Supplemental oxygen and surgical-site infections: an alternating intervention controlled trial.

BACKGROUND: The main defence against bacterial infection is oxidative killing by neutrophils, which requires molecular oxygen in wounded tissues. High inspired-oxygen fractions increase tissue oxygenation. But, whether improving tissue oxygenation actually reduces surgical-site infection (SSI) remains controversial. We therefore tested the primary hypothesis that supplemental oxygen (80% vs 30%) reduces the risk of a 30-day composite of deep tissue or organ-space SSI, healing-related wound complications, and mortality. METHODS: In an isolated suite of operating rooms, the inspired-oxygen concentration was alternated between 30% and 80% at 2-week intervals for 39 months. The analysis was restricted to patients who had major intestinal surgery lasting at least 2 h. Qualifying operations (5749) were analysed, including 2843 (49%) colorectal resections, 1866 (32%) lower gastrointestinal therapeutic procedures, 373 (6%) small-bowel resections, and 667 (13%) other colorectal procedures. RESULTS: The 80% and 30% oxygen groups were well balanced on all of the demographic, baseline, and procedural variables. The oxygen intervention had no effect on the composite primary outcome or any of its components. The overall observed incidence of the composite outcome was 10.8% (314/2896) in the 80% oxygen group and 11.0% (314/2853) in the 30% group. The estimated relative risk was 0.99 (95% CI: 0.85, 1.14) for 80% vs 30%, P=0.85. CONCLUSIONS: Supplemental oxygen does not prevent major infection and healing-related complications after major intestinal surgery. CLINICAL TRIAL REGISTRATION: NCT01777568.

Intraoperative tissue oxygenation and postoperative outcomes after major non-cardiac surgery: an observational study.

BACKGROUND: The relationship between tissue oxygen saturation (StO(2)) and serious postoperative complications remains unclear. We tested the hypothesis that perioperative in patients undergoing major non-cardiac surgery is inversely related to serious surgical outcomes. METHODS: We enrolled 124 patients, ASA physical status ≤IV, having elective major non-cardiac surgeries with general anaesthesia. An InSpectra Model 650 StO(2) monitor (Hutchinson Technology, Hutchinson, MN, USA) was used to measure at the thenar eminence throughout surgery and for two postoperative hours. Our primary outcome was a composite of 30 day mortality and serious in-hospital complications. The secondary outcome was an a priori subset of the primary composite outcome representing infectious and wound-healing complications. Multivariable logistic regression was used to evaluate the associations between our primary and secondary outcomes and time-weighted average (TWA) and minimum . RESULTS: Patients were 61 (12), mean (SD) yr old. The minimum was inversely associated with our primary composite outcome (P=0.02). The estimated odds ratio (97.5% CI) of having any major postoperative morbidity was 0.82 (0.67, 1.00) for a 5% increase in the minimum . In contrast, TWA was not significantly associated with major postoperative morbidity (P=0.35). Furthermore, neither TWA (P=0.65) nor minimum (P=0.70) was significantly associated with wound complications. CONCLUSIONS: Minimum perioperative peripheral tissue oxygenation predicted a composite of major complications and mortality from major non-cardiac surgery. This is an observational association and whether clinical interventions to augment tissue oxygenation will improve outcomes remains to be determined.