Continuous measurement of cerebral oxygenation by near infrared spectroscopy curing induction of anesthesia

Near infrared spectroscopy (NIRS) measures tissue oxygenation continuously at. the bedside, Major disturbances of cerebral oxygenation can be detected by using NIRS, but the ability to observe smaller changes is poorly docume nted. Although anesthetics generally depress cerebral metabolism and enhanc e oxygen delivery, the administration of etomidate has been associated with cerebral desaturation. We used this difference to study the ability of NIR S to detect the small changes associated, with the onset of anesthesia. Thi rty-six healthy patients were randomly allocated to have anesthesia induced with either etomidate, propofol, or thiopental. We found that there was a temporal association between the onset of anesthesia and NIRS-derived indic es of cerebral oxygenation. Etomidate was associated with a decrease in cer ebral oxygenation, whereas propofol and thiopental were associated with an increase in cerebral oxygenation. We conclude that NIRS is capable of detec ting the small changes in cerebral oxygenation associated with the inductio n of general anesthesia and shows promise as a bedside investigational tool for the noninvasive assessment of cerebral oxygenation. Implications: We c onclude that near infrared spectroscopy is capable of detecting the small c hanges in cerebral oxygenation associated with the induction of general ane sthesia and shows promise as a bedside investigational tool for the noninva sive assessment of cerebral oxygenation.