What is the treatment for a 59-year-old male in cardiac arrest due to an amitriptyline (tricyclic antidepressant) overdose?

Treatment of Amitriptyline Overdose in Cardiac Arrest

Immediately administer intravenous sodium bicarbonate 1-2 mEq/kg bolus while performing high-quality CPR, and prepare for VA-ECMO if the patient remains in refractory cardiac arrest. 1

Immediate Resuscitation Priorities

Airway and Circulation Management

• Secure the airway immediately with endotracheal intubation while maintaining high-quality CPR with continuous chest compressions 2, 3
• Establish intravenous access and initiate cardiac monitoring with continuous ECG 3
• Avoid respiratory acidosis during mechanical ventilation—maintain mild hyperventilation to support alkalemia (pH 7.45-7.55), as acidosis potentiates cardiotoxicity 2

Sodium Bicarbonate Administration (First-Line Therapy)

• Administer sodium bicarbonate 1-2 mEq/kg (1-2 mL/kg of 8.4% solution) IV bolus immediately for cardiac arrest due to tricyclic antidepressant poisoning 1, 4
• Repeat boluses every 3-5 minutes as needed until return of spontaneous circulation or clinical stability is achieved 4, 2
• Target serum pH of 7.45-7.55 and maintain serum sodium <150-155 mEq/L to avoid hypernatremia 1, 4, 2
• The American Heart Association gives this a Class 1 recommendation with B-NR level of evidence, making it the strongest evidence-based intervention 1

Mechanism and Rationale

• Sodium bicarbonate works through two synergistic mechanisms: sodium loading overcomes sodium channel blockade, and alkalinization improves cardiac conduction and reduces cardiotoxicity 4
• Amitriptyline blocks cardiac sodium channels similar to Class Ia antiarrhythmics, causing QRS prolongation, ventricular dysrhythmias, and cardiovascular collapse 1

Management of Refractory Cardiac Arrest

VA-ECMO Consideration

• Consider venoarterial extracorporeal membrane oxygenation (VA-ECMO) for refractory cardiac arrest or cardiogenic shock unresponsive to sodium bicarbonate and high-dose vasopressors 1, 2
• The American Heart Association gives this a Class 2a recommendation, making it reasonable for refractory cases 1

Antiarrhythmic Therapy

• Lidocaine (Class Ib antiarrhythmic) may be used as second-line therapy for ventricular dysrhythmias refractory to sodium bicarbonate 1, 4, 2
• Avoid Class IA (quinidine, procainamide, disopyramide) and Class IC antiarrhythmics, as they worsen sodium channel blockade and are contraindicated 2, 3

Intravenous Lipid Emulsion (Last Resort)

• Intravenous lipid emulsion (ILE) may be reasonable for life-threatening toxicity refractory to all other treatment modalities, though evidence is limited to case reports 1, 2, 5, 6
• The American Heart Association gives this a Class 2b recommendation (may be reasonable), indicating weaker evidence 1
• One case report showed successful resuscitation with ILE after failure of high-dose sodium bicarbonate 5

Post-Resuscitation Management

Gastrointestinal Decontamination

• Perform large-volume gastric lavage followed by activated charcoal once the airway is secured and the patient is stabilized 3
• Never induce emesis—this is contraindicated in tricyclic antidepressant overdose 3

Seizure Management

• Administer benzodiazepines (diazepam or midazolam) for seizures, which are common in tricyclic antidepressant toxicity 2, 3
• If benzodiazepines are ineffective, use other anticonvulsants as needed 3

Monitoring Requirements

• Maintain continuous cardiac monitoring for at least 6 hours minimum, though extended monitoring is required if any signs of toxicity persist 3
• Monitor serum potassium levels, as hypokalemia may develop during sodium bicarbonate therapy 2
• Monitor for QRS duration >100 ms, which indicates severe toxicity requiring immediate intervention 2, 3

Critical Pitfalls to Avoid

• Never administer flumazenil, even if benzodiazepine co-ingestion is suspected—this is absolutely contraindicated and may precipitate seizures or arrhythmias 2
• Never use physostigmine for anticholinergic symptoms, as it worsens cardiac toxicity 2
• Never allow respiratory acidosis during mechanical ventilation, as this potentiates cardiotoxicity 2
• Avoid Class IA and IC antiarrhythmics, which are contraindicated 2, 3
• Do not rely on plasma drug levels to guide management 3

Prognosis Considerations

• Case reports demonstrate survival after prolonged cardiac arrest (up to 3 hours of continuous CPR) with aggressive management, emphasizing the importance of continued resuscitation efforts in young, otherwise healthy patients 7, 8
• Deaths may occur late after overdose in patients who received inadequate decontamination, highlighting the importance of comprehensive initial management 3