The Impact Of Perioperative Oxygen Regimens On Recovery After Major Surgery

Background. Over 300 million people undergo major surgery under anaesthesia globally every year. Despite oxygen being an almost universally administered therapy, definitive evidence is lacking about the optimal perioperative oxygen regimen. As a result, international recommendations are conflicting. While a liberal perioperative oxygen regimen may reduce the risk of surgical site infection (SSI), there is observational evidence from other areas of medicine that liberal oxygen therapy may be harmful, resulting in an increased risk of organ injury, disability and death.

Main study findings We undertook a narrative review of the literature appraising the evidence for different perioperative oxygen regimens at the time of inception of this thesis work. We recommend titrated oxygen administration that achieves safe arterial oxygen saturations as measured by a pulse oximeter.

A survey of a sample of specialist anaesthetists was undertaken investigating beliefs about perioperative oxygen regimens. 58% of respondents indicated they titrate inspired oxygen to a safe level; 5% aimed to maximise oxygen administration. 0.7% believed that routine peri-operative administration of FiO2 ≥0.8 oxygen reduces SSI.

We undertook a prospective study to quantify standard care oxygen therapy administered by anaesthetists from 10 metropolitan hospitals. The median (IQR) intraoperative mean FiO2 was 0.47 (0.40–0.55). 2% administered intraoperative oxygen liberally.

We conducted a retrospective study using routinely collected healthcare data to determine associations between intraoperative oxygen exposure and postoperative recovery. Amongst the 15,449 patients included in the analyses, there was no association between FiO2 and days alive and out of hospital at 90 days (DAOH90). Low FiO2 was associated with increased SSI: Increasing FiO2 was associated with respiratory complications and incidence of being admitted to an intensive care unit.

A vanguard, multi-centre, patient- and assessor-blinded, parallel group, randomised feasibility trial was conducted to assess the feasibility of a definitive trial designed to investigate the effect of a restricted, standard care, or liberal peri-operative oxygen therapy regimen on recovery after surgery..We demonstrated effective treatment separation and protocol compliance. All feasibility endpoints were met.

Conclusions. There is insufficient evidence to inform practice with regard to perioperative oxygen therapies. A definitive prospective randomised trial designed informed by the findings of this work is both urgently needed to address the uncertainty, and is feasible to conduct without the need for major modifications to the trial protocol used in study five.