From the Guidelines
An ulnar nerve block is a medical procedure that temporarily numbs the ulnar nerve to provide pain relief and anesthesia to the pinky finger, half of the ring finger, and the inner side of the hand and wrist. To perform an ulnar nerve block, local anesthetic medication is injected near the ulnar nerve, typically at the elbow, wrist, or axilla (armpit) [ 1 ].
Key Considerations
- The ulnar nerve lies within the same neurovascular bundle as the ulnar artery, and palpation to identify the ulnar artery or use of ultrasound may be necessary to locate the nerve, especially in patients with peripheral edema [ 1 ].
- Common anesthetics used for ulnar nerve blocks include lidocaine (1-2%) for shorter procedures and bupivacaine (0.25-0.5%) for longer-lasting blocks.
- The procedure involves skin preparation, precise needle placement, and injection of the anesthetic, resulting in numbness within 5-15 minutes.
Important Details
- The block works by preventing sodium channels in the nerve from opening, which stops pain signals from traveling to the brain.
- Potential side effects include temporary weakness or numbness beyond the intended area, bruising at the injection site, and rarely, nerve injury or systemic toxicity from the anesthetic.
- The block typically wears off gradually as the body metabolizes the medication, providing temporary pain relief for hand and wrist surgeries, acute injuries, or chronic pain conditions.
From the Research
Ulnar Nerve Block Description
An ulnar nerve block is a procedure used to provide local anesthesia to the ulnar nerve, which is one of the three main nerves in the wrist, along with the radial and median nerves [ 2, 3 ]. This block can be used for various surgical procedures, including hand and finger surgeries, and is particularly useful for managing common problems such as fractures, lacerations, and infections [ 3 ].
Techniques for Ulnar Nerve Block
There are different techniques for performing an ulnar nerve block, including:
- The ulnar technique, which has been associated with no ulnar artery and/or ulnar nerve injury [ 2 ]
- The volar technique
- The transtendinous technique
- Ultrasound-guided nerve block, which can help reduce the volume of local anesthetic required and minimize the risk of complications [ 4, 5 ]
Anatomical Considerations
The ulnar nerve is typically located posterior to the flexor carpi ulnaris tendon in the distal wrist [ 2 ]. The ulnar artery is usually radial to the ulnar nerve, approximately 1 cm proximal to the pisiform [ 2 ]. Understanding the anatomy of the distal wrist is crucial for providing a safe and effective ulnar nerve block.
Local Anesthetic Volume
The volume of local anesthetic required for an ulnar nerve block can vary, but studies have estimated the 50% effective dose (ED50) and 95% effective dose (ED95) volumes for 1% mepivacaine [ 4 ]. The use of ultrasound guidance can help reduce the volume of local anesthetic required and improve the accuracy of the block [ 4, 5 ].
Clinical Applications
Ulnar nerve blocks can be used in various clinical settings, including: