I. Anatomy. The anatomy of the brachial plexus (Fig. 8.1) may appear overwhelming. However, one need only remember some key facts:

A. The brachial plexus can be divided into roots, trunks, divisions, cords, and terminal branches. End branches can also originate from roots (dorsal scapular and long thoracic
nerves), trunks (suprascapular and subclavian nerves), and cords (pectoral, subscapular, and thoracodorsal nerves).

B. The interscalene, supraclavicular, infraclavicular, and axillary approaches anesthetize the brachial plexus at the level of its roots/trunks, trunks/divisions, cords, and terminal branches, respectively.

C. The suprascapular nerve originates from the superior trunk and supplies the posterior two-thirds of the shoulder joint as well as the acromioclavicular joint. Thus, for shoulder surgery, it is important to block this nerve prior to its takeoff from the superior trunk. This is best achieved with an interscalene or supraclavicular approach.

D. The subclavian nerve originates from the superior trunk and is responsible for most of the bony innervation of the clavicle. Thus, for clavicular surgery, an interscalene or supraclavicular approach will anesthetize this nerve prior to its takeoff from the superior trunk.

E. Cutaneous innervation of the shoulder and upper arm is separate from the brachial plexus and originates from the superficial plexus (supraclavicular nerves) and the intercostobrachial nerve.

II. Drugs. In order to select the optimal local anesthetic agent, the operator must decide whether the aim is postoperative analgesia (in the context of concomitant general anesthesia) or surgical anesthesia (Table 8.1).

If the goal is to maximize postoperative analgesia, block duration should be the overriding concern. Thus, long-acting agents (such as bupivacaine or ropivacaine) should be selected. Moreover, adjuvants can prolong the duration of brachial plexus blocks. Epinephrine is useful as an intravascular injection marker and for increasing the duration of action of intermediate local anesthetic agents. Clonidine provides similar intermediate prolongation as epinephrine, but is associated with increased costs and potential side effects (hypotension, sedation) (3). Dexmedetomidine is effective with long-acting agents, but can be prohibitively expensive. Despite dexamethasone’s popularity, the optimal administration route (intravenous vs. perineural) remains controversial (4,5). Perineural dexamethasone has not received official FDA approval, and its use remains off-label for now. Moreover, dexamethasone may have a potential for neural toxicity in diabetic patients. In-depth discussion of adjuvants can be found in Chapter 5.

If the operator wishes to achieve surgical anesthesia, three options exist. Firstly, the brachial plexus block is performed with bupivacaine 0.5% or ropivacaine 0.75% at least 45 to 60 minutes before surgery to provide sufficient “soak time.” This strategy requires an induction room and efficient planning. Secondly, the brachial plexus block is performed with lidocaine or mepivacaine (1.25% to 1.5%), thereby ensuring a swift onset, and a perineural catheter is inserted. Postoperatively, the latter is injected with bupivacaine/ropivacaine prior to removal (if additional analgesia is required) or transitioned to a continuous local anesthetic infusion. Albeit the most versatile, this strategy requires increased technical skills, performance time, and equipment costs. Finally, a mix of lidocaine and bupivacaine/ropivacaine is employed. Although the mix may not have the swift onset of pure lidocaine or the long duration of bupivacaine/ropivacaine, its simplicity makes it attractive.

III. Techniques

A. Interscalene approach

a. Shoulder and proximal humerus surgery

a. Usual contraindications to peripheral nerve blocks (i.e., lack of consent, local infection at the injection site, allergy to local anesthetic agent).

b. Patients with preexisting obstructive or restrictive pulmonary pathology who are unable to withstand up to 30% reduction in pulmonary function consequent to ipsilateral phrenic nerve block/hemidiaphragmatic paralysis. In general, such patients have severe chronic obstructive pulmonary disease (COPD) and may be on home oxygen therapy.

3. Single injection technique. The patient is placed in a supine or semi-sitting position with the head turned toward the contralateral side. An ultrasound-guided traceback technique (starting from the supraclavicular fossa) is commonly used. The supraclavicular area is first scanned to locate the subclavian artery. The brachial plexus (cluster of trunks and divisions) can be found superolateral to the artery. Subsequently, the plexus is traced cephalad toward the cricoid cartilage until it becomes a column of hypoechoic nodules (roots/trunks) (Figs. 8.3 and 8.4). Using an in-plane technique and a lateral-to-medial direction, the subcutaneous tissues are infiltrated with local anesthesia. A 5-cm, shortbeveled block needle is then inserted. The target for this block is situated under the paraneurium, between the first and second hypoechoic nodules. Alternately, the operator can elect to deposit local anesthetic outside the paraneurium, between the middle scalene muscle and the brachial plexus. Extraparaneural injection will not affect the success rate, but the block will have a slightly shorter duration (6). A volume of 10 to 20 mL of local anesthetic is commonly used.