Estimated creatinine clearance instead of plasma creatinine level as prognostic test for postoperative renal function in patients undergoing coronary artery bypass surgery

Abstract

Background: Preoperative renal failure is a risk factor for adverse events in cardiac surgery. Serum creatinine (SCr) is the most used test for renal failure. However, patients can have significantly decreased glomerular filtration rates with normal SCr levels. More accurate approximation of renal function can be obtained using the Cockroft-Gault equation to calculate an estimated creatinine clearance (CrCl) rate from SCr.

Methods: This study included 627 patients undergoing an isolated CABG between January 2003 and September 2004. CrCl was calculated using the Cockroft-Gault formula. Patients were divided in group A-SCr, 576 patients (91.1%) with a good renal function, SCr < or =1.20 mg/dL for women and < or =1.40 mg/dL for men, and a group B-SCr, with impaired renal function, 51 patients (8.1%). CrCl < or = 50 mL/min was chosen to reflect renal impairment. Group A-CrCl (555 patients, 88.5%) had a normal renal function and group B-CrCl (72 patients,11.5%) an impaired renal function. The studied outcomes were hospital mortality, hospital morbidity, and postoperative renal failure.

Results: There was no statistical significant difference between A-SCr and B-SCr group according to the studied outcomes. On the contrary, using the CrCl there was a statistical significant difference between A-CrCl and B-CrCl for the percentage of postoperative renal failure 10 patients (1.8%) versus 5 patients (6.9%) (p=0.00), hospital morbidity 75 patients (13.5%) versus 16 patients (22.2%) (p=0.04). Hospital mortality, 11 patients (2%) versus 4 patients (5.6%), was not significantly (p=0.06) different. Postoperative dialysis, four patients (0.7%) versus three patients (4.2%) (p=0.00), stroke, three patients (0.5%) versus three patients (4.2%) (p=0.00), and hospital stay (7.6 days vs 11.0 days) (p=0.01) were significantly different.

Conclusion: This study documents that the association between preoperative renal failure and adverse outcomes after CABG is stronger with the estimated CrCl than with the routinely used SCr. Routine estimation or measurement of glomerular filtration rate should be preferred to SCr as screening method for the detection of higher risk patients undergoing CABG.