Creatinine clearance versus serum creatinine as a risk factor in cardiac surgery

Abstract

BackgroundRenal impairment is one of the predictors of mortality in cardiac surgery. Usually a binarized value of serum creatinine is used to assess the renal function in risk models. Creatinine clearance can be easily estimated by the Cockcroft and Gault equation from serum creatinine, gender, age and body weight. In this work we examine whether this estimation of the glomerular filtration rate can advantageously replace the serum creatinine in the EuroSCORE preoperative risk assessment.MethodsIn a group of 8138 patients out of a total of 11878 patients, who underwent cardiac surgery in our hospital between January 1996 and July 2002, the 18 standard EuroSCORE parameters could retrospectively be determined and logistic regression analysis performed. In all patients scored, creatinine clearance was calculated according to Cockcroft and Gault. The relationship between the predicted and observed 30-days mortality was evaluated in systematically selected intervals of creatinine clearance and significance values computed by employing Monte Carlo methods. Afterwards, risk scoring was performed using a continuous or a categorical value of creatinine clearance instead of serum creatinine. The predictive ability of several risk score models and the individual contribution of their predictor variables were studied using ROC curve analysis.ResultsThe comparison between the expected and observed 30-days mortalities, which were determined in different intervals of creatinine clearance, revealed the best threshold value of 55 ml/min. A significantly higher 30-days mortality was observed below this threshold and vice versa (both with p < 0.001). The local adaptation of the EuroSCORE is better than the standard EuroSCORE and was further improved by replacing serum creatinine (SC) by creatinine clearance (CC). Differential ROC analysis revealed that CC is superior to SC in providing predictive power within the logistic regression. Variable rank comparison identified CC as the best single variable predictor, even better than the variable age, former number 1, and SC, previously number 9 in the standard set of EuroSCORE variables.ConclusionThe renal function is an important determinant of mortality in heart surgery. This risk factor is not well captured in the standard EuroSCORE risk evaluation system. Our study shows that creatinine clearance, calculated according to the Cockcroft and Gault equation, should be applied to estimate the preoperative renal function instead of serum creatinine. This predictor variable replacement gains a significant improvement in the predictive accuracy of the scoring model.

A New Tool for the Risk Stratification of Patients With Complex Coronary Artery Disease

“…31,32 Conversely, CrCl has been shown to be a better predictor when compared with SCr of risk in patients undergoing surgical revascularization. 18,33 Incorporation of CrCl into the ACEF score can therefore be justified prospectively by extrapolation of these previous results and retrospectively by the improvements in the C-statistic for MACCE (0.60 versus 0.62) and mortality (0.67 versus 0.69) observed in this study when the CSS was calculated using the ACEF CrCl instead of ACEF SCr (Figure 4 and Table 5). …”

“…17 An acceptable modification to the ACEF score is to use the derived creatinine clearance (CrCl) instead of SCr because this not only represents a better estimate of underlying renal function but has also been previously shown to improve the predictive accuracy of cardiac risk models such as the euroSCORE. 18 The aim of this study was to investigate whether a Clinical SYNTAX Score (CSS), representing a multiplication of the SYNTAX score with a modified ACEF score (through the incorporation of CrCl), would improve the individual ability of either of these scores to predict mortality in patients with complex CAD undergoing PCI, who were enrolled in the Arterial Revascularization Therapies Study Part II (ARTS-II).…”

Preoperative Estimates of Glomerular Filtration Rate as Predictors of Outcome after Surgery

“…Ten studies did not adequately report attrition. 25,27,31,35,41,45,46,54,58,59 Otherwise most studies satisfied the qualitative assessments in the other domains of potential bias. Publication bias was detected in analysis of all cause mortality, demonstrated in the final sentence of paragraph 3 on this page, and also acute kidney injury, which is discussed in the second paragraph on page 14.…”

Risk Stratification in Assessing Risk in Coronary Artery Bypass Surgery

“…Both studies were critical of the use of subjective factors and the inclusion of factors not associated with mortality. An improvement to the EuroSCORE model on replacing the serum creatine factor by creatine clearance has been reported [17].…”