Effectiveness of doppler renal resistive index in early detection of postoperative acute kidney injury in prolonged cardiopulmonary bypass cardiac surgeries.

BACKGROUND: The aim of this study is to investigate the value of renal Doppler ultrasonography-derived Renal Resistive Index (RRI) for early prediction of cardiac surgery-associated acute kidney injury (CSA-AKI) in patients undergoing prolonged cardiopulmonary bypass (CPB) and aortic cross-clamp (ACC) times, and to assess perioperative risk factors, length of stay, and short-term outcomes. METHODS: Ninety adult patients (>18 years) scheduled for elective cardiac surgery under general anesthesia, with CPB >70 minutes and ACC >60 minutes, without preexisting acute or chronic renal failure. Patients were stratified according to KDIGO criteria as Group 1 (no CSA-AKI, N.=64) and Group 2 (CSA-AKI, N.=26). Preoperative and postoperative (first hour) RRI measurements were performed by a single radiologist. Demographic, intraoperative, and postoperative parameters including transfusion, urine output, fluid balance, vasoactive/inotropic agent and diuretic use, serum creatinine, and hematocrit levels were collected. RESULTS: The postoperative RRI cutoff of 0.70 predicted CSA-AKI with 76.9% sensitivity and 73.4% specificity (P<0.001). Group 2 had significantly lower hematocrit levels during CPB rewarming (P=0.04). On postoperative days 2 and 3, urine output and fluid balance differed significantly between groups (P: 0.004-0.005 and P<0.001 - P<0.001, respectively). Inotropic/vasopressor requirements were higher in Group 2 on day 3 (P=0.003). Stage 1 AKI was most common (80.8%), predominantly on postoperative day 2. Group 2 demonstrated longer mechanical ventilation, prolonged ICU stay, and higher 30-day mortality (P=0.016, P=0.012, and P=0.006). CONCLUSIONS: Routine postoperative assessment of RRI in high-risk cardiac surgeries may enable earlier detection of CSA-AKI compared with KDIGO criteria, allowing earlier initiation of renal-protective strategies and potentially improving patient outcomes.