Benzocaine-related methaemoglobinemia after transoesophageal echocardiography: a rare, life-threatening complication.

Methaemoglobinemia is an uncommon but potentially life-threatening complication of topical benzocaine use that requires prompt identification in patients who undergo transoesophageal echocardiography (TEE). In this case, a 21-year-old patient who had sustained a stroke with residual right-sided weakness a few days prior to presentation underwent TEE to evaluate for intracardiac shunt. She required intubation as part of her poststroke care with some instrumentation to the posterior oropharynx. Shortly after TEE, the patient experienced sudden onset respiratory distress and hypoxia that did not improve with supplemental oxygen. Chest X-ray did not reveal any acute cardiopulmonary process. Arterial blood gas co-oximetry panel with methaemoglobin level confirmed the diagnosis of methaemoglobinemia. The patient promptly received methylene blue, recovered quickly and did not have any additional episodes of hypoxia.