title: Methemoglobinemia in a patient undergoing gastrointestinal endoscopy.
abstract: OBJECTIVE
  To report a case of methemoglobinemia induced by benzocaine in a patient undergoing gastrointestinal endoscopy.
  
  
  METHODS
  Before undergoing an upper gastrointestinal endoscopy, a 15-year-old girl received 20% benzocaine as a spray, to locally anesthetize the pharyngeal mucosa. Thirty minutes after the endoscopy, the patient suddenly became cyanotic, short of breath, and comatose. She was intubated and transferred to the intensive care unit. Her blood methemoglobin concentration was 54 percent. The patient was treated with intravenous methylene blue. Four hours later she was extubated. She was alert, awake, and asymptomatic.
  
  
  CONCLUSIONS
  This is the fourth reported case of methemoglobinemia induced by benzocaine spray in patients undergoing gastrointestinal endoscopy. Pathways for the formation of methemoglobin in the body are reviewed. Intravenous methylene blue is the drug of choice for this condition, and produces rapid and dramatic reversal of methemoglobinemia.
  
  
  CONCLUSIONS
  It is common to use benzocaine spray prior to upper gastrointestinal endoscopy. Benzocaine rarely induces methemoglobinemia in these patients. Prompt diagnosis and treatment with intravenous methylene blue is warranted in such cases.
authors.affiliation: Department of Medicine, School of Medicine, Wright State University, Dayton, OH 45401.
authors.forename: A
authors.initials: A
authors.lastname: Bhutani
authors.forename: M S
authors.initials: MS
authors.lastname: Bhutani
authors.forename: R
authors.initials: R
authors.lastname: Patel
mesh_terms: D000293:Adolescent; D001566:Benzocaine / Q000009:adverse effects*; D016145:Endoscopy, Digestive System; D005260:Female; D006801:Humans; D008708:Methemoglobinemia / Q000139:chemically induced* / Q000188:drug therapy; D008751:Methylene Blue / Q000627:therapeutic use
chemical_list: D008751:Methylene Blue; D001566:Benzocaine