A number of things we do for patients in the ICU we simply do... because it has been always done. Maybe because it seems to make sense or because we were simply taught to do so. One of these treatments is the application of oxygen to patients suffering of myocardial infarction. But in fact the impact of this measure is not that well established and we know that high concentrations of oxygen can actually be harmful. Some previous studies suggest possible increase in myocardial injury.
Stub et al. therefore performed a multicenter, prospective, randomised controlled trial comparing oxygen (8 L/min) with no supplemental oxygen in patients with STEMI diagnosed on paramedic 12-lead electrocardiogram. They finally included 441 patients into their study.
Their primary endpoint was evaluation of infarction size assessed by the cardiac enzymes troponin (cTnI) and creatine kinase (CK). While troponin levels did not differ there was a significant difference in the mean peak CK levels, being higher in the group with oxygen applied. By looking at the secondary endpoints they also found an increase in the rate of recurrent myocardial infarctions and in the frequency of cardiac arrhythmia among the oxygen group. Finally at 6-months the oxygen group had an increase in myocardial infarct size on cardiac MRI.
They conclude that patients with myocardial infarction but without hypoxemia may actually not benefit of supplemental oxygen therapy.
Time to question our automatisms when treating patients.
Stub et al. Circulation. 2015 Jun 16;131(24):2143-50.