What is the recommended management for a patient with wide‑complex tachycardia due to sodium‑channel blocker overdose (e.g., tricyclic antidepressant or class I antiarrhythmic) that is refractory to intravenous sodium bicarbonate?

Treatment of Wide Complex Tachycardia Refractory to Sodium Bicarbonate in Sodium Channel Blocker Overdose

For wide-complex tachycardia due to sodium channel blocker toxicity that fails to respond to sodium bicarbonate, the American Heart Association recommends considering lidocaine (Class Ib antiarrhythmic) as second-line therapy, followed by intravenous lipid emulsion for refractory cases, and ultimately VA-ECMO for refractory cardiogenic shock. 1, 2

Immediate Assessment and Optimization

Before escalating therapy, ensure the following have been optimized:

• Verify adequate sodium bicarbonate dosing: Confirm that hypertonic sodium bicarbonate (1-2 mEq/kg IV bolus, repeated every 5-10 minutes) has been administered with target arterial pH of 7.45-7.55 and serum sodium <150-155 mEq/L 1, 2
• Assess for ongoing acidosis: Obtain arterial blood gas to confirm pH is maintained at 7.45-7.55, as acidosis potentiates cardiotoxicity and may require additional bicarbonate boluses or continuous infusion 1, 2
• Ensure adequate ventilation: Maintain mild hyperventilation (PaCO2 30-35 mmHg) to support alkalemia, as respiratory acidosis worsens sodium channel blockade 2, 3
• Monitor QRS duration continuously: Persistent QRS ≥120 ms despite adequate bicarbonate therapy indicates refractory toxicity requiring escalation 2, 3

Second-Line Therapy: Lidocaine

The American Heart Association states it may be reasonable to use Vaughan-Williams Class Ib antiarrhythmics (e.g., lidocaine) to treat life-threatening cardiotoxicity from Class Ia or Ic sodium channel blockers (Class 2b, Level C-LD). 1

• Administer lidocaine 1-1.5 mg/kg IV bolus slowly for persistent wide-complex tachycardia despite optimized sodium bicarbonate therapy 2, 4
• Lidocaine works by a different mechanism than Class Ia/Ic blockers and may reverse conduction defects in refractory cases 4, 5
• Critical caveat: Administer lidocaine cautiously to avoid precipitating seizures, which are common in sodium channel blocker toxicity 5
• Monitor for QRS narrowing and hemodynamic improvement after lidocaine administration 2, 4

Important Contraindications

• Never use Class Ia (quinidine, procainamide), Class Ic (flecainide), or Class III (amiodarone) antiarrhythmics, as these worsen sodium channel blockade, further slow conduction, and depress contractility 1, 2, 4
• Avoid beta-blockers (Class II agents), as they may precipitate hypotension and cardiac arrest 4

Third-Line Therapy: Intravenous Lipid Emulsion

The American Heart Association states it may be reasonable to use intravenous lipid emulsion to treat life-threatening sodium channel blocker poisoning refractory to other treatment modalities (Class 2b, Level C-LD). 1

• Consider 20% intravenous lipid emulsion (ILE) as a last resort for life-threatening toxicity refractory to sodium bicarbonate and lidocaine 2, 6
• Standard dosing: 1.5 mL/kg bolus of 20% lipid emulsion over 1 minute, followed by infusion of 0.25 mL/kg/min 2
• Case reports demonstrate successful use in amitriptyline-induced ventricular tachycardia when administered after 24 hours of refractory symptoms despite maximal sodium bicarbonate therapy 6
• The lipid emulsion acts as a "lipid sink" to sequester lipophilic drugs like tricyclic antidepressants and other sodium channel blockers 6

Fourth-Line Therapy: Extracorporeal Life Support

The American Heart Association recommends it is reasonable to use extracorporeal life support, such as VA-ECMO, to treat refractory cardiogenic shock from sodium channel blocker poisoning (Class 2a, Level C-LD). 1

• Consider VA-ECMO for refractory cardiogenic shock unresponsive to high-dose vasopressors, sodium bicarbonate, lidocaine, and intravenous lipid emulsion 1, 2
• VA-ECMO provides mechanical circulatory support while allowing time for drug metabolism and elimination 1, 2
• Early consultation with ECMO team is crucial, as outcomes are better when initiated before prolonged cardiac arrest 2
• One case report documented successful management of combined phenytoin and lacosamide toxicity using supportive care and hemodialysis for extracorporeal drug removal 7

Hemodynamic Support Algorithm

If hypotension persists despite the above interventions:

• Initial fluid resuscitation: Administer IV fluid boluses (10 mL/kg normal saline) guided by central venous pressure monitoring 2, 4, 8
• First-line vasopressor: Use norepinephrine or epinephrine for refractory hypotension, as experimental studies show epinephrine results in higher survival rates, especially when combined with sodium bicarbonate 4, 8
• Alternative inotropes: Dopamine, dobutamine, or glucagon may provide benefit in uncontrolled studies 4, 8
• Avoid physostigmine: Never use physostigmine for anticholinergic symptoms, as it worsens cardiac toxicity and is absolutely contraindicated 2

Monitoring Requirements During Refractory Cases

• Continuous cardiac monitoring with focus on QRS duration, which should narrow to <120 ms with effective therapy 2, 3
• Arterial blood gases every 2-4 hours to maintain pH 7.45-7.55 2
• Serum electrolytes every 2-4 hours: sodium (target <150-155 mEq/L), potassium (replace as needed, as alkalemia causes intracellular shift), and ionized calcium 2
• Core temperature monitoring, as hyperthermia worsens toxicity and requires immediate external cooling if >38.5°C 2, 3

Common Pitfalls to Avoid

• Do not delay escalation: If QRS remains ≥120 ms or hemodynamic instability persists after 2-3 boluses of sodium bicarbonate, proceed immediately to lidocaine rather than continuing ineffective bicarbonate therapy 2, 4
• Do not allow respiratory acidosis: Ensure adequate minute ventilation, as CO2 retention from bicarbonate therapy potentiates cardiotoxicity 2, 3
• Do not use conventional antiarrhythmics first: Sodium bicarbonate and lidocaine should precede any other antiarrhythmic therapy, as Class Ia/Ic/III agents are contraindicated 1, 2, 4
• Do not forget supportive care: Correct hypoxia, electrolyte abnormalities (especially hypokalemia and hypocalcemia), and maintain normothermia, as these factors independently worsen outcomes 2, 4, 8