Microalbuminuria is associated with high adverse event rate following cardiac surgery

Abstract

To examine if preoperative microalbuminuria is associated with an increased risk of long-term adverse outcomes following elective cardiac surgery and if it provides additional prognostic information beyond the European System for Cardiac Operative Risk Evaluation (EuroSCORE). In a prospective follow-up study, we included 1049 patients undergoing elective cardiac surgery from 1 April 2005 to 30 September 2007. Microalbuminuria (urine albumin/creatinine ratio between 2.5 and 25 mg mmol(-1)) was assessed preoperatively in a morning spot-urine sample. We used population-based medical registries for follow-up from day 31 until day 365 postoperatively, and compared all-cause death, myocardial infarction, cerebral stroke and a composite outcome of severe infections including septicaemia, deep or superficial sternal wound infection, or leg wound infection among patients with or without microalbuminuria using Cox proportional hazard and competing risk regressions. Microalbuminuria was found in 175 (18.5%) out of 947 patients available for follow-up. The adjusted risks of all-cause death (adjusted hazard ratio 2.3 (95% confidence interval 1.1-4.9)), stroke (adjusted hazard ratio 2.9 (95% confidence interval 1.1-7.8)) and severe infection composite outcome (adjusted hazard ratio 2.4 (95% confidence interval 1.2-4.9)) were doubled to tripled in patients with preoperative microalbuminuria. The risk of myocardial infarction was not increased. Adding information on microalbuminuria improved the predictive accuracy of the EuroSCORE regarding mortality (areas under receiver operating characteristic curves were: for the EuroSCORE 0.73 (95% confidence interval 0.65-0.81) and for EuroSCORE+microalbuminuria 0.76 (95% confidence interval 0.68-0.83). Preoperative microalbuminuria is associated with an increased risk of long-term adverse outcomes in patients undergoing elective cardiac surgery, and it appears to provide prognostic information on mortality.