Tricyclic Antidepressant (TCA) Poisoning

Meet the patient

A 25-year-old woman is brought to ED unconscious two hours after swallowing a potentially lethal amount of amitriptyline with alcohol. GCS 6, heart rate 132, blood pressure 76 over 40. The ECG shows sinus tachycardia with a widened QRS and a terminal R wave in aVR.^[1]

The two questions that decide her next hour are the two that decide every TCA overdose: is the maximal limb-lead QRS at or above 100 ms? (the threshold that predicts seizure and ventricular-arrhythmia risk, and the consensus trigger to stabilise and give sodium bicarbonate) and which drugs must I avoid? (class Ia and Ic antiarrhythmics and beta-blockers, and flumazenil is not recommended). The QRS width is the bedside electrophysiological readout of how many sodium channels are blocked — serum drug levels failed to predict risk in the original cohort, the ECG did not.^[7][25][4]

References28ShowHide

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