Intraoperative Renal Near-Infrared Spectroscopy Monitoring as a Predictor of Renal Outcomes in Cardiac Surgery

BACKGROUND Acute renal failure (ARF) is a critical complication following open-heart surgery, significantly impacting morbidity and mortality. This study aimed to evaluate the association between intraoperative renal near-infrared spectroscopy (NIRS) findings and postoperative ARF in 357 patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). MATERIAL AND METHODS This prospective study included 357 patients undergoing open-heart surgery with CPB. ARF diagnosis was based on KDIGO criteria. NIRS sensors were placed bilaterally at the T12/L2 level under ultrasound guidance, and renal oxygenation (rSO2) values were continuously monitored intraoperatively. Patients were categorized into ARF and non-ARF groups for comparative analysis. RESULTS ARF developed in 12.3% (n=44) of patients. ARF patients were older (p=0.024) and had longer surgery (p<0.001), CPB (p=0.004), and aortic cross-clamping durations (p=0.013). They required more blood products (p<0.001) and intra-aortic balloon pump support (p=0.027). Intensive care unit stays were significantly longer in ARF patients (p=0.036). NIRS analysis showed significant rSO2 reductions in ARF patients. Time spent with rSO2 below 80%, 70%, and 60% was a strong predictor of ARF. Receiver operating characteristic (ROC) analyses demonstrated that time exceeding 30 minutes below the 60% threshold predicted ARF with 96.5% specificity and 86.4% sensitivity. CONCLUSIONS Intraoperative NIRS monitoring is crucial for detecting renal perfusion abnormalities during high-risk surgeries. Declines below 80%, 70%, and 60% thresholds strongly predict ARF. Timely interventions, such as fluid resuscitation and hemodynamic support, can mitigate risks. ARF patients require intensive postoperative monitoring due to prolonged ICU stays and complications.