Acute kidney injury (AKI) is associated with cardiovascular mortality and morbidity especially in high-risk patients undergoing cardiac surgery. It ranges from 7.7% to 28.1% in different studies. The aim of this study was to compare cystatin C and neutrophil gelatinase-associated lipocalin (NGAL) with Creatinine as an early marker for acute kidney injury in geriatrics. From 2013 through 2015, 307 consecutive high-risk elderly patients older than 70 years undergoing emergency coronary artery bypass grafting using extracorporeal circulation were studied. All patients underwent diagnostic coronary angiography and the surgical procedure within 1 week in single hospital stay and were randomized according to timing of interval between coronary angiographyand cardiac procedure as follows: group I, less than 2 days; group II, between 2 and 4 days; and group III, higher than 4 days. Renal function was analyzed by serum cystatin C, NGAL, and creatinine. Blood samples were obtained from each patient at five time points: basal value before operation, in the four hours after operation, and on the first, third, and fifth postoperative days. Glomerular filtration rate (GFR) was calculated by Cockcroft-Gault (CG). A total of 56 patients developed postoperative acute kidney failure according to the risk, injury, and failure; and loss; and end-stage kidney disease classification. Perioperative fluid requirements, urine output, and vasopressor need during and after cardiopulmonary bypass were similar. 30-day mortality in groups was higher in group I than group II and group III (P = 0.025). AKI was least prominent in group III compared to group I and group II (P = 0.001) and expectedly, postoperative dialysis requirement was least common in group III (15, 16.66%). Patients in group III had the most favorable clinical outcome with regards to the length of ICU and hospital stay. Overall serum creatinine, cystatin C, and urine NGAL levels changed significantly throughout the entire length of following-up period in group I and group II, but not in group III. Changes in serum levels of cystatin, creatinine, and creatinine clearance were prominent in later than 24 hours. Urinary NGAL was the first variable to rise in the immediate postoperative period. Cystatin GFR was a more rapid marker than serum creatinine GFR to show acute kidney injury in three groups was a significant marker.
