Ovid: Peripheral Nerve Blocks: A Color Atlas

Terminal Nerve Blocks

A. Axillary Block

Ralf E. Gebhard

Patient Position: Supine, with the arm abducted at 90° to 110° at the shoulder and flexed 90° at the elbow.

Indications: Anesthesia and postoperative analgesia for surgery at the elbow and below (hand and forearm).

Needle Size: 22-gauge, 50-mm insulated needle.

Volume: 40 mL of a mixture of 0.5% ropivacaine and 1.5% mepivacaine v/v.

Anatomic Landmarks: Axillary artery in the middle portion of the axilla.

Approach and Technique: The axillary artery pulse is palpated and marked in the middle of the axilla. After disinfection, sterile draping, and local infiltration with 1% lidocaine, a 50-mm insulated needle connected to a nerve stimulator (1.5 mA, 2 Hz, 0.1 ms) is inserted above the artery, pointing in a proximal direction almost parallel to the artery at a 30° to 45° angle to the skin (Fig. 8-1A). After identification of a median nerve response (flexion of the fingers and the wrist) at a current below 0.5 mA, 15 mL of local anesthetic is injected slowly (10 mL/min) and in 5-mL increments. The 50-mm insulated needle is then withdrawn from the skin and redirected toward the coracobrachialis muscle (Fig. 8-1B). After identifying a musculocutaneous nerve response (biceps contraction, flexion of the elbow) at a current below 0.5 mA, 10 mL of local anesthetic is injected slowly (10 mL/min) and in 5-mL increments. The 50-mm insulated needle is then completely withdrawn and reinserted below the artery 45° to the skin and to the artery (Fig. 8-1C). After identification of a radial nerve response (extension of the fingers and the wrist) at a current below 0.5 mA, 15 mL of local anesthetic is injected in the same fashion as for the two other nerves. The

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axillary block is completed by a subcutaneous infiltration at the medial aspect of the upper arm at a high humeral level to block intercostobrachial nerve fibers.

Figure 8-1. A. Indicating an Axillary artery response, B. Indicating a Musculocutaneous nerve response and C. Indicating a Radial nerve response.

Tips

A separate stimulation and injection of the ulnar nerve has been shown to be unnecessary for a complete axillary block. if an ulnar nerve response (adduction of the thumb and the little finger) is encountered during the performance of an axillary block, 5 to 10 mL of local anesthetic can be injected after the response is maintained below 0.5 mA.
If one of the nerves is not completely blocked with this approach, the block can be easily completed by an injection at the midhumeral or elbow level after stimulating the nerve in question.
The radial nerve is probably the most difficult nerve to stimulate and block when performing an axillary block. Injecting after eliciting a distal twitch (wrist or finger extension) has been demonstrated to yield a higher success rate than accepting a proximal twitch (forearm extension).

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Distal digital pressure has been shown not to promote proximal local anesthetic spread and is therefore not necessary.
Axillary blocks significantly reduce the incidence of complex regional pain syndrome after Dupuytren's contracture surgery, when compared with general anesthesia or intravenous regional anesthesia with lidocaine.

Suggested Readings

Horlocker TT, Kufner RP, Bishop AT, et al. The risk of persistent paresthesia is not increased with repeated axillary block. Anaesth Analg 1999;88:382–387.

Koscielniak-Nielsen ZJ, Rotboll Nielsen P, Sorenson T, et al. Low dose axillary block by targeted injections of the terminal nerves. Can J Anaesth 1999;46:658–664.

Reubben SS, Pristas R, Dixon D, et al. The incidence of complex regional pain syndrome after fasciectomy for Dupuytren's contracture: a prospective observational study of four anesthetic techniques. Anesth Analg 2006;102:499–503.

Schroeder LE, Horlocker TT, Schroeder DE. The efficacy of axillary block for surgical procedures about the elbow. Anesth Analg 1996;83:747–751.

Sia S, Bartoli M. Selective ulnar nerve stimulation is not essential for axillary plexus block using a multiple stimulation technique. Reg Anesth Pain Med 2001;26:12–16.

Sia S, Lepri A, Magherini M, et al. A comparison of proximal and distal radial nerve motor responses in axillary block using triple stimulation. Reg Anesth Pain Med 2005;30:458–463.

Sia S, Lepri A, Ponzecchi P. Axillary brachial plexus block using peripheral nerve stimulator: a comparison between double- and triple-injection techniques. Reg Anesth Pain Med 2001;26:499–503.

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B. High Humeral Block

Louis-Jean Dupre

Patient Position: Supine, with the arm abducted at 90° and the forearm extended.

