Ultrasound-guided infraclavicular brachial plexus block is useful as a diagnostic maneuver to help identify if the brachial plexus is subserving pain from tumor, plexopathy, plexitis, abscess, or other pathology. Infraclavicular brachial plexus nerve block with local anesthetic may be used to palliate acute pain emergencies, including acute herpes zoster, brachial plexus neuritis, brachial plexopathy including Parsonage-Turner syndrome, upper extremity trauma, and cancer pain including Pancoast superior sulcus lung tumor, while waiting for pharmacologic, surgical, and antiblastic methods to become effective (Fig. 32.1). Infraclavicular brachial plexus nerve block is also useful as an alternative to stellate ganglion block when treating reflex sympathetic dystrophy and ischemic conditions of the upper extremity. The use of ultrasound imaging can identify the exact location and course of the brachial plexus when surgical procedures of the neck and clavicle are being contemplated. For surgery of the distal upper extremity, infraclavicular brachial plexus block offers the dual advantages of rapid onset and dense surgical anesthesia. Destruction of the brachial plexus via the infraclavicular approach is indicated for the palliation of cancer pain, including invasive tumors of the brachial plexus as well as tumors of the soft tissue and bone of the upper extremity.

The fibers that comprise the brachial plexus arise primarily from the fusion of the anterior rami of the C5, C6, C7, C8, and T1 spinal nerves. In some patients, there may also be a contribution of fibers from C4 to 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 (Fig. 32.2). After passing over the top of the first rib, the cords of the plexus continue their downward path in proximity to the subclavian artery and then the axillary artery (Fig. 32.3). In order to inject the brachial plexus at the
infraclavicular level, the needle must traverse skin, subcutaneous tissue, and the pectoralis major and minor muscles (Fig. 32.4).