title: Methemoglobinemia induced by topical anesthesia: a case report and review.
abstract: Topical anesthetic drugs are widely used by clinicians during hospital and outpatient procedures and are also available to the public in a variety of over-the-counter preparations. Although generally safe, they may cause potentially life-threatening methemoglobinemia. We describe a patient who developed repeated episodes of severe methemoglobinemia after administration of topical Cetacaine spray (a proprietary mixture of benzocaine, tetracaine, and butamben) employed for pharyngeal anesthesia before endotracheal intubation, and briefly review the etiology and pathophysiology of this disorder. Cautious interpretation of oxyhemoglobin saturation values obtained by pulse oximetry or estimated from arterial blood gas analysis is crucial lest the diagnosis of severe methemoglobinemia and the resulting hypoxemia are overlooked. If necessary, the condition is usually readily corrected by intravenous administration of methylene blue.
authors.affiliation: Section of Critical Care Medicine, Detroit Receiving Hospital, and Wayne State University School of Medicine, Michigan 48201, USA.
authors.forename: N A
authors.initials: NA
authors.lastname: Khan
authors.forename: J A
authors.initials: JA
authors.lastname: Kruse
mesh_terms: D010129:4-Aminobenzoic Acid / Q000009:adverse effects; D000368:Aged; D000772:Anesthesia, Local / Q000009:adverse effects; D000779:Anesthetics, Local / Q000009:adverse effects*; D001548:Benzalkonium Compounds / Q000009:adverse effects*; D001566:Benzocaine / Q000009:adverse effects*; D002593:Cetrimonium Compounds / Q000009:adverse effects*; D004338:Drug Combinations; D005260:Female; D006801:Humans; D008706:Methemoglobin / Q000378:metabolism; D008708:Methemoglobinemia / Q000097:blood / Q000139:chemically induced* / Q000188:drug therapy; D008751:Methylene Blue / Q000627:therapeutic use; D010092:Oximetry; D013748:Tetracaine / Q000009:adverse effects*; D013997:Time Factors; D062366:para-Aminobenzoates
chemical_list: D000779:Anesthetics, Local; D001548:Benzalkonium Compounds; D002593:Cetrimonium Compounds; D004338:Drug Combinations; C010071:benzocaine, butyl aminobenzoate, tetracaine drug combination; D062366:para-Aminobenzoates; D013748:Tetracaine; D008706:Methemoglobin; D008751:Methylene Blue; D010129:4-Aminobenzoic Acid; D001566:Benzocaine