Abstract
Drug overdose can lead to a range of symptoms, including potentially life-threatening cardiac arrhythmias. However, identifying the specific causative drug upon admission can be challenging in many cases. The toxidrome approach is a method that utilizes toxidromes, which are collections of findings obtained from physical examination and ancillary tests, that may be caused by a specific toxin. In this particular case, a man presented with an unknown drug overdose that caused symptoms indicative of anticholinergic effects and abnormal electrocardiogram (ECG) findings. The ECG revealed an R wave in lead aVR, S waves in leads I and aVL, and wide QRS tachycardia with a Brugada pattern. Shortly after arrival, the patient developed cardiac arrest due to a lethal arrhythmia. Prompt initiation of venoarterial extracorporeal cardiopulmonary membrane oxygenation (VA-ECMO) was performed. Fortunately, the patient achieved full neurological recovery, and the overdosed drug was identified as diphenhydramine. When diagnosing and treating drug overdose caused by an unidentified substance, diphenhydramine toxicity should be considered when an anticholinergic toxidrome is present and a Brugada pattern is observed on the ECG. VA-ECMO demonstrates potential as a viable treatment option when initial interventions prove ineffective.