Association between intraoperative plantar regional oxygen saturation and acute kidney injury after cardiac surgery.

Acute kidney injury (AKI) is one of the most common complications after cardiac surgery, associated with increased mortality and morbidity. Near-infrared spectroscopy (NIRS) continuously measures regional oxygen saturation(rSO) in real-time. This exploratory retrospective study aimed to investigate the association between intraoperative plantar rSO and postoperative AKI in cardiac surgery patients. Between August 2019 and March 2021, 394 patients were included. Plantar and cerebral rSO were monitored using NIRS intraoperatively. The primary outcome was AKI within 7 postoperative days. The nonlinear association between plantar rSO, cerebral rSO, and mean arterial blood pressure (MBP) and AKI was assessed, and plantar rSO<45% was related to an increased risk of AKI. Multivariable logistic regression analyses revealed that longer duration and higher area under the curve below plantar rSO<45% and MBP<65 mmHg were more likely to be associated with increased odds of AKI. In additional multivariable regression analyses, association between plantar rSO<45% and AKI was still maintained after adjusting the duration or AUC of MBP<65 mmHg as a covariate. Cerebral rSO levels were not associated with AKI. Independent of MAP, intraoperative plantar rSO was associated with AKI after cardiac surgery. However, intraoperative cerebral rSO was not associated with AKI. Intraoperative plantar rSO monitoring may be helpful in preventing AKI.