Amlodipine and Metoprolol Overdose With Refractory Shock
A 62-year-old woman with hypertension and depression ingests 300 mg amlodipine and 2 g metoprolol. Six hours later she is somnolent but protecting her airway. BP 68/38 mmHg, HR 42, glucose 340 mg/dL, pH 7.22, lactate 9 mmol/L, creatinine 1.3 mg/dL, potassium 4.1 mmol/L. ECG shows junctional bradycardia with QRS 120 ms. A central line and arterial line are placed. Available: calcium gluconate, glucagon, high-dose insulin, 50% dextrose, norepinephrine, lipid emulsion, and transcutaneous pacing. ECMO is available at a center 45 minutes away by ground.
1. Outline your first 30 minutes of pharmacologic therapy in priority order, explaining why each agent is chosen or deferred.
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Priorities: (1) IV calcium gluconate 3 g, or calcium chloride 1 g via the central line, as a bolus and repeat if hypotension persists; calcium is the first-line antagonist in calcium-channel blocker overdose. (2) Atropine 1 mg may be tried for bradycardia but often fails in severe poisoning; do not delay other therapy. (3) Glucagon 3-5 mg IV, then an infusion, to bypass beta-receptor blockade and increase cAMP. (4) Early norepinephrine for vasoplegia. (5) Start high-dose insulin euglycemia early rather than waiting for collapse. Defer lipid emulsion as first-line therapy; amlodipine is not highly lipophilic and the evidence is weaker. Pacing may capture but does not improve cardiac output.
2. How would you initiate and titrate high-dose insulin euglycemia, and which bedside and laboratory parameters determine whether it is working?
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HDIE: regular insulin 1 U/kg bolus with 0.5 g/kg dextrose, then insulin 0.5-1 U/kg/h and a dextrose infusion to keep glucose 100-250 mg/dL. Titrate insulin upward for persistent shock; doses can exceed 10 U/kg/h. Monitor glucose every 15-30 minutes initially and potassium every 1-2 hours; supplement potassium as needed. Working? Look for rising blood pressure, improving lactate and pH, and increasing cardiac output, not just a change in heart rate. If glucose falls, give dextrose boluses rather than stopping insulin. Watch for hypokalemia and fluid overload.
3. What features would make you arrange ECMO rather than continue escalating medical therapy?
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Call for ECMO if shock persists despite calcium, glucagon, vasopressors, and escalating HDIE, or if there is refractory acidosis with pH below 7.1, rising lactate, recurrent arrest, or inability to maintain perfusion. This patient is high risk because of the large amlodipine dose, early lactic acidosis, and conduction delay. Ground transfer is 45 minutes, so activate the ECMO team early rather than after arrest. Continue medical therapy during transfer; do not wait for a single parameter to worsen.