Local Anesthetic Systemic Toxicity During a Wide-Awake Hand Procedure
Mr. T is an 82-kg, 54-year-old man undergoing wide-awake open carpal tunnel release. The surgeon asks you to prepare a field block using 40 mL of 1% lidocaine with 1:100,000 epinephrine plus 20 mL of 0.5% bupivacaine, and he plans to infiltrate the entire volume. Ten minutes after 25 mL of the lidocaine solution is injected, Mr. T becomes agitated and reports tinnitus and a metallic taste. He then has a 30-second tonic-clonic seizure. His BP is 178/102, HR 128, and SpO2 is 94% on room air. The surgeon says, 'Give him more midazolam and let us keep going; we are almost done.' There is no anesthesiologist in the room. Sedation is being provided by the circulating nurse under the surgeon's direction, and the lipid emulsion kit is in the code cart but has not been opened.
1. What is the most likely diagnosis, and how do the dose and the clinical presentation support it?
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This is local anesthetic systemic toxicity (LAST). The early agitation, tinnitus, metallic taste, and seizure are a classic neurologic prodrome, and the hypertension and tachycardia reflect sympathetic stimulation. The dose matters but does not exclude the diagnosis. Twenty-five milliliters of 1% lidocaine is 250 mg, below the 7 mg/kg maximum with epinephrine, which is about 574 mg for an 82-kg patient. However, a calculated maximum is not a guarantee against toxicity, especially with inadvertent intravascular injection or rapid injection. If the planned full volumes were given, the patient would receive 400 mg of lidocaine plus 100 mg of bupivacaine. Bupivacaine is more cardiotoxic, and its maximum is roughly 2.5 to 3 mg/kg, or 175 to 205 mg, so the combination narrows the margin. The absence of an anesthesiologist and the surgeon's instruction to continue make this an emergency. Stop the injection and treat the clinical syndrome, not the calculated number.
2. Outline your immediate management, including drug doses and agents to avoid.
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Stop the injection immediately. Call for help and activate the emergency response. Bring the code cart and the lipid emulsion kit. Give 100% oxygen, support ventilation, and monitor ECG, SpO2, and blood pressure. For the seizure, give a benzodiazepine such as midazolam or diazepam and protect the airway. Start 20% lipid emulsion at 1.5 mL/kg lean body weight, about 120 mL for 82 kg, over 1 minute, then infuse at 0.25 mL/kg/min, about 15 mL/kg/hr. Repeat the bolus if instability persists. Avoid vasopressin, calcium-channel blockers, beta-blockers, and additional local anesthetic. If cardiac arrest occurs, use standard CPR but reduce epinephrine to 1 mcg/kg or less. Continue the lipid infusion for at least 15 minutes after stability and monitor for rebound for 4 to 6 hours. Document times, doses, and response.
3. How do you handle the surgeon's instruction to give more sedation and continue the case?
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Patient safety overrides the surgeon's convenience. I would say clearly: 'We have a confirmed seizure from local anesthetic. Continuing injections could cause cardiac arrest. We are stopping, treating, and transferring him for monitoring.' I would not give more midazolam as a way to suppress symptoms and continue. I would ask the circulator to call the charge nurse and anesthesia, and I would document the surgeon's request and my response objectively. If the surgeon continued to insist, I would escalate to the OR director and risk management. Advocacy is part of the RNFA role. The patient cannot consent to continue during a seizure, and the standard of care is to treat LAST aggressively. A post-event debriefing and an incident report should follow.