Which medication, if taken within the last 24-48 hours, would prevent a nurse from administering nitroglycerin?

Choice A rationale:

Dopamine was once considered a first-line vasopressor for cardiogenic shock. However, recent studies have shown that it is associated with increased mortality compared to norepinephrine.

Dopamine has dose-dependent effects on dopamine receptors, beta receptors, and alpha receptors. At low doses (1-5 mcg/kg/min), it primarily stimulates dopamine receptors, leading to renal vasodilation and increased urine output. At moderate doses (5-10 mcg/kg/min), it stimulates beta receptors, resulting in increased heart rate and contractility. At high doses (>10 mcg/kg/min), it stimulates alpha receptors, causing vasoconstriction.

The main concern with dopamine is its potential to cause arrhythmias, particularly at higher doses. This is due to its effects on beta receptors, which can increase heart rate and myocardial oxygen demand.

Additionally, dopamine can cause tachyphylaxis, meaning that its effects can diminish over time, requiring higher doses to achieve the same effect.

Choice B rationale:

Norepinephrine is a potent alpha-adrenergic agonist that causes vasoconstriction, leading to an increase in blood pressure. It has minimal effects on beta receptors, so it is less likely to cause tachycardia and arrhythmias compared to dopamine.

Norepinephrine also has some inotropic effects, meaning that it can increase the strength of contraction of the heart muscle.

Studies have shown that norepinephrine is associated with improved survival rates in patients with cardiogenic shock compared to dopamine.

It is generally well-tolerated, with the most common side effects being hypertension and peripheral vasoconstriction.

Choice C rationale:

Epinephrine is a potent alpha- and beta-adrenergic agonist that causes vasoconstriction, increased heart rate, and increased contractility.

It is typically used as a second-line agent in cardiogenic shock, after norepinephrine has failed to achieve adequate blood pressure.

Epinephrine can cause significant tachycardia and arrhythmias, so it should be used with caution in patients with underlying heart disease.

Choice D rationale:

Vasopressin is a hormone that causes vasoconstriction by acting on V1 receptors in vascular smooth muscle. It is sometimes used as an adjunct to norepinephrine in patients with refractory cardiogenic shock.

Vasopressin has the potential to cause coronary vasoconstriction, so it should be used with caution in patients with coronary artery disease.

Choice A rationale:

Amiodarone is an antiarrhythmic medication that is often used to treat ventricular tachycardia and ventricular fibrillation. However, it is not the first-line drug for Torsades de Pointes. In fact, amiodarone can actually worsen QT prolongation and increase the risk of Torsades de Pointes.

It's important to note that amiodarone has a long half-life and can accumulate in the body over time, further increasing the risk of QT prolongation.

Additionally, amiodarone can have several serious side effects, including pulmonary toxicity, thyroid dysfunction, and liver damage.

Choice B rationale:

Lidocaine is another antiarrhythmic medication that is sometimes used to treat ventricular arrhythmias. However, it is also not the first-line drug for Torsades de Pointes.

Lidocaine is less likely to worsen QT prolongation than amiodarone, but it can still have this effect in some patients.

Additionally, lidocaine has a short half-life and must be given as a continuous infusion, which can be challenging in a critical care setting.

Choice C rationale:

Atropine is a medication that is used to increase heart rate. It is not effective in treating Torsades de Pointes and is not indicated in this situation.

Atropine works by blocking the vagus nerve, which slows heart rate. In Torsades de Pointes, the heart rate is already very fast, so atropine would not be helpful.

Additionally, atropine can have several side effects, including dry mouth, blurred vision, and urinary retention.

Choice D rationale:

Magnesium sulfate is the first-line drug for treating Torsades de Pointes. It works by stabilizing the electrical activity of the heart and preventing further episodes of arrhythmia.

Magnesium sulfate is a relatively safe medication with few side effects. It can be given as an intravenous infusion or as an intramuscular injection.

Studies have shown that magnesium sulfate is effective in terminating Torsades de Pointes and preventing recurrences.