Are you newer to the ICU and worried about all of the different IV blood pressure medications that you are required to know? Here are a few of the common vasopressors, their normal doses, and what you should know about them.
A lot of the patients that I’ve cared for in the ICU that require blood pressure medications are in septic shock. Despite giving fluids, the patient is still hypotensive (has a low blood pressure). Check out this article on septic shock if you are having a hard time understanding the physiology of why septic shock decreases blood pressure. The most frequent nursing intervention when vasopressors are infusing is checking the patient's blood pressure. We check the blood pressure every 15 minutes or continuously (if the patient has an arterial line) and typically try to achieve a mean arterial pressure (MAP) of greater than 65.
Make sure to look at your hospital’s protocol for these different medications and nursing interventions for them. This is typically what I’ve seen in my medical/surgical ICU.
Quick Physiology Reminder, then onto the Meds…
Now let’s quickly go back to physiology class to remember alpha and beta receptors. When activated, alpha receptors cause vasoconstriction, increased peripheral vascular resistance, and increased arterial blood pressure. Beta 1 receptors increase myocardial contraction (strength of the heart beat) and increases the heart rate. Beta 2 receptors are located in the bronchioles of the lungs and the arteries of the skeletal muscles ; when activated, they cause bronchiole dilation and arterial dilation to the skeletal muscle. This will be important to remember as we go through these different vasopressors and how they work.
The dose of Norepinephrine that we usually give patients is 1-30 mcg/min continuously through a central line. In high doses, norephinephrine can cause acute kidney injury. This medication is narrowing the veins (including the renal veins) which causes decreased perfusion to the kidneys. All medications have side effects that may not be desirable. In this case, keeping the patient's blood pressure normal is the priority. It is a beta-1 and alpha-adrenergic agonist, meaning it activates those receptors.
Norepinephrine is a very potent medication and requires a central line for administration. We may sometimes give it in low doses through a large bore peripheral IV while the provider is placing the central line. If the IV were to infiltrate, give the required subcutaneous dose of tertbutaline to stop the necrosis caused by the norepinephrine.
Norepinephrine predominantly affects alpha receptors which cause an increase in blood pressure. Norepinephrine does not have a large effect on heart rate which makes it great for septic patients who are already tachycardic.
Onset: 1-2 min
Duration: 1-2 min (vasopressor)
Excretion: Urine (84-96%)
Epinephrine comes in a variety of doses depending on the reason for administration (epi-pens for severe anaphylaxis, IV injection for cardiac arrest, etc., IV infusion for hypotension). It has strong alpha-adrenergic effects, which increases cardiac output and heart rate as well as a decrease in renal perfusion and PVR. It causes systemic vasoconstriction raising blood pressure. It also has strong beta 1 and moderate beta 2 adrenergic effects, resulting in bronchial smooth muscle relaxation.
The recommended dose for continuous IV infusion is 0.01-2 mcg/kg/minute. You should titrate to whatever mean arterial pressure (MAP) goal the provider has asked you to keep (usually >65). Titrate the medication accordingly depending on whether the patient continues to be hypotensive or stabilizes.
Onset: 5-10 minutes
Duration: 4 hours
Dopamine is another medication used to increase blood pressure. Unlike Levophed, Dopamine also increases heart rate as well because of its effect on beta 1 receptors. Usually Dopamine is not used in patients in septic shock because their heart rates are already elevated. This medication is good for patients with low blood pressure and low heart rate. It has strong beta1-adrenergic, alpha-adrenergic, and dopaminergic effects.
Blood pressure should be monitored either through a central line or with q15 minute blood pressure checks. Titrate accordingly depending on whether the patient continues to be hypotensive or stabilizes, This is administered through a central line.
According to Medscape, the following are appropriate doses depending on the desired result:
5-15 mcg/kg/min IV (medium dose): May increase renal blood flow, cardiac output, heart rate, and cardiac contractitlity
20-50 mcg/kg/min IV (high dose): May increase blood pressure and stimulate vasoconstriction; may not have a beneficial effect in blood pressure; may increase risk of tachyarrhythmias
Onset: 5 minutes in adults
Duration: <10 minutes
Excretion: Urine (80%) with a half-life of 2 minutes
Phenylephrine is one of the vasopressors that we used in my ICU, but not as frequently as Norepinephrine. It seemed like the general order for which vasopressor we used went 1) Norepinephrine and 2) Vasopressin. If this is not sufficient to get the patient’s blood pressure up, then we would usually add Phenylephrine (assuming none of these were contraindicated). When titrating these vasopressors down, I usually would titrate the Phenylephrine down first and then the Levophed. We usually have Vasopressin at a set dose and then it would get turned off as the patient improves and the provider gives the go ahead to discontinue.
Phenylephrine has very strong alpha effects which increases both blood pressure and peripheral vascular resistance. Medscape says that, “IV administration may cause severe bradycardia and reduced cardiac output, resulting from increase in cardiac afterload especially in patients with preexisting cardiac dysfunction; use with caution in patients with preexisting bradycardia, partial heart block, nyocardial disease, or severe coronary artery disease; may also increase pulmonary arterial pressure and precipitate angina in patients with severe coronary artery disease.”
Onset: 10-15 minutes
Duration: 15 minutes
Excretion: 2-3 hour half-life and excreted out of urine
Vasopressin is not actually a vasopressor medication. It is antidiuretic hormone (ADH), which is a vasoconstrictor without the inotopic or chronotropic effects. It acts on the kidneys and blood vessels and retains fluid within the body. By increasing the fluid retained, this subsequently increases the patient’s blood pressure.
I’ve only had one situation where we infused Vasopressin at a titratable rate. Other than this, every time that I have infused Vasopressin it has been at a dose of 0/04 units/min. We always give this after we have Norepinephrine at a decently high dose to help with increasing the patient’s blood pressure. The Vasopressin stays at the set dose as your are able to titrate down on the Norepinphrine, and then it gets turned off at whatever point the provider states.
Onset: 30-60 minutes
Excretion: 10-20 minute half-life excreted in urine