Methemoglobinemia after transesophageal echocardiography: a life-threatening complication.

Abstract Methemoglobinemia is an uncommon cause of tissue hypoxemia that can be life-threatening if not promptly identified and treated. It can occur after exposure to an oxidizing agent from contaminated well water or from nitroglycerin, sodium nitroprusside, or certain local anesthetics. During oropharyngeal use of topical anesthetics for transesophageal echocardiography, systemic drug uptake is unpredictable and unexplained complications can ensue. Treatment of acquired methemoglobinemia may require methylene blue, as oxygen is not usually sufficient. Avoidance of the oxidizing agent, probably benzocaine in the cases presented, is prudent.