Indications: Surgery at or below the elbow.

Needle Size: 22-gauge, 50-mm b-beveled insulated needle.

Volume: 5 to 8 mL per nerve.

Anatomic Landmarks: Upper one-third of arm and the brachial artery. At the level of the brachial canal, the median, ulnar, radial, and musculocutaneous nerves are dispersed around the brachial artery (Fig. 8-2). The median nerve usually runs anterior and superior to the brachial artery, while the musculocutaneous nerve runs posterior and superior to the median nerve in a groove between the biceps and coracobrachialis muscle. The ulnar nerve runs medial to the brachial artery, and the radial nerve runs medial and posterior, between the triceps muscle and the medial border of the humerus. The closer to the elbow, the more separated are the nerves.

Figure 8-2. At the level of the brachial canal, the median, ulnar, radial, and musculocutaneous nerves are dispersed around the brachial artery.

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Approach and Technique: First, a line is drawn over the brachial artery. Then, a 22-gauge, 50-mm insulated needle connected to a nerve stimulator (2 mA, 2 Hz, 0.1 ms) is introduced almost tangentially to the skin, between the brachial artery and the palpating finger of the anesthesiologist, in the direction of the axilla in search of the median nerve. The stimulation of the median nerve (Fig. 8-3A) induces a contraction of the flexor carpi radialis and flexor digitorum superficialis of the fingers (flexion of the fingers). Once this response is obtained, the position of the needle is adjusted to maintain the same motor response with a current of 0.3 to 0.5 mA. Then, 8 mL of local anesthetic is injected slowly. Next, the needle is withdrawn to the skin, the current

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is increased to 5 mA, and the needle is redirected in search of the ulnar nerve (Fig. 8-3B). The stimulation of the ulnar nerve induces a contraction of the flexor carpi ulnaris (flexion of the little finger and opposition of the little finger and thumb). Once this response is obtained, the position of the needle is adjusted to maintain the same motor response with a current of 0.3 to 0.5 mA. Then, 8 mL of local anesthetic is injected slowly. Next, the needle is withdrawn to the skin, the current is increased to 5 mA, and the needle is redirected in search of the radial nerve (Fig. 8-3C). The stimulation of the radial nerve induces a contraction of the extensor muscles, including the extensor radialis (extension of the fingers and especially the thumb). Once this response is obtained, the position of the needle is adjusted to maintain the same motor response with a current of 0.3 to 0.5 mA. Then, 8 mL of local anesthetic is injected slowly. To block the musculocutaneous nerve, the needle is withdrawn to the skin and reintroduced in a superior and posterior direction toward the coracobrachialis muscle. The stimulation of the musculocutaneous nerve (Fig. 8-3D) induces contraction of the biceps muscle (flexion of the forearm). Once this response is obtained, the position of the needle is adjusted to maintain the same motor response with a current of 0.3 to 0.5 mA (Fig. 8-4). Then, 5 mL of local anesthetic is injected slowly. After disconnection of the nerve stimulator, 3 mL of local anesthetic is injected subcutaneously medially and laterally to the brachial artery to block the medial cutaneous nerve of the arm and the medial cutaneous nerve of the forearm.

Figure 8-3. An insulated needle connected to a nerve stimulator is introduced almost tangentially to the skin between the brachial artery and the palpating finger of the anesthesiologist, in the direction of the axilla in search of the median nerve.

Figure 8-4. Once the stimulation of the musculocutaneous nerve induces contraction of the biceps muscle, the position of the needle is adjusted to maintain the same motor response.

Tips

The intensity of the sensory block of the musculocutaneous nerve is tested on the lateral aspect of the forearm (Fig. 8-5B), while that of the radial nerve is tested on the posterior aspect of the forearm and hand, that of the ulnar nerve is tested on the medial aspect of the hand (Fig. 8-5C) and little finger, and that of the median nerve is tested on the palmar side of the hand and of the second and third fingers (Fig. 8-5A).
The onset of the block with ropivacaine occurs within 5 to 15 minutes.
This approach allows the different nerves to be blocked separately with only one cutaneous puncture point.
The high humeral block can be performed safely, effectively, and with a high success rate.
If the block is incomplete in one or more territories, it may be completed at the elbow or wrist.

The learning curve is steep. Speed and success increase quickly after only a few blocks.

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Figure 8-5. The intensity of the sensory block of the musculocutaneous nerve is tested on the lateral aspect of the forearm, while that of the radial nerve is tested on the posterior aspect of the forearm and hand, that of the ulnar nerve is tested on the medial aspect of the hand and little finger, and that of the median nerve is tested on the palmar side of the hand and of the second and third fingers.

