A patient has been admitted to the intensive care unit with cardiogenic shock and their blood pressure is 78/38. Which vasopressor medication is recognized as the first-line treatment for cardiogenic shock?

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.

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.