Figure 31-1. Cutaneous innervation of the upper extremity. Actual patients demonstrate large variation in the depicted pattern of innervation and have significant crossover between nerves.

This chapter discusses individual nerve blocks as a means of furthering the reader’s understanding of the indications and contraindications for selective upper extremity regional anesthesia. When considering the application of these various blocks, the reader is reminded that innervation of the upper extremity is often variable and overlapping.¹ Therefore, when faced with the choice of performing a single nerve block versus blocking several adjacent nerves, it is advisable to err on the side of multiple blocks, particularly in those adjacent cutaneous areas that represent potential crossover innervation (Figures 31–1 and 31–2). The relevant anatomy will be covered with specific nerve block description.

Local Anesthetic & Adjuvant Selection

Local anesthetics for individual upper extremity nerve blocks are selected for their desired duration of anesthesia and/or analgesia. If intermediate-acting local anesthetics are selected (lidocaine or mepivacaine), duration can be increased with either adjuvant epinephrine (2.5 mcg/mL) or clonidine (0.5 mcg/kg). Neither adjuvant significantly increases duration when a long-acting local anesthetic such as bupivacaine or ropivacaine is chosen.¹

SUPRACLAVICULAR NERVE BLOCK

Indications

The supraclavicular nerve provides sensory innervation to the “cape” of the shoulder (Figure 31-3). Commonly anesthetized as a component of cervical plexus block for carotid surgery, the supraclavicular nerve may also require blockade for surgery involving the shoulder or supraclavicular area. Local anesthetic spread in an interscalene approach to brachial plexus block is often adequate to block the supraclavicular nerve, but the nerve is frequently not anesthetized with a supraclavicular brachial plexus block. Particularly in patients undergoing supraclavicular or incomplete interscalene brachial plexus anesthesia without concomitant general anesthesia, the supraclavicular nerve can be blocked to accomplish more complete anesthesia for shoulder surgery.

Anatomy

The supraclavicular nerve is derived from the ventral rami of the third and fourth cervical nerve roots (C3-C4); it is thus separate from the brachial plexus. The nerve becomes superficial as it penetrates the mid-belly of the sternocleidomastoid muscle, thereafter forming three branches (Figure 31-3). These branches provide sensory innervation to the cape area, which spans from the midline to the deltoids, and from the second rib anteriorly to the top of the scapula posteriorly.

Figure 31-2. Idealized distribution of the cutaneous innervation of the upper arm and forearm.

Technique

Blockade of the supraclavicular nerve is accomplished with 10 mL of an intermediate or long-acting local anesthetic, depending on analgesic requirements. Three milliliters are deposited with a 22- to 25-gauge sharp needle into the mid-belly of the sternocleidomastoid muscle. The remaining volume of local anesthetic is then injected subcutaneously in a cephalad and caudad direction along the posterior border of the sternocleidomastoid (Figure 31-4).

Complications

Complications of the supraclavicular nerve block are minimal provided that aseptic technique is used and local anesthetic injection remains superficial. The external jugular vein should be avoided to prevent hematoma.

Clinical Pearls

The supraclavicular nerve block should be used as a supplement to supraclavicular brachial plexus block for patients undergoing shoulder surgery.

Figure 31-3. Supraclavicular nerve. This nerve is derived from C3-C4 nerve roots, is not part of the brachial plexus, and provides sensory innervation of the shoulder “cape.”

SUPRASCAPULAR NERVE BLOCK

Indications

Suprascapular nerve block (SSNB) can be used as an adjunct to arthroscopic shoulder surgery and total shoulder arthroplasty. When combined with general anesthesia for shoulder arthroscopy, SSNB improves analgesia, reduces opioid- related side effects, and hastens hospital discharge,² although SSNB is not superior to interscalene block in this setting.³ For anterior open shoulder surgery, supplemental SSNB does not affect outcome when combined with interscalene block.⁴ Because it provides major sensory innervation to the shoulder joint, it can be used to block supplementally the suprascapular nerve for analgesia after total shoulder arthroplasty. Furthermore, because it may send branches to the anterior axilla, the suprascapular nerve may require supplementation to anesthetize the anterior arthroscopic port site in awake patients who receive an interscalene block as the sole anesthetic for surgery.

Anatomy

The suprascapular nerve (C4-C5) branches from the superior trunk of the brachial plexus and therefore is usually anesthetized by an interscalene block. It traverses the suprascapular notch and continues laterally along the superior border of the scapular spine (Figure 31-5). The supraclavicular nerve provides sensory innervation to 70% of the posteriorsuperior shoulder joint, the acromioclavicular joint, and a portion of the anterior axilla in up to 10% of patients.¹ The suprascapular nerve provides motor innervation to the supraspinatus and infraspinatus muscles, but minimal if any cutaneous innervation over the scapula or posterior shoulder.

Technique

Surface landmarks are identified by drawing one line along the superior border of the scapular spine and then bisecting it with a second line drawn parallel with the vertebral spine. From where these two lines cross, the suprascapular notch underlies a point ~2–3 cm toward the middle of the upper/outer quadrant (see Figure 31-5). A 1.5-in. 22-gauge needle is placed at this entry mark and directed caudad in the parasagittal plane until it contacts the scapular spine, followed by injection of 10 mL of a long-acting local anesthetic. If a peripheral nerve stimulator is used, the suprascapular nerve is identified by the motor response of external shoulder rotation.

Complications

Pneumothorax can result from a needle that passes through the suprascapular notch and enters the pleural space. This complication is largely avoidable by directing the needle in a caudad, rather than anterior, direction.

Clinical Pearls

Suprascapular nerve block is a valuable analgesic adjunct for shoulder arthroscopy performed with the patient under general anesthesia.

Suprascapular nerve block does not add value to open shoulder procedures in which an interscalene block is the primary anesthetic.

Suprascapular nerve block is probably a valuable supplement to interscalene block during total shoulder arthroplasty or in the occasional patient who experiences pain at the anterior arthroscopic port site.