Differences and similarities in risk factors for postoperative acute kidney injury between younger and older adults undergoing cardiac surgery

Objectives Acute kidney injury is a frequent complication after cardiac surgery. The purpose of this study was to assess the risk factors for acute kidney injury in patients ≤60 years of age undergoing cardiac surgery and to compare these risk factors with those identified in patients ≥65 years of age. Methods From 2010 to 2012, 1253 patients ≤60 years (mean age 52 ± 9 years) and 2488 patients ≥65 years (mean age 74 ± 6 years) underwent cardiac surgery. Linear regression models using least absolute shrinkage and selection operator methods and mixed effects linear regression models were used to assess factors associated with maximum postoperative increase in serum creatinine in these two cohorts. Results In both age groups, the following variables were associated independently with greater degrees of postoperative increase in serum creatinine on multivariable analysis: greater body mass index, peripheral vascular disease, preoperative use of diuretics, lower preoperative hemoglobin, preoperative intra-aortic balloon pump, urgent or emergent status, long cardiopulmonary bypass time, and hemofiltration. In younger patients, a greater increase in serum creatinine was associated with diabetes, and previous cardiac surgery, whereas female sex was associated with a lower degree of increase in serum creatinine. In older patients, a greater increase in serum creatinine was associated with age, hypertension, smoking, and lower left ventricular left ejection fraction. Operation type and coronary artery disease had a different impact on postoperative creatinine increase between younger and older patients. Conclusions This study identified both common and distinct risk factors associated with postoperative increase in serum creatinine between patients ≤60 years and those ≥65 years undergoing cardiac surgery. Importantly, all potentially modifiable risk factors were present in both groups.