title: The risk of acute kidney injury with co-occurrence of anemia and hypotension during cardiopulmonary bypass relative to anemia alone.
abstract: BACKGROUND
  Postoperative acute kidney injury (AKI) is a common serious consequence of cardiac surgery. One recent study found higher AKI rates when anemia and hypotension occurred during cardiopulmonary bypass (CPB) relative to anemia alone. To revalidate this post hoc observation we analyzed detailed data from a large cardiac surgery cohort.
  
  
  METHODS
  Patient, procedural, and outcome data were collected for nonemergent aortocoronary bypass and valve surgeries between July 2001 and September 2012. The occurrence of AKI (as defined by the Acute Kidney Injury Network criteria) was analyzed relative to known renal risk factors, and CPB hematocrit and blood pressure determinations in univariate and multivariable linear regression analyses.
  
  
  RESULTS
  In our 3,963-patient cohort, we did not observe different AKI rates with the co-occurrence of anemia and hypotension relative to anemia alone (41.6% versus 44.3%; p = 0.39). Secondary analyses using linear definitions for AKI, CPB anemia, and hypotensive burden, and assessing for coincident timing also did not demonstrate significant association of anemia and hypotension with AKI risk relative to anemia alone.
  
  
  CONCLUSIONS
  In a large cohort of cardiac surgery patients, we did not confirm any association of cardiac surgery-related AKI risk with the co-occurrence of hypotension and anemia during CPB relative to anemia alone. More detailed analyses also failed to support an anemia-hypotension interaction. Additional studies are required to better understand the relationship among anemia, hypotension during CPB, and postoperative AKI, but existing evidence is insufficient to support changes in clinical practice.
authors.affiliation: Duke University School of Medicine, Duke University Medical Center, Durham, North Carolina.
authors.forename: Robert
authors.initials: R
authors.lastname: Sickeler
authors.affiliation: Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina.
authors.forename: Barbara
authors.initials: B
authors.lastname: Phillips-Bute
authors.affiliation: Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina.
authors.forename: Miklos D
authors.initials: MD
authors.lastname: Kertai
authors.affiliation: Department of Surgery, Duke University Medical Center, Durham, North Carolina.
authors.forename: Jacob
authors.initials: J
authors.lastname: Schroder
authors.affiliation: Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina.
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Mathew
authors.affiliation: Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina.
authors.forename: Madhav
authors.initials: M
authors.lastname: Swaminathan
authors.affiliation: Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina. Electronic address: mark.staffordsmit@dm.duke.edu.
authors.forename: Mark
authors.initials: M
authors.lastname: Stafford-Smith
mesh_terms: D058186:Acute Kidney Injury / Q000453:epidemiology* / Q000209:etiology*; D000368:Aged; D000740:Anemia / Q000150:complications*; D002315:Cardiopulmonary Bypass / Q000009:adverse effects*; D005260:Female; D006801:Humans; D007022:Hypotension / Q000150:complications*; D007431:Intraoperative Complications / Q000453:epidemiology* / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000453:epidemiology / Q000209:etiology; D012189:Retrospective Studies; D012307:Risk Factors