Chapter 29

The wrist block is a technique for blocking branches of the ulnar, medial, and radial nerves at the level of the wrist. The wrist block is a basic peripheral nerve block technique that involves anesthesia of the median, ulnar, and radial nerves, as well as the dorsal sensory branch of the ulnar nerve. The wrist block is simple to perform, essentially devoid of systemic complications, and highly effective for a variety of procedures on the hand and fingers. As such, skill in performing a wrist block should be in the armamentarium of every anesthesiologist. Wrist blocks can be used in the outpatient setting and office setting along with the standard operating room setting, resulting in safe, effective, and cost-effective anesthesia that is well accepted by both surgeons and patients.1–8 Wrist blocks are also useful in the emergency setting to provide anesthesia for repair of hand injuries in the emergency room because there is adequate anesthesia of the hand without motor blockade of the extrinsic hand muscles.9

A wrist block is most commonly used for carpal tunnel and hand and finger surgery.10,11 The most common hand surgery in the United States is carpal tunnel release. Paget described carpal tunnel syndrome in 1853.1,12 Although Learmonth reported release of the carpal tunnel at the wrist in 1933, it was not until the 1950s that the surgery became popular through the efforts of Phalen.13–15 Because of the ease of performing a wrist block, wrist blocks are used in a variety of settings including the emergency room, outpatient surgery centers, and office-based anesthesia practices. Hand surgeons also make use of the wrist block to perform minor procedures in their offices. A wrist block can be used in a patient with a full stomach requiring emergeny surgery, thereby obviating the need for general anesthesia and reducing the risk of aspiration.

The contraindications to wrist blocks are few, but include local infection at the sites of needle insertion, preexisting central or peripheral nervous systems disorders, and allergy to local anesthesia. Patients are usually able to tolerate a tourniquet on the arm without anesthesia for 20 min; a wrist tourniquet can be tolerated for about 120 min.

Innervation of the hand is shared by the ulnar, median, and radial nerves (Figure 29–1). The ulnar nerve innervates more intrinsic muscles than the median nerve, which in turn innervates digital branches to the skin of the medial one and a half digits (Figure 29–2). A corresponding area of the palm is innervated by palmar branches that arise from the ulnar nerve in the forearm. The deep branch of the ulnar nerve accompanies the deep palmar arch and supplies innervation to the three hypothenar muscles, the medial two lumbrical muscles, all the interossei, and the adductor pollicis. The ulnar nerve also innervates the palmaris brevis muscle.

Fig. 29-1

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