Beta-Blockers

β-blocker overdose causes ↓ HR, ↓ inotropy, and (possibly) vasodilation; the size of each effect depending on the:

Notably, propranolol penetrates the BBB and ↓↓ seizure threshold. Most deaths from β-blocker overdose are due to propranolol.

Epidemiology and Risk Factors

Pathophysiology

Aetiology

Clinical Features

Cardiac:

  • Bradyarrhythmias
    • ↓ HR
    • AV nodal blockade
      Full spectrum is possible.
    • Asystole
  • Hypotension
  • Cardiogenic shock
    • Pulmonary oedema

Extra-cardiac:

  • Bronchospasm
  • ↓ BSL
  • ↑ K+

Unlike β-blockers, calcium channel blockers do not cause bronchospasm, and will typically ↑ the BSL.

Diagnostic Approach and DDx

Investigations

Bedside:

Laboratory:

Imaging:

Other:

Management

  • Activated charcoal
  • Cardiovascular support
    • Chronotropy
    • Pacing
    • Glucagon
  • High-dose insulin euglycaemic therapy

Resuscitation:

  • C
    • Bradycardia
      • Atropine
        Reasonable for symptomatic bradycardia.
      • Adrenaline
      • Cardiac pacing
    • Hypotension
      • Volume resuscitation
      • Glucagon 10mg IV
      • High-dose insulin-euglycaemic therapy
      • Inotropes
      • Vasopressors
    • ECMO if refractory

Specific therapy:

  • Pharmacological

    • Activated charcoal

      • Ideally within 1-hour of immediate release ingestion
      • Any time after sustained release ingestion
        • Consider multiple (Q4H) dosing

    • Gastric lavage
      Consider if very recent (<1 hour) overdose.

    • High-dose Insulin Euglycaemic Therapy
      Overcomes cardiac metabolic starvation that occurs with cardiac toxidromes.

      • ↑ Glucose and lactate uptake by myocardium
      • Positive inotrope without ↑ oxygen demand
      • Initial therapy:
        • 25g 50mL 50% dextrose unless BSL >22mol/L
        • 1 unit/kg IV insulin
      • Continuation:
        • Dextrose 25g/hr, titrated to euglycaemia
          Monitor Q20min for first hour, and hourly thereafter.
        • Insulin at 0.5 unit/kg/hr up to 5unit/kg/hr
        • Insulin dose should be titrated to toxicity, and dextrose dose titrated to maintain euglycaemia
      • Replace potassium if K <2.5mmol/L
      • Cease when clinical resolution of toxicity and ECG abnormalities
  • Procedural
  • Physical

Supportive care:

  • A
  • B
    • Mechanical ventilation

Disposition:

Preventative:

Marginal and Ineffective Therapies

Anaesthetic Considerations

Complications

Prognosis

Key Studies

References

  1. Bersten, A. D., & Handy, J. M. (2018). Oh’s Intensive Care Manual. Elsevier Gezondheidszorg.