Kenneth L. Smith, Mercer College of Pharmacy
Myocardial Infarction (MI), commonly known as a heart attack, is caused by a lack of oxygen to the myocardium, which leads to ischemia followed by cell death. For more than a century, supplemental oxygen has been considered an integral part of treatment for suspected MI and is currently recommended in clinical guidelines.[2,3] The role of supplemental oxygen is to increase oxygen delivery to the myocardium tissue and prevent cell death. Above normal levels of oxygen can cause complications such as coronary vasoconstriction and formation of reactive oxygen species. Efficacy of routine oxygen therapy in patients with MI is considered uncertain. In this randomized clinical trial, one year all-cause mortality benefits of routine oxygen therapy in patients with MI was explored.
|Oxygen Therapy in Suspected Acute Myocardial Infarction |
|Design||Randomized controlled trial; N= 6,629|
|Objective||To determine if supplemental oxygen in patients with suspected myocardial infarction, without hypoxemia, causes a reduction in all cause mortality within one year compared to ambient air|
|Study Groups||Oxygen group (n= 3,311); ambient air (n= 3,318)|
|Methods||Patients were required to be 30 years of age or older and to have symptoms suggestive of myocardial infarction for less than 6 hours with an oxygen saturation of 90% or higher. Participants also had to have either electrocardiographic changes indicating ischemia or elevated cardiac troponin T or I levels on admission. Follow-up was done through the Swedish National Population Registry. Volunteers were evaluated from various areas including ambulance services, emergency departments, coronary care units, or catheterization laboratories of participating hospitals.|
|Primary Outcome Measure||Death from any cause within 1 year|
|Adverse Events||Common adverse events: N/A|
|Serious adverse events: N/A|
|Percentage that discontinued due to adverse events: N/A|
|Study Author Conclusions||There was no beneficial effect found with the use of oxygen treatment with respect to all-cause mortality at one year.|
This study concluded that one year all-cause mortality was not reduced in patients with MI in the absence of hypoxemia. A reported limitation in this study was the lack of pressurized air in Swedish ambulances and the inability to use a Hudson mask due to a risk of carbon dioxide retention. Since certain patients couldn’t use pressurized air or mask, blinding was limited in the study. The study was designed not to include those with hypoxemia even though these patients contribute considerably to the total mortality of a substantial number of MI patients that were excluded. It is unclear if this exclusion would alter the mortality result had they been included in the study.
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