Technique

Block at the humerus level

  • Position the patient supine with the arm abducted 45º and the hand resting comfortably on the abdomen. Radial nerve block land marks are shown in the image below.

Radial nerve block at the humerus level.

Radial nerve block at the humerus level.
  • Palpate deeply between the heads of the triceps muscle and the brachialis muscle to identify the musculospiral groove.
  • Prepare the skin with an antiseptic solution.
  • To facilitate needle entry, infiltrate the injection site with lidocaine 1% 0.5-1 mL.
  • Insert the 25-ga 1-in needle perpendicularly toward the musculospiral groove.
  • Identify the nerve by paresthesia or nerve stimulator technique. If no response is elicited, redirect the needle slightly more anteriorly or posteriorly until the response is elicited.
  • Aspirate gently to identify intravascular location of the needle.
  • If the aspiration is negative, slowly inject 7-10 mL of the local anesthetic in slow increments, with intermittent aspiration. The image below shows landmarks for a radial nerve block at the humerus level.

Radial nerve block at the humerus level.

Radial nerve block at the humerus level.

Block at the elbow level

  • Position the patient as described above.
  • Identify the lateral margin of the biceps tendon at the elbow crease by flexing the elbow.
  • Prepare the skin with an antiseptic solution.
  • Insert the needle just lateral to the tendon and advance it in a slightly medial and cephalad direction toward the humerus. Landmarks for a radial nerve block at the elbow are shown in the image below.

Radial nerve block at the elbow. The bicipital ap...

Radial nerve block at the elbow. The bicipital aponeurosis is visible. Needle entry is just lateral to the bicipital aponeurosis.
  • Identify the nerve with paresthesia, nerve stimulation, ultrasonographic guidance, or a combination thereof.
  • After negative aspiration, slowly inject 7-10 mL of the local anesthetic. Landmarks for a radial nerve block at the elbow are shown below.

Radial nerve block at the elbow.

Radial nerve block at the elbow.

Block at the wrist level

  • The radial nerve block at the wrist level (landmarks shown below) is essentially a field block and requires a more extensive infiltration because of its less predictable anatomic location and division into multiple, smaller, cutaneous branches.

Radial nerve block at the wrist level.

Radial nerve block at the wrist level.
  • Inject 5 mL of local anesthetic subcutaneously, just above the radial styloid, aiming medially. Additional landmarks for a radial nerve block at the wrist are shown below.

Radial nerve block at the wrist.

Radial nerve block at the wrist.
  • Extend the infiltration laterally, using an additional 5 mL of local anesthetic.

Pearls

  • The radial nerve block may be performed solely or in combination with ulnar and median nerve blocks.
  • The radial nerve block may supplement the brachial plexus block. If performing a brachial plexus block at the humeral canal, block the radial nerve before blocking the ulnar nerve.
  • This block can be performed at the humerus, elbow, and wrist levels.
  • Lidocaine, bupivacaine, ropivacaine are the local anesthetics typically used for this procedure.
  • Surface landmarks, paresthesia, nerve stimulation, and ultrasonographic guidance are all helpful in performing the radial nerve block.
  • Take care to avoid intraneural or intravascular injection of the local anesthetic.

Complications

  • Complications after wrist block are typically limited to residual paresthesia due to an inadvertent intraneuronal injection. Systemic toxicity is rare because of the distal location of the blockade.
  • Complications may be avoided by taking preventive measures (see Table 2).
Table 2. Prevention of Complications in Radial Nerve Block*  
Complication Prevention
Infection Use aseptic technique
Hematoma Limit number of insertions (1-2 for superficial block)

Use 25-ga needle to avoid puncturing superficial veins

Vascular puncture Do not use epinephrine with wrist and finger blocks
Nerve injury Do not inject when patient reports pain on injection

Do not inject when high pressure is detected on injection

Other injury Instruct the patient on care of the insensate extremity

*Table adapted from Wrist Block, New York School of Regional Anesthesia 

Source Emedicine.medscape.com

See also

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