title: Red blood cell storage is associated with length of stay and renal complications after cardiac surgery.
abstract: BACKGROUND
  The association of red blood cell (RBC) storage on morbidity outcome after cardiac surgery is debated. We sought to clarify the association of the age of transfused blood on outcome in patients undergoing cardiac surgery.
  
  
  METHODS
  Data were drawn from a prospective, observational cohort study of morbidity outcome in patients undergoing cardiac surgery. Blood transfusion data were obtained retrospectively via the Trust blood bank electronic records. Old blood was defined as more than 14 days old. The primary outcome measure was postoperative length of stay (PLOS). Secondary outcome measures included renal failure and morbidity as defined within the postoperative morbidity survey.
  
  
  RESULTS
  A total of 176 (39.6%) of 444 participants received a blood transfusion. Patients transfused with new blood had a reduced PLOS compared with patients receiving exclusively old or any old blood (old blood ± new blood; 7 days vs. 8 days, p = 0.04 and vs. 10 days, p = 0.002, respectively). In patients who only had 1 unit transfused, PLOS was longer in those receiving only old blood compared with those receiving only new blood (8 days vs. 6 days, p = 0.02) with a 3.8-fold risk of longer stay. Compared with patients receiving exclusively new blood, patients receiving any old blood had a higher incidence of new renal complications (65.7% vs. 43.9%, p = 0.008). Each 1-day increase in storage was associated with a 7% increase in risk of new renal complications.
  
  
  CONCLUSIONS
  Our data support previous suggestions of an association between transfusion of older RBCs and poorer outcome in cardiac surgery patients. Randomized controlled trials are required to determine the true causal nature of any such association.
authors.affiliation: From the UCL Centre for Cardiovascular Genetics, and UCL Institute for Human Health and Performance, University College London, London, UK. j.sanders@ucl.ac.uk
authors.forename: Julie
authors.initials: J
authors.lastname: Sanders
authors.forename: Sanjiv
authors.initials: S
authors.lastname: Patel
authors.forename: Jackie
authors.initials: J
authors.lastname: Cooper
authors.forename: Jennifer
authors.initials: J
authors.lastname: Berryman
authors.forename: Daniel
authors.initials: D
authors.lastname: Farrar
authors.forename: Michael
authors.initials: M
authors.lastname: Mythen
authors.forename: Hugh E
authors.initials: HE
authors.lastname: Montgomery
mesh_terms: D000368:Aged; D001793:Blood Preservation; D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D004905:Erythrocyte Aging / Q000502:physiology*; D017707:Erythrocyte Transfusion / Q000009:adverse effects*; D004912:Erythrocytes; D005260:Female; D006801:Humans; D007902:Length of Stay; D008297:Male; D008875:Middle Aged; D051437:Renal Insufficiency / Q000209:etiology*; D013997:Time Factors