A patient is admitted to the emergency department with chest pain and ECG findings showing ST-segment elevation. The nurse notes oxygen saturation at 89 Which intervention should the nurse prioritize to initiate first?

Choice A rationale Administering nitroglycerin is a standard treatment for chest pain because it induces vasodilation of the coronary arteries. However, prioritizing it over oxygen in a patient with an oxygen saturation of 89 percent is incorrect. Nitroglycerin can significantly lower blood pressure, and it should only be administered after assessing hemodynamic stability. In this clinical scenario, addressing the documented hypoxemia takes precedence to ensure myocardial tissue receives adequate oxygenation to prevent further ischemic damage. Choice B rationale Supplemental oxygen is the priority because the patient is hypoxemic, with a saturation below the normal range of 95 to 100 percent. Oxygen therapy increases the partial pressure of oxygen in the blood, enhancing delivery to the myocardium. Correcting hypoxemia reduces the workload on the heart and limits the size of the infarction. Current guidelines emphasize maintaining oxygen saturation at or above 94 percent to optimize cellular respiration and prevent systemic metabolic acidosis. Choice C rationale The supine position is not ideal for a patient experiencing chest pain and respiratory distress because it increases venous return and cardiac preload, potentially worsening pulmonary congestion. Positioning the patient in semi-Fowler or high-Fowler position is usually preferred to facilitate lung expansion. While morphine is used for pain that is unresponsive to nitrates, it is not the first priority. Oxygenation must be addressed immediately to mitigate the underlying cause of the myocardial hypoxia. Choice D rationale Thrombolytic therapy is a critical intervention for ST-segment elevation myocardial infarction when percutaneous intervention is unavailable, but it is never initiated before establishing vascular access and confirming the diagnosis via a 12-lead ECG. Furthermore, safety screening for contraindications like recent surgery or bleeding disorders is mandatory. Starting this treatment without basic stabilization, such as oxygen administration for a desaturating patient, violates the primary assessment sequence of airway, breathing, and circulation.