Increased long-term mortality after a high perioperative inspiratory oxygen fraction during abdominal surgery: follow-up of a randomized clinical trial

Abstract

Background: A high perioperative inspiratory oxygen fraction (80%) has been recommended to prevent postoperative wound infections. However, the most recent and one of the largest trials, the PROXI trial, found no reduction in surgical site infection, and 30-day mortality was higher in patients given 80% oxygen. In this follow-up study of the PROXI trial we assessed the association between long-term mortality and perioperative oxygen fraction in patients undergoing abdominal surgery.

Methods: From October 8, 2006, to October 6, 2008, 1386 patients underwent elective or emergency laparotomy and were randomized to receive either 80% or 30% oxygen during and for 2 hours after surgery. The follow-up date was February 24, 2010. Survival was analyzed using Kaplan-Meier statistics and the Cox proportional hazards model.

Results: Vital status was obtained in 1382 of 1386 patients after a median follow-up of 2.3 years (range 1.3 to 3.4 years). One hundred fifty-nine of 685 patients (23.2%) died in the 80% oxygen group compared to 128 of 701 patients (18.3%) assigned to 30% oxygen (HR, 1.30 [95% confidence interval, 1.03 to 1.64], P = 0.03). In patients undergoing cancer surgery, the HR was 1.45; 95% confidence interval, 1.10 to 1.90; P = 0.009; and after noncancer surgery, the HR was 1.06; 95% confidence interval, 0.69 to 1.65; P = 0.79.

Conclusions: Administration of 80% oxygen in the perioperative period was associated with significantly increased long-term mortality and this appeared to be statistically significant in patients undergoing cancer surgery but not in noncancer patients.