Near-infrared spectroscopy combined with vascular occlusion test to predict acute kidney injury in patients undergoing cardiac surgery: a prospective observational study

BackgroundNear-infrared spectroscopy (NIRS) enables a non-invasive measurement of tissue oxygen saturation (StO2) in regions illuminated by near-infrared lights. Vascular occlusion test (VOT) serves as a model to artificially induce forearm ischemia-reperfusion. The combination of StO2 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 StO2-VOT measurements and the occurrence of postoperative acute kidney injury (AKI), in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB).MethodsBetween 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. StO2 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 StO2-VOT parameters, were evaluated for their independent association with the occurrence of AKI following cardiac surgery. StO2-VOT parameters were also compared between patients with hyperlactatemia (peak blood lactate >= 4 mmol/L) and those without hyperlactatemia.ResultsIn 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%<middle dot>min- 1 in predicting AKI. Patients with hyperlactatemia had longer pre-CPB T1 and higher D-speed during CPB. However, ROC analysis indicated that T1 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.ConclusionsNIRS monitoring combined with VOT shows promise in predicting postoperative AKI in patients undergoing cardiac surgery with mild hypothermic CPB.Trial registrationChiCTR1900021436 with registered date 21/02/2019.