Ultrasound-guided median nerve block at the elbow is useful in the management of the pain subserved by the median nerve. This technique serves as an excellent adjunct to brachial plexus block and for general anesthesia when performing surgery below the elbow. Ultrasound-guided median nerve block at the elbow with local anesthetic may be used to palliate acute pain emergencies, including postoperative pain, pain secondary to trauma, and cancer pain, while waiting for pharmacologic, surgical, and antiblastic methods to become effective.

Ultrasound-guided median nerve block can also be used as a diagnostic tool when performing differential neural blockade on an anatomic basis in the evaluation of upper extremity pain as well as in a prognostic manner to determine the degree of neurologic impairment the patient will suffer when destruction of the median nerve is being considered or when there is a possibility that the nerve may be sacrificed during surgeries in the anatomic region of the median nerve at the level of the elbow. This technique may also be useful in those patients suffering symptoms from compromise of the median nerve at the elbow due to compression of the median nerve by the ligament of Struthers, the lacertus fibrosus, and the pronator syndrome (Figs. 53.1 and 53.2). Ultrasound-guided median nerve block at the elbow may also be used to palliate the pain and dysesthesias associated with stretch injuries to the median nerve.

The key landmark when performing ultrasound-guided median nerve block at the elbow is pulsation of the brachial artery in the antecubital fossa (Fig. 53.3). Arising from fibers from the ventral roots of C5 and C6 of the lateral cord and C8 and T1 of the medial cord of the brachial plexus, the median nerve lies anterior and superior to the axillary artery in the 12:00 o’clock to 3:00 o’clock quadrant as it passes through the axilla. As the median nerve exits the axilla, it passes inferiorly adjacent to the brachial artery. At the antecubital fossa, the median nerve lies just medial to the brachial artery. Continuing its downward path, the median nerve gives off a number of motor branches to the flexor muscles of the upper arm. These branches are susceptible to nerve entrapment by aberrant ligaments, muscle hypertrophy, and direct trauma. As the median nerve approaches the wrist, it overlies the radius where it is susceptible to trauma from radial fractures and lacerations. The nerve lies deep to and between the tendons of the palmaris longus muscle and the flexor carpi radialis muscle at the wrist. It is susceptible to entrapment as it passes through the carpal tunnel. The terminal branches of the median nerve provide sensory innervation to a portion of the palmar surface of the hand as well as the palmar surface of the thumb and index and middle fingers and the radial portion of the ring finger (Fig. 53.4). The median nerve also provides sensory innervation to the distal dorsal surface of the index and middle fingers and the radial portion of the ring finger.

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 arm resting comfortably at the patient’s side with the palm up. The physician stands at the side of the patient. The pulsation of the brachial artery is palpated just medial to the distal biceps tendon at the antecubital fossa (Fig. 53.5). With the patient in the above position, a high-frequency linear ultrasound transducer is placed in a transverse position over the pulsation of the brachial artery, and an ultrasound survey scan is taken (Fig. 53.6). The brachial artery is then identified as is the median nerve lying just medial to the artery (Fig. 53.7). Color Doppler can help identify the artery and other vasculature including the anterior recurrent ulnar artery, which lies just medial to the median nerve at the elbow (Fig. 53.8). After the median nerve has been identified just medial to the brachial artery, the skin overlying the area beneath the ultrasound transducer is prepped with antiseptic solution. A sterile syringe
containing 4.0 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 ultrasound 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 median nerve (Fig. 53.9). When the tip of the 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.