title: Severe methemoglobinemia due to ingestion of toxicants.
abstract: BACKGROUND
  Toxin-induced methemoglobinemia is seen in poisoning with oxidizing agents. We report the clinical features and outcome of patients admitted with severe methemoglobinemia due to intentional ingestion of toxicants.
  
  
  METHODS
  In this observational case series, patients admitted with toxin-induced methemoglobinemia between September 2011 and January 2014 were identified from the institutional poisoning database. Clinical profile and outcome of patients with methemoglobin concentration greater than or equal to 49% is reported.
  
  
  RESULTS
  Of the 824 patients admitted with poisoning, 5 patients with methemoglobin concentration greater than or equal to 49% were included. The implicated compounds were nitrobenzene, benzoylphenylurea, flubendamide and Rishab(TM). One patient refused to name the compound. All patients were managed in the intensive care unit. Altered sensorium [Glasgow coma scale (GCS) < 10] was common (80%); 2 patients presented with a GCS greater than 4. All patients manifested cyanosis, low oxygen saturation and chocolate-brown-colored blood despite supplemental oxygen therapy. The median methemoglobin concentration was 64.7% (range 49.8-91.6%); 2 patients had methemoglobin concentration greater than 70%. One patient needed inotropes. Four patients required mechanical ventilation for 4-14 days. All patients were treated with methylene blue; 4 received more than one dose. Three patients also received intravenous ascorbic acid 500 mg, once daily, for 3 days. Following treatment, there was evidence of haemolysis in all patients; 2 required blood transfusion. All patients survived.
  
  
  CONCLUSIONS
  Patients with severe toxin-induced methemoglobinemia present with altered sensorium and cyanosis and may require ventilatory support and inotropes. Though methemoglobin concentrations greater than 70% are considered fatal, aggressive management with methylene blue and supportive therapy can lead to survival.
authors.affiliation: Department of Critical Care, Christian Medical College and Hospital , Vellore , India.
authors.forename: S R
authors.initials: SR
authors.lastname: D'sa
authors.forename: P
authors.initials: P
authors.lastname: Victor
authors.forename: M
authors.initials: M
authors.lastname: Jagannati
authors.forename: T I
authors.initials: TI
authors.lastname: Sudarsan
authors.forename: R A B
authors.initials: RA
authors.lastname: Carey
authors.forename: J V
authors.initials: JV
authors.lastname: Peter
mesh_terms: D000284:Administration, Oral; D000328:Adult; D003490:Cyanosis / Q000139:chemically induced / Q000175:diagnosis / Q000188:drug therapy; D006801:Humans; D008706:Methemoglobin / Q000378:metabolism; D008708:Methemoglobinemia / Q000139:chemically induced / Q000175:diagnosis* / Q000188:drug therapy; D008751:Methylene Blue / Q000627:therapeutic use; D008875:Middle Aged; D009578:Nitrobenzenes / Q000633:toxicity; D011042:Poisons / Q000633:toxicity*; D055815:Young Adult
chemical_list: D009578:Nitrobenzenes; D011042:Poisons; D008706:Methemoglobin; C036077:nitrobenzene; D008751:Methylene Blue
keywords: Metabolic; Poisoning; Respiratory support