Different profiles of patients who require dialysis after cardiac surgery

Background. This study was aimed at evaluating the determinants of postoperative dialysis-requiring acute renal failure and at identifying eventual correlations between the different etiologic mechanisms and postoperative prognosis. Methods. We evaluated the preoperative and intraoperative features of the 69 out of 6,542 consecutive cardiac surgery patients who developed postoperative dialysis-requiring acute renal failure at our Institution during a 10-year period. Results. Age, valvular and aortic surgery, hypertension, extracardiac vasculopathy, timing of surgery, cardiopulmonary bypass time, and preoperative creatinine level greater than 2.0 mg/dL were identified as predictors by multivariate analysis. In a second analysis, patients were divided in two groups according to the preoperative creatinine level: group A (preoperative creatinine 2.0 mg/dL or less; 38 cases) and group B (preoperative creatinine 2.1 mg/dL or more; 31 cases). The two groups significantly differed in preoperative and intraoperative characteristics and in postoperative outcome: group A patients were younger, had a lower incidence of cardiac and vascular risk factors and comorbidities, were mainly operated on urgent or emergent basis for valvular or aortic pathologies, had longer cardiopulmonary bypass and cross-clamp time, and worse in-hospital outcome but higher midterm survival. Group B patients were older, had a higher prevalence of comorbidities, required more often in-hospital or after-discharge dialysis, had lower in-hospital mortality, but reduced midterm survival. Conclusions. Postoperative dialysis-requiring acute renal failure can be the result of two different pathophysiological pathways: complicated perioperative course due to urgent-emergent surgery or main intraoperative technical complications in patients with preoperative normal renal function and uncomplicated perioperative course associated with reduced preoperative kidney function. The two patient groups significantly differ in baseline preoperative features, as well as in in-hospital and in midterm outcome.