Higher intraoperative fractional-inspired O2 fails to reduce complications after major surgery

In a recent noninferiority randomized trial, the impact of high intraoperative oxygen therapy, specifically a fraction of inspired oxygen (FiO2) of 0.8, was compared to a standard FiO2 ranging from 0.3 to 0.4 in adults undergoing major elective or emergency surgery. The trial found that high intraoperative fiO2 was non-inferior to standard fiO2. 

The study results were published in the journal Surgery. 

While high intraoperative oxygen therapy may benefit surgical site infection, its impact on postoperative respiratory function is uncertain. It's unclear if hyperoxia, resulting from a high fraction of inspired oxygen alongside lung protective ventilation, increases postoperative pulmonary complications. Hence, researchers conducted a study to investigate whether the use of a higher FiO2, in conjunction with a lung protective ventilation strategy, could be associated with an increased incidence of postoperative pulmonary complications.

The study was conducted with a cohort of 226 patients, consisting of 130 individuals undergoing routine surgery and 96 facing emergency surgical procedures, the trial revealed intriguing insights into the potential clinical benefits of elevated intraoperative oxygen levels. The median age of the participants was 48 years, with approximately 47.3% being female.

Patients were randomly assigned to two groups: Group H, receiving the high FiO2 of 0.8, and Group S, receiving the standard FiO2 of 0.3 to 0.4. Notably, both groups adhered to a lung protective ventilation strategy that included volume control ventilation with a tidal volume of 6 to 8 mL/kg of predicted body weight, a respiratory rate of 12 beats per minute, and positive end-expiratory pressure ranging from 5 to 8 cm H2O.

The primary outcome measure focused on postoperative pulmonary complications, assessed on days 3 and 5 after surgery using the Melbourne group scale.

Results indicated that the Melbourne group scale scores at both postoperative days 3 and 5 were statistically similar between the two groups. The upper margin, crucial for determining noninferiority, fell within the predefined margin of 1. This suggests that the use of high intraoperative FiO2 did not result in a significantly different incidence of postoperative pulmonary complications compared to the standard FiO2.

Further exploration into secondary outcomes, including the incidence of surgical site infection, postoperative hospital stay duration, and the number of days alive without antibiotic therapy at postoperative day 28, revealed no substantial differences between the two groups. These findings were consistent across various metrics, with P-values ranging from 0.13 to 0.95, indicating no statistically significant variations.

In conclusion, the trial demonstrated that employing a high intraoperative FiO2 of 0.8, in combination with lung protective ventilation, was non-inferior to using the standard FiO2 of 0.3 to 0.4 in terms of postoperative pulmonary complications in adult patients undergoing major surgery. This suggests that the potential clinical benefits of high intraoperative oxygen levels on surgical site infection did not compromise postoperative respiratory function, providing valuable insights for perioperative care strategies. It is essential to note that while these results are promising, individual patient considerations and clinical judgment remain paramount in decision-making processes. 

Further reading: Kochupurackal JC, Bhattacharjee S, Baidya DK, et al. Postoperative pulmonary complications with high versus standard fiO2 in adult patients undergoing major abdominal surgery: A noninferiority trial. Surgery. Published online November 27, 2023. doi:10.1016/j.surg.2023.10.020