What is the treatment for a patient with a beta blocker overdose, particularly one who is hemodynamically unstable with bradycardia and hypotension?

Treatment of Beta Blocker Overdose

Immediate Management

For hemodynamically unstable patients with beta blocker overdose presenting with bradycardia and hypotension, initiate high-dose insulin euglycemia therapy and IV glucagon as first-line pharmacologic interventions, with ECMO reserved for refractory shock. 1, 2, 3

Initial Stabilization

• Establish continuous cardiac monitoring, secure IV access (preferably central if prolonged therapy anticipated), and assess airway protection 3, 4
• Follow standard BLS/ACLS protocols if cardiac arrest occurs 1, 3
• Obtain baseline labs: glucose, potassium, calcium, and renal function 5
• Consider activated charcoal (1-2 g/kg) if presentation within 1-2 hours and airway is protected 5

First-Line Pharmacologic Therapy

High-Dose Insulin Euglycemia Therapy (HIET)

This is the most effective therapy for restoring hemodynamic stability in severe beta blocker toxicity. 1, 2, 3, 4

• Initial bolus: 1 U/kg regular insulin IV with simultaneous 0.5 g/kg dextrose bolus 1, 6, 4
• Continuous infusion: 1 U/kg/hour insulin (can titrate 0.5-10 U/kg/hour based on response) with concurrent dextrose infusion 1, 6, 7
• Monitoring: Check glucose and potassium every 15 minutes initially, then hourly once stable; target glucose 100-250 mg/dL 4, 5
• Common adverse effects: Hypoglycemia and hypokalemia require aggressive monitoring and replacement 6, 7

The American Heart Association positions high-dose insulin as first-line for refractory shock, supported by 10 case series showing mortality benefit and clear haemodynamic improvement in timeframes consistent with insulin administration 4, 7

IV Glucagon

Glucagon is equally reasonable as first-line therapy, bypassing blocked beta-receptors by directly activating adenyl cyclase. 2, 6, 4

• Initial bolus: 3-10 mg IV over 3-5 minutes 6, 4
• Continuous infusion: 3-5 mg/hour (effects are transient, requiring infusion) 6, 4
• Expected response: Increased heart rate and improved contractility independent of beta-receptor status 4
• Side effects: Nausea and vomiting (particularly concerning if airway protection is compromised) 6, 4

Multiple case reports and case series consistently demonstrate increased heart rate with glucagon, though no randomized trials exist 6, 8

Second-Line Therapies

Vasopressor Support

• Norepinephrine: Increases blood pressure in vasoplegic shock 3, 4
• Epinephrine: Increases contractility and heart rate 3, 4
• Dopamine: Can be used but often requires high doses 7

Catecholamines and vasopressors were associated with reduced mortality and improved hemodynamics in systematic review of 16 case reports, 3 case series, and 2 animal studies 7

Calcium Administration

Calcium has weaker evidence for beta blocker overdose compared to calcium channel blocker toxicity, but may be considered. 1, 2

• The American Heart Association gives calcium a Class 2b recommendation (may be considered) for beta blocker overdose 1
• Limited animal data and rare case reports suggest possible utility 1
• More effective for calcium channel blocker toxicity than pure beta blocker overdose 2, 6

Rescue Therapy for Refractory Cases

Extracorporeal Membrane Oxygenation (ECMO)

ECMO should be considered for shock refractory to all pharmacological interventions. 1, 2, 3

• Class 2b recommendation from the American College of Cardiology for beta blocker overdose with refractory shock 1, 3
• Case reports and at least one retrospective observational study demonstrate survival after ECMO in refractory beta blocker overdose 1
• Associated with improved survival in severe cardiogenic shock or cardiac arrest 3, 7

Treatment Algorithm

1. Immediate: Cardiac monitoring, IV access, airway assessment, consider activated charcoal if early presentation 3, 4, 5

2. First-line pharmacotherapy (initiate simultaneously):

   • High-dose insulin: 1 U/kg bolus + 1 U/kg/hour infusion with dextrose 1, 4
   • Glucagon: 3-10 mg IV bolus + 3-5 mg/hour infusion 4

3. If refractory to first-line:

   • Add vasopressor support (norepinephrine or epinephrine) 3, 4
   • Consider calcium (though weaker evidence for beta blockers) 1, 2

4. If refractory to pharmacotherapy:

   • Initiate ECMO 1, 3, 7

Critical Monitoring Parameters

• Continuous cardiac telemetry for rhythm and conduction abnormalities 5
• Arterial line for blood pressure monitoring in shock states 5
• Glucose and potassium every 15 minutes initially, then hourly 4, 5
• Watch for tachyphylaxis with glucagon 4

Common Pitfalls to Avoid

• Do not use lipid emulsion therapy: Variable and inconsistent response reported in 10 case series and 21 case reports; not recommended by guidelines 7
• Do not underdose glucagon: Full 3-10 mg bolus required, not standard ACLS doses 4
• Do not delay escalation to high-dose insulin: Should be initiated early, not after prolonged failure of other therapies 4
• Do not use atropine as primary therapy: Minimal benefit in beta blocker overdose (only one case report showing improvement) 7
• Do not abruptly withdraw beta blockers in chronic users: Can lead to clinical deterioration 3

Special Considerations

• Consult medical toxicology or poison control center (1-800-222-1222) for all beta blocker overdoses 5
• For water-soluble beta blockers (atenolol), hemodialysis may assist elimination in massive overdose, though survival benefit not established 7
• Temporary cardiac pacing has limited utility except for specific arrhythmias (e.g., sotalol-induced torsades) 7