Information for health professionals

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TRIAL OVERVIEW

Each year, 5 million UK NHS patients have surgery, costing more than £11bn.¹In 1 in 5 operations complications will develop (e.g. surgical site infection (SSI), pneumonia, & acute kidney injury (AKI)) which ultimately delay recovery, prolong hospital stay and reduce the number of days spent at home after surgery.¹ Complications also lead to significant additional costs to the NHS.

Oxygen is a necessary and easily titratable drug that is administered during every general anaesthetic (GA) to prevent complications. However, despite being ubiquitous to anaesthetic practice, significant uncertainty remains about the optimal concentration to administer to patients during GA, and administration practices continue to vary widely.

Due to the large number of surgeries undertaken annually, even a modest effect of intraoperative oxygen administration on postoperative complication rates could yield substantial patient and healthcare-system benefits when scaled across routine surgical practice.

The PERI-Ox trial aims to quantify how three different perioperative oxygen administration strategies affect patient recovery and survival after surgery. Our results will ensure patients can benefit from the very safest anaesthesia care, promoting an early return home and reducing healthcare costs around the time of surgery.

References:

TRIAL SUMMARY

Trial Title	PERI-Ox: Perioperative Oxygen in Major Surgery
Chief Investigator	Dr Andrew Cumpstey
Research Aim	To determine whether 80% oxygen, 50% oxygen or the minimum oxygen concentration to keep peripheral oxygen saturations (SpO2) ≥94% during general anaesthesia for major abdominal surgery results in the most days alive and out of hospital at 90 days (DAH90).
Trial Design	Multicentre, phase III, 3 parallel group, patient and assessor blinded, individual patient randomised trial with a 12-month internal pilot and embedded process evaluation and cost effectiveness analysis
Participant Population	Adults (≥18 years) undergoing abdominal surgery under GA, with an anticipated operating time of ≥2 hours and anticipated to remain in hospital overnight
Inclusion Criteria	≥18 years and undergoing planned or unplanned surgery via any surgical technique (including open, laparoscopic or robotic) Undergoing GA for abdominal operation (inc. colorectal, hepatobiliary, UGI, urological, vascular, gynaecological operations) with an anticipated operating time of ≥2 hours Anticipated to remain in hospital overnight
Exclusion Criteria	ASA physical status 1 One lung ventilation One oxygen arm clearly indicated / contra-indicated Surgery for organ donation or transplantation Previous enrolment in PERI-Ox or another trial of an intervention with similar biological mechanism Purely groin incisions (e.g. inguinal hernia repair / vascular access), which do not count as abdominal surgery Obstetric surgery (including Caesarean sections)
Planned Sample Size	5000 participants
Health Technology being Assessed	80% Oxygen throughout anaesthesia, 15l oxygen for 6 hours after anaesthesia 50% Oxygen throughout anaesthesia, usual practice after anaesthesia Minimum concentration of oxygen to keep SpO₂ ≥ 94% throughout and for 6 hours after anaesthesia
Measurement of Outcomes and Costs	Primary Outcome: Days alive and out of hospital at 90 days (DAH90). Secondary Outcomes: Days alive and out of hospital at 30 days (DAH30) Surgical site infections up to day 30 after surgery (Modified CDC definition, as per UKHSA SSISS) Acute kidney injury within 7 days (Kidney Disease Improving Global Outcomes criteria) Highest level of postoperative respiratory support (face mask oxygen / HFNO / NIV / mechanical ventilation) up to 7 days after surgery Hospital readmissions up to 90 days All-cause mortality up to 90 days Health resource use and cost effectiveness up to 90 days after surgery
Follow-up Duration	90 days
Planned Trial Period	From 01 September 2026 to 31 August 2031 (5 years)

Enquiries:

If you have any questions about the PERI-Ox trial please feel free to contact the trial team.

Trial Manager: Dr Hannah Noordali
Tel: 024 761 50478

Trial Coordinator: Nadia Wustrack-Law
Tel: 024 761 51738

Email: perioxtrial@warwick.ac.uk

Address:
PERI-Ox trial
Warwick Clinical Trials Unit
Warwick Medical School
University of Warwick
Coventry
CV4 7AL