Which of the following medications does the nurse identify as a calcium channel blocker used to treat tachycardia and manage heart rate?
Digoxin
Diltiazem (Cardizem)
Nitroglycerin
Nitroprusside (Nipride)
The Correct Answer is B
Choice A rationale:
Digoxin is a cardiac glycoside, not a calcium channel blocker. It works by increasing the force of contraction of the heart muscle and slowing the heart rate. However, it is not typically used as a first-line treatment for tachycardia. It's more commonly used to treat heart failure and atrial fibrillation.
Mechanism of action: Digoxin inhibits the sodium-potassium ATPase pump in cardiac cells, leading to an increase in intracellular calcium. This increased calcium availability enhances myocardial contractility. Digoxin also indirectly affects the autonomic nervous system, leading to a decrease in heart rate.
Key points:
Digoxin is not a calcium channel blocker.
It's used primarily for heart failure and atrial fibrillation.
Its mechanism of action involves increasing intracellular calcium and decreasing heart rate.
Choice B rationale:
Diltiazem (Cardizem) is a calcium channel blocker that is commonly used to treat tachycardia and manage heart rate. It works by blocking the movement of calcium into cardiac cells, which slows down the electrical conduction system of the heart and leads to a decrease in heart rate.
Mechanism of action: Diltiazem blocks L-type calcium channels in cardiac and vascular smooth muscle cells. This reduces calcium influx, leading to:
Decreased myocardial contractility Vasodilation (relaxation of blood vessels)
Negative chronotropic effect (decreased heart rate)
Negative dromotropic effect (slowed conduction through the AV node) Key points:
Diltiazem is a calcium channel blocker.
It's effective in treating tachycardia and managing heart rate.
Its mechanism of action involves blocking calcium channels, leading to various cardiovascular effects.
Choice C rationale:
Nitroglycerin is a vasodilator, not a calcium channel blocker. It works by relaxing the smooth muscle in blood vessels, which widens the vessels and allows more blood to flow through them. This can help to relieve chest pain (angina) and lower blood pressure, but it does not directly affect heart rate.
Mechanism of action: Nitroglycerin is metabolized to nitric oxide, which activates guanylate cyclase, leading to increased production of cyclic guanosine monophosphate (cGMP). cGMP causes smooth muscle relaxation, resulting in vasodilation.
Key points:
Nitroglycerin is a vasodilator, not a calcium channel blocker. It's primarily used for angina and hypertension.
Its mechanism of action involves nitric oxide-mediated vasodilation.
Choice D rationale:
Nitroprusside (Nipride) is a potent vasodilator, not a calcium channel blocker. It is typically used in critical care settings to manage severe hypertension or heart failure. It works by relaxing the smooth muscle in blood vessels, which widens the vessels and allows more blood to flow through them. This can help to lower blood pressure, but it does not directly affect heart rate.
Mechanism of action: Nitroprusside directly releases nitric oxide, leading to vasodilation. Key points:
Nitroprusside is a potent vasodilator, not a calcium channel blocker.
It's used in critical care settings for severe hypertension or heart failure.
Its mechanism of action involves direct nitric oxide release and vasodilation.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
Choice A rationale:
COPD (Chronic Obstructive Pulmonary Disease) is a chronic lung disease that causes airflow obstruction. While labetalol can cause some bronchoconstriction, it is generally considered safe for use in patients with COPD. However, it's essential to monitor respiratory status closely, especially in those with severe COPD.
Choice B rationale:
Narrow-angle glaucoma is an eye condition characterized by increased intraocular pressure (IOP) due to impaired drainage of aqueous humor. Labetalol can exacerbate this condition by further increasing IOP through its beta-blocking effects. This can lead to acute angle-closure glaucoma, a medical emergency that can result in permanent vision loss.
Specific mechanisms by which labetalol can increase IOP:
Reduced aqueous humor production: Beta-blockers like labetalol can decrease the production of aqueous humor, the fluid that maintains eye pressure. While this might seem beneficial, a significant reduction can lead to anterior chamber shallowing, which can mechanically block the drainage angle and trigger angle closure.
Impaired uveoscleral outflow: Beta-blockers can also impair the uveoscleral outflow pathway, an alternative route for aqueous humor drainage that becomes more important in glaucoma patients. This can further contribute to IOP elevation.
Vasoconstriction of ciliary blood vessels: Labetalol's alpha-blocking effects can cause vasoconstriction of the ciliary blood vessels, which supply blood to the ciliary body responsible for aqueous humor production. This can reduce blood flow and indirectly hinder aqueous humor drainage.
Pupillary dilation: Beta-blockers can cause pupillary dilation, which can mechanically narrow the anterior chamber angle and obstruct aqueous humor outflow.
Therefore, labetalol is generally contraindicated in patients with known narrow-angle glaucoma.
Choice C rationale:
Hypertension (high blood pressure) is one of the primary indications for labetalol. It is an effective antihypertensive medication that works by blocking beta receptors, leading to decreased heart rate, contractility, and blood pressure.
Choice D rationale:
Tachycardia (fast heart rate) can also be treated with labetalol due to its beta-blocking effects. It helps to slow down the heart rate and restore a normal rhythm.
Correct Answer is B
Explanation
Choice A rationale:
Albuterol (Proventil) is a bronchodilator that is used to treat acute asthma attacks and chronic obstructive pulmonary disease (COPD). It works by relaxing the smooth muscles in the airways, which allows more air to flow into the lungs. While albuterol can be helpful in relieving shortness of breath, it is not the first-line treatment for a patient with chest pain and low oxygen saturation. This is because albuterol does not address the underlying cause of the chest pain, which is likely a lack of oxygen to the heart muscle.
Choice C rationale:
Nitroglycerin is a vasodilator that is used to treat angina (chest pain) and heart failure. It works by relaxing the blood vessels, which allows more blood to flow to the heart. Nitroglycerin can be helpful in relieving chest pain, but it is not the first-line treatment for a patient with low oxygen saturation. This is because nitroglycerin can actually worsen hypoxemia (low oxygen levels in the blood) by dilating blood vessels in the lungs.
Choice D rationale:
Aspirin is a blood thinner that is used to prevent and treat blood clots. It is often given to patients with chest pain who are suspected of having a heart attack. However, aspirin is not the first-line treatment for a patient with low oxygen saturation. This is because aspirin does not address the underlying cause of the low oxygen saturation, which is likely a problem with the lungs or heart.
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