Predicting postoperative renal failure requiring dialysis, and an analysis of long-term outcome in patients undergoing valve surgery.

BACKGROUND AND AIM OF THE STUDY: Previous studies have been unable to identify independent valve-related risk factors for the occurrence of renal failure requiring dialysis (RF-D) in patients undergoing valve surgery. The study aim was to determine the incidence and predictors of renal failure in these patients, and to create a model based on these risk factors that could serve as a tool to predict this complication.

METHODS: Between January 1998 and December 2006, a total of 2,690 consecutive patients (1,546 males, 1,144 females; mean age 64 +/- 15 years) underwent valve or combined valve/coronary artery bypass graft (CABG) surgery at the authors' institution. The main outcome investigated was postoperative RF-D; other postoperative parameters investigated included hospital mortality, major morbidity, length of hospital stay, discharge condition and late survival.

RESULTS: RF-D occurred in 70 patients (2.6%). Multivariate analysis revealed preoperative renal failure (creatinine >2.5 mg/dl) (OR = 4.3), endocarditis (OR = 3.0), congestive heart failure (OR = 2.4), reoperation (OR = 2.3), diabetes (OR = 3.1) and cardiopulmonary bypass time >180 min (OR = 1.7) as independent predictors for postoperative RF-D. Hospital mortality among patients with RF-D was 50% (n = 35) compared to a mortality rate of 3.2% (n = 87) in patients without this complication (p <0.001). The long-term survival of discharged patients with RF-D was significantly decreased compared to those without RF-D. A logistic equation which included the coefficients of the regression analysis was generated to calculate an individual patient's risk for the development of renal failure. The predictive accuracy of the model and validation was measured (ROC area under the curve = 0.750).

CONCLUSION: Renal failure requiring dialysis is a well-known complication, particularly in patients undergoing complex valve operations, such as surgery for endocarditis and double-valve procedures. The poor long-term survival of patients with RF-D underlines the need to direct more resources towards the prevention and treatment of this complication in valve surgery patients.