Esophageal manometry is best performed without anesthesia or sedation. However, with particularly anxious patients, some form of topical anesthetic or sedation may be used. Benzocaine spray, thought to be a safe topical anesthetic, has been reported to induce methemoglobinemia in adults(Gastroenterology 1990;98:211-213). However, this has not been reported to occur in children. We report an 11½-year-old Caucasian male with a history of achalasia. He developed methemoglobinemia as a result of topical benzocaine sprayed onto his pharynx prior to esophageal manometry at 10:10 a.m. (see table). Within 25 minutes of receiving the benzocaine spray, his oxygen saturation (%) dropped from 98% to 88%, and he became cyanotic. His oxygen saturation continued to drop even though he was receiving oxygen therapy and maintained a Po2 of> 300 mmHg. He remained awake and alert. Arterial blood (AB) for oxygen content was noted to be brown, and the diagnosis of methemoglobinemia was made. Blood for methemoglobin concentration showed an increase to 16% and 24% on two occasions(<1% WNL). Intravenous methylene blue (M.B.) was administered; 2 doses of 35 mg each (1 mg/kg ×2). Within 12 minutes of the second dose, the patient was pink, and after 22 minutes his oxygen saturation was 91%.
We conclude that in rare instances, benzocaine spray can produce methemoglobinemia. When this occurs, oxygen therapy and intravenous methylene blue should be administered, and unnecessary therapy such as endotracheal intubation and ventilation avoided.
