Renal dysfunction after myocardial revascularization: Risk factors, adverse outcomes, and hospital resource utilization

Background: Acute changes in renal function after elective coronary bypass surgery are incompletely characterized and represent a challenging clinical problem. Objective: To determine the incidence and characteristics of postoperative renal dysfunction and failure, perioperative predictors of dysfunction, and the effect of renal dysfunction and failure on in-hospital resource utilization and patient disposition after discharge. Design: Prospective, observational, multicenter study. Setting: 24 university hospitals. Patients: 2222 patients having myocardial revascularization with or without concurrent valvular surgery. Measurements: Prospective histories, physical examinations, and electrocardiographic and laboratory studies. The main outcome measure was renal dysfunction (defined as a postoperative serum creatinine level greater than or equal to 177 mu mol/L with a preoperative-to-postoperative increase greater than or equal to 62 mu mol/L). Results: 171 patients (7.7%) had postoperative renal dysfunction; 30 of these (1.4% overall) had oliguric renal failure that required dialysis. In-hospital mortality, length of stay in the intensive care unit, and hospitalization were significantly increased in patients who had renal failure and those who had renal dysfunction compared with those who had neither (mortality: 63%, 19%, and 0.9%; intensive care unit stay: 14.9 days, 6.5 days, and 3.1 days; hospitalization: 28.8 days, 18.2 days, and 10.6 days, respectively). Patients with renal dysfunction were three times as likely to be discharged to an extended-care facility. Multivariable analysis identified five independent preoperative predictors of renal dysfunction: age 70 to 79 years (relative risk [RR], 1.6 [95% CI, 1.1 to 2.3]) or age 80 to 95 years (RR 3.5 [CI, 1.9 to 6.3]); congestive heart failure (RR, 1.8 [CI, 1.3 to 2.6]); previous myocardial revascularization (RR, 1.8 [CI, 1.2 to 2.7]); type 1 diabetes mellitus (RR, 1.8 [CI, 1.1 to 3.0]) or preoperative serum glucose levels exceeding 16.6 mmol/L (RR, 3.7 [CI, 1.7 to 7.8]); and preoperative serum creatinine levels of 124 to 177 mu mol/L (RR, 2.3 [CI, 1.6 to 3.4]). Independent perioperative factors that exacerbated risk were cardiopulmonary bypass lasting 3 or more hours and three measures of ventricular dysfunction. Conclusions: Many patients having elective myocardial revascularization develop postoperative renal dysfunction and failure, which are associated with prolonged intensive care unit and hospital stays, significant increases in mortality, and greater need for specialized long-term care. Resources should be redirected to mitigate renal injury in high-risk patients.