A 58-year-old patient is recovering in the intensive care unit after a myocardial infarction (MI). The nurse notes an order for the beta-blocker metoprolol.
What is the purpose of this drug?
Dilate the coronary arteries.
Inhibit stimulation of the myocardium by circulating catecholamines.
Provide a positive inotropic effect.
Maintain the patient's blood pressure.
The Correct Answer is B
Choice A rationale
While some beta-blockers have a minor effect on vasodilation, their primary purpose in a post-MI patient is not to dilate the coronary arteries. Beta-blockers reduce myocardial oxygen demand by decreasing heart rate, contractility, and blood pressure. Vasodilators, such as nitrates or calcium channel blockers, are the drugs of choice for dilating coronary arteries.
Choice B rationale
After an MI, circulating catecholamines (epinephrine and norepinephrine) can increase heart rate and contractility, which raises myocardial oxygen demand and can extend the size of the infarct. Metoprolol, a beta-blocker, competitively blocks these catecholamines at the beta-1 adrenergic receptors, thereby reducing heart rate and myocardial contractility. This action decreases oxygen consumption and prevents further cardiac damage.
Choice C rationale
Beta-blockers like metoprolol have a negative inotropic effect, meaning they decrease the force of myocardial contraction. A positive inotropic effect, which increases the force of contraction, is seen with drugs like digoxin or dopamine and would be counterproductive in a post-MI setting where the goal is to reduce the heart's workload.
Choice D rationale
While metoprolol does lower blood pressure as a secondary effect by decreasing heart rate and reducing cardiac output, its primary purpose in a post-MI patient is to reduce the workload of the heart and decrease myocardial oxygen demand. The reduction in blood pressure is a beneficial side effect, but it is not the main indication for its use in this context.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
Choice A rationale
While increasing fluid intake might offer temporary relief for a dry cough, it does not address the underlying cause, which is a common side effect of ACE inhibitors. This cough is due to the accumulation of bradykinin, and fluid intake will not resolve this physiological process, making it an ineffective long-term solution.
Choice B rationale
Reassuring the patient and telling them to continue the medication is unsafe and inappropriate. The ACE inhibitor-induced cough can be very distressing and may indicate an intolerance to the drug. Continuing the medication could lead to non-adherence and does not address the patient's discomfort or the need for an alternative therapy.
Choice C rationale
Advising the patient to stop the medication immediately is not the most appropriate action as it can be dangerous and lead to a rebound of their underlying condition, such as hypertension or heart failure. The nurse should not unilaterally make a decision to discontinue a prescribed medication without consulting the healthcare provider.
Choice D rationale
The most appropriate nursing response is to notify the healthcare provider. The dry cough is a common and often bothersome side effect of ACE inhibitors caused by the buildup of bradykinin. It usually necessitates a change in medication to an alternative, such as an ARB, to address the side effect while maintaining therapeutic benefits.
Correct Answer is A
Explanation
Choice A rationale
Nitroglycerin works by relaxing vascular smooth muscle, primarily in veins, reducing preload and myocardial oxygen demand. The standard protocol for chest pain is to take one sublingual tablet, and if pain persists, repeat the dose every five minutes for a maximum of three doses in a 15-minute period. If the pain persists after three doses, the patient should seek emergency medical care.
Choice B rationale
Sublingual administration of nitroglycerin is designed for rapid absorption directly into the bloodstream through the mucous membranes under the tongue. Chewing the tablet would lead to slower and less predictable absorption because the medication would be swallowed and metabolized by the liver, reducing its bioavailability and effectiveness.
Choice C rationale
Nitroglycerin is a volatile compound that is sensitive to heat, light, and moisture. Storing the medication in a humid environment can cause it to lose its potency, rendering it ineffective when needed to treat acute angina. It should be kept in its original dark glass container, tightly capped, in a cool, dry place.
Choice D rationale
Alcohol can potentiate the hypotensive effects of nitroglycerin, leading to a significant and potentially dangerous drop in blood pressure. Combining these substances can cause severe orthostatic hypotension, syncope, and an increased risk of falls, making it a dangerous interaction that patients should be explicitly warned against.
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