Median and Ulnar Nerve Blocks

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    Median and Ulnar Nerve Blocks

    Injuries to the hands are a frequent complaint in the emergency department. When the injury isn’t limited to a single digit, or involves larger areas of the hand such as a burn or deep laceration, a nerve block can be an effective option for general pain control as well as any procedures you may need to do. It also reduces or eliminates the need for opiates.

    As with most nerve blocks, you typically want to use lidocaine (with or without epi), bupivacaine, or a mix of the two. Lidocaine has a faster onset but only lasts ~60 minutes, while bupivacaine has a slower onset but provides 2-4 hours of relief. Mixing the two can give you the best of both worlds. Use a 25 or 27-gauge needle for injection, and be sure to clean the overlying skin.

    The median nerve provides sensory innervation to the palmar aspect of the thumb, index, middle, and half the ring fingers as well as the majority of the palm. This is the easiest procedure to do based on landmarks alone as it runs between flexor carpi radialis and palmaris longus tendon. However, ultrasound can increase your accuracy as the nerve is fairly superficial and you may go too deep. If going by landmarks, inject 3-5cc of anesthetic between the flexor carpi radialis and palmaris longus 2-3cm proximal to the wrist crease, at a depth of ~1cm.

    The ulnar nerve sensory distribution includes the dorsal AND palmar aspects of the lateral hand (ulnar half of the 4th and the entire 5th digit). It runs along the ulnar artery just deep to the flexor carpi ulnaris. You should approach the nerve laterally (as opposed to volarly as you may hit the ulnar artery), and inject 1-2cc just under the flexor carpi ulnaris. Then angle your needle deeper, towards the ulna, and inject 3-5cc of anesthetic as you withdraw.

    Here is a video of ultrasound-guided median and ulnar nerve blocks. Note that they go more proximally in the arm than you would going based off landmarks alone.

    Thanks to Judah for the inspiration for this pearl, and for letting me do an ultrasound-guided median nerve block on him.

     

    References:

    • Roberts and Hedges’ Clinical Procedures in Emergency Medicine
    • https://wikem.org/wiki/Nerve_Block:_Median
    • http://www.emdocs.net/amateur-boxers-fracture/ (written by our very own David Cisewski, Ahra Joh, and Stephen Alerhand!)

     

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