Chapter 51 - Brachial Plexus Block: Axillary Approach

Abstract

The axillary approach to the brachial plexus is the preferred technique for brachial plexus block when dense anesthesia of the forearm and hand is required. Axillary brachial plexus nerve block with local anesthetic may be used for palliation in acute pain emergencies, including acute herpes zoster, brachial plexus neuritis, shoulder and upper extremity trauma, and cancer pain, during the wait for pharmacologic, surgical, and antiblastic methods to take effect. Axillary brachial plexus nerve block is also useful as an alternative to stellate ganglion block for treatment of reflex sympathetic dystrophy of the upper extremity. The brachial plexus is formed by the fusion of the anterior rami of the C5, C6, C7, C8, and T1 spinal nerves. There also may be a contribution of fibers from C4 and T2 spinal nerves. The nerves that make up the plexus exit the lateral aspect of the cervical spine and pass downward and laterally in conjunction with the subclavian artery. The nerves and artery run between the anterior scalene and middle scalene muscles, passing inferiorly behind the middle of the clavicle and above the top of the first rib to reach the axilla. The sheath that encloses the axillary artery and nerves (the neurovascular bundle) is less consistent than that which encloses the brachial plexus at the level at which interscalene and supraclavicular brachial plexus blocks are performed, which makes a single-injection technique less satisfactory. The median, radial, ulnar, and musculocutaneous nerves surround the artery within this imperfect sheath.