COMMENTARY

Higher Oxygen Fraction in Abdominal Surgery: Does It Reduce Long-Term Mortality?

Junping Chen, MD, PhD

Disclosures

November 06, 2012

Increased Long-Term Mortality After a High Perioperative Inspiratory Oxygen Fraction During Abdominal Surgery: Follow-up of a Randomized Clinical Trial

Meyhoff CS, Jorgensen LN, Wetterslev J, Christensen KB, Rasmussen LS; PROXI Trial Group
Anesth Analg. 2012;115:849-854

Summary

Use of 80% oxygen during surgery has been suggested to reduce the risk for postoperative wound infections.[1,2,3] However, the most recent and largest trial, the PROXI trial, found no reduction in surgical-site infection, and 30-day mortality was higher in patients given 80% oxygen.

In the current study, the researchers followed up the PROXI trial patients to assess the association between long-term mortality and perioperative oxygen fraction. The researchers randomized patients who underwent abdominal surgery according to those who received 80% oxygen and those who received 30% oxygen during and up to 2 hours after surgery. The patients' vital status was followed for an average of 2.3 years. Survival was analyzed using Kaplan-Meier statistics and a Cox proportional hazards model.

The results showed that 23.2% of the patients in the 80% oxygen group died, compared with 18.3% in the 30% oxygen group (P = .03). In patients undergoing cancer surgery, the P value was .009; in those undergoing noncancer surgery, it was .79.

The researchers concluded that administration of 80% oxygen in the perioperative period was associated with increased long-term mortality, and this appeared to be statistically significant in patients undergoing cancer surgery but not in those undergoing noncancer surgery.

Viewpoint

The effect of anesthetic management on long-term complications is increasingly recognized. One example is the oxygen fraction during the perioperative period. A high perioperative FiO2 has been shown to prevent surgical wound infection,[1,2,3] improve healing of colorectal anastomosis,[4] and reduce the frequency of postoperative nausea and vomiting.[5] However, high FiO2 has also been linked to detrimental effects, such as increased risk for pulmonary complications,[6] poor regulation of blood glucose levels,[7] and changes in cardiac index.[8]

This study provides evidence of the negative effects of high perioperative FiO2 on long-term mortality. However, the observed difference in long-term mortality is difficult to explain, and many aspects of the study must be very carefully considered in the interpretation of the results: for example, design, sample size, patient selection, lack of a conventional control group, and statistical error.

It is critical that this study's findings be replicated before we can draw a definitive conclusion. Nevertheless, although its main finding is not explained by any convincing mechanism, it definitely does not support the contention that a high perioperative FiO2 has a beneficial effect on long-term all-cause mortality.

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