 In this study, we will monitor tissue oxygenation of four different tissue beds including cerebral tissue SctO2 on the forehead, and 3 somatic tissue beds monitored on the forearm SarmO2, upper leg SlegO2, and the renal region SrrO2. The primary end point is AKI and the secondary end points are postoperative major non-renal complications e.g. stroke, delirium, myocardial infraction, heart failure, new or worsening arrhythmia, mechanical ventilation 24 hours, deep wound infection, etc. and mortality. The associations between tissue oxygenation of different tissue beds, i.e. SctO2, SarmO2, SlegO2, and SrrO2, and AKI and non-renal outcomes will be compared to explore the tissue beds whose oxygen saturation has a stronger association with the outcomes of interest. The strength of this study is to use the patient as self-control. 