title: Severe methemoglobinemia from topical anesthetic spray: case report, discussion and qualitative systematic review.
abstract: Few health care professionals realize that topical anesthetic spray can cause methemoglobinemia. We describe a 56-year-old woman who was transferred to our emergency department when severe cyanosis and chest pain developed after administration of topical oropharyngeal benzocaine and lidocaine during outpatient endoscopy. Investigations revealed a methemoglobin level of 51%. Despite rapid diagnosis and treatment with methylene blue, pulmonary edema consistent with adult respiratory distress syndrome developed, endotracheal intubation was required, and the patient suffered a lengthy course in the intensive care unit. This article presents a detailed discussion of the pathophysiology, diagnosis and treatment of methemoglobinemia, as well as a qualitative systematic review of the English literature on methemoglobinemia induced by topical anesthetic. The implications of this condition for emergency physicians are also outlined.
authors.affiliation: Department of Emergency Medicine, Vancouver General Hospital, Vancouver, British Columbia, Canada.
authors.forename: R B
authors.initials: RB
authors.lastname: Abu-Laban
authors.forename: P J
authors.initials: PJ
authors.lastname: Zed
authors.forename: R A
authors.initials: RA
authors.lastname: Purssell
authors.forename: K G
authors.initials: KG
authors.lastname: Evans