title: Exploratory studies on the age of transfused blood and in-hospital mortality in patients with cardiovascular diagnoses.
abstract: BACKGROUND
  The objective was to examine the association between blood storage duration and in-hospital mortality in a large cohort of cardiovascular patients transfused between 2002 and 2011.
  
  
  METHODS
  Cox regression models were fitted to assess the effect of red blood cell (RBC) storage duration on risk of in-hospital mortality in cardiovascular patients (2002-2011). Time-dependent covariates summarizing the maximum age of RBCs transfused per individual were included as continuous or categorical variables. Models were stratified by cumulative number of RBCs transfusions and other potential confounders. Exploratory analyses were performed by period (Period I, April 2002 to March 2006; Period II, April 2006 to October 2011) and controlling for fiscal year of admission.
  
  
  RESULTS
  A total of 9669 patients received 46,868 RBCs. The median number of RBC units transfused was 3 (interquartile range [IQR], 2-5); the median age of RBCs was 17 days (IQR, 13-23 days). The progressive increase in risk of in-hospital mortality with transfusion of older blood observed previously was not seen in the larger cohort (hazard ratio, 01.00; p = 0.692); significantly different effects were observed between periods (p = 0.016), but the difference between periods was no longer significant upon stratification by fiscal year of admission (interaction p = 0.094).
  
  
  CONCLUSIONS
  The analysis of a large cohort of cardiovascular patients showed no association between storage age of blood and in-hospital mortality. This finding is inconsistent with those of our previous report that analyzed a smaller cohort.
authors.affiliation: Department of Medicine, Faculty of Health Sciences, McMaster University, Hamilton, Ontario, Canada; Centre for Innovation, Canadian Blood Services, Hamilton, Ontario, Canada.
authors.forename: Nancy M
authors.initials: NM
authors.lastname: Heddle
authors.forename: John
authors.initials: J
authors.lastname: Eikelboom
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.forename: Rebecca
authors.initials: R
authors.lastname: Barty
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Cook
mesh_terms: D000368:Aged; D001793:Blood Preservation / Q000009:adverse effects*; D002318:Cardiovascular Diseases / Q000401:mortality / Q000628:therapy; D017707:Erythrocyte Transfusion / Q000401:mortality*; D005260:Female; D005500:Follow-Up Studies; D017052:Hospital Mortality; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors