What is the immediate treatment for a cyclic antidepressant overdose, including emergency medical services (EMS) and hospital care?

Immediate EMS and Hospital Management of Cyclic Antidepressant Overdose

Prehospital/EMS Management

EMS should prioritize airway management, cardiac monitoring, and immediate transport while avoiding flumazenil if benzodiazepine co-ingestion is suspected. 1

Critical Initial Actions

• Establish and maintain airway patency immediately with bag-mask ventilation for respiratory depression, progressing to endotracheal intubation if needed 2, 3
• Obtain IV access and initiate cardiac monitoring en route 2
• Administer sodium bicarbonate 1-2 mEq/kg IV bolus immediately if QRS duration >100 ms is observed on cardiac monitor 1, 2
• Provide supplemental oxygen to maintain SpO2 >95% 3
• Never administer flumazenil even if benzodiazepine co-ingestion is suspected, as this is absolutely contraindicated in tricyclic antidepressant overdose and may precipitate seizures or arrhythmias 1, 3

Emergency Department Management

Immediate Assessment (First 5 Minutes)

• Obtain 12-lead ECG or rhythm strip immediately - QRS duration >100 ms indicates severe toxicity requiring urgent intervention 2, 4
• Monitor for the triad of toxicity: altered mental status, seizures, and cardiac conduction abnormalities 5, 6
• Assess for anticholinergic signs: dilated pupils, dry mouth, urinary retention, hyperthermia 7

Sodium Bicarbonate Therapy (Primary Treatment)

Administer sodium bicarbonate 1-2 mEq/kg (1-2 mL/kg of 8.4% solution) IV bolus for any of the following: 1, 2

• QRS duration >100 ms 2, 4
• Ventricular arrhythmias 1, 8
• Hypotension unresponsive to initial fluid resuscitation 2, 8
• Terminal right-axis deviation >120 degrees 4

Repeat sodium bicarbonate boluses as needed to: 2, 8

• Maintain arterial pH 7.45-7.55 2
• Keep serum sodium <150-155 mEq/L 2
• Narrow QRS to <100 ms 4, 8

Airway and Ventilation Management

• Intubate for: respiratory depression, inability to protect airway, refractory seizures, or Glasgow Coma Scale <8 2, 6
• Avoid respiratory acidosis during mechanical ventilation - maintain mild hyperventilation to support alkalemia (pH 7.45-7.55) 1
• Monitor arterial blood gases to guide ventilator settings 7

Gastrointestinal Decontamination

• Administer activated charcoal 30-50 g orally or via nasogastric tube if patient presents within 1-2 hours of ingestion and airway is protected 4
• Consider with sorbitol 0.5 g/kg or magnesium sulfate 30 g as cathartic 4
• Do not perform gastric lavage unless massive ingestion (>750 mg) occurred within 1 hour 7

Management of Hypotension

Follow this algorithmic approach: 2, 8

1. First-line: IV fluid boluses of normal saline 10 mL/kg 2
2. Second-line: Continue/repeat sodium bicarbonate boluses 2, 8
3. Third-line: Norepinephrine or dopamine for persistent hypotension 1, 7
4. Last resort: Consider VA-ECMO for refractory shock unresponsive to high-dose vasopressors 1, 2

Seizure Management

• Administer benzodiazepines (lorazepam 0.1 mg/kg or diazepam 0.2 mg/kg IV) for seizures 6, 7
• If seizures persist despite benzodiazepines, proceed to neuromuscular paralysis with intubation and mechanical ventilation 7
• Never use physostigmine for seizure control - it can worsen cardiotoxicity 1, 7

Arrhythmia Management

Critical principle: Avoid Class IA, IC, and III antiarrhythmics (procainamide, quinidine, flecainide, amiodarone) as they worsen sodium channel blockade 1, 2

For ventricular arrhythmias: 1, 2

• Sodium bicarbonate remains first-line therapy 1, 8
• Lidocaine may be considered as second-line for wide-complex tachycardia refractory to bicarbonate 2
• Magnesium and phenytoin have shown no benefit 1

Refractory Cases

For life-threatening toxicity unresponsive to standard therapy: 1, 2

• Consider VA-ECMO for cardiac arrest or refractory cardiogenic shock 1, 2
• Intravenous lipid emulsion (ILE) therapy may be considered as last resort, though evidence is limited to animal studies 1

Monitoring Requirements

• Continuous cardiac monitoring for minimum 6-12 hours after QRS normalization 6, 7
• Serial ECGs every 2-4 hours until stable 4
• Monitor serum potassium (hypokalemia may develop during bicarbonate therapy) 2
• Monitor serum sodium and arterial pH during bicarbonate therapy 2
• Maintain normothermia - hyperthermia worsens toxicity 1

Critical Pitfalls to Avoid

• Never delay sodium bicarbonate while waiting for laboratory confirmation if ECG shows QRS >100 ms 2, 4
• Never use flumazenil even with suspected benzodiazepine co-ingestion - it precipitates seizures and arrhythmias in TCA toxicity 1, 3
• Never use physostigmine for anticholinergic symptoms - it worsens cardiac toxicity 1, 7
• Never allow respiratory acidosis during mechanical ventilation - this potentiates cardiotoxicity 1
• Never use Class IA, IC, or III antiarrhythmics - they worsen conduction delays 1, 2
• Do not rely on serum TCA levels for clinical decision-making - QRS duration >100 ms is a better predictor of severe complications 4

Disposition

• All patients require ICU admission if QRS >100 ms, seizures, arrhythmias, or altered mental status occurred 6, 7
• Patients may be medically cleared after 6-12 hours of observation if asymptomatic with normal ECG, but psychiatric evaluation is mandatory before discharge for intentional ingestions 9
• Despite multiple cardiac arrests, complete neurological recovery is possible with aggressive resuscitation 5