Is MONA in MI....evidence based..

Do I need this anymore !

Im referring to the mnemonic we all learned in our medical school, for management of Acute Myocardial infarction...........MONA standing for Morphine, Oxygen, Nitrates and Aspirin respectively.
We will discuss about the usefulness of Oxygen supplied through a mask or a cannula in the setting of an acute MI.

Although it is biologically plausible that oxygen is helpful, it is also biologically plausible that it may be harmful. Potentially harmful mechanisms include the paradoxical effect of oxygen in reducing coronary artery blood flow and increasing coronary vascular resistance(McNulty et al demonstrated this in a study on 29 pts during cardiac acth 2005 ) and also reperfusion injury from increased oxygen free radicals( AJP 2007)


A recent review by Wijesinghe (Heart 2009) looked at 2 controlled trials and  concluded that  routine use of high-flow oxygen in uncomplicated MI may result in a greater infarct size and possibly increase the risk of mortality. 
Subsequently, the most recent Cochrane review 2010 concluded that there was no evidence to support the use of supplemental oxygen. In fact, there were  3 times more likelihood of death in patients given O2 than not.(Since the total mortality was very low, this finding may be due to a chance)


Its surprising that the major evidence for the benefit of oxygen therapy in MI comes from studies of experimental coronary occlusion in animal models( AHJ 1995 ). 
The current AHA guidelines puts use of O2 in MI as level C evidence. In the accompanying text it says that it is ‘‘not known whether this therapy limits myocardial damage or reduces morbidity or mortality’’.


So it looks like..the age old mnemonic needs to be altered, as does the AHA guidelines !!