TCA Toxicity 

 

 

Background 

 

  • Multi-system effects due to: 

    • ​Blockade of cardiac fast sodium channels

    • Antagonism of:

      • Central & peripheral muscarinic acetylcholine receptors

      • Peripheral α-1 adrenergic receptors

      • Histamine (H1) receptors

      • CNS GABA A receptors

  • Greatest risk of seizure & arrhythmias occurs in first 6-8 hours of TCA ingestion

 

 

Considerations

 

  • Emergency/full stomach 

  • Co-ingestants 

  • Life threatening multi-system effects: 

    • CNS: sedation, coma, seizures 

    • CVS: tachyardia, hypotension, myocardial dysfunction, lethal arrhythmias 

    • Anticholinergic toxidrome (red, hot, mydriasis, dry, delirium)

 

 

Treatment

 

  • Consult toxicology/ICU immediately 

  • Admit to monitored setting 

  • Intubate & hyperventilate (promotes alkalosis)

  • Sedation with benzodiazepines & propofol (to ↑ seizure threshold)

  • Gastric decontamination (if ingestion < 1hr & airway is protected)

  • Hypotension: fluids & vasopressor (norepinephrine) 

  • QRS > 100 ms = high risk of arrhythmias & seizures: 

    • NaHCO3

      • 2-3 mEq/kg then 3 amps/L at 250 ml/hr or 2x maintenance

      • Goals: QRS < 100, stable BP, sodium ~ 150, pH ~ 7.5

      • 3% NaCl if pH > 7.50 & persistent QRS elevation

  • Arrhthmia treatment (VT/VF):

    • Run ACLS/defibrillate 

    • Lidocaine 1 mg/kg 

    • MgSO4 if prolonged QTc or Torsades develops 

    • Amiodarone/procainamide contraindicated 

  • Seizures:

    • Treat with midazolam

    • Do NOT use phenytoin 

  • Intralipid for cardiac arrest or refractory hypotension

  • ECMO as last resort

  • Hemodialysis NOT effective 

 

 

Contraindicated Therapies 

 

  • Anti-arrhythmic drugs:

    • ​Class IA (e.g., procainamide) & class IC agents (e.g., flecainide) due to their inhibition of rapid sodium channels (similar to TCA effect) 

    • Class III agents (e.g., amiodarone) due to QTc prolonging effect 

  • Phenytoin 

  • Flumazenil: can induce seizures 

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