High-Dose Insulin with Glucose is the Recommended Treatment
For a patient with metoprolol overdose presenting with refractory hypotension and bradycardia despite fluids and vasopressors, the American Heart Association recommends high-dose insulin with glucose as the first-line antidote therapy (Class 1, Level B-NR). 1
Why High-Dose Insulin is the Answer
The 2023 AHA focused update on poisoning management provides the strongest recommendation for high-dose insulin therapy in beta-blocker overdose with refractory shock 1. This represents an upgrade from the 2020 guidelines, which classified it as Class 2a 1. The mechanism involves improving myocardial inotropy and energy utilization in cardiogenic shock from beta-blocker poisoning 1.
Dosing Protocol for High-Dose Insulin
- Initial bolus: 1 U/kg regular insulin IV 1
- Continuous infusion: 1 U/kg/hour, titrated to hemodynamic response 1
- Mandatory co-administration: 0.5 g/kg dextrose bolus, followed by 0.5 g/kg/hour dextrose infusion 1
- Glucose monitoring: Every 15 minutes initially, targeting 100-250 mg/dL 1
- Potassium monitoring: Target 2.5-2.8 mEq/L (moderate hypokalemia is common and aggressive repletion can cause asystole) 1
Why the Other Options Are Incorrect
Atropine (Option C) - Limited Utility
While atropine may be reasonable for beta-blocker-induced bradycardia (Class 2b, Level C-LD), it has already failed in this patient who remains hypotensive despite vasopressor administration 1. Atropine works by blocking muscarinic receptors but cannot overcome the direct beta-receptor blockade causing myocardial depression 2. In beta-blocker overdose, atropine is often ineffective for reversing hemodynamic instability 3, 4.
Transcutaneous Pacing (Option D) - May Be Reasonable But Not First-Line
Electrical pacing may be reasonable for beta-blocker-induced bradycardia (Class 2b, Level C-LD), but it addresses only the rate problem, not the underlying myocardial depression and hypotension 1. Pacing cannot improve contractility, which is the primary pathophysiology in this case of refractory shock 1.
Cardioversion (Option A) - Not Indicated
There is no indication for cardioversion in this scenario. The patient has bradycardia, not a tachyarrhythmia requiring electrical cardioversion 1.
Additional Management Considerations
Second-Line Therapies if Insulin Fails
- Glucagon: 3-10 mg IV bolus over 3-5 minutes, followed by 3-5 mg/hour infusion (Class 2a, Level C-LD) 1
- Calcium: 0.3 mEq/kg (0.2 mL/kg of 10% calcium chloride) over 5-10 minutes, followed by infusion (Class 2b, Level C-LD) 1
Rescue Therapy for Refractory Cases
- VA-ECMO: Should be considered for shock refractory to all pharmacological interventions (Class 2a, Level C-LD) 1, 5
Critical Monitoring Requirements
- Continuous cardiac monitoring 6, 5
- Frequent glucose checks (every 15 minutes initially) 1
- Serum potassium monitoring 1
- Early echocardiography to assess myocardial function 5
Common Pitfalls to Avoid
- Do not use lipid emulsion therapy - The AHA explicitly recommends against ILE for beta-blocker poisoning (Class 3: No Benefit) 1, despite some case reports suggesting benefit 7
- Avoid dopamine - It is less effective than epinephrine or norepinephrine for hypotension in this setting 1, 5
- Do not under-dose insulin - The "high-dose" designation is critical; standard insulin doses will not achieve the desired hemodynamic effect 1