epinephrine, phenylephrine, ephedrine, propofol, thiopental, succinylcholine, amrinone, intralipid) should also be immediately available.
Monitoring
During the performance of regional anesthesia, it is vital tohave skilled personnel monitor the patient at all times(electrocardiography, noninvasive blood pressure, pulseoximetry, and level of consciousness of the patient shouldbe gauged frequently using verbal contact because vasovagalepisodes are common with many regional procedures).
The patient should be closely observed for systematic toxicity(within 2 minutes for at least 30 minutes after the procedure).
Before performing blocks with significant sympathetic effects, abaseline blood pressure reading should be obtained.

  1. Common Techniques: Ultrasound Imaging
  2. Basics of Technique and Equipment.Ultrasound images reflect contours, including those of anatomic structures, based on differing acoustic impedances of tissue or fluids. The Doppler effect can be very useful for identifying blood vessels during nerve localization using ultrasound guidance because many nerves are situated in close proximity to vascular structures.
  3. Practical Guidelines
  4. Probe sterility is paramount when performing real-time ultrasound guidance. For nerve localization

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during ultrasound-guided PNB, it is effective to first identify one or more reliable anatomical landmarks (bone or vessel) with a known relationship to the nerve structure (Table 38-2). The nerve structure is often placed in the center of the screen

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to guarantee that aligning the needle puncture with the center of the probe will ensure close needle tip–nerve alignment.

Table 38-2 Anatomical Landmarks for Localizing Nerves During Ultrasound-Guided Peripheral Nerve Blocks

Peripheral Nerve Block Location

Anatomical Landmark(s)

Approach for Ultrasound Imaging

Interscalene

Subclavian artery
Scalene muscles

Locate the plexus or trunk divisions superolateral to the artery at the supraclavicular fossa and trace proximally to where the roots or trunks lie between the scalenus anterior and medius muscles.

Supraclavicular

Subclavian artery

Scan from lateral to medial on the superior aspect of the clavicle to locate the pulsatile artery.
Plexus trunks or divisions lie lateral and often superior to the artery.
Color Doppler is useful.

Infraclavicular

Subclavian and axillary artery
Subclavian and axillary vein

Place the artery at the center of the field and locate the brachial plexus cords surrounding the artery.

Axillary

Axillary artery

Terminal nerves surround the artery.

Peripheral Nerves

Median nerve at the antecubital fossa

Brachial artery

The large anechoic artery lies immediately lateral to the nerve.

Radial nerve at the anterior elbow

Humerus at spiral groove
Deep brachial artery

Trace the nerve proximally and posteriorly toward the spiral groove of the humerus, just inferior to the deltoid muscle insertion (the nerve is adjacent to the deep brachial artery).

Ulnar nerve at the medial forearm

Ulnar artery

Scan at the anteromedial surface of the forearm approximately at the junction of its distal third and proximal two thirds to locate the ulnar nerve as it approaches the ulnar artery on its medial aspect.

Lumbar Plexus

Transverse processes

The plexus lies between and just deep to the lateral aspect (tips) of the processes.

Femoral

Femoral artery

The nerve lies lateral to the artery (vein most medial). See Fig. 38-11.

Sciatic

Classical

Ischial bone and inferior gluteal or pudendal vessels

The nerve lies lateral to the thinnest aspect of the ischial bone.
The inferior gluteal artery lies medial to and at the same depth as the nerve.

Subgluteal

Greater trochanter and ischial tuberosity

The nerve lies between the two bone structures.

Popliteal

Popliteal artery

Trace the tibial and common peroneal nerves from the popliteal crease to where they form the sciatic nerve.
At the crease, the tibial nerve lies adjacent to the popliteal artery.
Scanning proximally to the sciatic bifurcation, the artery becomes deeper and at a greater distance from the nerve.

Ankle

Tibial (posteriortibial)

Posterior tibial artery

The nerve lies posterior to the artery.

