What intervention should be added to the treatment regimen for a patient with severe hypotension, bradycardia, and refractory shock due to beta-blocker (metoprolol succinate) overdose?

Management of Beta-Blocker Overdose with Refractory Shock

High-dose insulin (hyperinsulinemic euglycemic therapy) should be immediately added to this patient's treatment regimen for refractory shock due to beta-blocker overdose. 1, 2

Rationale for High-Dose Insulin Therapy

The American Heart Association gives a Class 1, Level B-NR recommendation (highest level) for high-dose insulin in beta-blocker poisoning with refractory hypotension 1. This patient presents with classic signs of severe beta-blocker toxicity:

• Profound hypotension (68/40 mmHg) despite multiple vasopressors
• Bradycardia (42 beats/min)
• Widened QRS interval
• Refractory shock

High-dose insulin improves inotropy in cardiogenic shock from β-blocker poisoning by:

• Enhancing myocardial energy utilization
• Improving cardiac contractility
• Providing superior outcomes compared to vasopressor-only therapy 1, 2

Dosing Protocol for High-Dose Insulin

1. Initial bolus: 1 U/kg IV regular insulin
2. Concurrent dextrose: 0.5 g/kg IV (to prevent hypoglycemia)
3. Maintenance infusion: 0.5-1 U/kg/hour, titrated to hemodynamic response
4. Dextrose infusion: 0.5 g/kg/hour, titrated to maintain glucose 100-250 mg/dL 1, 2

Monitoring During Insulin Therapy

• Very frequent glucose monitoring (every 15 minutes initially)
• Potassium monitoring (expect moderate hypokalemia 2.5-2.8 mEq/L)
• Central venous access for concentrated dextrose solutions
• Continuous cardiac monitoring
• Frequent assessment of mental status and peripheral perfusion 2

Why Not Other Options?

Glucagon Infusion

• While reasonable (Class 2a, Level C-LD), glucagon is considered second-line after high-dose insulin 1, 2
• Glucagon commonly causes vomiting, which is a concern in this patient with altered mental status 1
• This patient is already on multiple vasopressors without adequate response, suggesting the need for a different mechanism of action

Lipid 20% Emulsion Therapy

• The AHA specifically states that intravenous lipid emulsion therapy is "not likely to be beneficial for life-threatening β-blocker poisoning" (Class 3: No Benefit, Level C-LD) 1

Phenylephrine Infusion

• Adding another vasopressor (phenylephrine) is unlikely to be beneficial when the patient is already on high-dose norepinephrine, epinephrine, and vasopressin without adequate response
• Phenylephrine is primarily an alpha-1 agonist without addressing the underlying cardiac depression from beta-blockade 3

Treatment Algorithm for Beta-Blocker Overdose

1. Initial stabilization with vasopressors (already implemented)
2. Add high-dose insulin therapy (recommended next step)
3. Consider glucagon if inadequate response (bolus 3-10 mg IV over 3-5 minutes, followed by infusion of 3-5 mg/hour) 1, 2
4. For refractory cases, consider VA-ECMO (the medical team is appropriately considering mechanical circulatory support) 1

Pitfalls to Avoid

• Delaying insulin therapy while trying additional vasopressors
• Inadequate glucose monitoring during insulin therapy
• Aggressive potassium repletion (moderate hypokalemia is expected and beneficial)
• Overlooking the need for central venous access for concentrated dextrose solutions
• Failure to recognize that beta-blocker overdose may require prolonged therapy, especially with long-acting agents like metoprolol succinate 4

High-dose insulin therapy has demonstrated superior outcomes in severe beta-blocker toxicity and represents the most appropriate next step in this patient with refractory shock despite multiple vasopressors.