Makindo Medical Notes

💉 Glucagon is the conventional antidote for beta-blocker overdose. It bypasses the blocked β-receptor by stimulating adenylate cyclase directly → ↑ cyclic AMP → improved inotropy, chronotropy, and reversal of hypoglycaemia. This makes it lifesaving in severe toxicity.

📖 About Beta-Blocker Toxicity

• Seen with overdose of propranolol, atenolol, metoprolol, carvedilol, and others.
• Can be accidental (children, elderly), intentional (self-harm), or iatrogenic (drug interactions, renal impairment).
• Non-selective agents (e.g. propranolol) may cause CNS toxicity and bronchospasm; water-soluble agents (atenolol, sotalol) may accumulate in renal impairment.

⚠️ Clinical Features

• Cardiovascular: Severe bradycardia, hypotension, AV block, junctional rhythms, cardiogenic shock, poor perfusion.
• Respiratory: Bronchospasm (esp. non-selective β-blockers), respiratory depression.
• CNS: Lethargy, seizures (notably propranolol), coma in severe cases.
• Metabolic: Hypoglycaemia (esp. children), hyperkalaemia (due to reduced cellular uptake).

🧪 Investigations

• FBC, U&E, LFTs, glucose, lactate.
• ECG: bradycardia, heart block, QT prolongation, arrhythmias.
• ABG: metabolic acidosis common in shock.

🛠️ Management

• Immediate: ABC, IV access, continuous ECG, IV fluids (0.9% saline boluses).
• Bradycardia: Atropine 500 mcg IV (repeat up to 3 mg). Temporary pacing if refractory.
• Glucagon: 2–10 mg IV bolus over 2–5 min + infusion 2–10 mg/hr. Improves HR and contractility.
• High-Dose Insulin Euglycaemia (HIE) Therapy: - Bolus 1 U/kg insulin + 0.5 g/kg IV glucose. - Continuous insulin infusion with dextrose + K⁺ monitoring. - Improves myocardial carbohydrate use and contractility.
• Inotropes: Dobutamine or noradrenaline if shock persists despite glucagon/HIE.
• Other rescue options: IV lipid emulsion (lipid sink effect), ECMO in refractory shock.
• Bronchospasm: Nebulised salbutamol.
• Seizures: Benzodiazepines (avoid phenytoin — can worsen conduction block).

📊 Prognosis

• Early recognition and antidote use improve survival.
• Massive overdoses (esp. propranolol) have high mortality without ICU-level support.

📚 References

• Beta Blocker Toxicity – StatPearls
• Enoximone in ICU – Cardiff SOP
• LITFL Toxicology Library – Beta-blocker overdose