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.