Deep peroneal

Anterior tibial artery

The nerve lies lateral to artery

  1. After one observes that the needle is seen to be close to the nerve(s), a 1- to 2-mL test dose of local anesthetic or D5W can be injected to visualize the spread. The solution will be seen as a hypoechoic expansion and often illuminates the surrounding area, enabling better visibility of the nerves and block needle.
  2. Other Related Equipment
  3. Needlesused for regional techniques are often modified from standard injection needles (continuous blocks require larger bore needles to facilitate catheter introduction).
  4. Cathetersamenable to stimulation (with an electrode placed into the catheter tip) may enable more accurate advancement of catheters for substantial distances to provide continuous analgesia.
  5. Avoiding Complications.Despite the excellent safety record of regional anesthesia, the incidence of some complications may be higher in PNB than other regional anesthesia or analgesia techniques, and these complications can be devastating. Choosing a suitable patient and applying the right dose of local anesthetic in the correct location are the primary considerations. Follow-up before and after discharge is equally important.
  6. Specific Techniques: Head and Neck, Upper Extremities, Chest, and Abdomen
  7. Head and Neck(Figs. 38-1, 38-2, 38-3 and 38-4)
  8. Cervical Plexus Blocks.Anesthesia of the deep or superficial cervical plexus or both can be used for procedures of the lateral or anterior neck such as parathyroidectomy and carotid endarterectomy. In carotid surgery, local infiltration of the carotid bifurcation may be necessary to block reflex hemodynamic changes associated with glossopharyngeal stimulation.
  9. Occipital Nerve Blocks.The greater and lesser occipital nerves can be blocked by superficial injection at the points on the posterior skull where they emerge from below the muscles of the neck. This block is rarely used for surgical procedures; it is more often

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applied as a diagnostic step in evaluating complaints of head and neck pain.

 

Figure 38-1. Schematic of the cervical plexus, which arises from the anterior primary rami of C2–C4. The motor branches (including the phrenic nerve) curl anteriorly around the anterior scalene muscle and travel caudad and medially to supply the deep muscles of the neck. The sensory branches exit at the lateral border of the sternocleidomastoid muscle to supply the skin of the neck and shoulder.

  1. Upper Extremity (Figs. 38-5, 38-6 and 38-7). The four anatomic locations where local anesthetics are placed are the (1) interscalene groove near the cervical transverse processes, (2) subclavian sheath at the first rib, (3) near the coracoid process in the infraclavicular fossa, and (4) surrounding the axillary artery in the axilla. Ultrasound imaging and nerve stimulation have greatly facilitated the use of upper extremity regional anesthesia. The

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terminal branches can also be anesthetized by local anesthetic injection along their peripheral course as they cross joint spaces, where they lie in close proximity to easily identifiable structures or by the injection of a dilute local anesthetic solution intravenously below a pneumatic tourniquet on the upper arm (“intravenous regional” or Bier block) (see Table 38-2).

 

Figure 38-2. Needle insertion points and angles for the deep cervical plexus blockade. The nerve roots exit the vertebral column via the troughs formed by the transverse processes. The needle is inserted at each nerve roots of C2–C4 in caudad and posterior direction.

 

Figure 38-3. The cervical, thoracic, lumbar, and sacral dermatomes of the body.

 

Figure 38-4. Greater and lesser occipital nerve distribution, supply, and block needle insertion sites.

  1. Brachial Plexus Blockade(Table 38-3)
  2. Terminal Upper Extremity Nerve Blocks.PNBs in the upper extremity are of particular value as rescue blocks to supplement incomplete surgical anesthesia and to provide long-lasting selective analgesia in the postoperative period. The peripheral nerves may be individually blocked at mid-humeral, elbow, or wrist locations, depending on the specific nerve. If using ultrasound guidance, the elbow and forearm regions appear to be the most suitable block regions, and blocks at these sites

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may improve the accuracy of nerve localization and local anesthetic spread. The wrist is highly populated with tendons and fascial tissues (flexor and extensor retinaculae), which can be difficult to distinguish from, and may obscure the images of, the nerves. Color Doppler combined with ultrasonography can be used to clearly identify the nerves at many desirable locations because they are often situated near blood vessels (see Table 38-1 and Figs. 38-7 and 38-8).

 

Figure 38-5. Schematic of the brachial plexus. Many branches, including the medial cutaneous nerves of the forearm and arm, which arise from the medial cord, are not shown here.

  1. Intravenous Regional Anesthesia (Bier Block).Arm anesthesia can be provided by the injection of local anesthetic into the venous system below an occluding tourniquet without using ultrasonography or nerve stimulation (Table 38-4).
  2. Intercostal Nerve Blockade.Anesthesia of the intercostal nerves provides both motor and sensory anesthesia of the abdominal wall from the xiphoid to the pubis. These

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nerve blocks involve injections along the easily palpated abrupt posterior angulation of the ribs, which occurs between 5 and 7 cm from the midline in the back. The anesthesiologist's other hand inserts a needle (22 gauge, 3.75 cm) directly onto the rib, maintaining a constant 10° cephalad angulation. After contact is made with the rib, the cephalad traction is slowly released, the cephalad hand takes over the needle and syringe, and the needle is allowed to “walk” down to below the rib at the same angle. The needle is then advanced approximately 4 mm under the rib. After it is in the groove, aspiration

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is performed, and 3 to 5 mL of a local anesthetic solution is injected. Generally, the intercostal nerves are well localized with the blind landmark-based technique. Alternatively, the rib can be easily visualized with the use of ultrasonography.