The sequence in which the nerves are blocked is not important.
This approach also allows only the nerves required to produce anesthesia in the surgical territory to be blocked (hyperselective blocks).
A block of different onset and duration can be achieved by injecting at the level of each nerve a different local anesthetic solution.

Suggested Readings

Bouaziz H, Narchi P, Mercier FJ, et al. Comparison between conventional axillary block and a new approach at the midhumeral level. Anesth Analg 1997;84:1058–1067.

Bouaziz H, Narchi P, Mercier FJ, et al. The use of selective axillary nerve block for outpatient hand surgery. Anesth Analg 1998;86:746–748.

Carles M, Pulcini A, Macchi P, et al. An evaluation of the brachial plexus block at the humeral canal using a neurostimulator (1417 patients): the efficacy, safety, and predictive criteria of failure. Anesth Analg 2001;92:194–198.

Dupré L-J. Bloc du plexus brachial au canal huméral. Cah Anesthésiol 1994;42:767–769.

Gaertner E, Kern O, Mahoudeau G, et al. Block of the brachial plexus branches by the humeral route: a prospective study in 503 ambulatory patients. Proposal of a nerve blocking sequence. Acta Anesthesiol Scand 1999;43:609–613.

Iskandar H, Guillaume F, Dixmerias F, et al. The enhancement of sensory blockade by clonidine selectively added to mepivacaine after midhumeral block. Anesth Analg 2001;93;771–775.

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C. Blocks at the Elbow

Jacques E. Chelly

Patient Position: The patient is placed in the supine position.

Indications: Anesthesia and immediate postoperative analgesia for forearm, wrist, and hand surgery. To complete the block of a nerve performed at the axilla or with a high humeral approach.

Needle Size: 24-gauge, 25-mm insulated needle.

Volume: 5 to 7 mL per nerve.

Anatomic Landmarks (Fig. 8-6): The median nerve is just medial to the brachial artery. The radial nerve is just lateral to the biceps tendon at the intercondylar fold. It is important to recognize that the radial nerve divides into a sensory and motor branch 2 to 3 cm before the elbow crease. At the elbow, the ulnar nerve runs between the medial epicondyle of the humerus and the olecranon process of the radius in the ulnar groove.

Approach and Technique: For the median and radial nerves, the patient's arm is supinated and abducted 90° at the shoulder.

Median Nerve Block

The brachial artery is palpated and marked. With a finger on the brachial artery pulse, the insulated needle connected to a nerve stimulator (1.5 mA, 2 Hz, 0.1 ms) is introduced

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immediately medial to the brachial artery at a depth of 1.0 to 1.5 cm in search of a stimulation of the median nerve (flexion of the first three fingers) (Fig. 8-7). The position of the needle is adjusted to maintain the motor response with a current less than 0.5 mA. After negative aspiration for blood, the local anesthetic solution is injected slowly.

Figure 8-6. Anatomic landmarks.

Figure 8-7. Median nerve block.

Radial Nerve Block

The lateral border of the biceps tendon is identified and marked. The insulated needle connected to a nerve stimulator (1.5 mA, 2 Hz, 0.1 ms) is introduced 2.0 to 2.5 cm lateral to the biceps tendon at least 3 cm cephalad from the elbow crease in search of a stimulation of the radial nerve (extension of the thumb) (Fig. 8-8). The position of the needle is

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adjusted to maintain the motor response with a current less than 0.5 mA. After negative aspiration for blood, the local anesthetic solution is injected slowly.

Figure 8-8. Radial nerve block.

Ulnar Nerve Block

The arm is abducted 90° at the shoulder, and the forearm is flexed approximately 60°. The medial epicondyle of the humerus and the olecranon process are identified along with the ulnar groove. A 25-mm insulated needle connected to a nerve stimulator (1.5 mA, 2 Hz, 0.1 ms) is introduced 2 to 3 cm cephalad to the middle between the olecranon and medial epicondyle in search of a stimulation of the ulnar nerve (Fig. 8-9A) (flexion of the fourth

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and fifth fingers with opposition of the thumb). The position of the needle is adjusted to maintain the same motor response with a current less than 0.5 mA. After negative aspiration for blood, the local anesthetic solution is injected slowly.

Figure 8-9. Ulnar nerve block.

Tips

Injection of the local anesthetic solution at the level of the ulnar groove should be avoided, because it can cause compression of the nerve and postoperative paresthesia (Fig. 8-9B).
Radial blocks performed at the level of the elbow crease often produce an incomplete sensory block because at this level the radial nerve is already divided into a sensory and motor branch.
Blocks at the elbow are easy to perform. However, it is important to search for motor responses at the level of the fingers and especially the thumb when blocking the radial nerve.

