Welcome to our video on blood pressure.
Now, this is going to fit right into
our other pharmacology videos,
but I want you to have a really clear
review of what blood pressure is.
So, we're going to look at the highs, the lows,
and what exactly those measurements mean.
So let's start with a definition
of blood pressure.
Now, I want you to think of your heart.
If we start with that right atrium,
you know we have all those veins
that lead up to your right atrium.
Your blood supply goes through
your heart, to your lungs,
and then back to your heart to go out to the
rest of your body through the arteries,
which connect back up to your veins.
So, we're supposed to be an intact system.
Veins and arteries connected through the
heart and the lungs and all the organs.
So, when we talk about blood pressure,
we're thinking about the pressure in
the blood in the circulatory system,
and that's going to include your arteries,
your veins, and your capillaries.
So, first off, I want you to get in mind to
thinking about we've got this whole system,
it's an amazing system, throughout your body
leading to the heart, through the heart,
to the lungs, back to the heart, and
then out through the rest of your body.
And when you take a simple
blood pressure measurement,
we're getting an idea of what's
going on in that internal system;
in your arteries, your veins,
and your capillaries.
So, cardiac output is a really important
part of your blood pressure.
Now it's made of two things.
If you talk about cardiac output,
we're talking about how much volume of blood the
heart can pump out through the blood vessels;
those arteries, veins, and capillaries.
Now, you hear me use those
terms over and over again
because I just want to reinforce those concepts.
That's called spaced repetition.
That's a really good way and a strategy
to use when you're studying.
The more repetition you
have over periods of time,
the better the information is
going to stick in your mind.
So, cardiac output is how much blood your
heart can put out with each of its beats.
So if I want to impact cardiac
output, first, it's the volume
and next it's the number of beats per
minute and the force of the contraction.
Now, don't let that get you confused
because that seems like a lot of words,
but I'm talking about…how much
blood my heart can put out, right?
So, if I have a lot of volume in this intact system,
I likely am going to put out more volume
with each beat than if I'm very dehydrated
and don't have much volume on board.
Now, the faster my heart pumps per minute,
the more blood I'm going to be putting out,
so my cardiac output will be higher.
The stronger my heart can pump, also,
the higher my output is going to be.
So, if we're thinking about cardiac output,
these are some concepts I want you to start to,
kind of, understand that it play a role
in maintaining a blood pressure.
So, the higher the volume of blood
I have in my introvascular space,
usually, the higher my blood
pressure is going to be.
The lower the volume in my introvascular space,
the lower my blood pressure is going to be.
The faster my heartbeat goes, the
higher my blood pressure should be.
And the stronger my heart beats
with the force of contractions,
the higher my blood pressure should be.
Now, I want you to start thinking about this when
we talk about fluid volume balance of patients.
This is one of the reasons when we control blood
pressure we put the patient on a diuretic.
That's a medication, like furosemide, that will
cause you to, literally, pee out lots of fluid.
Your body gets rid of a lot of fluid.
When you have less fluid in your introvascular
space, you have less volume in your blood.
So let me think that through.
If you have a patient, and we put them on
a medication that causes them to pee out
a lot of extra fluid from their body, what is
going to be the impact on their blood pressure?
Will it be higher, or will it be lower?
It should be lower.
Now, what if I put you on a medication that
causes your heart rate to…to get slower?
Well, what's going to happen there, my
blood pressure is also going to be lower
because remember, the number of beats per minute
impacts my blood pressure
through my cardiac output.
So, we have medications like beta blockers
that lower…directly lower your heart rate.
Also, some calcium channel blockers
will directly lower your heart rate.
So, in turn, that will also
decrease your blood pressure.
So when you're thinking about blood pressure,
I want you to just draw a little line from the word
"pressure" out to the left, and write the word "CO."
That will remind you that one of the main
components of blood pressure is cardiac output,
and then draw another line and make sure it
says "pulse," that'll be beats per minute,
so you can just put a "P" for pulse,
and then "force" to remind you how
fast and how strong it pumps,
and how much volume you have on board are
going to deal with your cardiac output.
Now, let's talk about systemic vascular
resistance, because we have these two features:
cardiac output, the second one
is systemic vascular resistance.
So, off to the side of blood pressure,
make a new column that writes "SVR."
These are going to be the main two components
in blood pressure: cardiac output and SVR.
Cardiac output is impacted by volume of blood,
and the number of beats per minute in force.
Systemic vascular resistance is the
amount of force it takes for that heart
to push against the walls of the
arteries that come after the heart.
Remember, when we talked
about the flow of the blood;
right atrium, right ventricle, over to the lungs,
then it comes back to the heart, left atrium,
left ventricle, right out to the body.
Stop right there.
When we talk about the left ventricle, when
we say "systemic vascular resistance,"
it's the amount of force it takes for the heart
to push against the walls of the
arteries immediately after the heart,
so that means right after the
blood leaves that left ventricle.
So, the higher the SVR, that
means the more effort it takes.
So usually, that means there are
some problems with those vessels;
the diameter of those arteries.
So, they're either…vasoconstricted,
that will mean a higher SVR and
usually, a higher blood pressure.
If I have a lot of plaque built
up in my arteries, right,
because I have some coronary artery desease,
that means it's going to be a smaller
diameter, my SVR will be higher,
and my blood pressure is also going to be higher.
So, plaque or atherosclerosis,
anything that causes the
diameter of those arteries
right after my left ventricle to be smaller,
will theoretically raise my blood pressure.
The more vasoconstriction or plaque, the
higher my blood pressure is going to be.
So, part of it, when we talk about the
medications for treating blood pressure,
we'll look at treating both high blood
pressure and low blood pressure.
But those are some of the
factors that we deal with.
So let's go back and review.
If I asked you what are the two main
components of blood pressure?
They are cardiac output and SVR.
See if you can remember the
definition of cardiac output
by the things that cardiac output is impacted by.
What's the definition of SVR?
What are the reasons that SVR would be higher?
Okay, and when SVR is higher, is my blood
pressure also high or is it usually low?
Now, that was kind of a trick question because
it can get really complex in certain patients.
But for the most part, as a
general rule from right now
when we're starting to talk about blood pressure,
know that when SVR is higher, your
blood pressure will also be higher.
Now let's do the reverse.
What if those arteries are dilated,
what happens to your blood pressure?
It's going to drop or be lower.