So we've learned our
human dynamic values.
Now we need to learn the concepts
and how to apply these values.
Let me go over a little bit of
definitions and principles for you.
Hemodynamics, what it means is
the measurement of blood flow.
That's all it is.
This was first
discovered in 1628.
What's important to know
is that the clinicians
must know how to
interpret the data,
and how to apply
the data correctly.
When we're just learning
this, there's a key to it.
And that key is to
simplify it into basic
terms and understanding
and then we can start
building on top of it.
I want you to remember that
oxygen delivery is the goal.
When I first started
I got these algorithms
of oxygen delivery is DO2
which equals cardiac output and calcium
and what is cardiac output and what caO2.
And then we learn about what's
oxygen consumption, that's your CVO2
and all this and it looks
all like a big mumble pile
of basically stuff that
I don't understand,
especially when I'm starting.
All you need to know is the goal of
our heart and our vascular system
is to get blood and
oxygen to the body.
That's all this is saying with oxygen
delivery and oxygen consumption.
Just keep in mind,
let's simplify it.
The goal of the heart and
the vasculature system
is to get blood and
oxygen to the body.
So if the goal of our
heart and our vasculature
is just to get enough
blood to the body,
how do we know that's happening?
How do we know that the heart
is getting up blood to the body?
Well, we have a value called
the mean arterial pressure.
This is the average pressure
in our clients arteries,
we have a systolic and
diastolic on our blood pressure.
But the mean arterial pressure is a
better indication of organ perfusion.
We want that mean arterial pressure
between 60 to 65 or greater.
If it's 65 or greater,
then we know that we're getting
enough perfusion to all of our organs.
If it's under 60 or under 65,
then we may not have
enough blood pressure
and enough blood volume
getting to all of the organs.
So how do we look at
the blood pressure?
And how do we look at
the determinants of that?
Well, I've divided these into what's
called the four parts of blood pressure.
So looking at a blood pressure,
what makes up a blood pressure?
What makes up the mean
They're divided into two areas,
two parts of the heart and
two parts of the vasculature.
Let's look at the heart.
So what determines the blood
pressure with the heart?
You have what's
called the heart rate,
and you have the
contractility of the heart.
We'll look at those a
little bit more in depth.
Then over to the vasculature,
what two parts of the vasculature or the
body make up a patient's blood pressure?
That's vascular resistance
and fluid volume status.
Let's look at these
a little bit closer.
Well, with heart rate we look at,
we can look at our ECG monitor
to get how fast our heart rate
is, we can also take a pulse.
But what's important to know
is that with heart rate,
we also need to know the heart
rate rhythm so that it's normal,
because you can affect
your blood pressure
if you're in a different rhythm,
like atrial fibrillation or sinus tach.
So it's not just the heart rate,
but also the heart rate rhythm.
So we really want to look at our ECG
monitor to see what our rhythm is.
Now, how do we look
Well, the best way to look at our
contractility is often echocardiogram,
so you can actually see the
heart and see how it's squeezing.
But we don't always
get an echocardiogram.
So you could secondarily look at your
contractility with cardiac output.
We're going to dive into that a little bit
deeper so that we have an understanding
because you can't look at your
cardiac output, and it's low and go,
"Okay, my contractility
is not strong enough."
because there's so many
determinants into it.
But we'll get into that
a little bit later.
Just know that the best way to look at
your contractility of your left ventricle
is your echocardiogram.
Now, how do we look at
How do we look how tight or
how dilated our vasculature is?
Well, we have our systemic
that lets us know if we're
vasoconstricted or if we are vasodilated.
And then fluid volume status.
How do we know if we're hypervolemic,
normal volimic, hypovolemic,
if we need fluid,
if we need to take some fluid out,
how do we know that?
we have our CVP and our PAD,
our central venous pressure and our
pulmonary artery diastolic pressure.
Those are the pressures going into the
right ventricle and into the left ventricle
that can indicate
fluid volume status.
But we're going to use those as trending
numbers not as absolute numbers.
We can also use what's called
your stroke volume variance,
or your delta stroke volume.
Let me talk about these a
little bit more in depth.
Stroke volume variance is just the change
in the stroke volume from beat to beat.
So let's say we have a
stroke volume of 80 mLs,
and then the next beat 72
mLs and the next beat 85 mLs.
So it's going to measure
the percentage of change,
we want it up under about 13%.
If it's above 13%, that's an indication
that we do not have enough fluid.
But there's some
barriers to this,
we have to make sure that
we are in a normal rhythm.
We cannot have any
What that means is that the atrial
contracts and then the ventricle contracts.
So we cannot be in AFib,
we cannot be in aflutter,
or we can't be in a heart block.
That will cause AV dissociation.
And that'll give us an
inaccurate stroke by variance.
We also have to be intubated
so that we have the same
amount of pressure in there.
If we breathe big one time,
and then we breathe smaller the next time,
that difference in pressure will
change our stroke volume variance.
Delta stroke volume is probably the best
way to identify our fluid volume status.
What that means,
what delta means is a change.
So what we're looking at is what's the
change in stroke volume after a bolus.
So we look at our stroke volume,
you can also use cardiac index.
And what you want to see is if you
give a bolus and I'm talking real fast,
it only has to be a
bolus of 250 to 500.
But we really need to bolus it in not
just put it to gravity really quickly,
or not just put it on the
pump to 999 mLs an hour,
but actually put a pressure bag in
and get it in there pretty quickly.
So once that said we're gonna
look at our stroke volume,
and if it increases
by 10 to 15%,
that lets us know that we are still
hypovolemic and we need to add more fluid.
So then we can keep giving
boluses of 250, 500,
maybe even 1000 depending on
what's going on with the patient
to get to our optimal
So, with delta stroke volume,
we're going to give a bolus,
we're going to give it
as quickly as we can,
and we're gonna see the percentage
of change in the stroke volume.
So if it's greater
than 10 to 15%,
then that lets you know you need to
keep giving a little bit more fluid
until we get under a
change of 10 to 15%.
Then we are called
what's fluid optimized,
meaning we don't
need any more fluid.