Beta-blocker Toxicity Summary

Key Features

  • Cardiovascular collapse
  • Bradycardia & hypotension
  • Conduction abnormalities
  • Pulmonary edema
  • Cardiogenic shock

CNS Effects

  • Lipid-soluble: Drowsiness, seizures, coma
  • Hydrophilic: Minimal CNS effects
  • Propranolol highest CNS penetration

ECG Findings

  • Bradycardia
  • AV block (1st/2nd degree)
  • QRS prolongation (propranolol)
  • QT prolongation (sotalol)
  • Asystole risk

Emergency Management

  • ABC with early intubation
  • Atropine for bradycardia
  • Glucagon for severe toxicity
  • High-dose insulin therapy
  • Vasopressors if needed

Monitoring

  • Observe 6 hours (regular)
  • Observe 12 hours (sustained-release)
  • Serial ECGs
  • Cardiac monitoring

Critical Interventions

  • Early HDU/ITU referral
  • Glucagon 5-10mg IV
  • High-dose insulin/dextrose
  • Correct metabolic acidosis
  • Consider pacing

Beta-blocker Toxicity

Life-threatening poisoning requiring aggressive cardiovascular support

Overview

Beta-blocker toxicity presents with cardiovascular collapse as the key feature in severe poisoning. Early recognition and aggressive management are crucial for patient survival.

Critical: Severe beta-blocker poisoning can cause rapid cardiovascular deterioration leading to cardiogenic shock and cardiac arrest.

Clinical Features

Cardiac Features

  • Bradycardia and hypotension
  • Pulmonary edema and cardiogenic shock
  • Syncope and conduction abnormalities
  • AV block (first or second degree)
  • Intraventricular conduction delays
  • Dysrhythmias including asystole
  • QRS prolongation (propranolol)
  • QT prolongation (sotalol - torsade risk)

CNS Features by Solubility

Lipid-Soluble (CNS Effects)

  • Carvedilol
  • Labetalol
  • Metoprolol
  • Oxprenolol
  • Pindolol
  • Propranolol

Effects: Drowsiness, confusion, convulsions, hallucinations, dilated pupils, coma

Hydrophilic (Minimal CNS Effects)

  • Acebutolol
  • Atenolol
  • Bisoprolol
  • Esmolol
  • Nadolol
  • Sotalol

Effects: Few CNS manifestations

Other Features

  • Bronchospasm (especially in asthmatics)
  • CNS-mediated respiratory depression
  • Hypoglycemia (rare)
  • Hypocalcemia (rare)

Initial Management

Primary Assessment & Stabilization
  1. Airway & Breathing: Maintain clear airway and adequate ventilation. Early tracheal intubation may be beneficial in severe poisoning.
  2. Circulation: Immediate cardiovascular assessment and monitoring.
  3. Gastric Decontamination: Consider activated charcoal (50g adults, 1g/kg children) if within 1 hour of toxic ingestion.

Cardiac Monitoring

This agent is cardiotoxic - careful ECG assessment is required:

  • Perform 12-lead ECG in all patients
  • Repeat ECGs in symptomatic patients
  • Monitor for sustained-release preparations
  • Check cardiac rhythm, QRS duration, QT interval

Observation Periods

Preparation Type Observation Period Discharge Criteria
Regular Release ≥6 hours Asymptomatic with normal ECG
Modified/Sustained Release ≥12 hours Asymptomatic with normal ECG

Specific Management

Consider early discussion with HDU/ITU for symptomatic patients or those with abnormal ECG.

Bradycardia Management

First-line: Atropine

  • Adult: 0.5-1.2 mg IV
  • Child: 0.02 mg/kg IV
  • Repeat doses may be necessary

Second-line Options

  • Dobutamine or Isoprenaline if bradycardia with hypotension
  • Temporary pacemaker insertion
  • External pacing as alternative

Hypotension Management

Step-wise Approach
  1. Fluid resuscitation - ensure adequate volume
  2. Treat bradyarrhythmias and tachyarrhythmias appropriately
  3. Early critical care referral for fluid-resistant hypotension
  4. Vasopressors and inotropes via peripheral access if urgent

CRITICAL: Vasopressors through peripheral venous access SHOULD ONLY BE DONE UNDER THE DIRECTION OF AN EXPERIENCED PHYSICIAN (SpR AND ABOVE).

Advanced Management

Glucagon Therapy

Indications: Severe hypotension, heart failure, or cardiogenic shock

  • Dose: 5-10 mg IV bolus
  • Infusion: 1-5 mg/hour after bolus
  • Mechanism: Bypasses beta-receptors via glucagon receptors
  • Side effects: Nausea, vomiting, hyperglycemia

High-Dose Insulin & Dextrose

Protocol

  • Indication: Severe cases with myocardial depression
  • Benefits: Improves myocardial contractility and systemic perfusion
  • Particularly useful in presence of acidosis

Administration

  • Insulin bolus: 1 unit/kg regular insulin
  • Infusion: 0.5-1 unit/kg/hour
  • Dextrose: 0.5 g/kg bolus, then 0.5 g/kg/hour
  • Monitor: Glucose and potassium frequently

Metabolic Acidosis Correction

If metabolic acidosis persists despite hypoxia correction and adequate fluid resuscitation:

  • Consider IV sodium bicarbonate
  • Rapid correction particularly important with QRS prolongation
  • Monitor arterial blood gases

Special Considerations

High-Risk Agents

  • Propranolol: QRS prolongation, seizures, coma
  • Sotalol: QT prolongation, torsade de pointes risk
  • Carvedilol: Additional alpha-blockade causes vasodilation

Pediatric Considerations

  • Higher risk of hypoglycemia
  • Small doses can cause significant toxicity
  • Weight-based dosing for all medications
  • Close glucose monitoring

Disposition

Clinical Scenario Disposition
Asymptomatic after observation period with normal ECG Consider discharge with return precautions
Symptomatic or abnormal ECG Admission with cardiac monitoring
Severe toxicity HDU/ITU admission
Sustained-release ingestion Extended observation (≥24 hours)