Supplemental postoperative oxygen does not decrease the risk of wound infections or healing-related complications from bariatric surgery. (Image source: Thinkstock)

Supplemental postoperative oxygen does not decrease the risk of wound infections or healing-related complications from bariatric surgery. (Image source: Thinkstock)

Bariatric surgery is a valuable treatment option in morbidly obese patients and those with type 2 diabetes mellitus.  These patients are at a high risk of postoperative complications including wound infections. Low tissue oxygenation is considered to play a key role in enhancing the risk of infection, and obese patients have been shown to have poor oxygenation both before and after surgery.

Dr. Anupama Wadhwa, Department of Anesthesiology, University of Louisville, Louisville, Kentucky (current affiliation: Department of Outcomes Research, Cleveland Clinic, Cleveland, Ohio), and coauthors examined the effects of postoperative supplemental oxygen (80% vs. 30%) on wound infection and healing-related complications after bariatric surgery in morbidly obese patients (mean BMI 46 kg/m2).  The results are discussed in the article titled “Supplemental postoperative oxygen does not reduce surgical site infection and major healing-related complications from bariatric surgery in morbidly obese patients: A randomized, blinded trial,” which was published in this month’s issue of Anesthesia and Analgesia. The plan for this study was to recruit 1,276 patients, but after an interim analysis of the first 307 patients, the Executive Committee closed the trial because of the futility of the intervention and recruitment difficulties. The results of the study are thus based on 402 randomized patients.

There were no significant differences between the wound infection rates (8% with 80% O2 and 9% with 30% O2) and composite major complications (13% with both 30% and 80% O2).  The authors concluded that supplemental postoperative oxygen does not decrease the risk of wound infections and healing-related complications in patients undergoing gastric bypass surgery.

The study was conducted at three centers and the design was pragmatic – CPAP was used after surgery when necessary. Values for tissue oxygenation are not reported and the effectiveness of enhanced oxygenation with 80% inspired O2 is assumed from previous work.  The results are at variance with a preliminary study from this group, and the authors suggest that the move to laparoscopic surgical techniques has markedly decreased the incidence of postoperative complications in bariatric surgery.

For anesthesiologists managing patients after bariatric surgery, this is an important study.  Taken in conjunction with Thibon P. et al Anesthesiology 2012; 117: 504-11, the evidence no longer supports the use of high inspired O2 concentrations after surgery. Maintenance of oxygen saturation above 90%, perhaps the key feature of this study, is sufficient.

A final thought also remains, namely should data obtained from open surgery be rejected when laparoscopic techniques are used?