TCA Overdose

TCA’s: -triptylene, -ipramine, and doxepin (the sneaky one!)

MOA: Non selective reuptake 5HT3 + NE reuptake inhibitors – initial hyperdynamic presentation progressing to catechol depletion and resultant refractory cardiogenic + distributive shock

Toxicity

Antimuscarinic – Anticholinergic toxidrome

Anticholinergic – AMS, drowsy, coma

Na+ channel blockade – Wide QRS, terminal R in AVR, dysrhythmias, seizures

K+ channel blockade – long QTc, Torsades

Alpha-1 blockade – Hypotension

GABA antagonism – Seizure

Toxic dose

Single pills are as much as 150 mg

5 mg/kg = sick

10 mg/kg = mortality

EKG

  • Typically RBBB pattern w/ large terminal R-wave (0.7 R:S in aVR)
  • That’s just b/c right bundle gets blocked 1st
  • Can also just be a non-specific wide complex

Management

Death is due to cardiogenic/distributive shock + severe metabolic acidosis due to seizures

  • Caution with AC – high risk for seizure and aspiration, probably don’t give unless intubated
  • If comatose or any seizure activity, intubate
  • NaHCO3 for QRS > 120 ms or acidemia
    • Goal QRS width 100-120
    • If pH > 7.55 would change to hypertonic saline if still unstable
    • OK to push Na+ to 155
  • As QRS widens out above 160 ms risk for VT
  • Mg++ for QTc> 500 ms
  • Can switch to lidocaine bolus and gtt for refractory dysrhythmia
  • Replace Ca++ and K+ as guided by labs
  • Benzos for seizures – consider prophylactically if QRS is wide
  • Dogmatic risk of Bradyasystolic arrest w/ physo in TCA OD is case report and poor quality – is probably okay but does cause bradycardia and increase seizure risk. Could consider if delirium was only symptom needing treatment but don’t routinely give.