Evaluation of Cystatin C as a marker of renal injury following on-pump and off-pump coronary surgery

Objective: Cardiopulmonary bypass is regarded as an important contributor to renal injury, whereas off-pump surgery is considered less damaging. Cystatin C, a cystine protease inhibitor, is more sensitive and specific than creatinine in the assessment of renal function. We assessed the value of Cystatin C in quantifying clinical and subclinical renal injury following on-pump and off-pump cardiac surgery. Methods: Sixty consecutive patients were recruited: 30 patients undergoing on-pump CABG and 30 patients undergoing off-pump CABG. Blood samples were collected pre-operatively and on days 1, 2 and 4 postoperatively to measure serum creatinine and serum Cystatin C. Urinary samples were collected concurrently to measure microalbumin and N-acetyl-beta-glucosaminidase, denoting changes in renal glomerular and tubular function respectively. Results: The off-pump group were older (65 +/- 11 vs. 61 +/- 8 years; P = 0.046), had a higher mean Parsonnet score (9.4 +/- 6.2 vs. 5.4 +/- 3.6, P < 0.01) and received fewer grafts (2.4 +/- 0.9 vs. 3.1 +/- 0.7; P < 0.01) compared to the on-pump group. The groups were otherwise matched with respect to preoperative renal function and left ventricular function. Patients undergoing on-pump CABG had greater increases in all four parameters of renal injury. Adjustment for preoperative differences increased the size and significance of the effect of off-pump vs. on-pump surgery (percent difference 13%; 95% CI 2-26 for creatinine, and 16%; 95% CI 4-29 for Cystatin C). Cystatin and creatinine were strongly correlated with each other. Conclusions: Avoidance of cardiopulmonary bypass may reduce renal injury particularly in higher risk patients. Cystatin C proved to be a simple and sensitive measure of overall renal function and can be used in the routine assessment of renoprotective strategies. (c) 2005 Elsevier B.V. All. rights reserved.