title: Perioperative Supplemental Oxygen Does Not Worsen Long-Term Mortality of Colorectal Surgery Patients.
abstract: A follow-up analysis from a large trial of oxygen and surgical-site infections reported increased long-term mortality among patients receiving supplemental oxygen, especially those having cancer surgery. Although concerning, there is no obvious mechanism linking oxygen to long-term mortality. We thus tested the hypothesis that supplemental oxygen does not increase long-term mortality in patients undergoing colorectal surgery. Secondarily, we evaluated whether the effect of supplemental oxygen on mortality depended on cancer status.
  
  
  
  Mortality data were obtained for 927 patients who participated in 2 randomized trials evaluating the effect of supplemental oxygen on wound infection. We assessed the effect of 80% vs 30% oxygen on long-term mortality across 4 clinical sites in the 2 trials using a Cox proportional hazards regression model stratified by study and site. Kaplan-Meier survival estimates were calculated for each trial. Finally, we report site-stratified hazard ratios for patients with and without cancer at baseline.
  
  
  
  There was no effect of 80% vs 30% oxygen on mortality, with an overall site-stratified hazard ratio of 0.93 (95% confidence interval [CI], 0.72-1.20; P = 0.57). The treatment effect was consistent across the 2 original studies (interaction P = 0.88) and across the 4 sites (P = 0.84). There was no difference between patients with (n = 451) and without (n = 450) cancer (interaction P = 0.51), with hazard ratio of 0.85 (95% CI, 0.64-1.1) for cancer patients and 0.97 (0.53-1.8) for noncancer patients.
  
  
  
  In contrast to the only previous publication, we found that supplemental oxygen had no influence on long-term mortality in the overall surgical population or in patients having cancer surgery.
authors.affiliation: From the *Departments of General Anesthesiology, †Outcomes Research, and ‡Quantitative Health Sciences, Cleveland Clinic, Cleveland, Ohio; §Department of Anaesthesiology and General Intensive Care Medicine, Medical University of Vienna, Vienna, Austria; ‖Department of Anesthesiology & Perioperative Medicine, University of Louisville, Louisville, Kentucky; and ¶Department of Anesthesiology and Pain Therapy, University of Bern, Bern, Switzerland.
authors.forename: Attila
authors.initials: A
authors.lastname: Podolyak
authors.forename: Daniel I
authors.initials: DI
authors.lastname: Sessler
authors.forename: Christian
authors.initials: C
authors.lastname: Reiterer
authors.forename: Edith
authors.initials: E
authors.lastname: Fleischmann
authors.forename: Ozan
authors.initials: O
authors.lastname: Akça
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Mascha
authors.forename: Robert
authors.initials: R
authors.lastname: Greif
authors.forename: Andrea
authors.initials: A
authors.lastname: Kurz
mesh_terms: D000328:Adult; D000368:Aged; D015179:Colorectal Neoplasms / Q000401:mortality / Q000601:surgery*; D013505:Digestive System Surgical Procedures / Q000009:adverse effects / Q000401:mortality*; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D010102:Oxygen Inhalation Therapy / Q000009:adverse effects / Q000401:mortality*; D019990:Perioperative Care; D016016:Proportional Hazards Models; D016032:Randomized Controlled Trials as Topic; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome