Perioperative hyperoxia - Long-term impact on cardiovascular complications after abdominal surgery, a post hoc analysis of the PROXI trial

BACKGROUND: Increased long-term mortality was found in patients exposed to perioperative hyperoxia in the PROXI trial, where patients undergoing laparotomy were randomised to 80% versus 30% oxygen during and after surgery. This post hoc follow-up study assessed the impact of perioperative hyperoxia on long-term risk of cardiovascular events.

METHODS: A total of 1386 patients undergoing either elective or emergency laparotomy were randomised to 80% versus 30% oxygen during and two hours after surgery. At follow-up, the primary outcome of acute coronary syndrome was assessed. Secondary outcomes included myocardial infarction, other heart disease, and acute coronary syndrome or death. Data were analysed in the Cox proportional hazards model.

RESULTS: The primary outcome, acute coronary syndrome, occurred in 2.5% versus 1.3% in the 80% versus 30% oxygen group; HR 2.15 (95% CI 0.96-4.84). Patients in the 80% oxygen group had significantly increased risk of myocardial infarction; HR 2.86 (95% CI 1.10-7.44), other heart disease; HR 1.40 (95% 1.06-1.83), and acute coronary syndrome or death; HR 1.22 (95% CI 1.01-1.49).

CONCLUSIONS: Perioperative hyperoxia may be associated with an increased long-term risk of myocardial infarction and other heart disease.