Refractory Amlodipine Overdose With Marginal ECMO Access
A 47-year-old man with depression is brought 2 hours after ingesting 300 mg of amlodipine and an unknown amount of alcohol. On arrival he is drowsy but arousable. Blood pressure is 74/40 mmHg, heart rate 42/min, respiratory rate 12/min, and SpO2 is 96% on room air; glucose is 260 mg/dL. ECG shows sinus bradycardia with PR 0.24 s and QRS 110 ms. He has received 2 L of 0.9% saline and one 1 mg dose of naloxone without change; atropine 1 mg produced no response. Bedside ultrasound shows a hyperdynamic left ventricle. The pharmacy has calcium gluconate, glucagon, high-dose insulin, and lipid emulsion; the intensivist is 30 minutes away. The nearest extracorporeal support center is 90 minutes away by air, but weather is marginal.
1. What is the initial antidotal and vasopressor sequence for this calcium-channel blocker overdose?
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Initial antidotal sequence. This is severe calcium-channel blocker toxicity with bradycardia and hypotension. Give IV calcium gluconate 10% 30 mL or calcium chloride 10% 10 mL via central line, and repeat or start an infusion if there is no response. Atropine is unlikely to help but has been given. Start vasopressors, preferably norepinephrine, and consider glucagon 3-5 mg IV if calcium and pressors are insufficient. Do not give more fluid after 2 L without reassessing for pulmonary edema. The reasoning is that CCBs block L-type calcium channels, so calcium and catecholamines are temporizing; high-dose insulin is the next definitive medical therapy. The hyperdynamic ventricle on ultrasound suggests vasoplegia and reflex tachycardia rather than pump failure, but toxicity can evolve.
2. How would you prescribe high-dose insulin euglycemia therapy, and what must be monitored?
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High-dose insulin euglycemia therapy. Give a bolus of regular insulin 1 unit/kg with 25 g dextrose, then infuse 0.5-1 unit/kg/hour, up to 2 units/kg/hour in refractory cases, and monitor glucose every 15-30 minutes. Add a dextrose infusion to maintain euglycemia; insulin is being used as an inotrope, not for hyperglycemia. Monitor potassium, magnesium, and phosphate, and watch for hypoglycemia and hypokalemia. The reasoning is that insulin improves myocardial carbohydrate utilization and contractility in CCB overdose. It should be started early in severe poisoning rather than after cardiac arrest. If hypotension persists despite calcium, vasopressors, glucagon, and high-dose insulin, consider lipid emulsion for amlodipine because it is lipophilic, and evaluate for ECMO.
3. When should you consider pacing, lipid emulsion, or ECMO?
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ECMO and pacing. Transcutaneous pacing is often ineffective in CCB overdose because the myocardium is not responsive to electrical capture, but it can be tried if bradycardia is the dominant problem. The patient is refractory to atropine and hypotensive, so pacing is a bridge at best. Early consultation with the extracorporeal support center is indicated; a 90-minute air transfer is acceptable if the patient can be stabilized and the weather improves, but do not wait for ECMO before giving calcium, vasopressors, glucagon, and high-dose insulin. The reasoning is that ECMO is the definitive support for refractory cardiogenic shock, but outcomes depend on early cannulation before irreversible organ failure. The marginal weather makes pre-transfer stabilization essential.