Methemoglobinemia: early intraoperative detection by clinical observation

Head and neck surgery patients often receive topical anesthetics in the office for examination or in the operating room for nasotracheal intubation. Benzocaine (a component of many topical preparations) is frequently employed for this purpose. Acute methemoglobinemia is a rare but potentially lethal complication of benzocaine administration. Early recognition and treatment may prevent complications or death. We report a case of acute intraoperative methemoglobinemia, caused by benzocaine spray, which was diagnosed (and reversed) quickly after the clinical observation of "chocolate brown blood" in the surgical field.