Abstract
BACKGROUND: Near-infrared spectroscopy (NIRS) enables a non-invasive measurement of tissue oxygen saturation (StO(2)) in regions illuminated by near-infrared lights. Vascular occlusion test (VOT) serves as a model to artificially induce forearm ischemia-reperfusion. The combination of StO(2) monitoring and VOT allows for dynamic evaluation of the balance between oxygen delivery and consumption in tissue, as well as the functional reserve of microcirculation. However, the implications of these measurements for patient outcomes remain inadequately understood. This study aimed to investigate the association between StO(2)-VOT measurements and the occurrence of postoperative acute kidney injury (AKI), in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). METHODS: Between March 2020 and March 2021, 100 adult patients who scheduled to undergo cardiac surgery with mild hypothermic CPB were enrolled to this prospective observational study. StO(2) was continuously monitored at the right forearm and ipsilateral VOT procedure was performed before initiation of CPB, at the time before weaning from CPB, and at the end of surgery. Preoperative and intraoperative factors, along with StO(2)-VOT parameters, were evaluated for their independent association with the occurrence of AKI following cardiac surgery. StO(2)-VOT parameters were also compared between patients with hyperlactatemia (peak blood lactate ≥ 4 mmol/L) and those without hyperlactatemia. RESULTS: In our patient population (n = 87), 13.79% (12/87) patients developed AKI after surgery. Multivariable analysis revealed that CPB time and post-CPB desaturation speed (D-speed) were independently associated with AKI. Post-CPB D-speed had an area under receiver operating characteristic (ROC) curve of 0.79 (95% CI, 0.66-0.93) with a cutoff value of 0.08%·min(- 1) in predicting AKI. Patients with hyperlactatemia had longer pre-CPB T(1) and higher D-speed during CPB. However, ROC analysis indicated that T(1) and D-speed exhibited limited predictive capacity for hyperlactatemia. Patients with AKI exhibited an increased risk of prolonged ICU stays, postoperative stroke, reoperation, and in-hospital mortality. CONCLUSIONS: NIRS monitoring combined with VOT shows promise in predicting postoperative AKI in patients undergoing cardiac surgery with mild hypothermic CPB. TRIAL REGISTRATION: ChiCTR1900021436 with registered date 21/02/2019.