What are the MONA components for ACS management and key contraindications?

• A. M: Morphine; O: Oxygen if sat < 90-92%; N: Nitroglycerin not if hypotensive or right ventricular infarct or PDE-5 inhibitor use; A: Aspirin 162-325 mg chewable. Contraindications: hypotension and sildenafil within 24-48 hours.
• B. M: Morphine only; O: Oxygen always; N: Nitroglycerin always; A: Aspirin 81 mg; Contraindication: allergy to aspirin.
• C. M: Morphine; O: Oxygen only if sat < 95%; N: Nitroglycerin if BP high; A: Aspirin 81 mg; Contraindication: diabetes.
• D. M: Morphine; O: Oxygen if sat < 95%; N: Nitroglycerin not allowed in any infarct; A: Aspirin 300 mg; Contraindication: nitrates safety.

Answer: (A)

In ACS, MONA is about quickly addressing pain, oxygenation, perfusion, and platelet activity to limit myocardial injury. Morphine provides analgesia and helps reduce the stress response that increases oxygen demand. Oxygen is given when the patient is hypoxemic (often indicated by a low SpO2), because supplying adequate oxygen helps myocardial tissue during ischemia. Nitroglycerin relaxes veins to reduce preload and improve coronary perfusion, which lowers myocardial oxygen demand, but it must not be used if the patient is hypotensive, has a suspected right ventricular infarct (where preload dependence is critical), or is taking nitrates or PDE-5 inhibitors. Aspirin, given as a chewable dose of about 162-325 mg, inhibits platelets and helps prevent further thrombus formation, setting the stage for reperfusion therapy. Contraindications to these steps include low blood pressure, use of sildenafil or similar PDE-5 inhibitors within the past 24-48 hours (due to risk of severe hypotension), and, with nitroglycerin, the presence of a right ventricular infarct or other conditions that make hypotension likely. This combination best matches the intended MONA approach and its safest administration in the context of ACS.