Data on the benefit or or harmful effects of oxygen level on ischemic reperfusion injuries in cardiac surgery are insufficient. We hypothesized that hyperoxia during cardiopulmonary bypass decreases the incidence of postoperative atrial fibrillation (POAF) and ventricular fibrillation, and therefore decreases cardiovascular morbidity (CARDIOX study).An open-label, randomized clinical trial including adults undergoing elective cardiac surgery, i.e. cardiopulmonary bypass (CPB) randomized 1:1 to an intervention group or standard group at two French University Hospitals from June 2016 to October 2018. The intervention consisted in delivering of an inspired fraction of oxygen of one to one during CPB. The standard care consisted in delivering oxygen to achieve a partial arterial blood pressure less than 150 mmHg. The primary endpoint was the occurrence of POAF and/or ventricular tachycardia/ventricular fibrillation (VT/VF) within the 15 days following cardiac surgery. The secondary endpoint was the occurrence of major adverse cardiovascular events (MACCE: in-hospital mortality, stroke, cardiac arrest, acute kidney injury, and mesenteric ischemia).
330 patients were randomly assigned to either the intervention group (n = 161) or the standard group (n = 163). Mean PaO2 was 447 ± 98 mmHg and 161 ± 60 mmHg during CPB, for the intervention and standard group (p < 0.0001) respectively. The incidence of POAF or VT/VF were similar in the intervention group and the standard group (30% [49 of 161 patients] and 30% [49 of 163 patients], absolute risk reduction 0.4%; 95% CI, - 9.6-10.4; p = 0.94). MACCE was similar between groups with, an occurrence of 24% and 21% for the intervention group and the standard groups (absolute risk reduction 3.4%; 95% CI, - 5.7-12.5; p = 0.47) respectively. After adjustment, the primary and secondary endpoints remained similar for both groups.Hyperoxia did not decrease POAF and cardiovascular morbidity following cardiac surgery with CPB. CLINICALTRIAL.NCT02819739.