To the Editor:
The mnemonic, MONA, which stands for morphine, oxygen, nitroglycerin, and aspirin, is used to recall the initial management of patients with chest pain (ie, suspected acute coronary syndrome). However, in the era of evidenced-based medicine, a review of this mnemonic is needed (Fig. 1).
Although morphine is effective at relieving patient anxiety and pain, evidence suggests its use might be harmful. In a recent cardiac magnetic resonance imaging trial it was found that morphine was associated with larger infarct size and suboptimal reperfusion success in ST-elevation myocardial infarction.
1In the non-ST-elevation myocardial infarction population, patients who receive morphine in the first 24 hours had a greater risk of death (odds ratio, 1.48; 95% confidence interval, 1.33-1.64).
2Additionally, there are concerns that morphine delays the absorption and activity of antiplatelet agents. Although we acknowledge the importance of managing patient's symptoms and the limitations of post hoc analyses, these data suggest that morphine should be used if needed for pain relief and not on a routine basis.
For decades, oxygen has been administered to patients with chest pain. However, excessive oxygen can have paradoxical effects because of increased coronary vascular resistance and reperfusion injury from toxic oxygen free radicals. A Cochrane review showed increased mortality with the use of high-flow oxygen therapy (relative risk: 2.11; 95% confidence interval, 0.78-5.68) with no evidence of decreased perception of pain.
3Recently, a randomized trial of 441 patients reported event rates with oxygen (recurrent myocardial infarction: 5.5% vs 0.9%) and an increase in infarct size at 6 months.
4The Determination of the Role of Oxygen Is Suspected Acute Myocardial Infarction (DETO2X-AMI) trial is currently under way, and will randomize 6600 patients to receive either supplemental oxygen or room air, with 1-year all-cause mortality as their primary end point.
Nitroglycerin remains a commonly used medication in the treatment of chest pain. Although there are multiple benefits associated with nitroglycerin use, some studies suggest that nitroglycerin might cause endothelial dysfunction and toxic pro-oxidant effects. As well, when patients administer nitroglycerin symptoms could be masked, which could delay activation of the emergency response system.
Uniquely, aspirin is the only drug with clear benefits and is supported by strong evidence. Immediate therapy with aspirin has become standard, because of the commensurate benefits observed in decades of trials in patients with suspected acute myocardial infarction.
Although there are situations that warrant the use of morphine, oxygen, and/or nitroglycerin, their “routine” use in all patients is not supported by evidence-based medicine. The acronym, MONA, should be reconsidered as a teaching aid.
R.B. has received research funding from Abbott Vascular, Alere, Astra Zeneca, Bayer, Boehringer Ingelheim, Canadian Institute of Health Research, CSL Behring LLC, Edwards Lifesciences, Eli Lilly, Jansen, Johnson & Johnson, Matrizyme Pharma, Pfizer, Population Health Research Institute, and University of Alberta Hospital Foundation; and personal funding from Astra Zeneca, Bayer, and Bristol Myers-Squibb/Pfizer. The remaining authors have no conflicts of interest to disclose.
- Intravenous morphine administration and reperfusion success in ST-elevation myocardial infarction: insights from cardiac magnetic resonance imaging.Clin Res Cardiol. 2015; 104: 727-734
- Association of intravenous morphine use and outcomes in acute coronary syndromes: results from the CRUSADE Quality Improvement Initiative.Am Heart J. 2015; 149: 1043-1049
- Oxygen therapy for acute myocardial infarction.Cochrane Database Syst Rev. 2013; 8: CD007160
- Air versus oxygen in ST-segment elevation myocardial infarction.Circulation. 2015; 131: 2143-2145
Published online: November 02, 2015
© 2016 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.