title: Changes in serum cystatin C, creatinine, and C-reactive protein after cardiopulmonary bypass in patients with normal preoperative kidney function.
abstract: OBJECTIVE
  The use of cardiopulmonary bypass (CPB) can cause changes in serum creatinine and cystatin C independent of glomerular filtration rate. We aimed to quantify the temporal changes of these biomarkers and C-reactive protein (CRP) after CPB.
  
  
  METHODS
  This was a prospective study at an academic medical centre between April and October 2013. We compared postoperative changes in serum creatinine and cystatin C in 38 patients with normal preoperative kidney function who underwent cardiac surgery using CPB and did not develop perioperative acute kidney injury (AKI). The effect of inflammation on intra-individual changes was examined in mixed effects regressions, using measurements of pre- and postoperative CRP.
  
  
  RESULTS
  Both serum creatinine (79.9 ± 22.7 vs. 92.6 ± 21.4 µmol/L, P = 0.001) and cystatin C (1.16 ± 0.39 vs. 1.33 ± 0.37 mg/L, P = 0.012) decreased significantly in the first 8 h postoperatively compared to preoperatively, as a result of haemodilution. Thereafter serum creatinine returned to preoperative levels, whereas serum cystatin C continued to rise and was significantly elevated at 72 h post-CPB compared to preoperative levels (1.53 ± 0.48 vs. 1.33 ± 0.37 mg/L, P = 0.003). CRP levels increased significantly post-CPB and were significantly associated with increases in both serum creatinine and cystatin C.
  
  
  CONCLUSIONS
  Serum creatinine and cystatin C appear not to be interchangeable biomarkers during and immediately after CPB. Processes unrelated to kidney function such as acute inflammation have a significant effect on post-CPB changes in these biomarkers, and may result in significant increases in serum cystatin C that could erroneously be interpreted as AKI.
authors.affiliation: Department of Cardiothoracic Surgery and Anaesthesia, Linköping University Hospital, Linköping, Sweden.|Division of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden.
authors.forename: Anders S
authors.initials: AS
authors.lastname: Svensson
authors.affiliation: Department of Cardiothoracic Surgery and Anaesthesia, Linköping University Hospital, Linköping, Sweden.|Division of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden.
authors.forename: John-Peder Escobar
authors.initials: JP
authors.lastname: Kvitting
authors.affiliation: Division of Nephrology, University of Tennessee Health Science Center, Memphis, Tennessee, USA.|Memphis Veterans Affairs Medical Center, Memphis, Tennessee, USA.
authors.forename: Csaba P
authors.initials: CP
authors.lastname: Kovesdy
authors.affiliation: Department of Cardiothoracic Surgery and Anaesthesia, Linköping University Hospital, Linköping, Sweden.|Division of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden.
authors.forename: Ingemar
authors.initials: I
authors.lastname: Cederholm
authors.affiliation: Department of Cardiothoracic Surgery and Anaesthesia, Linköping University Hospital, Linköping, Sweden.|Division of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Szabó
mesh_terms: D000046:Academic Medical Centers; D058186:Acute Kidney Injury / Q000097:blood / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000378:metabolism*; D006348:Cardiac Surgical Procedures / Q000009:adverse effects; D002315:Cardiopulmonary Bypass / Q000009:adverse effects; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C / Q000097:blood*; D005260:Female; D006438:Hemodilution; D006801:Humans; D007249:Inflammation / Q000097:blood* / Q000175:diagnosis / Q000209:etiology; D007668:Kidney / Q000503:physiopathology*; D007677:Kidney Function Tests; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results; D013548:Sweden; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D015415:Biomarkers; C525030:CST3 protein, human; D055316:Cystatin C; D002097:C-Reactive Protein; D003404:Creatinine
keywords: C-reactive protein; acute kidney injury; cardiac surgery; cardiopulmonary bypass; creatinine; cystatin C