Influence of minimal changes in preoperative renal function on outcomes of cardiac surgery

Cardiovascular morbidity and mortality are high in patients with chronic kidney disease. We evaluated the influence of small differences in preoperative kidney function on mortality and complications following cardiac surgery.

This is an observational study that included adult patients undergoing cardiac surgery. Preoperative estimated glomerular filtration rate (eGFR) was estimated by the 4-component Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations based on preoperative creatinine levels. For analysis, patients were divided into groups according to their preoperative creatinine (0.2 mg/dl increments) and eGFR levels (15-30 ml/min/1.73 m(2) decrements).

Data on 5,340 patients were analyzed. A significant increase in postoperative mortality was demonstrated with preoperative creatinine at high-normal versus low-normal values (OR 1.7, 95% CI: 1-2.5; p = 0.02). For preoperative creatinine >1.2 mg/dl, adjusted OR for in-hospital mortality increased stepwise with every 0.2-mg/dl increment of creatinine. In addition, a statistically significant increment of mortality was detected with every 15-ml/min/1.73 m(2) decrement in preoperative eGFR.

Minimal changes of preoperative kidney function are associated with a substantial increase in the risk of mortality and morbidity following cardiac surgery. Even within the 'normal' range, minimal increases in serum creatinine levels are associated with increased risk of adverse events postoperatively.