Refractory Bradycardia After Mixed Verapamil and Metoprolol Overdose
A 54-year-old man arrives 3 hours after swallowing ten 480 mg verapamil SR tablets and ten 100 mg metoprolol succinate tablets in a suicide attempt. He is drowsy, withdraws to pain, and protects his airway. Heart rate 42/min, blood pressure 68/40 mmHg, respiratory rate 14, SpO2 96% on room air, temperature 36.1°C. Point-of-care glucose is 284 mg/dL. The ECG shows a junctional bradycardia with a QRS of 130 ms. He has one 18-gauge peripheral IV, no central access, and no pacing pads applied. The nearest ECMO center is 90 minutes away by ground; the local ICU has one bed and a nurse who has never run high-dose insulin euglycemia therapy.
1. Prioritize the first 60 minutes. Which interventions come first, which can wait, and what findings would make you change course?
Read the worked answer
First, do not be distracted by the heart rate number. The lethal problem is pump failure, so priority goes to airway protection, reliable access, and inotropy.
- Airway and access: jaw thrust, suction, oxygen; place a second large-bore IV or an intraosseous line. Central access is ideal before starting concentrated calcium but must not delay therapy.
- Pads on the chest, but atropine is only a temporizing move: 1 mg IV, repeated once or twice. Atropine rarely helps in calcium-channel blocker poisoning because the block is downstream of the vagus, so do not spend 15 minutes repeating it.
- Calcium: calcium gluconate 10% 60 mL (or calcium chloride 10% 20 mL through a large peripheral line, accepting vein irritation) IV over 10 minutes, repeated every 10–20 minutes guided by blood pressure and ionized calcium. This is first-line for verapamil.
- Glucagon 5 mg IV for the beta-blocker component, then an infusion of 1–5 mg/h if there is a response.
- Start a catecholamine infusion early (epinephrine, titrated) rather than large fluid boluses, which this failing ventricle will not tolerate. A push-dose vasopressor is the bridge while the drip is prepared.
- Prepare high-dose insulin euglycemia therapy while the above runs; it takes 15–30 minutes to work, so it must be started before collapse.
- Decontamination and disposition: activated charcoal 1 g/kg only if the airway is protected and the dose can be given safely; call the poison center and the ECMO center now, because transfer happens best before arrest. Change course if he develops pulmonary edema, a widening QRS, or worsening acidosis - those are triggers to escalate and transfer immediately.
2. The ICU nurse asks how you will run high-dose insulin euglycemia therapy, what to monitor, and why the glucose is already high. Explain the plan and the practical constraints of a peripheral line.
Read the worked answer
The hyperglycemia is expected: verapamil blocks pancreatic beta-cell calcium channels, catecholamines are high, and peripheral insulin resistance is increased. It is not a reason to withhold insulin therapy.
Regimen: give a bolus of 1 unit/kg regular insulin with 0.5 g/kg dextrose (in practice 25 g as D25W or D10W, since glucose is already high). Then infuse insulin at 0.5 unit/kg/h, titrating by 0.5–1 unit/kg/h every 20–30 minutes toward a clinical effect, with doses up to 10 units/kg/h reported in refractory cases. Run dextrose (D10W at roughly 0.5–1× maintenance, or higher) to hold glucose between 100 and 200 mg/dL.
Monitoring: glucose every 15–20 minutes during titration, then hourly; potassium and magnesium hourly at first; arterial blood gas; watch for hypoglycemia, hypokalemia (replete aggressively, the insulin drives potassium intracellularly), hypomagnesemia, and fluid overload from the dextrose load.
Peripheral-line constraints: never push D50W peripherally in this setting - use D10W or D25W diluted. Regular insulin can be given in a concentrated drip; carrier fluids and dextrose can share a second pump. If glucose falls below 100 mg/dL, increase dextrose rather than stopping insulin, because stopping insulin abruptly can precipitate cardiovascular collapse. Continue the infusion until hemodynamic stability has been sustained for several hours and vasopressors are weaned - the effect outlasts the infusion by roughly the drug's half-life.
3. The patient remains hypotensive at 60 minutes. Rank your next options - transcutaneous pacing, intravenous lipid emulsion, whole-bowel irrigation, vasopressin, transfer - and justify the order.
Read the worked answer
Pacing is worth applying but should not displace pharmacologic inotropy. Transcutaneous pacing may capture electrically without generating a pulse in a verapamil-poisoned myocardium; if there is no mechanical capture within a few minutes, do not escalate energy indefinitely, move on.
Lipid emulsion is the next plausible rescue for a lipophilic drug like verapamil with refractory collapse: 20% emulsion 1.5 mL/kg bolus, then 0.25 mL/kg/min for 30–60 minutes, respecting an upper limit around 10–12 mL/kg. Evidence is anecdotal and it can interfere with laboratory assays and with ECMO oxygenation, so reserve it for collapse refractory to calcium, catecholamines, glucagon, and insulin.
Vasopressin can be added as a catecholamine-sparing adjunct in vasodilatory shock but will not fix the inotropy problem; norepinephrine or epinephrine remains the backbone.
Whole-bowel irrigation is reasonable for this sustained-release preparation if there is no bowel obstruction and the airway is protected: polyethylene glycol 1–2 L/h until clear effluent. It is low risk and may reduce ongoing absorption, but it is not a rescue therapy and should not delay transfer or occupy the only nurse.
Transfer dominates the list. Sustained-release verapamil produces prolonged toxicity, and this patient's trajectory is deterioration. Arrange ECMO-capable transfer while he is still perfusing; do not wait for arrest, and do not allow irrigation or pacing to consume the 90-minute window.