Postoperative oxygen saturation and surgical-site infection after major non-cardiac surgery: A retrospective analysis.

Objective and background: Tissue hypoxia impairs wound healing, oxidative killing by neutrophils, and production of superoxide radicals, thus potentially increasing susceptibility to bacterial infections. We tested the primary hypothesis that postoperative hypoxemia, defined as the area under curve (AUC) for oxygen saturation below 90 %, is associated with increased incidence of a 30-day composite of surgical site infections, wound complications, sepsis, and in-hospital mortality in patients recovering from noncardiac surgery.

Methods: We included adult inpatients who had major noncardiac surgery and continuous postoperative oximetry for 48 h or until discharge. Our primary outcome was a composite including the components of 30-day superficial, deep or organ-space surgical site infections, sepsis, pneumonia, and/or in-hospital mortality. We primarily assessed the average relative effect of hypoxemia (AUC SpO₂ < 90 %) across the six components using a multivariate generalized estimating equation model to account for within-patient correlations among the components.

Results: Among 1355 patients (mean age 55 years, 61 % female), the median continuous postoperative monitoring time was 42 h and the overall AUC SpO₂ < 90 % was 75 [4, 417] min*%, with a median time under a saturation below 90 % of 38 [2.4, 187] min. 85 (6.3 %) patients experienced at least one component of the primary outcome composite. Patients experiencing at least one component had AUC <90 % of 253 [40, 617] and those without had 69 [3, 402] min*%. Adjusting for confounding, there was no association found between postoperative AUC SpO₂ < 90 % and the primary composite outcome, with an average relative effect odds ratio of 1.00 (95 %CI, 0.99, 1.01) for an increase of 30 min*% beyond the threshold, P = 0.61. There were also no significant saturation-related differences in any of the composite components. Sensitivity analyses found similar results.

Conclusion: Postoperative hypoxemia was not significantly associated with a composite of surgical site infections and in-hospital mortality. Hypoxemia during recovery from major surgery does not appear to enhance infection or mortality risk.