What is an ulnar nerve block?
An ulnar nerve block is an injection of anesthesia to numb parts of the hand for surgery.
An ulnar nerve block is a procedure to numb the side of the hand with the little finger. An anesthetic solution is injected adjacent to the ulnar nerve in the wrist or the elbow. The anesthetic blocks the transmission of pain signals from an injured portion of the hand to the brain.
The ulnar nerve is one of the terminal branches of the brachial plexus, a network of nerves under the collarbone that transmits sensory and motor information of the shoulder, arm, forearm, and hand. The brachial plexus nerve roots emerge from the spine in the neck and pass behind the collarbone and down the arm, dividing into multiple branches.
The following three nerves and their branches provide sensation to the hand:
- Radial nerve
- Median nerve
- Ulnar nerve
The ulnar nerve and its branches provide sensation and motor function to the side of the hand with the little finger. The ulnar nerve block provides anesthesia to:
- The little finger
- One side of the ring finger
- The part of the palm and back of the hand below the little finger and mid-line of the ring finger
Why is an ulnar nerve block performed?
An ulnar nerve block may be performed as a single procedure or in combination with a radial and/or median block, as needed. An ulnar nerve block is usually done for one of the following reasons:
- Anesthesia for surgical procedures.
- Pain relief (analgesia) for acute pain, post-surgery or from injury.
- Pain management for chronic pain from certain conditions such as:
- Ulnar nerve neuropathy: Numbness, weakness, tingling and pain, due to ulnar nerve irritation.
- Failed ulnar nerve transposition: Lack of pain relief from changing the position of the ulnar nerve to prevent irritation.
An ulnar nerve block is administered in situations that include:
- Incomplete anesthesia in the hand from a brachial plexus nerve block (administered in the neck or under the collarbone)
- Creation of a surgical connection between an artery and vein in the hand (arteriovenous fistula) for the purpose of hemodialysis
- Surgical procedures involving the hand and fingers
- Repair of lacerations and fractures in the hand and fingers
- Treatment of
- Cellulitis in the hand
- Nail infections
- Abscesses
- Burn injuries
- Implantation of a nerve stimulator to treat chronic pain from neuropathy
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How is an ulnar nerve block done?
An ulnar nerve block is most often performed by a hand surgeon as an outpatient procedure in the emergency room. The two most common approaches for the ulnar block injection are:
- Above the elbow joint on the inside of the arm
- Above the wrist crease on the inside of the forearm
Anesthesia
The anesthetic agent used may be
- Lidocaine or mepivacaine for short- and fast-acting blocks
- Bupivacaine or ropivacaine for longer-lasting blocks
Preparation
- The patient lies flat with their hand appropriately positioned.
- The doctor does a physical examination of the hand to assess its neurovascular function.
- The injection site is sterilized with an antiseptic solution.
Procedure
The doctor
- Uses ultrasound guidance during the entire procedure for accurate positioning and needle angle and administration of the anesthetic.
- May use a nerve stimulator to confirm the correct location of the nerve by producing a tingling sensation.
- Sterilizes the injection site with antiseptic.
- Inserts the needle and slowly injects the anesthetic.
- Withdraws the needle and massages the injection site gently to help the solution spread in the tissues.
- Waits for up to 10 minutes for the nerve block to take effect.
- Will instruct the patient on caring for their hand as anesthetized extremities are at a greater risk of injury, especially with long-lasting anesthetics.
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How long does an ulnar nerve block last?
The duration of the ulnar nerve block’s effects depends on the kind and quantity of anesthetic agent used. Anesthetic effects may last for up to five hours, but analgesic effects may last for approximately
- Lidocaine/mepivacaine: Three to eight hours
- Bupivacaine: Five to 30 hours
The patient may experience tingling, discomfort or pain as the ulnar nerve block wears off. Residual pain may be resolved with oral painkillers.
What are the risks and complications of an ulnar nerve block?
Ulnar nerve blocks are generally safe, especially as they are performed with ultrasound guidance. Potential complications include:
- Infection at the injection site
- Pain at the injection site
- Bleeding at the injection site
- Hematoma
- Nerve injury
- Injury to blood vessel
- Allergic reaction to the local anesthetic
- Local anesthetic systemic toxicity
- Unsuccessful nerve block