Ovid: Peripheral Nerve Blocks: A Color Atlas

Indications for Upper Extremity Blocks

Jacques E. Chelly

Regional anesthesia of the upper extremity is most frequently based on either a block of the brachial plexus (interscalene, supraclavicular, and classical infraclavicular) or a block of terminal nerves (median, ulnar, radial, and musculocutaneous nerves) at either the axilla (axillary block) or proximal part of the humerus (high-humeral approach). The choice of the approach often depends on the patient's condition, the surgical indication, and the anesthesiologist's experience. In this regard, it is important to recognize that for surgeries at the wrist and fingers scheduled for less than 30 minutes, a more distal approach either at the elbow or the wrist may satisfy all surgical requirements and allow for specific blocking of the nerve(s) implicated as well as for a preferential sensory block (at the wrist), preserving the motor function and allowing the patient to move his or her fingers at the request of the surgeon (release of trigger fingers). This “hyperselective” approach to regional anesthesia has been proven to be safe and effective and to facilitate rapid patient discharge after ambulatory surgery. For example, a short procedure on the fifth finger can be performed using a block of the ulnar nerve at the wrist. This technique is very quick to perform, satisfies all surgical requirements, provides effective postoperative analgesia, and allows the preservation of motor function not only of the thumb, index finger, and middle finger, but also of the fourth and fifth fingers. This chapter focuses on providing some rationales for choosing the most appropriate strategy for anesthesia and postoperative analgesia in patients undergoing upper extremity surgery.

Anatomic Considerations

A good knowledge and understanding of upper extremity innervation is essential to define the minimum anesthetic and analgesic requirements for a given indication, even if a more global approach is chosen because of other considerations (i.e., the anesthesiologist's experience and the length of surgery), and even if ultimately the surgeon determines the technique. For example, a median, ulnar, and lateral cutaneous nerve block at the wrist represents the minimum requirement for anesthesia for carpal tunnel release, even if an axillary block is often performed.

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Table 5-1. Most Common Anastomoses Between the Brachial Plexus Nerves

Nerves	Median	Ulnar	Radial
Musculocutaneous	Brachial area	Posterior wrist	Elbow
		Upper part of the forearm	Palmar, dorsal fingers Collateral nerves
		Hand	Thenar area Posterior wrist

Three factors need to be recognized when considering the role of anatomy in performing a peripheral block of the upper extremity: the level at which the nerves branch, anastomosis between nerves, and global innervation.

Level at Which the Nerves Branch

Each nerve of the brachial plexus divides into a sensory branch and a motor branch below the axilla, with a number of collaterals. For example, the radial nerve divides into a sensory and motor branch above the elbow crease, with the sensory branch running more superficially. The median and ulnar nerve divide into a sensory and motor branch above the wrist, whereas the musculocutaneous nerve supplies a motor branch to the biceps muscle and remains sensory thereafter. Consequently, a radial nerve block performed in the axilla results in a sensory and motor block of the posterolateral aspect of the forearm. In contrast, when the radial nerve is blocked at the elbow and below, the nerve has already divided into motor and sensory branches. Therefore, it is important to block the radial nerve 2 to 3 cm above the elbow crease, especially when using a nerve stimulation technique. The same is true when blocking the median nerve at the wrist: The motor and sensory fibers are distinctly separated. In addition, at the wrist, the median and ulnar nerves provide collateral sensory fibers to the anterior and medial aspects of the wrist, respectively, which originate above the wrist. Consequently, blocking these nerves at the level of the wrist crease produces only incomplete blocks. Wrist blocks need to be performed at least 4 cm above the wrist crease.

Anastomosis Between Nerves of the Brachial Plexus

Anastomosis between the nerves constituting the brachial plexus is frequent and may explain, at least in part, individual variations after a nerve block. To increase the reliability of the block, it is necessary to take this factor into consideration, especially when considering the use of specific distal blocks (see Table 5-1, which lists the most frequent nerve anastomoses).

Global Innervation

Although in most representations of the upper extremity innervation is based on superficial distribution, it is important to recognize that the muscular and bone innervation is not strictly superimposed (Fig. 5-1). The only location at which a single nerve innervates all structures is the lateral edge of the hand and the fifth finger, both of which are innervated by the ulnar nerve. There are some significant differences between the superficial, muscular, and skeletal innervations. These differences must be taken into account in determining the most appropriate block(s) for a specific surgical procedure. Thus, the surgical exploration of a second interdigital wound requires radial and median blocks, whereas an ulnar block is also necessary if interosseous muscle exploration is indicated.

