Intra-Operative Inspired Fraction of Oxygen and the Risk of Surgical Site Infections in Patients with Type 1 Surgical Incisions

Background: Whether the fraction of inspired oxygen (FIO2) influences the risk of surgical site infection (SSI) is controversial. The World Health Organization and the World Federation of Societies of Anesthesiologists offer conflicting recommendations. In this study, we evaluate simultaneously three different definitions of FIO2 exposure and the risk of SSI in a large surgical population. Patients and Methods: Patients with clean (type 1) surgical incisions who developed superficial and deep organ/space SSI within 30 days after surgery from January 2003 through December 2012 in five surgical specialties were matched to specialty-specific controls. Fraction of inspired oxygen exposure was defined as (1) nadir FIO2, (2) percentage of operative time with FIO2 greater than 50%, and (3) cumulative hyperoxia exposure, calculated as the area under the curve (AUC) of FIO2 by time for the duration in which FIO2 greater than 50%. Stratified univariable and multivariable logistic regression models tested associations between FIO2 and SSI. Results: One thousand two hundred fifty cases of SSI were matched to 3,248 controls. Increased oxygen exposure, by any of the three measures, was not associated with the outcome of any SSI in a multivariable logistic regression model. Elevated body mass index (BMI; 35+ vs. <25, odds ratio [OR] 1.78, 95% confidence interval [CI] 1.43-2.24), surgical duration (250+ min vs. <100min, OR 1.93, 95% CI 1.48-2.52), diabetes mellitus (OR 1.37, 95% CI 1.13-1.65), peripheral vascular disease (OR 1.52, 95% CI 1.10-2.10), and liver cirrhosis (OR 2.48, 95% CI 1.53-4.02) were statistically significantly associated with greater odds of any SSI. Surgical sub-group analyses found higher intra-operative oxygen exposure was associated with higher odds of SSI in the neurosurgical and spine populations. Conclusion: Increased intra-operative inspired fraction of oxygen was not associated with a reduction in SSI. These findings do not support the practice of increasing FIO2 for the purpose of SSI reduction in patients with clean surgical incisions.