title: Age of red blood cells and mortality in the critically ill.
abstract: BACKGROUND
  In critically ill patients, it is uncertain whether exposure to older red blood cells (RBCs) may contribute to mortality. We therefore aimed to evaluate the association between the age of RBCs and outcome in a large unselected cohort of critically ill patients in Australia and New Zealand. We hypothesized that exposure to even a single unit of older RBCs may be associated with an increased risk of death.
  
  
  METHODS
  We conducted a prospective, multicenter observational study in 47 ICUs during a 5-week period between August 2008 and September 2008. We included 757 critically ill adult patients receiving at least one unit of RBCs. To test our hypothesis we compared hospital mortality according to quartiles of exposure to maximum age of RBCs without and with adjustment for possible confounding factors.
  
  
  RESULTS
  Compared with other quartiles (mean maximum red cell age 22.7 days; mortality 121/568 (21.3%)), patients treated with exposure to the lowest quartile of oldest RBCs (mean maximum red cell age 7.7 days; hospital mortality 25/189 (13.2%)) had an unadjusted absolute risk reduction in hospital mortality of 8.1% (95% confidence interval = 2.2 to 14.0%). After adjustment for Acute Physiology and Chronic Health Evaluation III score, other blood component transfusions, number of RBC transfusions, pretransfusion hemoglobin concentration, and cardiac surgery, the odds ratio for hospital mortality for patients exposed to the older three quartiles compared with the lowest quartile was 2.01 (95% confidence interval = 1.07 to 3.77).
  
  
  CONCLUSIONS
  In critically ill patients, in Australia and New Zealand, exposure to older RBCs is independently associated with an increased risk of death.
authors.affiliation: Australian and New Zealand Intensive Care Research Centre, Department of Epidemiology and Preventive Medicine, Monash University, Commercial Road, Melbourne 3004, Victoria, Australia. ville.pettila@hus.fi
authors.forename: Ville
authors.initials: V
authors.lastname: Pettilä
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Westbrook
authors.forename: Alistair D
authors.initials: AD
authors.lastname: Nichol
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Bailey
authors.forename: Erica M
authors.initials: EM
authors.lastname: Wood
authors.forename: Gillian
authors.initials: G
authors.lastname: Syres
authors.forename: Louise E
authors.initials: LE
authors.lastname: Phillips
authors.forename: Alison
authors.initials: A
authors.lastname: Street
authors.forename: Craig
authors.initials: C
authors.lastname: French
authors.forename: Lynnette
authors.initials: L
authors.lastname: Murray
authors.forename: Neil
authors.initials: N
authors.lastname: Orford
authors.forename: John D
authors.initials: JD
authors.lastname: Santamaria
authors.forename: Rinaldo
authors.initials: R
authors.lastname: Bellomo
authors.forename: David J
authors.initials: DJ
authors.lastname: Cooper
mesh_terms: D000368:Aged; D001315:Australia / Q000453:epidemiology; D016638:Critical Illness; D004905:Erythrocyte Aging; D017707:Erythrocyte Transfusion / Q000401:mortality*; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D007362:Intensive Care Units / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D009520:New Zealand / Q000453:epidemiology; D011446:Prospective Studies; D018570:Risk Assessment; D016896:Treatment Outcome