AVOID Study: Harm with oxygen in MI?

Air Versus Oxygen In ST-elevation MyocarDial Infarction (AVOID Study)

Air Versus Oxygen In ST-elevation MyocarDial Infarction (AVOID Study) presented at the AHA Scientific Sessions, 2014, checked whether there is any harmful effect for supplemental oxygen given to patients with ST elevation myocardial infarction (STEMI) in the absence of hypoxemia. Patients with STEMI undergoing primary angioplasty and having oxygen saturation of 94% or more were randomized to receive supplemental oxygen at 8 liters/ minute or air.

Of about four hundred and forty patients, half each were randomized to either receive oxygen or no oxygen. At baseline, fifteen percent had diabetes mellitus, eighty nine percent were in Killip class I and thirty five percent had anterior wall myocardial infarction. Cardiogenic shock was noted in five percent and four percent had resuscitated cardiac arrest. Median door to balloon time was fifty five minutes and about half of them received drug eluting stent and thrombus aspiration.

The AVOID study was published in Circulation [1] and concluded that supplemental oxygen in patients with STEMI in the absence of hypoxia may increase myocardial injury and was associated with larger infarct size assessed at 6 months.

Peak creatinine kinase levels were higher in those who were given supplemental oxygen therapy. Troponin values were also higher in the oxygen arm and so was recurrent myocardial infarction during hospital stay and at six months. Harm was more evident in females than in males.
Authors presume that the harm due to oxygen are probably due to the detrimental effects of free radicals and superoxides. They are unsure whether supplemental oxygen at lower levels of two liters per minute will have similar detrimental effects.

Some of the criticisms raised on this study are the high flow of oxygen using face mask which is not routinely used by most physicians in the absence of pulmonary edema. Another question is on the low usage of drug eluting stents with about half of them receiving bare metal stents.

An online survey of health professionals on the use of supplemental oxygen in acute myocardial infarction had shown that 98% of them do use supplemental oxygen [2]. Hence it was opined that it would be difficult to conduct a randomized study on this aspect due to the widespread belief in the benefit of oxygen.

The results of the current study are intriguing considering the fact there was even evidence from small studies which showed that hyperbaric oxygen  reduces myocardial damage and mortality in acute coronary syndrome [3]. But the reviewers had commented that the studies reviewed had only small number of participants  and there were methodological shortcomings and poor reporting. They suggested conducting an appropriately powered trial with rigorous methodology.

References

1. Dion Stub, Karen Smith, Stephen Bernard, Ziad Nehme, Michael Stephenson, Janet E Bray, Peter Cameron, Bill Barger, Andris H Ellims, Andrew J Taylor, Ian T Meredith, David M Kaye, AVOID Investigators.  Air Versus Oxygen in ST-Segment-Elevation Myocardial Infarction. Circulation. 2015 Jun 16;131(24):2143-50.
2. Burls A et al. Oxygen use in acute myocardial infarction: an online survey of health professionals’ practice and beliefs. Emerg Med J. 2010;27:283-286.
3. Bennett MH et al. Hyperbaric oxygen therapy for acute coronary syndrome. Cochrane Database Syst Rev. 2011;8:CD004818.