Now, all drugs have some risks.
There's 3 big ones with vasodilators.
So, stop for a minute and
make sure we have these
3 clear in your mind just as a list and
then we'll break them down.
So falls risk is a big one with
Now, reflex means this is a response,
tachy means fast, cardia means heart.
So, reflex tachycardia is a
really fast heart response.
We also, over a long period of time,
will have an increase in blood volume.
So, for now, let's make sure you have
those 3 solid in your mind.
What happens to a patient or risk for
a patient on vasodilators?
They have orthostatic hypotension,
puts them at an increased risk for falls.
They have reflex tachycardia,
and they're going to have an
increase in blood volume
if they're on a vasodilator for
a long period of time.
So, why is someone at falls risk when
you're on a vasodilator?
Well, with that venous dilation, remember
a lot of blood stays out in my periphery.
So, if I go from a lying to sitting
or sitting to standing point too quickly,
I'm going to be at a risk for falls.
So their blood pressure takes
a little while to stabilize.
So, particularly patients on vasodilators,
you want to teach them, as an
educator and as a nurse,
you want to teach them that,
"Hey, when you're laying down,
sit up and kind of get your bearings first.
Don't go immediately to standing
up because they're going to
increase their risk for falling and
really hurting themselves."
Help them to understand this is normal.
For patients that are on vasodilators,
most people feel this way.
So it's not a big deal if they
just take their time.
Now, reflex tachycardia. Remember, we're
talking about sinus tachycardia means
everything's going okay with the electrical
conductivity of the heart, right?
It's going SA node, AV node,
all the way it's supposed to.
It's just going too fast.
Well, the heart senses, "Wait a minute.
Now my blood pressure's dropped.
We must have low volume," so it
tries to move it around faster.
That's what reflex tachycardia means.
That's what the strip is showing you there.
See how fast those heartbeats are?
That's a response to the vasodilators.
Now, I don't want to just leave it there.
Let's break it down a little bit.
Why do vasodilators cause a fast heart rate?
Well, it's a barrel receptor response. That's
what leads to that elevated heart rate.
When we dilate arterioles,
those tiny branches of the artery,
remember, the arterial blood pressure drops.
When we've dilate veins, it indirectly
lowers the arterial blood pressure.
Long story short, vasodilators
drop your blood pressure. Now,
this is one of my favorite
graphics that they have here. Look at --
this is brilliant. Look what they have.
See the red vessels, obviously,
those are your arteries,
they've got the aortic arch, and then you
see those yellow vessels going up.
That's talking about the baroreceptor reflex
that sends a message to your brain.
So they've done a brilliant job giving you a
graphic representation of what happens.
Remember, it's the baroreceptor reflex,
that's the one that can set
the rate of your heart.
It senses a decrease in arterial pressure.
There you see, the little yellow guys
attached right to the aorta,
so they sense a drop in that pressure.
When they sense that drop, they'll
send a signal to your brain,
to the medulla. So see how they've got them
all the way up connected to your brain.
Then the medulla sends a signal through
the sympathetic nerves
to increase heart rate because an effort
they want to raise the blood pressure.
So when we put patients on a vasodilator,
it's this baroreceptor reflex that
will cause them to --
have that superfast heart rate response.
So they sense that drop in
the baroreceptors send a
signal to the medulla.
The medulla sends a signal to the
sympathetic nervous system,
and your heart rate goes up.
So to, kind of, deal with this, sometimes, we
have to put patients on vasodilators on
Remember, when the sympathetic nervous
system sends those signals down,
it will attack -- it will connect,
not attack, it will connect
to those receptors on your heart, right, the
beta 1 receptors and make it beat faster,
unless we give you a beta
blocker, like metoprolol.
This can help prevent that
that's brought on by this
barrel receptor reflex.
Now I want to walk through that
again with you just briefly.
How does a beta blocker
help us deal with that reflex tachycardia?
Well, the deal is,
when that sympathetic nervous
system is stimulated,
it's going to send a transmitter to those
beta 1 receptors on the heart,
whose job is to make the heart beat faster.
But see, a-ha!
You've given the patient metoprolol,
so that drug has already filled up
those beta 1 receptors.
So when those transmitters come and
try to tell the heart rate to go faster,
it won't happen because you've already
medicated the patient
with a beta blocker.
Now, the increase in blood volume,
that's kind of a weird one, right?
We've got a picture of a blood pressure cuff
meeting right there. You see, it's 140.
That's too high. We know that we want your
blood pressure to be much lower than that.
But when you have increased volume, you're
going to have an increased blood pressure.
So, how can a vasodilator drug
that dilates give you increase blood volume
and sometimes a higher blood pressure?
Well, the answer is our friend, aldosterone.
I've talked about that before.
Aldosterone is a hormone,
and it's a hormone that tells my
body to hang on to sodium.
When my body hangs on to sodium,
then you know what follows, water.
So, aldosterone is a hormone that
is a chemical messenger.
Tells my body to hang on to sodium.
When you hang on to sodium, water follows.
That means you've got an increase in volume.
Aldosterone leads to sodium retention.
Sodium retention leads to
reabsorbing more water in your kidney,
so your volume goes up.
When your volume goes up, so does
your blood pressure.
So if my blood pressure over a
long period of time is low,
because I've been taking vasodilators,
the body's going to pick up on that and it
might stimulate aldosterone to be released.
So the more aldosterone my body puts out,
the more sodium and water I retain.
So just like we used beta
blockers to treat that
we can use diuretics to help minimize
that extra volume
and make sure we're getting the effect
we want from the vasodilators,
which is the decreased blood pressure.