BackgroundConsiderable controversy remains about how much oxygen patients should receive during surgery. The 2016 World Health Organization (WHO) guidelines recommend that intubated patients receive a fractional inspired oxygen concentration (FIO2) of 0.8 throughout abdominal surgery to reduce the risk of surgical site infection. However, this recommendation has been widely criticised by anaesthetists and evidence from other clinical contexts has suggested that giving a high concentration of oxygen might worsen patient outcomes. This retrospective multi-centre observational study aimed to ascertain intraoperative oxygen administration practice by anaesthetists across parts of the UK.MethodsPatients undergoing general anaesthesia with an arterial catheter in situ across hospitals affiliated with two anaesthetic trainee audit networks (PLAN, SPARC) were eligible for inclusion unless undergoing cardiopulmonary bypass. Demographic and intraoperative oxygenation data, haemoglobin saturation and positive end-expiratory pressure were retrieved from anaesthetic charts and arterial blood gases (ABGs) over five consecutive weekdays in April and May 2017.ResultsThree hundred seventy-eight patients from 29 hospitals were included. Median age was 66 years, 205 (54.2%) were male and median ASA grade was 3. One hundred eight (28.6%) were emergency cases. An anticipated difficult airway or raised BMI was documented preoperatively in 31 (8.2%) and 45 (11.9%) respectively. Respiratory or cardiac comorbidity was documented in 103 (27%) and 83 (22%) respectively. SpO2 < 96% was documented in 83 (22%) patients, with 7 (1.9%) patients desaturating < 88% at any point intraoperatively. The intraoperative FIO2 ranged from 0.25 to 1.0, and median PaO2/FIO2 ratios for the first four arterial blood gases taken in each case were 24.6/0.5, 23.4/0.49, 25.7/0.46 and 25.4/0.47 respectively.ConclusionsIntraoperative oxygenation currently varies widely. An intraoperative FIO2 of 0.5 currently represents standard intraoperative practice in the UK, with surgical patients often experiencing moderate levels of hyperoxaemia. This differs from both WHO’s recommendation of using an FIO2 of 0.8 intraoperatively, and also, the value most previous interventional oxygen therapy trials have used to represent standard care (typically FIO2 = 0.3). These findings should be used to aid the design of future intraoperative oxygen studies.

OBJECTIVES: Patients admitted to intensive care often require treatment with invasive mechanical ventilation and high concentrations of oxygen. Mechanical ventilation can cause acute lung injury that may be exacerbated by oxygen therapy. Uncertainty remains about which oxygen therapy targets result in the best clinical outcomes for these patients. This review aims to determine whether higher or lower oxygenation targets are beneficial for mechanically ventilated adult patients. DATA SOURCES: Excerpta Medica dataBASE, Medical Literature Analysis and Retrieval System Online, and Cochrane medical databases were searched from inception through to February 28, 2021. STUDY SELECTION: Randomized controlled trials comparing higher and lower oxygen targets in adult patients receiving invasive mechanical ventilation via an endotracheal tube or tracheostomy in an intensive care setting. DATA EXTRACTION: Study setting, participant type, participant numbers, and intervention targets were captured. Outcome measures included “mortality at longest follow-up” (primary), mechanical ventilator duration and free days, vasopressor-free days, patients on renal replacement therapy, renal replacement free days, cost benefit, and quality of life scores. Evidence certainty and risk of bias were evaluated using Grading of Recommendations Assessment, Development and Evaluation and the Cochrane Risk of Bias tool. A random-effects models was used. Post hoc subgroup analysis looked separately at studies comparing hypoxemia versus normoxemia and normoxemia versus hyperoxemia. DATA SYNTHESIS: Data from eight trials (4,415 participants) were analyzed. Comparing higher and lower oxygen targets, there was no difference in mortality (odds ratio, 0.95; 95% CI, 0.74–1.22), but heterogeneous and overlapping target ranges limit the validity and clinical relevance of this finding. Data from seven studies (n = 4,245) demonstrated targeting normoxemia compared with hyperoxemia may reduce mortality at longest follow-up (0.73 [0.57–0.95]) but this estimate had very low certainty. There was no difference in mortality between targeting relative hypoxemia or normoxemia (1.20 [0.83–1.73]). CONCLUSIONS: This systematic review and meta-analysis identified possible increased mortality with liberal oxygen targeting strategies and no difference in morbidity between high or low oxygen targets in mechanically ventilated adults. Findings were limited by substantial heterogeneity in study methodology and further research is urgently required to define optimal oxygen therapy targets.

Oxygen targets in the intensive care unit during mechanical ventilation for acute respiratory distress syndrome: a rapid review (Review)

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