Intraoperative oxygenation in adult patients undergoing surgery (iOPS): a retrospective observational study across 29 UK hospitals

Abstract

Background: Considerable 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.

Methods: Patients 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.

Results: Three 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.

Conclusions: Intraoperative 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.

Keywords: Hyperoxia; Operative; Oxygen; Surgical procedures.

Conflict of interest statement

Research and development departments at both the Royal Free Hospital and University Hospital Southampton reviewed the study separately and agreed that as the study was a service evaluation, research ethics approval was not required. Local governance approval was obtained at every participating centre.Not applicable.Professor Michael P. W. Grocott (MPWG) serves on the medical advisory board of Sphere Medical Ltd. and is a director of Oxygen Control Systems Ltd. He has received honoraria for speaking for and/or travel expenses from BOC Medical (Linde Group), Edwards Lifesciences and Cortex GmBH. MPWG leads the Xtreme Everest Oxygen Research Consortium and the Fit-4-Surgery research collaboration. Some of this work was undertaken at University Southampton NHS Foundation Trust–University of Southampton NIHR Biomedical Research Centre. MPWG serves as the UK NIHR CRN national specialty group lead for Anaesthesia Perioperative Medicine and Pain and is an elected council member of the Royal College of Anaesthetists, an elected board member of the Faculty of Intensive Care Medicine and president of the Critical Care Medicine Section of the Royal Society of Medicine. Daniel Martin has received consultancy fees from Siemens Healthcare and Masimo and lecture honoraria from Edwards Lifesciences and Deltex Medical. He is also a Director of Oxygen Control Ltd. Dr. Andrew Cumpstey is currently funded through the NIHR as an Academic Clinical Fellow. The other authors declare that they have no competing interests.Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1

Intraoperative oxygenation illustrated by a box and whisker plot illustrating FIO2 administered over first five ABGs. Boxes are drawn between 25th and 75th percentiles with the median represented by a line and the whiskers indicating the minimum and maximum values. b Scatter plot and linear relationship between FIO2 and PaO2 for each ABG. The continuous line represents the relationship between partial pressure of arterial oxygen recorded and the fraction of inspired oxygen delivered (r = 0.22, p ≤  0.001)

Fig. 2

Sample traces demonstrating of cumulative oxygen dose for four individual patients. The solid line represents the actual PaO2 recorded in successive blood gases, whilst the dashed line represents the physiological upper limit (13.3 kPa). Area under the curve (shaded) was calculated between the times of the first and final ABGs