Cyanosis following transesophageal echocardiogram.

Topical anesthesia is routinely employed to facilitate diagnostic and therapeutic procedures that involve the oropharynx. Although this practice is usually safe, there is always the potential that methemoglobinemia might be induced by the topical anesthetic agent. The clinician should consider this possible complication when the patient experiences signs or symptoms of oxygen desaturation in the absence of another explanation. Because methemoglobinemia can be life-threatening, early recognition and treatment are extremely important.