Wrist Block

Published on 16/03/2015 by admin

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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

1. Patient positioning:

a. The patient should be seated and a bedside table should be available to position the extremity.
b. For median and ulnar nerve blocks, lay the extremity on a bedside table with the elbow extended and the hand supinated.
c. For radial nerve blocks, lay the extremity on a bedside table with the elbow extended and the hand pronated.

2. Landmarks:

a. Ulnar nerve:

(1) FCU tendon
(2) Ulnar styloid
(3) Injection of the ulnar nerve is carried out 0.5 cm proximal to the ulnar styloid under the FCU tendon.

b. Median nerve:

(1) Palmaris longus tendon
(2) Flexor carpi radialis (FCR) tendon

(a) The palmaris longus tendon is the more prominent and more medial tendon.
(b) Be aware that the palmaris longus is absent in about 10% to 20% of patients. If only one tendon can be palpated, it is the FCR tendon.

(3) Wrist crease
(4) Injection of the median nerve is carried out 2 cm proximal to the wrist crease between the FCR and palmaris longus tendons.

c. Radial nerve:

(1) Radial styloid

3. Steps:

a. Block the ulnar nerve.
b. Block the median nerve.
c. Block the radial and lateral antebrachial cutaneous nerves.

Detailed technique

Prepare the anesthetic; three 10-mL syringes should be prepared.

Ulnar Nerve

1. Position the patient and palpate landmarks:

a. Palpate the FCU tendon (Figure 4-1) and ulnar styloid.
b. Mark the FCU tendon and ulnar styloid.
c. Mark the injection site 0.5 cm proximal to the ulnar styloid under the FCU tendon.

2. Prepare the skin with an antiseptic solution.
3. Numb the skin with ethyl chloride (if desired).
4. Inject the anesthetic (Figure 4-2).

a. Insert the needle at a 90-degree angle to the skin under the FCU tendon.
b. Maintain patient contact to ensure no paresthesias are noted.
c. Aspirate the needle before injection to ensure that intravascular placement has been avoided.
d. Advance the needle 0.5 to 1 cm.
e. Inject 3 to 5 mL of anesthetic. Be vigilant for any warning signs of intravascular injection. Withdraw the needle to a subcutaneous position.
f. Redirect the needle dorsally and advance the length of the needle to cover the dorsal sensory branch of the ulnar nerve (Figure 4-3).
g. Withdraw the needle slowly while injecting 2 to 3 mL of anesthetic subcutaneously.
5. Place a sterile bandage over the injection site.
image

Figure 4-1

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Figure 4-2

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Figure 4-3

Median Nerve

1. Position the patient.
2. Palpate landmarks:

a. Palpate the FCR tendon and palmaris longus.
b. Mark the FCR tendon and palmaris longus.
c. Mark the injection site at the wrist crease just ulnar to the palmaris longus.

3. Prepare the skin with an antiseptic solution.
4. Numb the skin with ethyl chloride (if desired).
5. Inject anesthetic:

a. Enter at a 45-degree angle to the skin (Figure 4-4).
b. Immediately inject 1 to 2 mL of anesthetic subcutaneously to block the palmar cutaneous branch (supplying the skin of the central palm).
c. Maintain contact with the patient to ensure no paresthesias are noted.
d. Advance the needle until the fascia has been penetrated (a click or pop sometimes can be felt) or the needle contacts bone. If the needle contacts bone, withdraw 2 to 3 mm.
e. Inject 3 to 5 mL of anesthetic.

6. Place a sterile bandage over the injection site.
image

Figure 4-4

Radial Nerve

1. Position the patient.
2. Palpate landmarks:

a. Feel the radial styloid.
b. Mark the injection site 0.5 cm proximal to the radial styloid and slightly dorsal.

3. Prepare the skin with an antiseptic solution.
4. Numb the skin with ethyl chloride (if desired).
5. Inject anesthetic (Figures 4-5 and 4-6):

a. Enter at a 90-degree angle to the skin.
b. Insert the needle, aimed in a volar direction.
c. Maintain contact with the patient to determine if paresthesias are noted.
d. Aspirate the needle before injection to ensure that intravascular placement has been avoided.
e. Advance the needle its full length.
f. Inject 5 mL of anesthetic. Be vigilant for any warning signs of intravascular injection.
g. Slowly withdraw the needle until it is in a subcutaneous position.
h. Redirect the needle dorsally.
i. Advance the needle subcutaneously along the dorsum of the wrist.
j. Inject 5 mL of anesthetic in a ring fashion.
6. Place a sterile bandage over the injection site.
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Figure 4-5

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Figure 4-6

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