A nurse in an emergency department is planning care for a client who is having an acute myocardial infarction (MI). The nurse should plan to administer which of the following medications after the initial acute phase to manage the client's pain and anxiety?

Choice A rationale Morphine is the drug of choice after the initial phase of an MI to manage pain that is unresponsive to nitroglycerin. It acts as an opioid analgesic and provides significant peripheral vasodilation, which reduces both preload and afterload, thereby decreasing myocardial oxygen demand. Furthermore, morphine has a calming effect on the central nervous system, effectively reducing the intense anxiety and sympathetic nervous system activation that can further strain an injured heart during the recovery phase. Choice B rationale Aspirin is an antiplatelet medication that is administered immediately upon suspicion of a myocardial infarction to prevent the further growth of a coronary thrombus. It is considered part of the initial acute management phase rather than a medication used specifically for the ongoing management of pain and anxiety. While it is essential for long-term secondary prevention, its primary mechanism of action is hematological and does not provide any analgesic or sedative benefits for the patient. Choice C rationale Oxygen therapy is indicated in the early stages of a myocardial infarction if the patient's oxygen saturation falls below 90 percent or if they are in respiratory distress. The goal is to increase the oxygen supply to the ischemic myocardial tissue. However, oxygen is a gas used to support oxygenation and is not a pharmacological agent for pain relief or anxiety. Recent guidelines suggest avoiding routine supplemental oxygen in non-hypoxic patients as it may cause vasoconstriction. Choice D rationale Nitroglycerin is a potent vasodilator used in the initial acute phase to relieve chest pain by improving coronary artery blood flow and reducing myocardial workload. While it is excellent for managing ischemic pain, it does not address the psychological anxiety or the severe, persistent pain that often follows a major infarction. Once the initial vessel dilation is achieved, morphine is often required to manage the remaining discomfort and the patient's heightened emotional and physiological stress response.