Ultrasound-guided axillary brachial plexus block is useful as a diagnostic maneuver to help identify if the distal brachial plexus is subserving pain from tumor, plexopathy, plexitis, abscess, or other pathology. Axillary brachial plexus nerve block with local anesthetic may be used to provide surgical anesthesia for upper extremity surgery as well as to palliate acute pain emergencies, including acute herpes zoster, upper extremity trauma, and cancer pain while waiting for pharmacologic, surgical, and antiblastic methods to become effective. Axillary brachial plexus nerve block is also useful as an alternative to stellate ganglion block when treating reflex sympathetic dystrophy and ischemic conditions of the distal upper extremity (Fig. 34.1). The use of ultrasound imaging can identify the exact location and course of the brachial plexus when surgical procedures of the axilla proximal upper extremity are being contemplated. For surgery of the distal upper extremity, axillary brachial plexus block offers the dual advantages of rapid onset and dense surgical anesthesia. Destruction of the brachial plexus via the axillary 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. 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. 34.2). The sheath that encloses the axillary artery and nerves, as it travels downwards through the axilla, is less well developed than that which encloses the brachial plexus at the level at which interscalene and supraclavicular brachial plexus blocks are performed, making single injection technique less satisfactory in many patients (Fig. 34.3). The median, radial, ulnar, and musculocutaneous nerves surround the artery within this imperfect sheath. David Brown, M.D., has suggested that the position of these nerves relative to the axillary artery can best be visualized by placing them in the quadrants as represented on the face of a clock, with the axillary artery being at the center of the clock (Fig. 34.4). The median nerve is found in the 12:00 o’clock to 3:00 o’clock quadrant, the ulnar nerve is found in the 3:00 o’clock to 6:00 o’clock quadrant, the radial nerve is found in the 6:00 o’clock to 9:00 o’clock quadrant, and the musculocutaneous nerve is found in the 9:00 o’clock to 12:00 o’clock quadrant. To ensure adequate block of these nerves, drugs must be injected in each quadrant to place medication in proximity to each of these nerves (see Fig. 34.4).

To perform ultrasound-guided injection technique for axillary brachial plexus block, place the patient in the supine position with the arm abducted to 90 degrees and externally rotated, which brings the artery and plexus closer to the skin facilitating ultrasound visualization. At a point 2 inches distal to the axillary crease, the pulse of the axillary artery is palpated and the skin overlying the pulsations is marked (Fig. 34.5). After preliminary identification of the surface landmarks is completed, the skin is prepped with antiseptic solution, and 20 mL of local anesthetic is drawn up in a 20-mL sterile syringe, with 40 to 80 mg of depot steroid added if the condition being treated is thought to have an inflammatory component.

A linear high-frequency ultrasound transducer is then placed in a transverse orientation over the previously identified arterial pulse, and a survey scan is taken (Fig. 34.6). Placement of the transducer in this position will provide a short-axis view of the axillary artery and nerves of the terminal brachial plexus with the artery appearing as a round pulsatile structure surrounded by the median, ulnar, and radial nerves (Fig. 34.7). The musculocutaneous nerve, which


should be at 9:00 o’clock to 10:00 o’clock relative to the axillary artery lying in the flexor compartment between the biceps and the coracobrachialis muscle or in some patients within the body of the coracobrachialis muscle, must also be blocked to provide complete anesthesia for the distal upper extremity. Color Doppler can be utilized to further delineate the axillary artery and any other vascular structures (Fig. 34.8). When the axillary artery and surrounding nerves are identified, a 22-gauge, 2-inch needle is advanced toward the 12:00 o’clock position of the axillary artery under real-time ultrasound guidance using an in-plane approach until the needle tip rests adjacent to the axillary artery in proximity to the median nerve (Fig. 34.9). After careful aspiration for blood or cerebrospinal fluid, 5 mL of solution
should be slowly injected in incremental doses. The needle is then repositioned until the needle tip rests at the 3:00 o’clock position relative to the axillary artery and in proximity to the ulnar nerve, and after careful aspiration for blood or cerebrospinal fluid, an additional 5 mL of solution is slowly injected in incremental doses. These steps are repeated with the needle tip being repositioned to the 6:00 o’clock position to block the radial nerve and then to the
9:00 o’clock position to block the musculocutaneous nerve. A good periarterial arterial flow of local anesthetic and/or steroid should be observed, and it may not be necessary to reposition the needle to block all nerves in those patients who have a well-developed neurovascular sheath. The needle is removed, and pressure is placed on the injection site to avoid bleeding complications.