00:01
Our next hemodynamic concept and
value is Systemic Vascular Resistance.
00:06
We've kind of talked about
this a little bit more,
let's dive in a
little bit deeper.
00:10
Systemic vascular resistance
normal is 800-1200 dynes.
00:15
Remember that, 800 to 1200.
00:18
Basically, it's the resistance to blood
flow of coming out of that left ventricle.
00:24
What's the pressure that that
left ventricle has to overcome
to get the blood
flow to come out.
00:30
What affects systemic
vascular resistance,
the diameter of our arteries,
the length of our arteries,
and the viscosity of our blood affect
a systemic vascular resistance.
00:42
Now, like I said,
the normal is 800-1200.
00:45
If you have a systemic vascular
resistance more than 800,
that means your arteries
are more dilated.
00:52
And if you have a systemic vascular
resistance closer to 1200 or greater,
your more vasoconstricted.
00:58
We'll look at that with a little
bit of animation here later.
01:04
Now, increased afterload.
01:06
What increases the pressure that
your heart has to beat against
to get that blood flow out?
Hyperthermia, aortic stenosis,
cardiogenic shock and certain medications.
01:17
Anything that would cause your
vasculature to vasoconstrict
is going to increase that
systemic vascular resistance.
01:24
Hyperthermia, if you're cold,
you're vasoconstricting,
you're shutting all
that blood to your core.
01:29
Aortic stenosis is actually that
aortic valve is really tight.
01:32
And in order to pop
that valve open,
that left ventricle has to contract
really hard to get the blood flow out.
01:38
So the SVR is
really high on that.
01:40
Cardiogenic shock causes extreme
vasoconstriction of your vasculature.
01:45
And there's specific medications
like Levophed, vasopressin,
phenylephrine and dopamine.
01:50
Well, they cause vasoconstriction
as well increasing that afterload.
01:54
So we talked about what
increases afterload,
let's talk about what
decreases afterload.
01:59
Anything that causes
vasodilation of your arteries
would cause a
decrease in afterload.
02:05
So anaphylactic or neurogenic shock,
extremely vasodilates those arteries.
02:10
Hyperthermia, when you're running a
fever, you're going to vasodilate.
02:15
Sepsis causes vasodilation
and specific medications
such as nitroglycerin, nitroprusside,
nicardipine and cleviprex
causes vasodilation of those arteries
and decreasing that afterload.