Regional Hand Anesthesia with Ultrasound |
Emergency Department Critical CareRegional Anesthesia of the Hand from MMC
Department of Emergency Medicine 
Regional Anesthesia – Hand
General:
These blocks are excellent block for lacerations, puncture wounds or bony dislocations of the hand. They can be used in parts or in combination to provide anesthesia to the entire hand. When performing a complete hand block, the ulna, median and radial nerves should be blocked.
Ulnar Nerve • Median Nerve • Radial Nerve
Ulnar Nerve
Anatomy:
Identify the flexor carpi ulnaris and ulnar artery by having the have the patient deviate their hand in an ulnar direction at the wrist (giving the thumbs up). The flexor carpi ulnaris is the most medial (ulnar) tendon. The ulnar artery can be palpated just medial and dorsal to the tendon. The nerve lies between the artery and the flexor carpi ulnaris tendon.
Innervation:
The ulnar nerve innervates the flexor pollicis brevis, abductor pollicis, palmaris brevis, abductor digiti minimi, flexor digiti minimi opponens digiti minimi, the medial two lumbicals and all the interossei muscles.
Distribution of anesthesia:
This procedure provides anesthesia to the entire fifth digit, half of the fourth digit and the medial aspect of the hand and wrist.
Technique:
The surgical field should be prepared just proximal (1-2 cm) to the most distal wrist crease. Raise a wheal of anesthetic in the subcutaneous space and insert the needle under the flexor carpi ulnaris one centimeter just palmar to the ulnar styloid. If blood is aspirated, withdraw the needle a few millimeters and aspirate again, the nerve is more superficial from the injection point. Inject approximately 5 to 7 milliliters of anesthetic. To block the cutaneous branches of the ulnar nerve, inject 3 to 5 milliliters of anesthetic just above the tendon of the flexor carpi ulnaris.
Pitfalls:
- If bone is struck withdraw the needle and direct it more palmar.
- Intraneural injection will cause significant pain, therefore withdraw the needle a few millimeters and continue injecting the anesthetic.
Median Nerve
Anatomy:
Identify the flexor carpi radialis and the palmaris longus tendons at the palmar aspect of the wrist. The palmaris longus, if present, is usually the more prominent of the two tendons and can be identified by having the patient flex at the wrist. To help identify the flexor carpi radialis, have the patient flex and abduct the wrist. The median nerve is lateral (radial) to the palmaris longus tendon and between the palmaris longus and the flexor carpi radialis.
Innervation:
The median nerve provides motor innervation to the thenar muscles (abductor pollicis brevis, flexor pollicis brevis, opponens pollicis) and the first and second lumbricals.
Distribution of anesthesia:
The median nerve provides sensory to the lateral three and a half digits except the dorsal aspect of the thumb, and the corresponding area of the palm.
Technique:
The surgical field should be prepared across the entire volar surface of the wrist at the proximal palmar crease. Raise a wheal of anesthetic in a subcutaneous space and insert the needle until it pierces the deep fascia.
If the “pop” of the deep fascia can not be felt, continue to insert the needle until it contacts the bone. Withdraw the needle 2 to 5 millimeters and inject 5 to 7 milliliters of anesthetic. A fan like technique is recommended to ensure complete anesthesia of the median nerve. This can be accomplished by reinserting the needle in the same position approximately 30 degrees medial and 30 degrees lateral and injecting 2 to 5 additional milliliters of anesthetic. The palmar branch of the medial nerve is quite superficial and can be blocked by withdrawing the needle to the subcutaneous space and injecting 3 to 5 milliliters of anesthesia.
Pitfalls:
- Avoid injecting too distal within the carpal tunnel which may exacerbate any carpal tunnel syndrome.
- Intraneural injection will cause significant pain, therefore withdraw the needle a few millimeters and continue injecting the anesthetic.
Radial Nerve
Anatomy:
Locate the radial styloid at the proximal portion of the anatomic snuff box. The anatomic snuff box is just distal to the radial styloid and formed by the extensor tendon of the palmaris brevis and longus. The superficial branch of the radial nerve runs just above the styloid process of the radius. It gives off digital branches to the dorsum of the thumb, index finger and lateral half of the middle finger. Several branches run over the anatomic snuff box. The nerve divides into two major branches about two finger breadths proximal to the distal wrist crease (or anatomical snuff box).
Distribution of anesthesia:
The radial nerve provides sensory innervation to the dorsal lateral half of the hand and the dorsal aspect of the thumb. The radial nerve provides no motor innervation to the intrinsic muscles of the hand however; it does provide innervation for all of the extensor muscles in the posterior forearm.
Technique:
The surgical field should be prepared across the entire dorsal surface of the wrist, including the radial styloid and the anatomic snuff box. Raise a wheal of anesthesia in the subcutaneous space and inject 5 to 7 milliliters of anesthetic just above the radial styloid, aiming the needle first medially and then laterally.
Alternative method:
Using the non-injecting hand, straddle the anatomic snuffbox with the index and middle fingers and press them firmly against the radius. Slowly inject the anesthetic which will spread across the path of the nerve.
Pitfalls:
The distribution of the radial nerve is less predictable; therefore, a generous amount of anesthesia should be injected.
Intraneural injection will cause significant, therefore withdraw the needle a few millimeters and continue injecting the anesthetic.
= Radial Nerve = Median Nerve = Ulnar Nerve
