Role of Tissue Oxygen Saturation Monitoring in the Perioperative Phase

In perioperative medicine, the preservation of organ function is also achieved by keeping an adequate balance between oxygen delivery and consumption in organs and tissues, since alterations of these processes can worsen postoperative outcomes. The local assessment of oxygenation adequacy can be performed using near-infrared spectroscopy monitoring. But does this monitoring allow clinicians to predict postoperative outcomes? A central focus of this thesis is the association between intraoperative oxygen desaturation and postoperative acute kidney injury in pediatric cardiac surgery, explored first by a systematic review of the existing literature, and then through the presentation of a prospective observational study. Some studies found an increased risk of acute kidney injury in children experiencing an intraoperative decrease in renal tissue oxygenation, whereas cerebral desaturation was generally not associated with kidney injury. However, our prospective study, which focused on patients with non-cyanotic congenital heart disease, found no association between renal or cerebral oxygen desaturation and postoperative AKI. In this study, the O3® Regional Oximetry was used to monitor cerebral and renal tissue oxygenation. The thesis also includes a validation study testing the accuracy of this device in monitoring renal and somatic tissue oxygenation in healthy adult volunteers, demonstrating a good agreement between O3-derived tissue oxygenation values and invasively measured somatic reference values, whereas renal oxygenation values were underestimated. Finally, the applications of a vascular occlusion test performed in association with near-infrared spectroscopy monitoring—used to assess local tissue oxygen consumption and vascular reactivity—are reviewed, showing some sparse association with select postoperative outcomes.