 

Figure 38-6. Courses of the terminal nerves of the upper extremity. The posterior view (A) illustrates the branches from the posterior cord (axillary and radial nerves), and the anterior view. (B) illustrates the branches from the lateral (musculocutaneous and median nerves) and medial (median and ulnar nerves) cords.

 

Figure 38-7. Cutaneous innervation of the upper extremity nerves.

Table 38-3 Techniques for Brachial Plexus Blockade

Interscalene Block
This block frequently spares the lowest branches of the plexus, the C8 and T1 fibers (which innervate the caudad [ulnar] borderof the forearm).
Pneumothorax should be considered if cough or chest pain isproduced while exploring for the nerve (cupola of the lungnear block site).
Direct injection into the vertebral artery can rapidly producecentral nervous system toxicity and convulsions.
Supraclavicular Block
The midpoint of the clavicle is identified. The subclavian arterypulse serves as a reliable landmark in thinner individuals becausethe plexus lies immediately cephaloposterior to the subclavianartery.
Ultrasound imaging and nerve stimulation help avoid puncturing the pleura. There is a risk of pneumothorax because the cupolaof the lung lies just medial to the first rib; risk of pneumothoraxis greater on the right side because the cupola of the lung ishigher on that side; the risk is also greater in tall, thin patients.
Infraclavicular Block
This block provides excellent analgesia of the entire arm (blocksthe musculocutaneous and axillary nerves more consistently)and allows introduction of continuous catheters to provideprolonged postoperative pain relief.
There is a lower risk of blocking the phrenic nerve or stellateganglion.
Vessel puncture is a potential complication.
Lateral needle insertion helps avoid the risk of pneumothorax.
Axillary Block
This block is useful for surgery of the elbow, forearm, and hand(the musculocutaneous nerve may be blocked separately).
This block is associated with minimal complications (neuropathyfrom needle puncture or intraneural injection of local anesthetic).

  1. Paravertebral Block.This block technique is useful for segmental anesthesia, particularly of the upper thoracic segments. It is also useful if a more proximal (central) blockade than that of the intercostal nerves is needed,

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such as to relieve the pain of herpes zoster or of a proximal rib fracture.

 

Figure 38-8. Probe placement (A) and ultrasound image (B) during paravertebral block in the thoracic spine. The probe is first placed in the midline of the spine to capture a transverse view of the vertebral and costal (if thoracic spine) elements. L = lamina; S = spinous process; T = transverse process.

Table 38-4 Intravenous Regional Anesthesia

A small-gauge (20- or 22-gauge) intravenous catheter is placedand taped on the dorsum of the hand in the arm to be blocked.
The arm is elevated to promote venous drainage (an Esmarchbandage is used).
After exsanguination, the tourniquet is inflated to 300 mm Hgor 2.5 times the patient's systolic blood pressure.
A 50-mL syringe with 0.5% lidocaine is attached to the previouslyinserted cannula, and the contents are injected slowly.
For short procedures, the cannula can be removed at this point, but if surgery may extend beyond 1 hour, the cannula can beleft in place and reinjected after 90 minutes.
Beyond 45 minutes of surgery, many patients experiencediscomfort at the level of the tourniquet (double-cuff tourniquetsalleviate this problem).
If surgery is completed in less than 20 minutes, the tourniquet isleft inflated for at least that total period of time.
If 40 minutes has elapsed, the tourniquet can be deflated as asingle maneuver.
Between 20 and 40 minutes, the cuff can be deflated, reinflatedimmediately, and finally deflated after 1 minute to delay thesudden absorption of anesthetic into the systemic circulation.
The duration of anesthesia is minimal beyond the time oftourniquet release.

  1. Inguinal Nerve Block.This block is performed easily with blind technique, although ultrasound imaging may be performed to help improve the success rate. Side effects include systemic toxicity and transient femoral nerve palsy.
  2. Penile blockis used in children and adults for surgical procedures of the glans and shaft of the penis.

III. Specific Techniques: Lower Extremity

Combined blocks of the lumbar and sciatic plexuses provide effective surgical anesthesia to the entire lower extremity (Figs. 38-3, 38-4, 38-5, 38-6, 38-7, 38-8, 38-9 and 38-10).

