Effect of mild renal dysfunction (s-crea 1.2-2.2 mg/dl) on presentation characteristics and short- and long-term outcomes of on-pump cardiac surgery patients.

Objectives: The objective of this study is to evaluate differences in patient presentation and short- and long-term outcomes between patients dichotomized by the level of preoperative s-creatinine (s-crea) without renal failure and to use EuroSCORE (ES) risk stratification for validating differences and for predictive purposes.

Methods: A thousand consecutive cardiac surgery patients from January 1999 through May 2000 were analyzed. Patients with off-pump surgery or s-crea >200 micromol/l (>2.2 mg/dl) were excluded leaving 885 patients for analysis. Group 1 (n=703) had s-crea 0.5-1.2 mg/dl and Group 2 (n=182) had elevated s-crea 1.3-2.2 mg/dl but no renal insufficiency.

Results: Group 2 patients were older (P<0.0001), had a higher percentage of males (P=0.008), had lower left ventricular ejection fraction (LVEF) (P=0.001), had higher New York Heart Association (NYHA) classification (P<0.0001), had more diabetics (P=0.001) and had more patients with a history of congestive heart failure (CHF) (P<0.0001). Both additive ES (AES) and logistic ES (LES) variables were higher in Group 2 patients, AES 8.45+/-4.28% vs. 6.05+/-3.80% (P<0.0001) and LES 17.7+/-19.1% vs. 9.57+/-13.3% (P<0.0001). Proportions of emergency operations and use of intra-aortic balloon pulsation (IABP) support did not differ. There were more coronary artery bypass grafting (CABG) with or without concomitant procedures in Group 1 but otherwise the procedures performed were similar. Cardiopulmonary bypass (CPB) times did not differ (P=0.1). Operative mortality was similar (P=0.06) but hospital mortality was higher in Group 2: 19/10.4% vs. 25/3.6% (P<0.0001), odds ratio (OR) 3.16. Total length of stay (LOS) and length of stay in the postoperative intensive care unit (ICU) did not differ. Postoperative renal failure (PORF) (s-crea increase to >2.25 mg/dl or >200 micromol/l) developed in 38/4.5% patients in Group 1 and in 41/22.5% patients in Group 2 (P<0.0001), OR=5.08. Follow-up all-cause mortality was higher in Group 2: 68/37.4% vs. 167/23.8% (P<0.0001), OR=1.91. Both ES definitions predicted hospital mortality, LOS, ICU, PORF and long-term mortality well, while increased s-crea predicted PORF and long-term mortality in both groups.

Conclusions: Mild increase in s-crea is a marker for patients with increased cardiac risk factors and the risk for poor outcomes. Both ES definitions are highly predictive of the outcomes.