AGITATED, ALTERED, AND ELONGATED: THE RISKS OF DIPHENHYDRAMINE OVERDOSE

Abstract

TOPIC: Critical Care TYPE: Medical Student/Resident Case Reports INTRODUCTION: Overdose has become a leading cause of injury-related death in the United States. Rapid recognition of a toxidrome is vital in determining management. CASE PRESENTATION: A young, unknown female was brought to the ED after being found agitated and combative. Evaluation was notable for tachycardia, mydriasis and diaphoresis. She received intramuscular diphenhydramine (DPH), haloperidol and lorazepam for agitation.She developed a wide QRS complex with polymorphic ventricular tachycardia (VT) concerning for Torsades de pointes, terminated by precordial thump. She was intubated for airway protection. Magnesium and sodium bicarbonate (NaHCO) pushes were administered for sustained monomorphic VT with return to sinus tachycardia. Electrocardiogram was significant for prolonged QTc of 607ms and QRS >150ms. Initial toxicology was negative for acetaminophen, salicylate and ethanol.NaHCO infusion with goal pH 7.5 to maintain a narrow QRS was started. She had persistently prolonged QT interval. Overdrive transcutaneous pacing was unsuccessful, so isoproterenol (IPN) infusion was started. NaHCO and IPN infusions were discontinued at 48 hours with no further arrhythmias. Extended toxicology screen was positive for DPH. On extubation, she endorsed consumption of >1.25g DPH. DISCUSSION: Classic anticholinergic symptoms of tachycardia, mydriasis and delirium are also the toxidrome for DPH overdose. Severe toxicity is observed after ingestion of >1.0g (1). Cardiac toxicity is exhibited as widening of QRS and QTc intervals (1-3). Similar to TCA overdose, QRS widening is manifested from blockade of the fast-closing myocardial sodium channels (2-3). Treatment for QRS widening with NaHCO is anecdotally recommended (2-3). In this case, bolus and infusion of NaHCO successfully shortened the patient's QRS duration. One case report suggested using lipid emulsion therapy(3); however, DPH intoxication was not suspected initially thereby limiting its use. Since presenting symptoms of DPH and anticholinergic toxicity overlap, physostigmine must be avoided due to QRS prolonging effects (2). This case reminds of cautious administration of the "B52" cocktail for agitated patients. The use of intravenous DPH, haloperidol and lorazepam can be used to calm acutely agitated or aggressive patients; yet, it should be avoided with unknown ingestions.Further, QT prolongation and polymorphic VT can result from DPH's ability to weakly block the delayed rectifier potassium channels (2). Traditionally resolving this includes overdrive pacing and magnesium supplementation, which were administered in this case. However, failed overdrive transcutaneous pacing led to IPN infusion to induce tachycardia-associated QTc shortening. CONCLUSIONS: High suspicion and familiarity with toxidromes can lead to early diagnosis and intervention for critically ill patients presenting with agitated altered mental status. REFERENCE #1: Radovanovic D, Meier PJ, Guirguis M, Lorent JP, Kupferschmidt H. Dose-dependent toxicity of diphenhydramine overdose. Hum Exp Toxicol. 2000 Sep;19(9):489-95. doi: 10.1191/096032700671040438 REFERENCE #2: Jang DH, Manini AF, Trueger NS, et al. Status epilepticus and wide-complex tachycardia secondary to diphenhydramine overdose. Clin Toxicol (Phila). 2010;48(9):945-948. doi:10.3109/15563650.2010.527850 REFERENCE #3: Abdi A, Rose E, Levine M. Diphenhydramine overdose with intraventricular conduction delay treated with hypertonic sodium bicarbonate and i.v. lipid emulsion. West J Emerg Med. 2014;15(7):855-858. doi:10.5811/westjem.2014.8.23407 DISCLOSURES: No relevant relationships by Joy Ayyoub, source=Web Response No relevant relationships by Lauren Catalano, source=Web Response No relevant relationships by Sydney Emerson, source=Web Response No relevant relationships by Shahrzad Zonoozi, source=Web Response