Effects Of Lowering Inspiratory Oxygen Fraction During Microvascular Decompression On Postoperative Gas Exchange: A Pre-Post Study

BackgroundDespite many previous studies, the optimal oxygen fraction during general anesthesia remains controversial. This study aimed to evaluate the effects of lowering intraoperative fraction of inspired oxygen on postoperative gas exchange in patients undergoing microvascular decompression (MVD).MethodsWe conducted a pre-post study to compare postoperative gas exchange with different intraoperative oxygen fractions. From April 2010 to June 2017, 1456 consecutive patients who underwent MVD were enrolled. Starting in January 2014, routine oxygen fraction was lowered from 1.0 to 0.3 during anesthetic induction/awakening and from 0.5 to 0.3 during anesthetic maintenance. Postoperative gas exchange, presented as the minimum value of PaO2/F1O2 ratio within 48 hours, were compared along with adverse events.ResultsAmong 1456 patients, 623 (42.8%) patients were stratified into group H (high F1O2) and 833 (57.2%) patients into group L (low F1O2). lntraoperative positive end-expiratory pressure was used in 126 (15.1%) patients in group H and 90 (14.4%) patients in group L (p = 0.77). The minimum value of PaO2/ F1O2 ratio within 48 hours after surgery was significantly greater in the group L (226.13 vs. 323.12; p < 0.001) without increasing any adverse events.ConclusionIn patients undergoing MVD, lowering routine F102 and avoiding 100% 02 improved postoperative gas exchange.