title: Transfusion of older stored blood and risk of death: a meta-analysis.
abstract: BACKGROUND
  Blood for transfusion is stored for up to 42 days. Older blood develops lesions and accumulates potentially injurious substances. Some studies report increasing toxicity as blood ages. We assessed the safety of transfused older versus newer stored blood.
  
  
  METHODS
  PubMed, Scopus, and Embase were searched using terms new and old and red blood cell and storage through May 6, 2011, for observational and randomized controlled studies comparing outcomes using transfused blood having longer and shorter storage times. Death was the outcome of interest.
  
  
  RESULTS
  Twenty-one studies were identified, predominantly in cardiac surgery (n=6) and trauma (n=6) patients, including 409,966 patients. A test for heterogeneity of these studies' results was not significant for mortality (I(2)=3.7%, p=0.41). Older blood was associated with a significantly increased risk of death (odds ratio, 1.16; 95% confidence interval [CI], 1.07-1.24). Using available mortality data, 97 (95% CI, 63-199) patients need to be treated with only new blood to save one life. Subgroup analysis of these trials indicated that the increased risk was not restricted to a particular type of patient, size of trial, or amount of blood transfused.
  
  
  CONCLUSIONS
  Based on available data, use of older stored blood is associated with a significantly increased risk of death.
authors.affiliation: Critical Care Medicine Department, National Institutes of Health, Bethesda, Maryland 20892, USA. wangd4@cc.nih.gov
authors.forename: Dong
authors.initials: D
authors.lastname: Wang
authors.forename: Junfeng
authors.initials: J
authors.lastname: Sun
authors.forename: Steven B
authors.initials: SB
authors.lastname: Solomon
authors.forename: Harvey G
authors.initials: HG
authors.lastname: Klein
authors.forename: Charles
authors.initials: C
authors.lastname: Natanson
mesh_terms: D000465:Algorithms; D001793:Blood Preservation / Q000009:adverse effects / Q000379:methods / Q000401:mortality / Q000706:statistics & numerical data; D058731:Blood Safety / Q000592:standards; D001803:Blood Transfusion / Q000379:methods* / Q000401:mortality* / Q000706:statistics & numerical data; D003643:Death; D017707:Erythrocyte Transfusion / Q000009:adverse effects / Q000401:mortality / Q000706:statistics & numerical data; D006801:Humans; D016032:Randomized Controlled Trials as Topic / Q000401:mortality / Q000706:statistics & numerical data; D012307:Risk Factors; D065227:Transfusion Reaction