Extent of Upper Extremity Blocks

Upper extremity nerve conduction can be interrupted at the level of the brachial plexus or the individual nerves. Approaches to the brachial plexus include the interscalene, subclavicular,

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infraclavicular, and axillary blocks. Other blocks of the upper extremity are high humeral, elbow, wrist, and digital blocks. Each injection site is associated with a defined probability of achieving a complete block for a given nerve. The orientation of the plexus vis-à-vis the injection site is an important factor to take into consideration. Although experience is an important determinant of success, the extent of the sensory and motor blocks also depends on the site at which the block is performed. To maximize the correlation between the block resulting from the use of a given approach and the surgical requirements, it is important to choose an approach with the highest probability of producing a complete block in the surgical territory. This can only be achieved by gaining experience in the different approaches. Finally, when using peripheral nerve blocks as the main anesthesia technique, it is also important to account for all surgical requirements, such as the prevention of tourniquet pain, especially if the tourniquet is placed at the level of the arm and the surgery lasts more than 30 minutes.

Figure 5-1. Upper extremity innervation.

Brachial Plexus Blocks

Interscalene Block

With an interscalene block, the brachial plexus is approached at the level of the trunks or roots. The anatomy of the plexus relative to the site of injection with this approach explains why the upper (C5-6) and middle (C7) trunks are preferentially blocked. The lower trunk (C8-T1), which is more posterior, is often blocked incompletely. Consequently, the shoulder and the lateral aspect of the upper arm represent the territory with the highest probability of block. In addition, the proximity of the phrenic nerve, the large volume of local anesthetic usually injected (40 to 50 mL), and the diffusion of the local anesthetic solution toward the cervical region explain why the phrenic nerve, which runs anterior, is also almost always blocked and why the sensory block may extend up to C2 (Fig. 5-2).

Supraclavicular and Infraclavicular Blocks

Of all the approaches to the brachial plexus, the supraclavicular and infraclavicular approaches are associated with the greatest diffusion of local anesthetic solution after a single injection because, at these levels, the brachial plexus is the most compact. However, supraclavicular injection preferentially blocks the axillary, radial, and musculocutaneous nerves. Because at this level the middle trunk is deeper, blockade of the median and, more importantly, the ulnar nerves requires a longer onset time and is often incomplete (Fig. 5-3).

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Figure 5-2. Anterior and posterior view of an interscalene block.

Figure 5-3. Anterior and posterior view of a supraclavicular block.

Axillary Block

At the level of the axilla, the different nerves of the brachial plexus are individualized. As with the other sites, a single injection does not produce complete upper limb anesthesia because (a) the axillary and musculocutaneous nerves have already left the plexus sheath, and (b) diffusion of the local anesthetic solution can be incomplete. Although there is no anatomically defined separation between the nerves, the presence of fibrous septa limits diffusion of the local anesthetic solution. Therefore, it is difficult to achieve a complete block with a single injection. However, the extent of the block and the success rate can be increased by a multiple-injection technique around the axillary artery (>90%). In this technique, the use of a nerve stimulator greatly facilitates individual nerve localization (Fig. 5-4).

Figure 5-4. Anterior and posterior view of an axillary block using one injection and an anterior and posterior view of an axillary block using multiple injections.

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Terminal Nerve Blocks

High-Humeral Approach

At the level of the high humerus, a common vasculonervous anatomic space exists only between the brachial artery and the median nerve. The other nerves (i.e., radial, ulnar, and musculocutaneous) are completely separated. Therefore, such an approach allows each nerve to be blocked according to the surgical requirement. In practice, the extent and success rate achieved with this approach are comparable with those in a multiple-injection axillary block.

Elbow and Wrist Blocks

To achieve complete anesthesia below the elbow or the wrist, multiple injections are required. At the elbow, six nerves need to be blocked. Three of these nerves are superficial (musculocutaneous, posterior cutaneous nerve of the forearm, and middle cutaneous of the forearm) and three are deep (median, ulnar, and radial). At the wrist, or more precisely, at the lower third of the forearm, eight nerves provide innervation of the hand and the wrist. Four are superficial (musculocutaneous, cutaneous middle of the forearm, superficial radial, and posterior cutaneous nerve of the forearm) and four are deep (median, ulnar, anterior interosseous, and posterior interosseous). At the wrist, the use of epinephrine solutions is contraindicated.

