Intra-operative oxygen concentration could affect postoperative morbidity-results of a randomised controlled feasibility trial (PULSE Ox).

The World Health Organisation recommends that all anaesthetised patients receive FIO2 0.8 during surgery to reduce the risk of surgical site infections but did not consider the effect this might have on other clinical outcomes. A Cochrane systematic review concluded that insufficient evidence exists for routinely administering high oxygen concentrations intra-operatively to reduce surgical site infections, and that doing so might increase mortality. A feasibility trial was conducted looking at the feasibility of controlling intra-operative FIO2 and measuring systemic redox state. Here we explore further clinical outcomes from this study regarding postoperative complications and cognitive recovery. Twenty-eight adult patients undergoing major abdominal surgery for cancer resection were randomly allocated to receive either conservative (FIO2 = 0.3, n = 8), typical (FIO2 = 0.55, n = 10) or recommended (FIO2 = 0.8, n = 10) oxygen throughout anaesthesia. Rates of radiologically reported atelectasis, cognitive recovery and infective postoperative morbidity were all collected up to 7 days after surgery. Total intensive care unit length of stay was also recorded. Higher FIO2 levels were associated with lower rates of atelectasis - 6 (75%) versus 8 (80%) versus 3 (30%) for FIO2 = 0.30 versus 0.55 versus 0.80, respectively; p = 0.045. Postoperative cognitive recovery scores (0.7 (3.1) versus -0.1 (2.5) versus -1.8 (3.3), p = 0.277), Postoperative Morbidity Survey infection scores (5 (71%) versus 5 (56%) versus 3 (33%), p = 0.307) and intensive care unit length of stay (3 (2-4) versus 2.5 (2.00-3.75) versus 3 (2.00-5.25) days, p = 0.870) did not differ between groups. Changing the administered intra-operative oxygen concentration may alter postoperative clinical outcomes, and adequately powered clinical studies are urgently needed to investigate the impact of this.