title: Acquired methemoglobinemia: a retrospective series of 138 cases at 2 teaching hospitals.
abstract: Methemoglobin is a form of hemoglobin that does not bind oxygen. When its concentration is elevated in red blood cells, functional anemia and tissue hypoxia may occur. We performed a retrospective case series to describe the cases of acquired methemoglobinemia (methemoglobin level >2%) detected and the clinical circumstances under which they occurred at 2 tertiary care hospitals and affiliated outpatient clinics over 28 months. We surveyed co-oximetry laboratory data to identify patients with methemoglobinemia. We reviewed these patients' medical records to extract the clinical information and context. One hundred thirty-eight cases of acquired methemoglobinemia were detected over the 28 months. There was no gender predisposition, and the condition occurred over a wide range of ages (patients aged 4 days to 86 years). Cases occurred in many areas of the hospital, including outpatient clinics. One fatality and 3 near-fatalities were directly attributable to methemoglobinemia. Dapsone was the most common etiology of acquired methemoglobinemia, accounting for 42% of all cases. The mean peak methemoglobin level among these individuals was 7.6%. In 5 of the patients with the most severely elevated levels, 20% benzocaine spray (Hurricaine Topical Anesthetic spray, Beutlich Pharmaceuticals, Waukegan, IL) was the etiology, associated with a mean peak methemoglobin level of 43.8%. Eleven pediatric patients developed methemoglobinemia either from exogenous exposure, such as drugs, or due to serious illness, such as gastrointestinal infections with dehydration. Almost all (94%) patients with methemoglobinemia were anemic. Drugs that cause acquired methemoglobinemia are ubiquitous in both the hospital and the outpatient setting. Acquired methemoglobinemia is a treatable condition that causes significant morbidity and even mortality. We hope that a heightened awareness of methemoglobinemia will result in improved recognition and treatment. Primary prevention efforts have the potential to reduce the morbidity and mortality associated with this condition.
authors.affiliation: From Divisions of General Internal Medicine (RAB, SMW) and Pulmonary Medicine (RW), Johns Hopkins Bayview Medical Center, Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: Rachel
authors.initials: R
authors.lastname: Ash-Bernal
authors.forename: Robert
authors.initials: R
authors.lastname: Wise
authors.forename: Scott M
authors.initials: SM
authors.lastname: Wright
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000008:administration & dosage / Q000009:adverse effects; D015415:Biomarkers / Q000097:blood; D002648:Child; D002675:Child, Preschool; D003622:Dapsone / Q000008:administration & dosage / Q000009:adverse effects; D005260:Female; D005955:Glucosephosphate Dehydrogenase Deficiency / Q000150:complications / Q000378:metabolism; D006784:Hospitals, Teaching; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008396:Maryland / Q000453:epidemiology; D008706:Methemoglobin / Q000378:metabolism; D008708:Methemoglobinemia / Q000175:diagnosis* / Q000209:etiology / Q000378:metabolism; D008875:Middle Aged; D015337:Multicenter Studies as Topic; D010092:Oximetry; D012189:Retrospective Studies
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D015415:Biomarkers; D003622:Dapsone; D008706:Methemoglobin