Study objectives: Preoperative renal dysfunction is a risk factor for adverse events in cardiac surgery. This study compared creatinine clearance (ClCr), estimated from the Cockroft and Gault formula, and plasma creatinine level as predictors of outcome after cardiac surgery.
Design: Prospective, observational.
Setting: University hospital.
Patients: A total of 6,364 cardiac surgical patients.
Methods: The measured outcomes were postoperative renal failure requiring dialysis, and mortality and major morbidity. For each outcome, two multivariable risk models were developed, using either estimated ClCr as a measure of renal function, or plasma creatinine level. Risk-adjusted odds ratios (ORs) and their 95% confidence intervals (CIs) were calculated for each outcome. Discrimination was compared using receiver operating characteristic (ROC) curves.
Results: For each 10 mL/min/1.73 m2 decrement of estimated ClCr, the ORs for renal failure requiring dialysis, mortality, and major morbidity in the whole population were 1.52 (95% CI, 1.35 to 1.67), 1.27 (95% CI, 1.19 to 1.35), and 1.18 (95% CI, 1.14 to 1.21), respectively; for each 0.2 mg/dL increment of plasma creatinine, ORs were 1.20 (95% CI, 1.15 to 1.26), 1.08 (95% CI, 1.04 to 1.13), and 1.12 (95% CI, 1.09 to 1.15), respectively. The areas under the ROC curves for prediction of renal failure requiring dialysis were 0.83 with both risk models. For prediction of mortality and major morbidity, areas under the ROC curves were 0.83 and 0.72, respectively, with the models using estimated ClCr, and 0.74 and 0.65, respectively, with the models using plasma creatinine level (p < 0.001 vs estimated ClCr for both outcomes). In patients with normal plasma creatinine levels (n = 4,603), estimated ClCr remained a significant predictor of each outcome with similar ORs, but plasma creatinine level was not a predictor of any outcome.
Conclusion: The risk-adjusted association between preoperative renal dysfunction and adverse events after cardiac surgery is stronger with estimated ClCr than with plasma creatinine level, particularly in patients with normal plasma creatinine levels. The routine preoperative estimation of ClCr may improve the identification of higher-risk cardiac surgical patients.