How do you treat a patient with a suspected propranolol overdose?

Propranolol Overdose Management

Propranolol overdose requires immediate supportive care with airway management, aggressive treatment of bradycardia and hypotension with glucagon as first-line antidote, and consideration of high-dose insulin therapy for refractory shock.

Immediate Assessment and Stabilization

Secure the airway and provide ventilatory support as the absolute first priority, particularly if the patient has altered mental status or seizures. 1, 2

• Check for responsiveness, breathing, and pulse within 10 seconds and activate emergency response immediately. 3
• If respiratory depression is present, open the airway and begin bag-mask ventilation or rescue breathing until spontaneous breathing returns. 4
• Proceed to endotracheal intubation if Glasgow Coma Scale ≤8 or protective airway reflexes are absent, as propranolol can cause profound CNS depression and seizures. 5, 2

Gastrointestinal Decontamination

If ingestion was recent (within 1-2 hours), evacuate gastric contents while taking care to prevent pulmonary aspiration. 1 This is particularly important given propranolol's high lipid solubility and potential for delayed absorption.

Cardiovascular Monitoring and Support

Continuously monitor ECG, blood pressure, heart rate, and neurobehavioral status. 1

Key Toxicity Thresholds to Recognize:

• Hypotension (SBP <90 mmHg) can occur with doses as low as 400 mg in isolated ingestions 2
• Bradycardia (<50 bpm) typically occurs with doses ≥800 mg 2
• Severe toxicity (seizures, coma, cardiac arrest) has a threshold of approximately 2,000 mg in isolated propranolol overdoses, with 53% of patients ingesting ≥2,000 mg developing severe toxicity 2
• Cardiac arrest has been reported with doses ranging from 2,400-16,000 mg 2

Electrocardiographic Findings:

Monitor for sodium channel blockade (QRS widening, QTc prolongation), which occurs in approximately 8% of overdoses, as propranolol has membrane-stabilizing properties beyond beta-blockade. 2

Pharmacologic Management

First-Line Antidote: Glucagon

Administer glucagon 50-150 mcg/kg IV bolus followed by continuous infusion of 1-5 mg/hour, as glucagon exerts potent inotropic and chronotropic effects independent of beta-receptors and is particularly useful for hypotension and depressed myocardial function. 1

Bradycardia Management:

• Atropine 0.5-1 mg IV for symptomatic bradycardia 1
• Isoproterenol infusion if atropine fails 1
• Temporary transvenous cardiac pacing for serious refractory bradycardia, which may be necessary in massive overdoses 1, 6

Hypotension and Shock Management:

For refractory hypotension despite glucagon:

• High-dose insulin euglycemic therapy (HIET) is recommended as second-line treatment, with doses of insulin used successfully in case reports 7, 6
• Dopamine or phosphodiesterase inhibitors (e.g., milrinone) may be useful 1
• Isoproterenol can provide both inotropic and chronotropic support 1

Critical caveat: Avoid epinephrine as it may provoke uncontrolled hypertension due to unopposed alpha-adrenergic stimulation. 1

Sodium Channel Blockade:

If ECG shows evidence of sodium channel blockade (QRS >100-120 ms), administer sodium bicarbonate boluses (1-2 mEq/kg IV) to overcome membrane-stabilizing effects. 7 This is particularly important as propranolol has class I antiarrhythmic properties at toxic doses.

Seizure Management:

Seizures occur in approximately 8% of propranolol overdoses and should be treated with benzodiazepines as first-line therapy. 2 Seizures have been reported with doses as low as 2,000 mg in isolated ingestions. 2

Bronchospasm:

Isoproterenol and aminophylline may be used for bronchospasm, though this is less common than cardiovascular toxicity. 1

Refractory Cases: Extracorporeal Support

For patients with refractory cardiogenic shock despite maximal medical therapy (glucagon, high-dose insulin, vasopressors, sodium bicarbonate), consider extracorporeal membrane oxygenation (ECMO) or cardiopulmonary bypass. 6, 8

• ECMO has been successfully used in massive propranolol overdoses with complete recovery, even when conventional therapies failed 6, 8
• Early consultation with cardiothoracic surgery and critical care is essential when doses exceed 4,000 mg or when severe toxicity develops 9

Observation and Disposition

Admit all patients with propranolol overdose ≥2,000 mg or any patient with bradycardia, hypotension, altered mental status, or ECG abnormalities to an intensive care setting. 2

• Median length of stay for propranolol overdoses is 17 hours (IQR 11-32 hours) 2
• Patients with severe toxicity require prolonged monitoring until cardiovascular stability is achieved and neurological function normalizes 2
• Monitor intake and output balance closely, as propranolol is not significantly dialyzable 1

Common Pitfalls to Avoid

• Never delay airway management while attempting pharmacologic interventions – respiratory failure and seizures can occur rapidly 2, 9
• Do not use epinephrine for hypotension – it can cause paradoxical hypertension 1
• Do not underestimate co-ingestions – 74% of propranolol overdoses involve other substances, most commonly benzodiazepines, which can complicate the clinical picture 2
• Do not assume safety with doses <2,000 mg – cardiovascular effects can occur at much lower doses (400-800 mg) 2
• Time to treatment is critical – delays of several hours between ingestion and treatment initiation significantly worsen prognosis, with cardiac arrest and death reported when treatment is delayed 9

Prognosis

With aggressive supportive care and appropriate antidotal therapy, outcomes are usually favorable even in severe toxicity. 2 However, mortality has been reported with massive ingestions (4,000-16,000 mg), particularly when treatment is delayed. 9