title: Serum creatinine measurement immediately after cardiac surgery and prediction of acute kidney injury.
abstract: BACKGROUND
  After heart surgery, acute kidney injury (AKI) confers substantial long-term risk of death and chronic kidney disease. We hypothesized that small changes in serum creatinine (SCr) levels measured within a few hours of exit from the operating room could help discriminate those at low versus high risk of AKI.
  
  
  METHODS
  Prospective cohort of 350 elective cardiac surgery patients (valve or coronary artery bypass grafting) recruited in Winnipeg, Canada. Baseline SCr level was obtained at the preoperative visit 2 weeks before surgery. The postoperative SCr level was drawn within 6 hours of completion of surgery and then daily while the patient was in the hospital.
  
  
  METHODS
  Immediate (ie, <6 hours) postoperative SCr level change (ΔSCr), categorized as within 10% (reference), decrease >10%, or increase >10% relative to baseline.
  
  
  RESULTS
  AKI, defined according to the new KDIGO (Kidney Disease: Improving Global Outcomes) consensus definition as an increase in SCr level >0.3 mg/dL within 48 hours or >1.5 times baseline within 1 week.
  
  
  METHODS
  We compared the C statistic of logistic models with and without inclusion of immediate postoperative ΔSCr.
  
  
  RESULTS
  After surgery, 176 patients (52%) experienced a decrease >10% in SCr level, 26 (7.4%) experienced an increase >10%, and 143 had ΔSCr within ±10% of baseline. During hospitalization, 53 (14%) developed AKI. Bypass pump time, baseline estimated glomerular filtration rate, and European System for Cardiac Operative Risk Evaluation (euroSCORE) were associated with AKI in a parsimonious base logistic model. Added to the base model, immediate postoperative ΔSCr was associated strongly with subsequent AKI and significantly improved model discrimination over the base model (C statistic, 0.78 [95% CI, 0.71-0.85] vs 0.69 [95% CI, 0.62-0.77]; P < 0.001). A ≥10% SCr level decrease predicted significantly lower AKI risk (OR, 0.37; 95% CI, 0.18-0.76), whereas a ≥10% SCr level increase predicted significantly higher (OR, 6.38; 95% CI, 2.37-17.2) AKI risk compared with the reference category.
  
  
  CONCLUSIONS
  We used a surrogate marker of AKI. External validation of our results is warranted.
  
  
  CONCLUSIONS
  In elective cardiac surgery patients, measurement of immediate postoperative ΔSCr improves prediction of AKI.
authors.affiliation: Department of Internal Medicine, University of Manitoba, Winnipeg, Canada.
authors.forename: Julie
authors.initials: J
authors.lastname: Ho
authors.forename: Martina
authors.initials: M
authors.lastname: Reslerova
authors.forename: Brent
authors.initials: B
authors.lastname: Gali
authors.forename: Peter W
authors.initials: PW
authors.lastname: Nickerson
authors.forename: David N
authors.initials: DN
authors.lastname: Rush
authors.forename: Manish M
authors.initials: MM
authors.lastname: Sood
authors.forename: Joe
authors.initials: J
authors.lastname: Bueti
authors.forename: Paul
authors.initials: P
authors.lastname: Komenda
authors.forename: Edward
authors.initials: E
authors.lastname: Pascoe
authors.forename: Rakesh C
authors.initials: RC
authors.lastname: Arora
authors.forename: Claudio
authors.initials: C
authors.lastname: Rigatto
mesh_terms: D058186:Acute Kidney Injury / Q000097:blood* / Q000453:epidemiology*; D000368:Aged; D015415:Biomarkers / Q000097:blood; D002170:Canada; D002404:Catheterization; D015331:Cohort Studies; D001026:Coronary Artery Bypass; D003404:Creatinine / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors
chemical_list: D015415:Biomarkers; D003404:Creatinine