A nurse is caring for a patient with a confirmed myocardial infarction. The physician orders morphine for pain relief. What is the primary action of morphine in the management of MI?

Choice A rationale Morphine does not possess anticoagulant or antiplatelet properties. The prevention of blood clot formation in the coronary arteries is managed by medications such as aspirin, heparin, or clopidogrel. While morphine is essential for comfort, it does not directly interfere with the coagulation cascade or the aggregation of platelets at the site of a ruptured atherosclerotic plaque. Standard laboratory monitoring for anticoagulation includes the activated partial thromboplastin time, which normally ranges from 30 to 40 seconds. Choice B rationale Morphine is the gold standard for MI pain because it serves multiple purposes. Beyond its analgesic effects, it acts as a venodilator, which reduces preload and the workload of the heart. By relieving intense pain and the associated anxiety, it blunts the sympathetic nervous system response, leading to a decrease in heart rate and myocardial oxygen consumption. This helps balance the oxygen supply-demand mismatch in the ischemic heart tissue, potentially limiting the size of the infarction. Choice C rationale Nitroglycerin is the primary medication used to dilate coronary arteries and increase oxygen delivery to the myocardium. While morphine has some minor vasodilatory effects, its primary benefit in myocardial infarction is not active coronary artery dilation. Morphine focuses more on reducing the oxygen demand of the heart through systemic venous relaxation and sedation. Oxygen saturation should ideally be maintained above 90. Choice D rationale Morphine actually causes vasodilation, not vasoconstriction. Therefore, it tends to lower blood pressure rather than improve it. Nurses must be vigilant in monitoring for hypotension after administration. Vasoconstrictors like norepinephrine would be used in cardiogenic shock to increase blood pressure, but they would increase the workload of the heart, which is counterproductive in an uncomplicated myocardial infarction. A normal systolic blood pressure is generally considered to be less than 120 mmHg and greater than 90 mmHg. .