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D. Blocks at the Wrist

Jacques E. Chelly

Patient Position: With the patient in supine position, the forearm is supinated with the palm facing upward.

Indications: Hand surgery.

Needle Size: 24-gauge, 25-mm insulated needle.

Volume: 5 to 6 mL per nerve.

Anatomic Landmarks (Fig. 8-10): The ulnar nerve is located medially to the ulnar artery and posteriorly to the flexor carpi ulnaris tendon. The median nerve is located medially to the flexor carpi radialis tendon. The radial nerve is located in the anatomic snuffbox.

Approach and Technique: For each of these blocks, the needle is introduced 6 to 8 cm cephalad to the wrist crease.

Ulnar Nerve Block

With a finger on the flexor carpi ulnaris tendon, a 25-mm insulated needle connected to a nerve stimulator (1.5 mA, 2 Hz, 0.1 ms) is introduced 0.8 to 1.5 cm immediately posterior to the tendon in search of a stimulation of the ulnar nerve (Fig. 8-11). The needle is positioned to maintain the motor response (flexion of the fourth and fifth fingers with an opposition of the thumb)

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with a current less than 0.5 mA. After negative aspiration for blood, the local anesthetic solution is slowly injected.

Figure 8-10. Anatomic landmarks.

Figure 8-11. Ulnar nerve block.

Median Nerve Block

The needle is introduced 1.5 cm deep medially to the flexor carpi radialis tendon (Fig. 8-12). After negative aspiration for blood, the local anesthetic solution is slowly injected.

Figure 8-12. Median nerve block.

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Radial Nerve Block

At the level of the wrist, the radial nerve is only sensory and therefore the block of the radial nerve is produced by injecting the local anesthetic solution subcutaneously at the level of the anatomic snuffbox using two injections (X shape) (Fig. 8-13).

Figure 8-13. Radial nerve block.

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Tips

Wrist blocks preserve most of the motor function of the fingers.
The use of a nerve stimulator is only helpful in performing an ulnar block.
The use of a nerve stimulator to block the median nerve at the wrist is associated with a 20% to 30% incomplete block because at this level the median nerve has already divided into a motor and sensory branch (the motor branch running more posteriorly).

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E. Digital Sheath Block

Marcos Masson

Patient Position: The patient's hand is supine.

Needle Size: 25-gauge, 2.5-cm needle.

Indications: Transthecal blocks are indicated for short digital procedures, especially in emergency situations.

Volume: 3 mL per digit.

Anatomic Landmarks: The anesthetic solution is injected into the space between the digital sheath and flexor tendon (Fig. 8-14).

Approach and Technique: With the hand in full supination, the patient is asked to extend and flex the fingers gently. The operator palpates the flexor tendon as it glides over the protuberance of the metacarpal head and then marks it with a skin pencil. The skin is penetrated at a 45° angle at the level of the distal skin crease of the palm distal to the metacarpophalangeal joint (Fig. 8-15A). Resistance is felt as the needle penetrates the flexor tendon sheath. The needle is then withdrawn slightly to sit above the tendon, at which point the local anesthetic solution is injected with the operator's index finger pressing down on the flexor tendon proximal to the metacarpophalangeal joint crease to prevent

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proximal flow of the local anesthetic solution (Fig. 8-15B). The bulging of the flexor tendon can be felt as the local anesthetic solution flows freely. Pressure is applied at the injection site for 3 or 4 minutes.

Figure 8-14. Anatomic landmarks.

Figure 8-15. A: The skin is penetrated at a 45° angle at the level of the distal skin crease of the palm distal to the metacarpal joint. B: The needle is withdrawn slightly to sit above the tendon, at which point the local anesthetic solution is injected with the operator's index finger pressing down on the flexor tendon proximal to the metacarpophalangeal joint crease to prevent proximal flow of the local anesthetic solution.

Tips

Lidocaine 1% is the local anesthetic of choice.
When anesthetic solution is injected, the patient may experience a feeling of finger expansion.
This block produces analgesia distal to the palmar–digital crease that is more intense on the palmar side than on the dorsal side.
Considerable care must be taken to use sterile techniques when performing this block to avoid contamination of the flexor tendon sheath. In this regard, the hands of both the operator and the patient should be disinfected with povidone-iodine, then with alcohol.
The onset of anesthesia is rapid, within 3 to 4 minutes of injection.
Compared with the conventional distal nerve block technique, the risk for mechanical trauma to the neurovascular bundle is minimal with this technique.