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

Immediate Assessment: Check for Signs of Hand Ischemia

The next step is to immediately assess for signs of hand ischemia (Option C), including skin color changes (pallor, mottling, cyanosis), capillary refill time, temperature, and pulses. 1

Rationale for This Approach

The clinical presentation of increased pain and numbness after lidocaine injection during carpal tunnel surgery raises two critical concerns that must be differentiated immediately:

Primary Concern: Iatrogenic Ischemia

• Local anesthetic solutions containing vasoconstrictors (commonly epinephrine mixed with lidocaine) can cause ischemic injury or necrosis in areas supplied by end arteries or with compromised blood supply. 2
• The hand is particularly vulnerable to vasoconstrictor-induced ischemia, making this the most urgent assessment priority 2
• Increased pain paradoxically occurring after local anesthetic administration is a red flag for ischemia rather than the expected analgesia 1

Specific Assessment Components Required

The immediate physical examination should evaluate: 1

• Skin color: Look for pallor, mottling, or cyanosis of the hand/fingers
• Capillary refill time: Delayed (>2 seconds) or absent refill indicates ischemia
• Temperature: Compare the affected hand to the contralateral side for coldness
• Pulses: Palpate radial and ulnar artery pulses, plus digital pulses if accessible
• Motor function: Assess ability to move fingers

Why Other Options Are Secondary

Blood Pressure and Heart Rate (Option A)

While cardiovascular monitoring is important for detecting systemic lidocaine toxicity, it is not the immediate priority in this scenario: 3, 2

• Systemic toxicity typically presents with CNS symptoms first (perioral tingling, tinnitus, light-headedness, restlessness) before cardiovascular changes 3, 4
• The patient's presentation of localized increased pain and numbness suggests a local vascular problem rather than systemic toxicity
• However, continuous ECG and pulse oximetry should be maintained as standard monitoring 3

Phentolamine Administration (Option B)

This is a potential treatment, not an assessment step: 1

• Phentolamine is an alpha-blocker used to reverse epinephrine-induced vasospasm
• It should only be administered after confirming ischemia through physical examination
• Having it prepared and ready is appropriate, but assessment must precede treatment 1

IV Fluids (Option D)

This addresses neither ischemia nor systemic toxicity as the primary concern and is not indicated as the next immediate step.

Critical Management Algorithm After Assessment

If ischemia is confirmed: 1

1. Stop any ongoing injection immediately
2. Consider phentolamine for epinephrine-induced vasospasm
3. Ensure lipid emulsion 20% is readily available for potential systemic toxicity 4, 1
4. Document findings and preserve equipment for investigation

If systemic toxicity is suspected instead: 3, 4

• Early CNS signs include restlessness, anxiety, tinnitus, dizziness, blurred vision, tremors
• More severe signs progress to muscle twitching, slurred speech, loss of consciousness, seizures, and ultimately cardiovascular collapse
• Treatment requires immediate lipid emulsion therapy per local anesthetic systemic toxicity (LAST) protocols

Common Pitfall to Avoid

Do not assume increased pain after local anesthetic is simply "inadequate anesthesia" requiring more injection. 2 This paradoxical pain response, especially when accompanied by numbness, strongly suggests vascular compromise and warrants immediate cessation of injection and thorough ischemia assessment before any additional intervention.