Respiratory Exchange Ratio guided management in high-risk noncardiac surgery: The OPHIQUE multicentre randomised controlled trial.

Background: There is a need to develop non-invasive markers to identify the occurrence of anaerobic metabolism in high-risk surgery. Our objective was to demonstrate that a goal-directed therapy algorithm incorporating the respiratory exchange ratio (ratio between CO production and O consumption) can reduce postoperative complications.

Methods: We conducted a randomized, multicenter, controlled clinical trial in four university medical centers and one non-university hospital from December 26, 2018, to September 9, 2021. 350 patients with a high risk of postoperative complications undergoing high-risk noncardiac surgery lasting 2 h or longer under general anesthesia were enrolled. The control group was treated according to current hemodynamic guidelines. The interventional group was treated according to an algorithm based on the measurement of the respiratory exchange ratio. The primary outcome was a composite of major complications or death within seven days of surgery. The secondary outcomes were the length of hospital stay, 30-day mortality, and the total intraoperative volume of fluids administered.

Results: The primary outcome occurred for 78 patients (45.6%) in the interventional group and 83 patients (48.8%) in the control group (relative risk: 0.93, 95% confidence interval [CI]: 0.75-1.17; p = 0.55). There were no clinically relevant differences between the two groups for secondary outcomes.

Conclusions: In high-risk surgery, a goal-directed therapy algorithm integrating the measurement of the respiratory-exchange ratio did not reduce a composite outcome of major postoperative complications or death within seven days after surgery compared to routine care.

Trial Registration: ClinicalTrials.gov, NCT03852147.