A 17-year-old girl is brought to the emergency department by a friend an hour after she was observed having a seizure. The patient has no known history of a seizure disorder. Her friend reports she has a history of depression and substance use disorder and was released yesterday from a psychiatric hospital after 3 days of inpatient treatment. The patient's medications are unknown. Temperature is 38.3 C (100.9 F), blood pressure is 90/50 mm Hg, and pulse is 130/min. On examination, the patient is sedated and disoriented. The pupils are dilated and bowel sounds are decreased. She has 700 mL of urine return when a urinary catheter is placed. ECG reveals sinus tachycardia and a QRS duration of 130 msec. Which of the following is the most likely cause of this patient's symptoms?

Question

A 17-year-old girl is brought to the emergency department by a friend an hour after she was observed having a seizure.  The patient has no known history of a seizure disorder.  Her friend reports she has a history of depression and substance use disorder and was released yesterday from a psychiatric hospital after 3 days of inpatient treatment.  The patient's medications are unknown.  Temperature is 38.3 C (100.9 F), blood pressure is 90/50 mm Hg, and pulse is 130/min.  On examination, the patient is sedated and disoriented.  The pupils are dilated and bowel sounds are decreased.  She has 700 mL of urine return when a urinary catheter is placed.  ECG reveals sinus tachycardia and a QRS duration of 130 msec.  Which of the following is the most likely cause of this patient's symptoms?

Quizplus · Accepted Answer

11ec160b_3c45_a0d8_9249_95a9a458e3d5_MD0001_00 This patient's new-onset seizure, signs of anticholinergic toxicity (ie, dilated pupils, hyperthermia, tachycardia, decreased bowel sounds, urinary retention), and QRS widening are most likely due to tricyclic antidepressant (TCA) overdose. Although newer classes of antidepressants (eg, selective serotonin reuptake inhibitors) are commonly used as first-line therapy, TCAs continue to have a role in the treatment of major depression. TCAs have an inhibitory effect on multiple receptor types, thereby causing a variety of symptoms in the case of overdose: Inhibiton of central nervous system receptors can cause sedation (histamine [H₁] receptors), seizures (GABA A receptors), and agitation or delirium (central muscarinic acetylcholine receptors). Antagonism of central and peripheral muscarinic acetylcholine receptors results in anticholinergic symptoms, including hyperthermia, dry and flushed skin, dilated pupils, tachycardia, decreased bowel sounds, and urinary retention. Cardiovascular toxicity may lead to QRS widening, with increased risk for ventricular arrhythmia due to inhibition of cardiac fast sodium channels. Hypotension can also occur due to blockade of alpha-1 adrenergic receptors. Cardiovascular toxicity is the major cause of mortality in TCA overdose. (Choice A) Symptoms of benzodiazepine withdrawal include seizures and tachycardia. Psychosis, tremors, sweating, and anxiety are also common. QRS widening, hypotension, and anticholinergic symptoms would not be expected. (Choice B) Cocaine overdose has sympathomimetic characteristics that can cause seizures, hyperthermia, and tachycardia, as well as myocardial infarctions and cardiac arrhythmias. However, hypertension (vs hypotension) and diaphoresis (vs dry skin) are expected in a cocaine overdose. (Choice C) Opioid withdrawal is associated with dilated pupils, mild hyperthermia, and hypertension (not hypotension) but would not cause seizures or cardiac conduction delay. Diarrhea and cramps, as opposed to decreased bowel sounds, are also common in opioid withdrawal. (Choice D) Salicylate toxicity can present with hyperthermia, altered mental status, and seizures (due to neuroglycopenia). Tachypnea, tinnitus, and acid-base abnormalities are also common. QRS widening, urinary retention, dilated pupils, and decreased bowel sounds are typically not present. (Choice E) Serotonin syndrome can occur with an overdose of serotonergic antidepressants or interaction between serotonergic medications. It can typically cause hyperthermia and tachycardia but also often presents with agitation, diaphoresis (vs dry skin), hypertension (vs hypotension), and neuromuscular hyperactivity (eg, hyperreflexia, clonus); it is not generally associated with QRS widening. Educational objective: Symptoms of tricyclic antidepressant overdose include seizures, anticholinergic toxicity, hypotension, and cardiac toxicity (eg, QRS widening, ventricular arrhythmias).

A 17-Year-Old Girl Is Brought to the Emergency Department by a Friend