What is the management of propranolol (beta blocker) toxicity?

Management of Propranolol Toxicity

High-dose insulin therapy with glucose supplementation is the first-line treatment for propranolol toxicity, followed by glucagon administration and vasopressors for patients in refractory shock. 1

Initial Assessment and Stabilization

• Assess for severity of toxicity:

  • Bradycardia (heart rate <50 beats/min)
  • Hypotension (systolic BP <90 mmHg)
  • Altered mental status, seizures, or coma
  • ECG changes (QRS widening indicating sodium channel blockade)

• Immediate interventions:

  • Secure airway, breathing, and circulation
  • Continuous cardiac monitoring
  • Frequent blood pressure measurements
  • Serial ECGs
  • Blood glucose and potassium monitoring
  • Consider activated charcoal for recent ingestions (within 1-2 hours) if airway is protected 1

Pharmacological Management Algorithm

First-Line Treatments

1. High-Dose Insulin Euglycemic Therapy (Class 1, B-NR evidence) 1

   • Initial bolus: 1 U/kg IV
   • Continuous infusion: 1 U/kg/hour
   • Titrate up based on clinical response
   • Co-administer with dextrose
   • Monitor glucose every 15-30 minutes initially

2. IV Glucagon (Class 2a, C-LD evidence) 1, 2

   • Bolus: 50-150 mcg/kg IV (or 5-10 mg) over 3-5 minutes
   • Continuous infusion: 1-5 mg/hour
   • Caution: May cause vomiting; protect airway

3. Vasopressors (Class 1, C-LD evidence) 1

   • Epinephrine, norepinephrine, or dopamine
   • Titrate to effect based on blood pressure response
   • Note: Epinephrine may provoke uncontrolled hypertension in some cases 2

Second-Line Treatments

1. Calcium Administration (Class 2b, C-LD evidence) 1

   • Calcium chloride or calcium gluconate IV
   • May repeat every 10-20 minutes for 3-4 doses if beneficial

2. Atropine (Class 2b, C-LD evidence) 1, 2

   • Dose: 0.5-1 mg IV for symptomatic bradycardia
   • Note: Often has limited efficacy in beta-blocker overdose

3. Phosphodiesterase Inhibitors 2

   • May be useful for positive inotropic effect

Advanced Life Support

• Extracorporeal Life Support (VA-ECMO) (Class 2a, C-LD evidence) 1
  • Consider for life-threatening poisoning with cardiogenic shock unresponsive to pharmacological interventions
  • Early consultation with ECMO team recommended

Important Clinical Considerations

Dose-Related Toxicity

• Severe toxicity threshold appears to be ≥2,000 mg in isolated propranolol overdose 3
• Lowest reported dose for:
  • Hypotension: 400 mg
  • Bradycardia: 800 mg
  • Severe toxicity (seizures, coma, need for inotropes): 2,000 mg 3

Limitations of Specific Treatments

• Hemodialysis: Not recommended for propranolol toxicity as it is not significantly dialyzable due to high protein binding and lipophilicity 4, 2
• Gastric Decontamination: Consider only for recent ingestions with protected airway 1, 2

Monitoring Parameters

• Continuous cardiac monitoring until clinical improvement
• Blood glucose, potassium, and lactate levels
• Hemodynamic parameters
• Neurobehavioral status
• Intake and output balance 1, 2

Special Considerations

• Time interval between ingestion and treatment initiation is critical for prognosis 5
• Propranolol toxicity can present with:
  • Cardiac manifestations: Bradycardia, hypotension, cardiogenic shock
  • Neurological manifestations: Seizures, altered consciousness, coma
  • Respiratory: Bronchospasm (treat with isoproterenol and aminophylline) 2, 5

Treatment Tapering

• Begin tapering vasopressors and insulin therapy as the patient stabilizes
• Continue monitoring for rebound hypotension or bradycardia

Pitfalls to Avoid

• Patients may look deceptively well before sudden deterioration 6
• Propranolol overdose can cause shock due to decreased systemic vascular resistance, not just myocardial depression 7
• Delayed treatment significantly worsens outcomes 5
• Epinephrine may cause paradoxical hypertension and should be used with caution 2