Oxidative stress injury during cardiac surgery: how important is it?

The concept that the reintroduction of oxygen to the ischaemic myocardium causes significant injury has long been known [1], and it is now well-established [2] that oxidative stress is one of the major initiators of myocardial injury during ischaemia and reperfusion. Cardiac surgery for coronary artery bypass generally involves cardiopulmonary bypass with cardioplegic arrest and elective global ischaemia of the heart. It would appear to represent the ideal situation to evaluate the potential injury induced by oxidative stress during ischaemia and subsequent reperfusion, since in this clinical situation (and unusually for most ischaemic conditions) the time of onset and the duration of ischaemia are known as is the time and conditions of reperfusion, and all are under the control of the operating surgeon. This means that studies in patients undergoing surgery are able to be controlled in a similar manner to that of experimental studies involving animal models. In experimental studies on isolated rat hearts, ischaemia and reperfusion are known to generate oxygen-derived free radicals; the use of electron-spinresonance techniques has allowed the direct detection of reactive oxygen species produced when ischaemic myocardium is reperfused [3] and has also shown that this production can be prevented by various antioxidant or scavenger agents [4]. A large number of experimental studies that simulate this surgical ischaemia and reperfusion have shown that various antioxidant agents can ameliorate the detrimental effects of oxidative stress resulting from