Digital Blocks

The interdigital block corresponds to a local anesthetic infiltration on each side of the P1 base (Fig. 5-5). To be effective, it is necessary to block the dorsal and palmar collateral nerves. The use of epinephrine solutions is contraindicated. In addition, for the second, third, and fourth fingers, the palmar collateral nerves provide innervation to the whole finger on the palmar side and the first two phalanges on the dorsal side (Fig. 5-6). An injection at or above the flexion tendon sheath facing the metacarpophalangeal joint produces a block of the collateral palmar nerves, thus providing anesthesia of three-fourths of the finger with a single injection. The dorsal surface of the thumb is innervated by the superficial radial

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nerve, which can be blocked through an injection in the flexor sheath. For the fifth finger, an upper branch of the ulnar nerve innervates the entire dorsal side. In this case, rather than two injections (one in the sheath and one at the level of the ulnar upper branch), it is easier to make a single injection and block the ulnar nerve 5 cm above the wrist.

Figure 5-5. Interdigital block.

Figure 5-6. The palmar collateral nerves provide innervation to the whole finger on the palmar side and the first two phalanges on the dorsal side.

Surgical Indications for Upper Extremity Blocks

Once the indication for regional anesthesia has been established, the location, extent of the surgery, and expected tourniquet duration guide the choice for the most appropriate technique.

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Shoulder Surgery

The interscalene block is the most appropriate block for shoulder surgery. It can be performed in the absence of general contraindications, including (a) absolute contraindications (e.g., allergies to local anesthetics, infections at the injection site, uncontrolled seizure disorder, major coagulation abnormality, uncooperative patient); (b) relative contraindications (e.g., neurologic abnormalities in the territory affected by surgery); and (c) specific contraindications (e.g., respiratory insufficiency). If the surgical site also includes the supraclavicular region, a superficial cervical plexus block is also required. Although interscalene block alone is adequate for shoulder surgery, consideration should also be given to its combination with general anesthesia, especially when the surgery is expected to last for more than 2 hours. In these cases, the block minimizes the requirement for opioids during surgery and the immediate postoperative period. However, to minimize the risk for complications (intravascular and epidural injections), it is highly recommended that the block be performed before the induction of anesthesia, while the patient is awake and under minimum sedation. If the postoperative pain is expected to last more than 24 hours (rotator cuff repair, total shoulder replacement, Bankart repair), the placement of a catheter is indicated.

Surgery Above the Elbow

Although some anesthesiologists consider that interscalene, supraclavicular, and infraclavicular blocks are equally indicated for patients undergoing surgery below the shoulder and above the elbow, the use of supraclavicular and infraclavicular blocks are most likely to result in a higher success rate. However, the risk for pneumothorax (immediate or delayed) represents a relative contraindication of the supraclavicular block approach, especially for ambulatory surgery. If prolonged postoperative pain control is required, the placement of a catheter is indicated with an infraclavicular approach.

Elbow and Forearm Surgery

Axillary blocks using multiple injections or a high-humeral approach yield the best results for surgery at or below the elbow. In contrast, interscalene blocks are not advised given their insufficient extension in the C8–T1 territory. The use of a supraclavicular block is possible, but the risk for pneumothorax needs to be balanced against the specific benefit of such an approach. On the other hand, the infraclavicular placement of a catheter for continuous infusion may represent a viable alternative, especially in trauma cases in which upper limb mobilization makes access difficult. Sometimes, forearm surgery can also be performed with elbow blocks, allowing anesthesia to be provided only to the surgical territory. This requires an appropriate evaluation of the surgical field and knowledge of the innervation, not only superficial but also muscular and skeletal. However, the requirement for multiple injections may not always be well tolerated by the patient.

Blocks at the elbow are also used to complete a block performed initially at a higher level (interscalene, supraclavicular, infraclavicular, axillary, and even high humeral).

