Wrist Block
A systematic approach to ultrasonography of the forearm was developed by the authors to identify the nerve(s) innervating the injured region of the hand. The radial nerve was identified using a 2-step procedure. First, the probe was placed over the radial artery at the wrist so that the artery was seen in cross-section. Second, the probe was moved proximally to the midforearm, keeping the radial artery in the middle of the screen. The radial nerve was visualized adjacent to the radial side of the radial artery. The ulnar nerve was identified using the same 2-step procedure, starting at the distal ulnar artery. The ulnar nerve was visualized adjacent to the ulnar side of the ulnar artery. The median nerve does not have an associated median artery, except in rare anatomic variants. Therefore, in the first step, the probe was centered over the volar wrist, between the ulnar and radial arteries, and moved proximally. The median nerve was visualized in the midforearm among the flexor digitorum muscle bundles (Figure). (71K) Figure. Ulnar, median, and radial nerves (arrow) and arteries (arrowheads) in the forearm. The skin was prepared with povidone-iodine. Under real-time ultrasonographic guidance, the sonographer or an assisting physician, using a 25-gauge needle, injected 2 to 3 mL of a mixture of 1% lidocaine and 0.25% bupivacaine lateral and medial to the identified nerve. (Ann Emerg Med 2007;48(5):558)
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