Today I would like to share with you two easy steps to be competent in all vasopressor drips in the ICU. If you are a brand new nurse who hope to land an ICU job fresh out of nursing school by impressing the ICU director during the interview, this article is for you. If you are a veteran ICU nurse who need some refreshment, this article is for you also. I hope you find this helpful in your daily practice as much as I do when I study to prepare to write this article. From the bottom of my heart, I hope to present this information as accurate as possible. Yet, if there is any discrepancy between what you read in my article and your text book, please don’t hesitate to leave me a comment below. I would love to clarify it with you with my best capability. Without further ado, Lets learn about the vasopressor drips and start saving lives.
Most of us probably already known what vasopressors is and how they affect the body, the blood pressure specially. Let’s break it down. Vaso (means vessels/blood vessels) pressor (means constricted). By definition, vasopressor is medication that constricts the blood vessels to increase blood pressure in hemodynamically unstable patients.
There are only a handful of vasopressor drip medications which you will encounter for the rest of your nursing career. Those medication include norepinephrine (Levophed), dobutamine, dopamine, vasopressin, and phenylephrine (Neo Synephrine or Neo for short). To be able to understand why a physician prescribed dopamine but not norepinephrine in patients with cardiogenic shock, we need to know each medication and its mechanism. There are two easy steps to know all your vasopressor drips:
- You need to know the receptor sites and how they affect on the body
- You need to know what receptor sites each medication target on
Step 1: There are many receptor sites in the our body, we are only going to discuss about Alpha 1, Alpha 2, Beta 1, Beta 2, Vasopressin (V1) and dopamine receptors:
- Alpha 1 Receptors: located mainly in the peripheral blood vessels which have sympathetic properties thus cause vasoconstriction.
- Alpha 2 Receptors: an antagonist with Alpha 1 Receptor which cause dilatation in peripheral blood vessels. For the purpose of this article, you don’t need to memorize Alpha 2 Receptors.
- Beta 1 Receptors: located mainly in the heart which have sympathetic properties thus cause vasoconstriction mainly in the heart.
- Beta 2 Receptors: located mainly in the bronchioles of the lungs and the arteries of the skeletal muscles. Beta 2 Receptor cause vasodilation in peripheral blood vessels.
- V1 Receptors: located mainly in the peripheral blood vessels and cause vasoconstriction. They also located in vascular and GI smooth muscle with an anti-diuretic effect.
Before moving to step 2, I suggest you taking sometimes to be familiarize with those receptors.
Steps 2: Now that you know which effect each receptor has, let’s move on specific mechanism of each drug:
- Norepinephrine (Levophed) affects on Alpha 1 and Beta 1 receptors thus it cause peripheral vasoconstriction and vasoconstriction in the heart to increase cardiac output. Norepinephrine is the most popular vasopressor drip drug because it affects both the heart and peripheral system. Norepinephrine is widely used in patients with septic shock or unknown types of shock. Norepinephrine can cause reflex bradycardia if you increase the doses too quickly. Dosage 2-30 mcg/min.
- Dopamine affects on Alpha 1 and Beta 1 receptors thus it causes peripheral vasoconstriction and vasoconstriction in the heart. It has the same receptor sites as norepinephrine but is used with different purpose. Dopamine affects mainly on the Beta 1 receptors which is in the heart, thus it increase contractility and cardiac output. With that property, Dopamine is mainly used for patients with cardiogenic shock. With the same token, it is not a drug of choice for patients with elevated heart rate. Norepinephrine or phenylephrine (Neo) may be a better option. Dosage 2-20 mcg/kg/min.
- Dobutamine affects in Beta 1 and Beta 2 receptor. Similar to Dopamine, Dobutamine mainly cause vasoconstriction in the heart. However, due to its Beta 2 property, Dobutamine can cause vasodilation in peripheral blood vessels. Dobutamine is also used in cardiogenic shock. Dosage 2-20 mcg/kg/min
- Phenylephrine (Neo) affects in Alpha 1 receptors thus it does not have any control of the heart. Because it is purely peripheral vasoconstrictor, (Neo) is mainly used in neurogenic shock. Dosage 25-300 mcg/min.
- Vasopressin affects on V1 receptor which causes peripheral vasoconstriction. Due to other effects on vascular and GI smooth muscle, Vasopressin is rarely used (or at least in my facility). Dosage 0.03-0.06 units/min.
As you learn about vasopressor drips, I suggest you review the four types of shock also. If you understand the causes, it will make more sense as you tie in the treatment with the condition patients have.
Below is youtube video from Strong Medicine Channel of Dr. Eric Strong.