Lacerations and fractures on the ulnar side of the hand, including boxer's fractures of the fifth metacarpal, often need analgesia for repair or manipulation. A forearm ulnar nerve block numbs the little finger, the ulnar half of the ring finger and the ulnar side of the palm. The ulnar artery is your landmark.
Scan images in the graphic are illustrations, not patient scans.
Before you block
- Record motor and sensory function of the hand, including two-point discrimination, before the block.
- Record consent and calculate the dose. Three to five millilitres is usually enough.
The scan
- Rest the forearm palm up.
- Place the linear probe transversely on the ulnar side of the forearm, just above the wrist.
- Find the ulnar artery with colour Doppler. The nerve lies on its ulnar side, under flexor carpi ulnaris.
- Slide the probe up the forearm. The nerve moves away from the artery, which gives a safer target.
- Insert the needle in plane from the ulnar side, so it meets the nerve before the artery.
- Inject small amounts and watch the fluid surround the nerve.
Reading the view
- Ulnar artery. Round, black and pulsating, with colour on Doppler.
- Ulnar nerve. A small honeycomb oval on the ulnar side of the artery.
- Flexor carpi ulnaris. The muscle and tendon lying over the nerve.
- Correct spread. Fluid surrounding the nerve, away from the artery.
