For years it has been standard practice to give oxygen to patients with Myocardial Infarctions, even if they are not hypoxaemic. The logic seemed obvious: the heart muscle was short of oxygen, so bonus oxygen could only help.
Or could it? We know also that excess oxygen generates free radicals, which are a key driver of reperfusion injury.
An article in the May 22 issue of Circulation may help. A multimeter trial enrolling 441 patients with confirmed ST Elevation MI, who were not hypoxaemic. Giving oxygen worsened outcomes: higher peak CK, increased recurrent MI (5.5% vR 0.9%), more arrhythmias, and a 50% bigger infarction size at 6 months.
Note that these were vessel occlusion type MIs – things may be different in non-STEMI infarcts where global oxygen supply is reduced, but there is no absolute flow occlusion. But still, this study means that oxygen should be carefully prescribed, and in the setting of STEMI, should only be given to patients who actually have hypoxaemia.
vraiida 