Ultrasound-guided intercostobrachial cutaneous nerve block is used primarily as an adjunct to brachial plexus block rather than as a stand-alone regional anesthesia and pain management procedure. The intercostobrachial cutaneous nerve is not part of the brachial plexus and is often not adequately blocked when performing standard brachial plexus block techniques. This means that the medial and posterior aspect of the arm just below the axilla remains unanesthetized making prolonged use of a pneumatic tourniquet or the performance of surgical procedures in this region problematic. The intercostobrachial cutaneous nerve is often damaged or transected during radical mastectomy surgery and has been implicated in the evolution of postmastectomy pain syndrome. The nerve may also subserve referred pain from the cardiac region.

The intercostobrachial cutaneous nerve is derived from fibers of the lateral cutaneous branch of the second intercostal nerve. After piercing the intercostalis and serratus anterior muscles, the intercostobrachial cutaneous nerve traverses the axilla where it provides communicating branches to the median cutaneous nerve. The intercostobrachial cutaneous nerve exits the axilla along with the median cutaneous nerve to provide cutaneous sensory innervation to medial and posterior aspect of the upper extremity (Figs. 44.1 and 44.2). The superficial location of this nerve makes it easily accessible for ultrasoundguided nerve block.

The benefits, risks, and alternative treatments are explained to the patient, and informed consent is obtained. The patient is then placed in the supine position with the affected upper extremity abducted 90 degrees and the palm facing upward (Fig. 44.3). With the patient in the above position, at a point just below the axilla, the pulsations of the axillary artery are palpated (Fig. 44.4). A high-frequency linear ultrasound transducer is placed in a transverse position over the previously identified arterial pulsations (Fig. 44.5). An ultrasound survey image is obtained, and the axillary artery and vein and the deep fascia are identified (Fig. 44.6). Color Doppler can aid in the identifications of these vessels (Fig. 44.7). Just superficial to the deep fascia lies the intercostobrachial cutaneous nerve, which will appear as an oval hyperechoic structure (Fig. 44.8). The skin overlying the area beneath the ultrasound transducer is prepped with antiseptic solution. A sterile syringe containing 3.0 mL of 0.25% preservative-free bupivacaine and 40 mg of methylprednisolone is attached to a 1½-inch, 22-gauge needle using strict aseptic technique. The needle is placed through the skin just below the center of the transducer and is then advanced using an out-of-plane approach with the needle trajectory adjusted under real-time ultrasound guidance so that the needle tip ultimately rests in proximity to the intercostobrachial cutaneous nerve (Fig. 44.9). When the tip of needle is thought to be in satisfactory position, after careful aspiration, a small amount of local anesthetic and steroid is injected under real-time ultrasound guidance to confirm that the needle tip is in the proper position. After proper needle tip placement is confirmed, the remainder of the contents of the syringe is slowly injected. There should be minimal resistance to injection.