A 26-year-old man is brought to the emergency department after an attempted suicide by medication overdose. He has had 2 seizures in the past hour. Temperature is 38.8 C (102 F), blood pressure is 90/60 mm Hg, pulse is 110/min, and respirations are 22/min. The patient is not oriented to time, place, and person. Pupils are dilated and respond poorly to light; the skin is flushed and dry. Abdominal examination shows reduced bowel sounds. ECG shows prolonged QRS complexes (0.19 sec). Toxicology studies are pending. Which of the following is the best predictor of complications due to overdose of the suspected drug?

Question

A 26-year-old man is brought to the emergency department after an attempted suicide by medication overdose.  He has had 2 seizures in the past hour.  Temperature is 38.8 C (102 F), blood pressure is 90/60 mm Hg, pulse is 110/min, and respirations are 22/min.  The patient is not oriented to time, place, and person.  Pupils are dilated and respond poorly to light; the skin is flushed and dry.  Abdominal examination shows reduced bowel sounds.  ECG shows prolonged QRS complexes (0.19 sec).  Toxicology studies are pending.  Which of the following is the best predictor of complications due to overdose of the suspected drug?

Quizplus · Accepted Answer

This patient's history is consistent with tricyclic antidepressant (TCA) overdose, which causes mental status changes, seizures, tachycardia, hypotension, cardiac conduction delay, and anticholinergic effects (eg, dilated pupils, hyperthermia, flushed and dry skin, intestinal ileus). Cardiotoxicity is due to blockade of cardiac fast sodium channels, leading to QRS prolongation and risk of developing ventricular arrhythmia (similar to class IA antiarrhythmic drugs such as quinidine). ECG should be obtained immediately and monitored frequently in suspected TCA overdose. QRS duration >100 msec is associated with increased risk for ventricular arrhythmia and seizures and is used as an indication for sodium bicarbonate therapy. (Choices A and B) Pupillary dilation and decreased bowel sounds are common in TCA overdose due to anticholinergic effects, but these findings do not carry any prognostic value. (Choices D and E) TCA overdose is typically diagnosed based on history and characteristic clinical and ECG findings. Qualitative (urine) and quantitative (serum) TCA testing can help confirm overdose but have no correlation with systemic toxicity and limited prognostic utility. Furthermore, serum TCA levels are not available in a clinically relevant time frame. Educational objective: Tricyclic antidepressant overdose is characterized by mental status changes, seizures, cardiac conduction delay, and anticholinergic toxicity (eg, dilated pupils, hyperthermia, flushed and dry skin, intestinal ileus). QRS duration >100 msec has been associated with an increased risk of arrhythmias and/or seizures and is an indication for treatment with sodium bicarbonate. References: Tricyclic antidepressant poisoning. (http://www.ncbi.nlm.nih.gov/pubmed/11060957) Rapid diagnosis and treatment of severe tricyclic antidepressant toxicity. (http://www.ncbi.nlm.nih.gov/pubmed/26468220)

A 26-Year-Old Man Is Brought to the Emergency Department After