What is a median nerve block procedure?
A median nerve block is a procedure to anesthetize part of the palm and fingers by injecting an anesthetic solution to numb the median nerve of the forearm. The median nerve block is often performed along with an ulnar and radial nerve block to anesthetize the whole hand and the palm. The median nerve, along with the ulnar and radial nerve, provides sensation to the hand and fingers.
The median nerve provides sensation to the palm side (palmar/volar aspect) of the thumb, index and middle fingers, half of the ring finger and the palm area from the thumb to the middle of the ring finger.
The median nerve also provides sensation to a part of the index, middle and half of the ring finger on the back of the hand. The median nerve is also responsible for the motor function of the forearm and the thumb.
The median nerve block may be administered on the inside of the elbow, forearm or the wrist, but it is most often performed in the wrist, as the numbing effect may be more effective when administered via this approach.
Why is a median nerve block performed?
A median nerve block may be performed solely or in combination with an ulnar and radial block:
- To treat simultaneous injury to several fingers
- For surgical repair of
- To lance and drain abscesses or cysts
- During surgical procedures on the hand and fingers such as
Median nerve block is not performed in patients who have:
- Allergy to the local anesthetic
- Anatomical distortion due to injury or from previous surgeries in the wrist
- A surgical connection (fistula) between an artery and a vein for hemodialysis
- Additional injuries in other parts of the arm that require a greater area of anesthesia
- Infection or cellulitis in the injection site
- Liver disease or failure
Benefits of median nerve block over other local anesthesia procedures include:
How is a median nerve block performed?
The anesthetic agents commonly used for a median nerve block are lidocaine and bupivacaine depending on the length of time that anesthesia is required. The injection is administered between the two flexor tendons in the middle of the wrist.
- The patient lies flat with the 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.
- May use ultrasound guidance to position the needle.
- Inserts the needle up to 2 cm into the skin at a perpendicular angle.
- Aspirates the needle to ensure that it is not inside a blood vessel.
- Injects 3-5 ml of the anesthetic solution.
- Injects another tiny quantity of anesthetic in the tissues under the skin to form a small bump (wheal) while withdrawing the needle.
- 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.
The doctor will instruct the patient on caring for the hand because anesthetized extremities are at a greater risk of injury, especially with long-lasting anesthetics.
How long does a median nerve block last?
The duration of the median nerve block’s effects depends on the kind and quantity of anesthetic agent used.
Approximate duration of effects:
- Lidocaine: Two to five hours
- Bupivacaine: Five to 15 hours
What are the risks and complications of a median nerve block?
Median nerve blocks are generally safe and effective for surgical procedures involving the hand. Potential complications include: