title: Risk of topical anesthetic-induced methemoglobinemia: a 10-year retrospective case-control study.
abstract: OBJECTIVE
  Methemoglobinemia is a rare but serious disorder, defined as an increase in oxidized hemoglobin resulting in a reduction of oxygen-carrying capacity. Although methemoglobinemia is a known complication of topical anesthetic use, few data exist on the incidence of and risk factors for this potentially life-threatening disorder.
  
  
  OBJECTIVE
  To examine the incidence of and risk factors for procedure-related methemoglobinemia to identify patient populations at high risk for this complication.
  
  
  METHODS
  Retrospective study in an academic research setting.
  
  
  METHODS
  Medical records for all patients diagnosed as having methemoglobinemia during a 10-year period were reviewed.
  
  
  METHODS
  All cases of methemoglobinemia that occurred after the following procedures were included in the analysis: bronchoscopy, nasogastric tube placement, esophagogastroduodenoscopy, transesophageal echocardiography, and endoscopic retrograde cholangiopancreatography.
  
  
  METHODS
  Comorbidities, demographics, concurrent laboratory values, and specific topical anesthetic used were recorded for all cases. Each case was compared with matched inpatient and outpatient cases.
  
  
  RESULTS
  In total, 33 cases of methemoglobinemia were identified during the 10-year period among 94,694 total procedures. The mean (SD) methemoglobin concentration was 32.0% (12.4%). The methemoglobinemia prevalence rates were 0.160% for bronchoscopy, 0.005% for esophagogastroduodenoscopy, 0.250% for transesophageal echocardiogram, and 0.030% for endoscopic retrograde cholangiopancreatography. Hospitalization at the time of the procedure was a major risk factor for the development of methemoglobinemia (0.14 cases per 10,000 outpatient procedures vs 13.7 cases per 10,000 inpatient procedures, P < .001).
  
  
  CONCLUSIONS
  The overall prevalence of methemoglobinemia is low at 0.035%; however, an increased risk was seen in hospitalized patients and with benzocaine-based anesthetics. Given the potential severity of methemoglobinemia, the risks and benefits of the use of topical anesthetics should be carefully considered in inpatient populations.
authors.affiliation: Division of Gastroenterology, Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA 02215, USA.
authors.forename: Sejal
authors.initials: S
authors.lastname: Chowdhary
authors.forename: Bolanle
authors.initials: B
authors.lastname: Bukoye
authors.forename: Arjun M
authors.initials: AM
authors.lastname: Bhansali
authors.forename: Alexander R
authors.initials: AR
authors.lastname: Carbo
authors.forename: May
authors.initials: M
authors.lastname: Adra
authors.forename: Sheila
authors.initials: S
authors.lastname: Barnett
authors.forename: Mark D
authors.initials: MD
authors.lastname: Aronson
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Leffler
mesh_terms: D000328:Adult; D000368:Aged; D000772:Anesthesia, Local / Q000379:methods*; D000779:Anesthetics, Local / Q000008:administration & dosage* / Q000009:adverse effects*; D000931:Antidotes / Q000627:therapeutic use; D001566:Benzocaine / Q000008:administration & dosage / Q000009:adverse effects; D001999:Bronchoscopy; D016022:Case-Control Studies; D002760:Cholangiopancreatography, Endoscopic Retrograde; D015897:Comorbidity; D017548:Echocardiography, Transesophageal; D016145:Endoscopy, Digestive System; D005260:Female; D006801:Humans; D015994:Incidence; D007297:Inpatients / Q000706:statistics & numerical data; D007441:Intubation, Gastrointestinal; D008297:Male; D008404:Massachusetts / Q000453:epidemiology; D008499:Medical Records; D008708:Methemoglobinemia / Q000139:chemically induced* / Q000188:drug therapy / Q000453:epidemiology*; D008751:Methylene Blue / Q000627:therapeutic use; D008875:Middle Aged; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors
chemical_list: D000779:Anesthetics, Local; D000931:Antidotes; D008751:Methylene Blue; D001566:Benzocaine