Wrist Block

Published on 16/03/2015 by admin

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Last modified 16/03/2015

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Chapter 4 Wrist Block

Overview

The following three nerves are involved in an wrist block: radial, median, and ulnar.

1. The ulnar nerve has a dorsal sensory branch that arises 5 cm proximal to the wrist crease.
2. Two techniques can be used to block the ulnar nerve.

a. Proximal block:

(1) A proximal block anesthetizes the ulnar nerve approximately 6 cm proximal to the wrist crease.
(2) In most cases, a proximal block will block both branches.
(3) Variable anatomy is always a risk.

b. Distal block:

(1) The ulnar nerve is anesthetized near the wrist crease and the injection of anesthetic is directed both volarly to anesthetize the ulnar nerve and dorsally to anesthetize the dorsal cutaneous branch.
(2) The distal block technique ensures that both branches are consistently blocked.
(3) The distal block is the favored technique.

Indications for use

1. A complete wrist block can be used when soft tissue procedures that cross dermatomal boundaries are performed.
2. Selective nerve blocks:

a. Ulnar: Reduction of fractures about the small finger (particularly boxer’s fractures) and ulnar-sided soft tissue concerns
b. Median: Fingertip injuries to the index and long fingers
c. Radial: Reduction of fractures about the thumb and dorsal hand soft tissue concerns

Precautions

1. Intravascular injection is of particular concern when injecting anesthetic around the wrist.
2. Use of epinephrine should be avoided in wrist blocks.

Pearls

1. Asking the patient to make a fist can aid in palpation of anatomic landmarks.
2. When injecting anesthetic near the ulnar nerve, look for a fullness in the area radial to the flexor carpi ulnaris (FCU) tendon to confirm correct placement.

Equipment

1. Antiseptic: Chlorhexidine prep stick or alcohol-soaked gauze
2. Syringe: Three 10-mL syringes
3. Needle:

a. Large-bore, blunt-tipped, drawing-up needles
b. 1-inch, 25-gauge needle

4. Anesthetic (for a typical adult):

a. Lidocaine: 15 mL of 1%
b. Bupivacaine: 15 mL of 0.5%

(1) Ulnar nerve: 8 to 10 mL of anesthetic
(2) Median nerve: 3 to 5 mL of anesthetic
(3) Radial nerve: 5 to 8 mL of anesthetic

5. Sterile gloves
6. 4 × 4 inch gauze

Basic technique

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