What is the next step in assessment for a patient who develops increased pain and possible numbness after receiving lidocaine for carpal tunnel syndrome surgery?

Immediate Assessment: Check for Signs of Hand Ischemia

The next step is to immediately assess for signs of ischemia in the hand (Option C), as increased pain and numbness after lidocaine injection during carpal tunnel surgery may indicate either local anesthetic systemic toxicity (LAST) or vascular compromise from inadvertent epinephrine injection or arterial injury. 1

Primary Assessment Protocol

The immediate evaluation should focus on hand perfusion assessment including:

• Skin color changes: Look for pallor, mottling, or cyanosis of the hand and fingers 1
• Capillary refill time: Delayed (>2 seconds) or absent refill indicates ischemia 1
• Temperature assessment: Compare the affected hand to the contralateral side; cold fingers suggest compromised perfusion 1
• Pulse examination: Palpate radial and ulnar artery pulses, and digital pulses if accessible 1
• Motor function: Assess the patient's ability to move fingers 1

Concurrent Vital Sign Monitoring

While assessing hand perfusion, simultaneously monitor for systemic toxicity (which addresses Option A):

• Cardiovascular monitoring: ECG, pulse oximetry, and blood pressure should be checked every 5 minutes during the initial assessment period 2, 1
• Early neurological signs of LAST: The FDA drug label indicates that CNS manifestations typically precede cardiovascular toxicity and include light-headedness, nervousness, confusion, dizziness, tinnitus, sensations of numbness, and drowsiness 3
• Restlessness, anxiety, tinnitus, dizziness, blurred vision, tremors, or drowsiness may be early warning signs of CNS toxicity 3

Critical Safety Measures

Stop any ongoing injection immediately if not already done 1

Ensure lipid emulsion 20% is readily available at the bedside, as recommended by both the American Heart Association and American Society of Anesthesiologists for potential LAST treatment 1, 2

Why Hand Ischemia Assessment Takes Priority

The clinical scenario describes increased pain after lidocaine application, which is paradoxical since local anesthetics should reduce pain. This suggests:

1. Potential epinephrine-induced vasospasm if lidocaine with epinephrine was used (common in carpal tunnel surgery for hemostasis) 1
2. Inadvertent intra-arterial injection causing local ischemia
3. Compartment syndrome from injection volume or hematoma
4. LAST presenting with altered sensation

The combination of pain AND numbness specifically points toward a vascular or compartment issue rather than pure systemic toxicity, which would present with CNS symptoms (tinnitus, perioral numbness, metallic taste) before progressing to cardiovascular instability 2, 3.

Pharmacologic Intervention Readiness

Be prepared to administer phentolamine (Option B) if epinephrine-induced vasospasm is confirmed, as this alpha-blocker can reverse vasoconstriction 1. However, this is a treatment step, not an assessment step.

Common Pitfall to Avoid

Do not assume the symptoms are simply "normal" postoperative discomfort. Increased pain after local anesthetic injection is never normal and demands immediate investigation. Small doses of local anesthetics injected into the hand and wrist area can produce adverse reactions, including intra-arterial injection with resultant ischemia 3.

The FDA label specifically warns that local anesthetic solutions containing vasoconstrictors "should be used cautiously and in carefully circumscribed quantities in areas of the body supplied by end arteries or having otherwise compromised blood supply" as "ischemic injury or necrosis may result" 3.