Radial Nerve Block for Palmar Laceration
For palmar lacerations requiring anesthesia, perform a wrist-level nerve block targeting the median and ulnar nerves rather than a radial nerve block alone, as the radial nerve does not provide sensory innervation to the palmar surface of the hand. 1, 2
Anatomic Rationale
The palmar surface of the hand receives sensory innervation primarily from:
- Median nerve: Supplies the palmar aspect of the thumb, index, middle, and radial half of the ring finger 1
- Ulnar nerve: Supplies the palmar aspect of the small finger and ulnar half of the ring finger 1, 2
- Radial nerve: Only provides sensory innervation to the dorsal aspect of the hand (anatomic snuffbox region) and does NOT innervate the palm 2
Recommended Technique: Combined Median and Ulnar Nerve Block at the Wrist
Perform ultrasound-guided or landmark-based nerve blocks at the wrist level using 3 mL of 1% lidocaine (or mepivacaine) for each nerve. 2
Procedural Steps:
- Prepare the injection site with antiseptic solution before performing the nerve block 3
- Aspirate before each injection to ensure the needle is not intravascular 3
- Inject slowly to minimize discomfort and tissue trauma 3
- Wait 5-10 minutes for complete anesthesia onset before proceeding with laceration repair 1
Expected Outcomes:
- This technique provides a 56% reduction in procedural pain compared to direct local infiltration 1
- 88% of patients prefer wrist-level nerve blocks over direct palmar injection 1
- Pain intensity with this approach averages 1.03 on a 0-10 verbal numerical scale 2
Alternative Technique: Single Palmar Injection (Transthecal Block)
If wrist-level blocks are not feasible, consider a single subcutaneous palmar injection at the base of the affected digit:
- This technique achieves equivalent anesthesia to traditional two-injection digital blocks 4
- Use lidocaine with epinephrine (avoiding epinephrine in digits with compromised perfusion) 4
- Provides rapid onset of total digital analgesia 5
Critical Safety Considerations
- Maximum lidocaine dose: Do not exceed 7.0 mg/kg (or 500 mg total) to avoid systemic toxicity 6
- Avoid epinephrine in digits with suspected vascular compromise or in patients with peripheral vascular disease 4
- Monitor continuously for signs of local anesthetic systemic toxicity, particularly with larger volumes 6
Common Pitfall to Avoid
Do not attempt a "radial block" for palmar lacerations—this is anatomically inappropriate as the radial nerve does not innervate the palm. The radial nerve only provides sensation to the dorsal hand, specifically the anatomic snuffbox region. 2 Attempting this would result in inadequate anesthesia and necessitate rescue local infiltration, defeating the purpose of the regional block.