Toxic methemoglobinemia: a rare but serious complication of transesophageal echocardiography.

Cyanosis occurring during a transesophageal echocardiogram (TEE) is usually related to the respiratory depressant effect of the administered sedative. However, acute toxic methemoglobinemia related to topical benzocaine is a rare and not well recognized but potentially life threatening cause of cyanosis during or after TEE. A case of this condition is presented and the literature on its frequency, diagnosis and management is briefly reviewed.