Effects of Cerebral Oxygen Desaturation during One Lung Ventilation on Postoperative Cognitive Function as assessed by Cerebral Oximetry: a Prospective, Observational Study

Purpose: In thoracic surgery, there are many physiologic disturbances that affect tissue oxygenation and cause cerebral desaturation. The causes of cerebral desaturation are more related to perioperative hypoxemia than hemodynamic deterioration. The aim of our study is to evaluate the effects of cerebral oxygen desaturation during one-lung ventilation, on the postoperative early and late period cognitive functions. Methods: Regional cerebral tissue oxygen saturation (SctO2 ) was continuously monitored intraoperatively using near-infrared spectroscopy (NIRS) starting before anesthesia induction until extubation on 83 consecutive patients undergoing thoracic surgery with one-lung ventilation (OLV) in this prospective, observational study. The mini–mental state examination (MMSE) was performed before surgery to exclude the preoperative sub clinical dementia or cognitive dysfunction. Cognitive function was assessed post operatively, in prior to discharge and at one month using a battery of standardized neurocognitive tests. We used the test battery which included Trail Making Test A and B, Digit Span Test, Stroop Test to evaluate cognitive decline. Cerebral desaturation events (CDE) was accepted as 20% or greater decrease from baseline saturation that was measured while the patient was in room air. The association between intraoperative CDE and postoperative cognitive decline was estimated. Results: Our study showed significant impairments in postoperative early and late period Trail Making Tests' and Stroop Tests' performances in desaturation group patients, whereas desaturation and non-desaturation groups' test performance trends showed improvement at 1 month. Conclusion : Cerebral desaturation events have an adverse impact on postoperative cognitive function. This adverse effect has declined over time but has continued till the end of the first postoperative month. Prolonged desaturation periods results in a more deterioration of cognitive function. Thus, cerebral desaturations should be prevented and treated. Cerebral oximetry guided therapy may reduce postoperative cognitive dysfunction while increasing the quality of life.