tricyclic antidepressant overdose

management:

these patients have a tendency to suddenly develop seizures, reduced conscious state, or, if widened QRS, VT or VF
consider activated charcoal 1g/kg unless altered conscious state (protect airway first by intubation and then give via NG tube)
IV access, cardiac monitoring, ECG
if altered conscious state, consider early emergency intubation to protect the airway, assist ventilation and avoid respiratory acidosis which worsens toxicity
- hyperventilate to maintain a pH of 7.50 – 7.55
if asymptomatic, cardiac monitor for 6 hrs and if normal ECG and still well, consider discharge.
all symptomatic patients should be admitted for cardiac monitoring for 12-24hrs
if widened QRS on ECG or arrhythmias develop:
- QRS > 100 ms is predictive of seizures
- QRS > 160 ms is predictive of ventricular arrhythmias (e.g. VT)
- then start sodium bicarbonate:
  - IV sodium bicarbonate 100 mEq (1-2 mEq / kg), repeat every few minutes until BP improves and QRS complexes begin to narrow
- if VT occurs despite sodium bicarbonate, lignocaine (1.5mg/kg) IV is a second line agent once pH is > 7.5
  - avoid class Ia (procainamide) and Ic (flecainide) antiarrhythmics, beta-blockers and amiodarone as they may worsen hypotension and conduction abnormalities
if hypotension, give 10-20ml/kg 0.9% saline, and if still hypotense start noradrenaline / norepinephrine infusion
if seizures, Rx with benzodiazepines as per usual

“On current best evidence alkalinisation to a Ph of 7.55 appears to be appropriate therapy for patients with dysrhythmias following tricyclic overdose.”
- BestBets.org