Benzocaine-induced methemoglobinemia: a potentially fatal complication of transesophageal echocardiography.

We describe the cases of 2 patients who developed benzocaine-induced methemoglobinemia after the administration of benzocaine as premedication for transesophageal echocardiography. The use of intravenous methylene blue resolved the cyanosis in both patients. Physicians who perform procedures involving the application of topical anesthesia need to be aware of this side effect to prevent morbidity and mortality.