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:

Insulin glargine (Lantus) is a long-acting insulin that does not have any immediate effect on blood glucose levels. It is not typically a concern for patients undergoing CT scans with contrast.

However, it is important to monitor blood glucose levels closely in patients with diabetes who are receiving insulin therapy, as the contrast media used in CT scans can sometimes cause hyperglycemia.

Choice B rationale:

Acarbose (Precose) is an alpha-glucosidase inhibitor that works by slowing the absorption of carbohydrates from the intestines. This can help to reduce blood glucose levels after meals.

Acarbose is not typically a concern for patients undergoing CT scans with contrast. However, it is important to note that acarbose can sometimes cause gastrointestinal side effects, such as bloating, gas, and diarrhea. These side effects may be worsened by the contrast media used in CT scans.

Choice C rationale:

Metformin (Glucophage) is a biguanide that works by reducing glucose production in the liver and increasing insulin sensitivity in the muscles. It is a commonly used medication for the treatment of type 2 diabetes.

Metformin is a concern for patients undergoing CT scans with contrast because it can increase the risk of lactic acidosis. Lactic acidosis is a serious condition that can occur when there is a buildup of lactic acid in the blood. It can be caused by metformin, as well as by other factors such as dehydration, kidney problems, and liver problems.

The contrast media used in CT scans can also increase the risk of lactic acidosis. This is because the contrast media can sometimes cause kidney damage, which can impair the body's ability to remove lactic acid from the blood.

For this reason, metformin is typically discontinued for 48 hours before a CT scan with contrast. It is also important to ensure that patients are well-hydrated before and after the scan.

Choice D rationale:

Glipizide (Glucotrol) is a sulfonylurea that works by stimulating the release of insulin from the pancreas. It is a commonly used medication for the treatment of type 2 diabetes.

Glipizide is not typically a concern for patients undergoing CT scans with contrast. However, it is important to monitor blood glucose levels closely in patients with diabetes who are receiving sulfonylurea therapy, as the contrast media used in CT scans can sometimes cause hypoglycemia.