Supplemental Oxygen - Effect on Occurrence of Subsequent Cancer After Abdominal Surgery (Follow-up of the PROXI Trial)

Perioperative Inspiratory Oxygen Fraction - Effect on Occurrence of Subsequent Cancer After Abdominal Surgery (Follow-up of the PROXI Trial)

Aim: to investigate the effect of a high inspiratory oxygen fraction (FiO2) given during and after laparotomy procedures on occurrence of a subsequent, new or recurrent, cancer diagnosis at a long-term follow-up.

Background: A high inspiratory oxygen fraction (FiO2 = 0.80) has been linked to prevention of surgical site infection, but the Danish randomized clinical multicenter trial, the PROXI trial, found no difference in frequency of surgical site infection. In fact, long-term mortality was significantly increased with a hazards ratio of 1.30 in patients receiving 80% oxygen, and this appeared to be statistically significant in patients undergoing cancer surgery, but not in non-cancer patients.

At this point, no convincing mechanism explains the observed increased mortality after hyperoxia, as the long-term pathophysiological effects of oxygen are not fully understood.

Primary hypothesis of this follow-up study of the PROXI trial: Use of 80% oxygen increase the frequency of patients with a subsequent, new or recurrent, cancer.

Inclusion Criteria:

• Age 18 years or older.
• Laparotomy, acute or elective. In case of gynaecological surgery only if malignancy is suspected (defined as risk of ovarian malignancy index >200 or a specimen with atypical or neoplastic cells).

Exclusion Criteria:

• Other surgery within 30 days (except surgery in local anaesthesia).
• Chemotherapy within 3 months.
• Inability to give informed consent.
• Inability to keep oxygen saturation above 90% without supplemental oxygen (measured preoperatively by pulse oximetry).