Hi, welcome to our video
topic on vasodilators.
We're going to take a look at drugs
that dilate blood vessels.
Okay, so we're going to start with a question.
Do vasodilator medications dilate
the arteries, or the veins, or both?
So before you go on, stop
and pick your answer.
Okay, it was a little bit of
a trick question.
Vasodilator drug groups have
1 of 3 specific targets.
First one is primarily the arterioles.
Wait a minute, the question
said arteries or veins?
Well, arterioles are just the tiniest
branches of the arteries.
So, if we can impact those, if we
can vasodilate arterioles,
you're going to have a really significant
impact on blood pressure.
It's definitely going to lower
your blood pressure.
So when you see the words
"artery" or "arterioles,"
they're part of the same vessels,
just arterioles are those
tiny little branches that have a really
significant impact on blood pressure.
The second group are primarily the veins.
So vasodilator drugs might go
after just the arterioles –
remember, small branches of the artery --
the veins, or both.
So, while it was a trick question,
we just wanted to open with
that to help you know that
using these drugs, drugs that
make vessels bigger,
go after 1 of 3 targets: the arteries
or the arterioles, the veins, or both.
Okay. So, let's break that down a little bit.
Since we're studying pharmacology,
let's put some drug names in there
to help you make sense of this.
Hydralazine is a drug that goes
after the arterioles.
That's when it primarily will open up.
So if I give you hydralazine, your
blood pressure is going to drop.
Now, when the veins are the target
with a drug like nitroglycerin,
remember, that's probably familiar to you.
We give that to patients
who have chest pain.
We can give them a little tiny tablet
underneath their tongue,
we can give it to them IV, sprays,
gels, all kinds of things. But when
we give a patient nitroglycerin,
we predominantly dilate their veins.
That'll leave more blood in the periphery.
We'll talk about what the impact
of that is on our next topic.
A drug like nitroglycerin will
vasodilate the veins.
Now, you're probably pretty familiar
with that drug already.
If you've watched any medical show on TV,
you know, we give nitroglycerin for
somebody who has chest pain.
Prazosin will go after both the
arterioles and the veins.
All 3 of these medications will
drop someone's blood pressure.
But I want to break it down for
you just a little bit more.
Don't let these terms frighten you.
I'm going to explain what they mean,
but you'll hear these terms in nursing,
especially when you're conversing
So, we talked about hydralazine,
dilating arterioles. Remember, those
are the tiny branches of the artery.
And when we do that,
you're going to see a pretty big drop
in a patient's blood pressure.
Hydralazine will also decrease
Now, that's the word I didn't want
you to be afraid of. Okay, so
cardiac afterload is not as complicated
as it might sound to you.
Think about your heart. When it's pumping,
if the vessels right outside that
heart are tightened down,
the heart's going to have to work really,
really hard to pump that blood out.
But if we can dilate those vessels
right outside the heart,
those arterioles, then the heart is not
going to have to work as hard.
That's what afterload is.
Cardiac afterload means how hard
your heart has to work
afterwards as it's pumping blood
out to the rest of the body.
Now if we dilate the veins,
it's going to decrease cardiac preload.
We just talked about afterload,
right? That's what happens
after the heart, how hard
the heart is working.
But preload is the amount of blood
that returns to the heart.
It's easier to remember if you think about
preload means before the heart,
So if my veins are dilated more, the blood
kind of hangs out there in the periphery,
like kind of down in my legs and stuff.
So I have less blood returning
to the heart.
That's a decreased cardiac preload.
Now, when we hit both of those,
we -- it's a full game, right?
Prazosin or nitroprusside,
sometimes you may have heard
that called as nipride,
those are medications that go after
both the arterioles and the veins.