Hyperoxia During Cardiopulmonary Bypass Does Not Increase Respiratory or Neurological Complications: A Post Hoc Analysis of The CARDIOX Study

Despite advances in surgical techniques and anaesthetic management, morbidity after cardiac surgery with cardiopulmonary bypass (CPB) is still high. Such morbidity includes cardiovascular, renal, pulmonary, and neurological complications. One of the mechanisms linked to such complications is oxidative stress and the formation of reactive oxygen species (ROS) associated with ischaemia–reperfusion. Hyperoxia has thus been suggested to be associated with the enhancement of ischaemia–reperfusion injuries and increased ROS generation. In the operating theatre, hyperoxia is generally avoided as a safety precaution, as it has been associated with worse outcomes for critically ill adult patients and is not recommended. However, hyperoxia during CPB has a preconditioning effect on the heart and brain, and can decrease gas microemboli. A recent randomised study showed no increase in the cardiovascular complication rate with the use of hyperoxia during CPB.

We do not suggest applying a high concentration of oxygen during CPB. However, because oxygen delivery during and after CPB is fundamental for positive clinical outcomes, physicians should not be afraid of using supraphysiological concentrations of oxygen to optimise oxygen delivery. Indeed, a recent study performed in the ICU found that a conservative oxygen strategy was associated with worse outcomes, reflecting organ ischaemia. Based on this post hoc analysis of the CARDIOX study, hyperoxia during CPB did not increase neurological or pulmonary complications. Controlled studies with a larger sample size are required to better address this specific issue.