Cystatin C and glomerular filtration rate in the cardiac surgery with cardiopulmonary bypass.

OBJECTIVE: The aim of this study was to compare cystatin C versus creatinine as a marker for acute kidney injury in patients submitted to cardiac surgery with cardiopulmonary bypass.

METHODS: Fifty consecutive patients submitted to coronary artery bypass grafting were studied. Renal function was evaluated by serum cystatin C and creatinine. Blood samples were obtained from each patient at three time points: before operation, and on the first and fifth postoperative days. Glomerular filtration rate (GFR) was calculated by Cockcroft-Gault (CG), Modification of Diet in Renal Disease (MDRD), and Larsson (Cys-GFR) formulas.

RESULTS: Creatinine and GFR by CG and MDRD formulas did not show statistical difference between study times. After renal injury from surgery, there was an increase in cystatin C on the 1st and 5th day after surgery, being significantly different on the 5th postoperative (P<0.01). The GFR by Larson formula was higher in the preoperative time (105.2 +/- 41.0 ml/min) than in the 5th postoperative day (89.5+/- 31.5 ml/min; P<0.012).

CONCLUSION: The cystatin C and the Cys-GFR showed significant changes after cardiac surgery when compared with the creatinine and respective GFR calculated by the Cockcroft-Gault and MDRD formulas.