title: Interrelationship of preoperative anemia, intraoperative anemia, and red blood cell transfusion as potentially modifiable risk factors for acute kidney injury in cardiac surgery: a historical multicentre cohort study.
abstract: OBJECTIVE
  Acute kidney injury (AKI) is a potentially serious complication of cardiac surgery. Anemia and red blood cell (RBC) transfusion have individually been identified as potentially modifiable risk factors, but their interrelationship with AKI has not been clearly defined. The purpose of this study was to explore the interrelationship of preoperative anemia, intraoperative anemia, and RBC transfusion on the day of surgery with AKI in cardiac surgery.
  
  
  METHODS
  This historical cohort study included 16 hospitals, each contributing data on approximately 100 consecutive patients who underwent cardiac surgery with cardiopulmonary bypass. Acute kidney injury was defined as a > 50% increase in creatinine levels during the first postoperative week. Multivariable regression was used to identify the interrelationship between preoperative anemia (hemoglobin < 130 g·L(-1) in males and < 120 g·L(-1) in females), intraoperative anemia (hemoglobin < 80 g·L(-1) during cardiopulmonary bypass), RBC transfusion on the day of surgery, and their interaction terms, after adjusting for site and baseline AKI risk.
  
  
  RESULTS
  Of the 1,444 patients included in the study, 541 (37%) had preoperative anemia, 501 (35%) developed intraoperative anemia, 619 (43%) received RBC transfusions, and 238 (16%) developed AKI. After risk-adjustment, an individual with the combination of these three risk factors had a 2.6-fold (95% confidence interval 2.0 to 3.3) increase in the relative risk of AKI over an individual with none of these risk factors.
  
  
  CONCLUSIONS
  Preoperative anemia, intraoperative anemia, and RBC transfusion on the day of surgery are interrelated risk factors for AKI after cardiac surgery. Targeting these risk factors may reduce the burden of AKI.
authors.affiliation: Department of Anesthesia and Pain Management, Toronto General Hospital, University Health Network, University of Toronto, 200 Elizabeth Street, 3EN, Toronto, ON, M5G 2C4, Canada, keyvan.karkouti@uhn.ca.
authors.forename: Keyvan
authors.initials: K
authors.lastname: Karkouti
authors.forename: Hilary P
authors.initials: HP
authors.lastname: Grocott
authors.forename: Richard
authors.initials: R
authors.lastname: Hall
authors.forename: Michael E
authors.initials: ME
authors.lastname: Jessen
authors.forename: Cornelis
authors.initials: C
authors.lastname: Kruger
authors.forename: Adam B
authors.initials: AB
authors.lastname: Lerner
authors.forename: Charles
authors.initials: C
authors.lastname: MacAdams
authors.forename: C David
authors.initials: CD
authors.lastname: Mazer
authors.forename: Étienne
authors.initials: É
authors.lastname: de Medicis
authors.forename: Paul
authors.initials: P
authors.lastname: Myles
authors.forename: Fiona
authors.initials: F
authors.lastname: Ralley
authors.forename: Michel R
authors.initials: MR
authors.lastname: Rheault
authors.forename: Antoine
authors.initials: A
authors.lastname: Rochon
authors.forename: Mark S
authors.initials: MS
authors.lastname: Slaughter
authors.forename: Andrew
authors.initials: A
authors.lastname: Sternlicht
authors.forename: Summer
authors.initials: S
authors.lastname: Syed
authors.forename: Terrence
authors.initials: T
authors.lastname: Waters
mesh_terms: D058186:Acute Kidney Injury / Q000453:epidemiology / Q000209:etiology* / Q000517:prevention & control; D000368:Aged; D000740:Anemia / Q000150:complications* / Q000453:epidemiology; D002315:Cardiopulmonary Bypass / Q000009:adverse effects / Q000379:methods*; D015331:Cohort Studies; D017707:Erythrocyte Transfusion / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D012044:Regression Analysis; D012189:Retrospective Studies; D012307:Risk Factors