Hand and Wrist Surgery

Axillary or high-humeral blocks yield the best results for hand and wrist surgery. In addition, the use of a high-humeral approach also allows the local anesthetic solution to be selected for each nerve according to the surgical need. For example, 0.5% to 0.75% ropivacaine may be used to block nerves directly involved with the surgical territory for both anesthesia and immediate postoperative analgesia, whereas 1.5% mepivacaine or lidocaine may be used to produce a short-lasting sensory block to prevent tourniquet pain. This may also limit the duration of the motor block while providing adequate postoperative analgesia. Individual nerve blocks at the elbow and at the wrist may also be indicated to complete a block in a specific territory. Although these distal blocks have the reputation of being more prone to inducing nerve damage, this has never been established.

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Table 5-2. Most Common Upper Limb Procedures and Their Proposed Peripheral Blocks

Procedure/condition	Proposed peripheral block	Remarks
Shoulder surgery	Interscalene block	A continuous nerve block is indicated for major shoulder surgery (rotator cuff repair, Bankart, total shoulder replacement).
Humerus Open Reduction and Internal Fixation (ORIF)	Interscalene Supra/infraclavicular block	Because of the postoperative risk of compression syndrome and injury of the radial nerve, this condition is considered by certain orthopedic surgeons as a contraindication for a block.
Epicondylitis	Axillary block Supra/infraclavicular block	Painful surgery. A catheter is often required for postoperative pain management and physical therapy.
Ulnar neurolysis at the elbow	Axillary block High-humeral block	Blocks of the radial and medial cutaneous nerves of the arm are required.
Forearm arteriovenous fistula	Axillary block Lateral antebrachial cutaneous	Subcutaneous injection of 5 mL of local anesthetic solution at the lateral aspect of the elbow crease nerve block and medial and subcutaneous injection of 5 mL of local antebrachial cutaneous anesthetic solution along the medial aspect of nerve block the elbow crease.
Posterior synovial cyst at the wrist	Axillary block Blocks at the wrist: radial, posterior cutaneous nerve of forearm (a branch of the ulnar nerve), and posterior interosseous nerve	If the surgery is <15–20 min, blocks at the elbow are an interesting alternative. Do not forget the posterior interosseous nerve, which innervates the articular capsule.
Colles fracture	Axillary block	A median, ulnar, and radial block is required.
Carpal tunnel release	Median, ulnar, and cutaneous lateral nerve	Median nerve block by injecting 6–8 mL of local anesthetic without the use of a nerve stimulator. Ulnar nerve block performed with the use of a nerve stimulator and by injecting 6–8 mL of local anesthetic and cutaneous lateral nerve block by injecting 2–3 mL of local anesthetic at the level of the wrist crease.
Dupuytren disease	Axillary block
Trigger finger 1st finger 2nd 3rd and 4th	Blocks at the wrist: Ulnar + median blocks Median block Median + ulnar blocks	These blocks preserve the finger motricity and allow an active mobilization during surgery by the patient and an evaluation of trigger disappearance by the surgeon.
5th	Ulnar block

The prevention of tourniquet pain deserves specific consideration. First, the tourniquet can be placed at different levels: arm, forearm, and even fingers. Tourniquets are usually well tolerated by the patient as long as the inflation is not too high and they are inflated for less than 30 minutes. After that, it is necessary to block the patient accordingly. For example, a subcutaneous injection of lidocaine 1% along the medial aspect of the arm to block the intercostobrachial and medial cutaneous nerves of the arm may be used to prevent pain from a tourniquet placed at the level of the arm.

Most hand and wrist surgeries are performed as outpatient procedures. In this environment, it is important to provide adequate postsurgical analgesia even after discharge. This requires educating the patient about the risks and symptoms of a persistent sensory or motor block (e.g., vascular or nerve compression). An alternative approach can be to perform a short-duration axillary block using mepivacaine or lidocaine completed by either an elbow or wrist block with ropivacaine for immediate postoperative analgesia.

A number of short surgical procedures on the hand and fingers can be performed using a hyperselective technique at the wrist (carpal tunnel release, trigger finger release, open

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reduction, and internal fixation of the fifth finger). These blocks are better suited for ambulatory surgery. They preserve the mobility of the fingers, allow early discharge, and are also better accepted by patients. However, these blocks should be restricted to procedures involving less than 20 to 30 minutes of tourniquet time, and they require good cooperation among the patient, the anesthesiologist, and the surgeon.

Table 5-2 lists the most common procedures in upper limb surgery with proposed peripheral blocks.