Emergency Pharmacology: A Highlight on Vasopressors (Dopamine)

Vasopressors are life-saving drugs that are commonly seen in an emergency setting. But what are vasopressors, and what are their mechanisms of action?

Vasopressors Defined

Vasopressors are types of medications that exert pressure on the veins, on the vascular beds to promote vasoconstriction. When this happens, there is an increase in blood flow to the heart, lungs, and the brain. Aside from these organs, the kidneys are also directly affected by vasopressors.

Upon administration of vasopressors, the kidneys are alerted to hold all the fluid in the body or what is also known as fluid retention, causing dilation in the renal cavity or arteries; this will be explained further as we go along.

Examples of Vasopressors

There are many examples of vasopressors available in the market, but there are only two that are commonly utilized inside the hospital, especially in emergency scenarios. These drugs are:

• Norepinephrine (Levophed)
• Dopamine

Between the two, we’ll focus our attention on dopamine.

Dopamine

Dopamine is usually the first line of drug given to anyone who is suffering from hypotension.

Much like any other vasopressors, the introduction of dopamine is going to prompt vasoconstriction, putting pressure on the vessels. The primary goal for the administration of dopamine is to increase blood pressure. Aside from boosting blood pressure, dopamine can also inadvertently increase heart rate.

As mentioned, the kidneys are also going to be affected through perfusion, holding the fluid in to retain blood and distribute it to the rest of the body.

Hypotensive Crisis

Vasopressors are given especially during a hypotensive crisis. A hypotensive crisis is a situation wherein the body is losing a lot of blood drastically, which can either be caused by the following:

• Trauma, example: gunshot wound
• Excessive vomiting
• Diarrhea

Any of these events can lead to hypovolemic shock, which is a deficiency of blood or fluids within the vascular spaces. If there is the extremely low amount of blood perfusion, it will compromise the distribution of oxygen. Remember, without oxygen, the body will eventually expire.

The Function of the Kidneys

So, during a hypotensive crisis, the kidneys will swoop in to save what is left of the little blood in the body by ceasing the mechanism of urination. The kidneys will not allow pee to go out of the body, keeping it inside the vascular spaces until blood pressure will rise naturally.

Route of Dopamine

Dopamine is usually given with an intravenous infusion as a piggyback or slow infusion; this will help increase blood pressure and dilate the renal arteries. This is true during emergencies.

Dopamine and ARF

Dopamine is also given to clients who are suffering from acute renal failure (ARF). When the kidneys are failing, dopamine will ignite the opening up of the renal arteries, causing more perfusion by shunting blood down to the kidneys so the client won’t go into chronic renal failure, and potentially losing the kidneys.

How does one determine that there is low perfusion in the kidneys?

The mean arterial pressure (MAP) determines how much blood flow is getting around the body. Normally the MAP is from 85 – 100. However, if there are problems with the kidneys, the MAP will go below 65. If this happens, the perfusion becomes compromised. To prevent this, dopamine is given.

For our next lecture, we’ll be focusing on the second vasopressor we’ve mentioned – norepinephrine (Levophed). Check out all our nursing resources on pharmacology and every nursing school topic.