title: Arterial carboxyhemoglobin level and outcome in critically ill patients.
abstract: OBJECTIVE
  Arterial carboxyhemoglobin is elevated in patients with critical illness. It is an indicator of the endogenous production of carbon monoxide by the enzyme heme oxygenase, which modulates the response to oxidant stress. The objective was to explore the hypothesis that arterial carboxyhemoglobin level is associated with inflammation and survival in patients requiring cardiothoracic intensive care.
  
  
  METHODS
  Prospective, observational study.
  
  
  METHODS
  A cardiothoracic intensive care unit.
  
  
  METHODS
  All patients admitted over a 15-month period.
  
  
  METHODS
  None.
  
  
  RESULTS
  Arterial carboxyhemoglobin, bilirubin, and standard biochemical, hematologic, and physiologic markers of inflammation were measured in 1,267 patients. Associations were sought between levels of arterial carboxyhemoglobin, markers of the inflammatory response, and clinical outcome. Intensive care unit mortality was associated with lower minimum and greater maximal carboxyhemoglobin levels (p < .0001 and p < .001, respectively). After adjustment for age, gender, illness severity, and other relevant variables, a lower minimum arterial carboxyhemoglobin was associated with an increased risk of death from all causes (odds risk of death, 0.391; 95% confidence interval, 0.190-0.807; p = .011). Arterial carboxyhemoglobin correlated with markers of the inflammatory response.
  
  
  CONCLUSIONS
  Both low minimum and high maximum levels of arterial carboxyhemoglobin were associated with increased intensive care mortality. Although the heme oxygenase system is protective, excessive induction may be deleterious. This suggests that there may be an optimal range for heme oxygenase-1 induction.
authors.affiliation: Department of Critical Care Medicine, Imperial College School of Medicine, Royal Brompton Hospital, London, UK.
authors.forename: Daniel D
authors.initials: DD
authors.lastname: Melley
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Finney
authors.forename: Androula
authors.initials: A
authors.lastname: Elia
authors.forename: Anna L
authors.initials: AL
authors.lastname: Lagan
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Quinlan
authors.forename: Timothy W
authors.initials: TW
authors.lastname: Evans
mesh_terms: D000368:Aged; D001663:Bilirubin / Q000097:blood; D015415:Biomarkers / Q000378:metabolism; D002248:Carbon Monoxide / Q000097:blood*; D002263:Carboxyhemoglobin / Q000378:metabolism*; D016638:Critical Illness / Q000401:mortality; D005260:Female; D051547:Heme Oxygenase-1 / Q000097:blood; D017052:Hospital Mortality; D006801:Humans; D007362:Intensive Care Units; D007902:Length of Stay; D016015:Logistic Models; D008131:London / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011446:Prospective Studies; D012372:ROC Curve; D012720:Severity of Illness Index; D015996:Survival Rate; D016896:Treatment Outcome
chemical_list: D015415:Biomarkers; D002248:Carbon Monoxide; D002263:Carboxyhemoglobin; D051547:Heme Oxygenase-1; D001663:Bilirubin