title: Evaluation of cystatin C with iohexol clearance in cardiac surgery.
abstract: BACKGROUND
  Post-operative renal dysfunction after cardiac surgery is not uncommon and can lead to adverse outcome. The ability to accurately monitor renal function is therefore important. Cystatin C is known to be a sensitive marker of the glomerular filtration rate (GFR), but it has not been fully evaluated in cardiac surgery. Iohexol clearance is considered a reliable reference method for the determination of GFR. The aim of this study is to, for the first time, evaluate the diagnostic accuracy of plasma cystatin C compared with iohexol clearance in cardiac surgery.
  
  
  METHODS
  Twenty-one patients scheduled for elective coronary artery bypass grafting were prospectively enrolled in the study. Before surgery and on the second post-operative day, an iohexol clearance was performed. Plasma cystatin C, plasma creatinine and plasma C-reactive protein were determined before surgery and on the first, second, third and fifth post-operative day. Estimated creatinine and cystatin C clearances were determined.
  
  
  RESULTS
  Post-operative cystatin C and 1/cystatin C correlated strongly to iohexol clearance (r=-0.90 and 0.86) and so did creatinine and 1/creatinine (r=-0.83 and 0.78). Estimated creatinine clearance differed from iohexol clearance (P<0.01), whereas estimated cystatin C clearance did not differ from iohexol clearance (P=0.81). No correlation was found between C-reactive protein and cystatin C.
  
  
  CONCLUSIONS
  This study indicates that clearance estimations based on cystatin C are more accurate compared with estimations based on creatinine in determining GFR in cardiac surgery. Cystatin C has, in this study population, a stronger correlation to iohexol clearance than creatinine.
authors.affiliation: Department of Anaesthesia and Intensive Care, Lund University, Sweden. bjornbronden@hotmail.com
authors.forename: B
authors.initials: B
authors.lastname: Brondén
authors.forename: A
authors.initials: A
authors.lastname: Eyjolfsson
authors.forename: S
authors.initials: S
authors.lastname: Blomquist
authors.forename: A
authors.initials: A
authors.lastname: Dardashti
authors.forename: P
authors.initials: P
authors.lastname: Ederoth
authors.forename: H
authors.initials: H
authors.lastname: Bjursten
mesh_terms: D000368:Aged; D000758:Anesthesia; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000378:metabolism; D006348:Cardiac Surgical Procedures; D001026:Coronary Artery Bypass; D003404:Creatinine / Q000097:blood; D055316:Cystatin C / Q000097:blood*; D003627:Data Interpretation, Statistical; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology; D006334:Heart Function Tests; D006801:Humans; D007472:Iohexol; D007677:Kidney Function Tests; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D011446:Prospective Studies; D013318:Stroke Volume / Q000502:physiology
chemical_list: D015415:Biomarkers; D055316:Cystatin C; D007472:Iohexol; D002097:C-Reactive Protein; D003404:Creatinine