Methemoglobinemia following transesophageal echocardiography: a case report and review.

Benzocaine (ethyl aminobenzoate) is a topical anesthetic widely used for oropharyngeal anesthesia prior to transesophageal echocardiography (TEE). Topical anesthetics have been reported to cause methemoglobinemia, but this adverse event is extremely rare and has not been listed as one of the possible complications of TEE. However, recently the number of published case reports of TEE-associated methemoglobinemia has increased. Since its first description in 1950, 65 cases of methemoglobinemia have been reported including a recent report of five cases from a single center. Physicians who are not familiar with the association of TEE with benzocaine-induced methemoglobinemia may not recognize the idiosyncratic and often nonspecific characteristic of this condition. Recognition is critical, however, since left untreated methemoglobinemia can lead to cardiopulmonary compromise, neurological sequelae, and even death. The current report documents an additional case of TEE-associated methemoglobinemia from a high-volume (8000 cases /year including 400-450 TEE/year) echo lab. A review of the literature suggests that this complication may be more prevalent, than generally appreciated. This case report emphasizes the importance of appropriate dose, recognition, and the treatment of this entity to cardiologists performing TEE.