Evaluation of cerebral oxygen saturation during hypotensive anesthesia in functional endoscopic sinus surgery

Background and Aims: Controlled hypotensive anesthesia in endoscopic sinus surgery would provide a clean surgical field. Cerebral oxygen saturation (ScO2) is important in endoscopic sinus surgery patients and it may be low during controlled hypotension.The aim of the present study was to assess ScO2 in these patients. Material and Methods: In this observational study, 41 patients who underwent endoscopic sinus surgery with hypotensive anesthesia were enrolled for the study and all of the patients received the same anesthetic medication, nitroglycerin for controlled hypotension. Variables were measured prior to surgery, after induction of anesthesia, 5 min, and every 30 min after controlled hypotension. Near-infrared spectroscopy was used for ScO2 evaluation. Mean arterial blood pressure (MAP) was maintained at 55–60 mmHg in the surgical duration. We used t-test, Wilcoxon, and repeated measures analysis of variance (ANOVA). We examined the cross-correlation functions of the time series data between end-tidal carbon dioxide (ETCO2)/MAP and ScO2. Results: The mean of intraoperative ScO2 was not significantly different from the baseline evaluation (P > 0.05). ETCO2 was cross correlated with current ScO2 [r: 0.618, confidence interval (CI) 95%: 0.46–0.78]. We found moderate cross correlation between the MAP and current ScO2 (r: 0.728, CI 95%: 0.56–0.88). About 92% of the patients recovered within 30 min. Recovery time was associated with intraoperative MAP (P: 0.004, r: 0.438), intraoperative ETCO2 (P: 0.003, r: 0.450), and ScO2(P: 0.026, r: 0.348). Conclusions: Based on our findings, the assessment of ScO2 and maintained MAP >55 mmHg may provide safe conditions for endoscopic sinus surgery.