  1. Terminal Nerves of the Lumbar Plexus(Table 38-5)
  2. Sacral Plexus: Formation and Branches.The anterior primary rami of S1–S4 join the lumbosacral trunk to form the sacral plexus (Fig. 38-9).
  3. Sciatic, Tibial, and Common Peroneal Nerves.At a variable distance within the posterior thigh (often high in the popliteal fossa), the sciatic nerve bifurcates into common peroneal and tibial nerves.
  4. Nerves at the Ankle.By the time the femoral, tibial, and common peroneal nerves reach the ankle, five branches cross this joint to provide innervation for the skin and muscles of the foot (Table 38-6) (Fig. 38-10).
  5. Psoas Compartment Block.This block has the advantage of blocking the entire lumbar plexus and therefore provides anesthesia/analgesia of the anterolateral and medial thigh, the knee, and the cutaneous distribution of the saphenous nerve below the knee.
  6. Separate Blocks of the Terminal Nerves of the Lumbar Plexus.Anesthesia can be performed for four terminal nerves (lateral femoral cutaneous, femoral, obturator, and saphenous), although a lumbar plexus block is preferable if anesthesia of all these nerves is required.
  7. Anesthesia of the lateral femoral cutaneous nerve is occasionally used to provide sensory anesthesia for obtaining a skin graft from the lateral thigh. It can also be blocked as a diagnostic tool to identify cases of meralgia paresthetica.
  8. Obturator nerve block can be effective to prevent obturator reflex during transurethral bladder tumor resections, for treatment of pain in the hip area, for

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adductor spasm (as seen in multiple sclerosis patients), or as a diagnostic tool when studying hip mobility.

 

Figure 38-9. The lumbar (A; L1–L4) and sacral (B; L4–S4) plexuses.

 

Figure 38-10. Cutaneous innervation from the terminal nerves of the lower extremity.

Table 38-5 Terminal Nerves of the Lumbar Plexus

Genitofemoral Nerve (L1–L2)
Innervates the skin immediately below the crease of groin anteriorto the upper part of the femoral triangle
Lateral Cutaneous Nerve of the Thigh (lateral femoral cutaneousnerve; L2–L3)
Supplies skin over the anterolateral aspect of the thigh and skinon the lateral aspect of the thigh from the greater trochanter tothe mid-thigh branches
Femoral Nerve (L2–L4)
Largest nerve of the lumbar plexus, supplying muscles and skinon the anterior aspect of the thigh
Lies slightly deeper (0.5 to 1.0 cm) and lateral (approximately1.5 cm) to the femoral artery (VAN is the mnemonic for theanatomical relationship, starting medially)
Obturator Nerve (L2–L4)
Divides into its anterior and posterior branches near the obturatorforamen

Table 38-6 Nerves at the Ankle

Deep peroneal nerve (L5–S1)
Tibial nerve (posterior tibial nerve, (S1–S3)
Superficial peroneal nerve
Sural nerve
Saphenous nerve

  1. Procedures on the knee require anesthesia of the femoral and obturator nerves, although postoperative analgesia of the knee can usually be provided by femoral nerve block alone.
  2. Femoral nerve block is used extensively for analgesia (Fig. 38-11).
  3. Sciatic Nerve Blockade Using Posterior, Anterior, and Posterior Popliteal Approaches.A sciatic nerve block can be used with lumbar plexus block for anesthesia of the lower extremity. Together with saphenous nerve block, the block produces adequate anesthesia to the sole of the

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foot and the lower leg. The sciatic nerve is deep within the gluteal region and may be difficult to locate blindly or with ultrasonography. Of benefit during ultrasound-guided blockade of the sciatic nerve and its terminal branches (tibial and common peroneal nerves) are the numerous bony and vascular landmarks that can be used for ease of identification (Fig. 38-12).

 

Figure 38-11. Ultrasound-guided femoral nerve block. A. The probe is placed in a slightly oblique plane (at the level of and parallel to the inguinal crease) to capture the nerve in short-axis lateral to the femoral artery (FA). B. The needle is seen (not shown) as it transects the fascia lata and iliaca. The dotted line indicates the femoral nerve.

 

Figure 38-12. Landmarks for the sciatic nerve block using a posterior gluteal approach when a nerve stimulation procedure is used. This location will serve as a reference point when applying ultrasound imaging. The asterisk indicates the approximate location of the sciatic nerve. PSIS = posterior superior iliac spine.

  1. Ankle Block.All five nerves of the foot can be blocked at the level of the ankle. The superficial nerves (sural, superficial peroneal, and saphenous nerves) can be blocked by simple infiltration techniques. Ultrasound guidance can be useful for blocking the posterior tibial and deep peroneal (fibular) nerves because their locations can be easily identified next to reliable landmarks (bones and vessels) that are clearly visible.

Editors: Barash, Paul G.; Cullen, Bruce F.; Stoelting, Robert K.; Cahalan, Michael K.; Stock, M. Christine

Title: Handbook of Clinical Anesthesia, 6th Edition

Copyright ©2009 Lippincott Williams & Wilkins

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