Three Part Question
In [patients with acute uncomplicated myocardial infarction] does [oxygen therapy] lead to [reduced mortality]?
A 60-year-old man presents to the Emergency Department with acute severe crushing chest pain. ECG shows changes consistent with acute myocardial infarction. You prescribe aspirin, thrombolysis, nitroglycerin, beta-blockers and high-flow oxygen. You know that oxygen therapy is traditionally held to be beneficial in this situation, but wonder if there is any evidence that it reduces mortality.
Medline 1966-10/03 using the OVID interface.
[exp myocardial infarction OR myocardial infarct$.mp OR MI.mp OR heart attack.mp OR exp Coronary Thrombosis OR acute coronary syndrome.mp] AND [exp oxygen OR oxygen.mp OR O2.mp OR exp oxygen inhalation therapy] AND [exp Mortality OR exp Hospital Mortality OR mortality.mp OR exp Death OR death.mp] LIMIT to human AND English.
Altogether 290 papers were identified, only one of which was relevant to the question.
|Author, date and country
||Study type (level of evidence)
|Rawles JM & Kenmure ACR,|
|157 patients with acute uncomplicated myocardial infarction
Oxygen vs. compressed air via MC mask at 6l/min for 24 hours||PRCT||Incidence of arrhythmias||More sinus tachycardia in oxygen group (p<0.05); no other significant differences||No power calculation
No assessment of pain scores
Effect of implementing intention to treat analysis not discussed|
|Number of patients given analgesics/number of doses given (diamorphine)||No significant difference|
|Mortality||9 vs 3 deaths (not significant)|
The routine use of oxygen in myocardial infarction has been widely advocated for many years. However, the only study to investigate the efficacy of this approach was underpowered to show a difference in mortality.
Clinical Bottom Line
In patients with uncomplicated acute myocardial infarction there is no evidence that supplemental oxygen reduces mortality. However the there is no evidence of harm. Further research is required before changes in current practice should be recommended.
- Rawles JM, Kenmure ACF. Controlled trial of oxygen in uncomplicated myocardial infarction. BMJ 1976;1(6018):1121-1123.