In several of our prior columns on use of oxygen (see our Patient Safety Tips of the Week April 8, 2008 “Oxygen as a Medication” and January 27, 2009 “Oxygen Therapy: Everything You Wanted to Know and More!”) we have commented that in the past we often routinely gave oxygen to patients with myocardial infarction or stroke. But such use was more reflexive in nature and not necessarily evidence-based.
Now a new Cochrane Review suggests that not only is oxygen not likely beneficial in acute MI patients, it may even cause harm. They reviewed the literature but could find only 3 randomized trials of oxygen vs. room air in MI patients. Only 387 patients were included in these 3 trials and only 14 patients died. The pooled relative risk for death was almost 3.00 in the oxygen group but the confidence interval was wide. The authors conclude that there is no evidence to support the routine use of oxygen in the acute MI patient. They suggest that the issue of whether oxygen is harmful could only be answered in a more definitive randomized trial.
This Cochrane Review certainly challenges many existing clinical guidelines for management of acute MI. Many standardized order sets for MI include routine use of oxygen. We concur with the authors that a definitive randomized trial is needed. But will it get done? We doubt it. Since there is no potentially lucrative drug patent here there won’t be pharmaceutical funding for such a trial. And the suppliers of oxygen are unlikely to fund a trial that has the potential to significantly reduce use of oxygen. This, however, is a good candidate for funding under the “comparative effectiveness” parts of the healthcare reform bill.
So what do we do in the interim? At least one editorialist (Atar 2010) argues that the quality of the studies included in the Cochrane review was poor and that the study did not conclusively demonstrate increased mortality from oxygen. He states that what we know about the physiology of myocardial ischemia, with no strong current evidence of a deleterious effect of oxygen, still merits treatment of MI patients with oxygen. Of course a similar argument has been used for the use of hi-dose oxygen in post-cardiac arrest patients and recent studies have now demonstrated a deleterious effect of oxygen in that setting (Kilgannon 2010). So stay tuned.
Cabello JB, Burls A, Emparanza JI, Bayliss S, Quinn T.
Oxygen therapy for acute myocardial infarction. Cochrane Reviews 2010; Published online June 16, 2010
Atar D. Should oxygen be given in myocardial infarction? BMJ 2010; 340: c3287 (Published 17 June 2010)
Kilgannon JH, Jones AE, Shapiro NI et al. Association
Between Arterial Hyperoxia Following Resuscitation From Cardiac Arrest and
JAMA. 2010; 303(21): 2165-2171