title: The age of transfused blood predicts hematocrit response among critically ill surgical patients.
abstract: BACKGROUND
  In vitro data suggest that erythrocytes undergo storage time-dependent degradation, eventuating in hemolysis. We hypothesize that transfusion of old blood, as compared with newer blood, results in a smaller increment in hematocrit.
  
  
  METHODS
  We performed an analysis of packed red blood cell transfusions administered in the surgical intensive care unit. Age of blood was analyzed as continuous, dichotomized at 14 days (old vs new), and grouped by weeks old.
  
  
  RESULTS
  A total of 136 U of packed red blood cells were given to 52 patients; 110 (80.9%) were 14 days old or more. A linear, inverse correlation was observed between the age of blood and the increment in hematocrit (r(2) = -.18, P = .04). The increment in hematocrit was greater after transfusion of new as compared with old blood (5.6% vs 3.5%, respectively; P = .005). A linear relationship also was observed between the age of transfused blood in weeks and the increment in hematocrit (P = .02).
  
  
  CONCLUSIONS
  There is an inverse relationship between the age of blood and the increment in hematocrit. The age of blood should be considered before transfusion of surgical patients with intensive care unit anemia.
authors.affiliation: Department of Surgery, Denver Health Medical Center/University of Colorado Health Science Center, 777 Bannock St., MC0206, Denver, CO 80206, USA.
authors.forename: Fredric M
authors.initials: FM
authors.lastname: Pieracci
authors.forename: Ernest E
authors.initials: EE
authors.lastname: Moore
authors.forename: Teresa
authors.initials: T
authors.lastname: Chin
authors.forename: Nicole
authors.initials: N
authors.lastname: Townsend
authors.forename: Eduardo
authors.initials: E
authors.lastname: Gonzalez
authors.forename: Clay C
authors.initials: CC
authors.lastname: Burlew
authors.forename: Carlton C
authors.initials: CC
authors.lastname: Barnett
mesh_terms: D000046:Academic Medical Centers; D000328:Adult; D000368:Aged; D016009:Chi-Square Distribution; D003422:Critical Care / Q000379:methods / Q000592:standards; D016638:Critical Illness; D003430:Cross-Sectional Studies; D017707:Erythrocyte Transfusion / Q000592:standards*; D005260:Female; D006400:Hematocrit; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D013997:Time Factors; D016896:Treatment Outcome