Now, we talk about the
opposite end of this spectrum,
we just talked about high blood pressure.
I want to talk about low blood pressure,
that's also called hypotension,
which is pretty easy to remember,
because high blood pressure is hypertension,
so low blood pressure is hypotension.
So, the problem comes at when I
don't have enough blood pressure,
that means I'm not moving enough of the
oxygenated blood around in my body
to adequately take care of all
my cells and tissues and organs.
So, when my blood pressure is too low,
I have inadequate tissue perfusion.
I don't get enough oxygen to
my organs and my tissues.
So, be very clear as we step through, why
is low blood pressure such a big deal,
because if it's low enough, then I'm not
getting good tissue or organ perfusion,
you're not going to feel good.
Let's talk about the things that you start to feel.
The patient might become, kind of, dizzy
and lightheaded and they could even faint.
They won't be able to really
think clearly because,
again, their brain is not getting perfused.
They might have some vision changes and get
kind of blurry or can't really focus on things.
Their skin is going to become
very cold and clammy.
Do you know why?
So, super cool thing that your body does.
When the body says, "Whoa, blood pressure is low,"
it tries to shunt all the blood toward
the most important things;
your brain and your heart.
So your skin gets cold and clammy because…
it shunts everything away from fingers
and toes and extremities into the trunk,
and particularly selfish,
is the heart and the brain.
So that's why the extremities get cold and clammy.
You're also going to feel pretty
nauseated, that's not a real warm feeling.
When someone's blood pressure is really
low, that's going to be problematic.
I actually was hospitalized 1
time for a pulmonary embolism.
They didn't know that at the time, but
my blood pressure was in the 60s,
and that is the absolute worst
nausea I've ever experienced.
I've never taken chemotherapy, but that
nausea would come over me like a wave,
and I have never experiencing
anything like it before or since,
nor am I interested in
experiencing anything like that.
But low blood pressure can cause
some really significant nausea.
Of course, you are going to be pretty tired
and you say just don't have the energy.
Sometimes, even patients who had
previously had a high blood pressure
and we put them on antihypertensives
to lower their blood pressure,
they can feel the same things.
They can feel kind of tired and
fatigued as we go through it.
But these are definite symptoms
that a patient will feel
if their blood pressure is too low to perfuse
the tissues and organs in their body.
So you want to recognize, we almost have
more symptoms for low blood pressure
that the patient can actually feel and report
to you, than we do for high blood pressure.
Some people actually may tell you things that
they normally feel with high blood pressure,
but usually, the patient can relate to
the symptoms of low blood pressure
and can communicate those to you much
more clearly than high blood pressure.
So how do you end up with low blood pressure?
Well, think back to what we
know about blood pressure.
2 things: cardiac output and
systemic vascular resistance.
So, as far as cardiac output goes,
if the heart rate is lower,
we call that Brady, meaning
slow, cardia, slow heart.
So if you have a lower heart rate, that
can cause your blood pressure to be low.
If you have a significant
decrease in blood volume,
hey, those are 2 factors that are
significant with cardiac output.
So, if I have less volume on board, I'm dehydrated,
maybe I took a diuretic, maybe I was…
I had extended vomiting or severe diarrhea,
you know, anytime you have
a high fever for a long time,
you're vomiting, or you have severe
diarrhea, you're losing lots of fluid.
So, fevers for a long period of
time cause you to be dehydrated.
Vomiting, you're losing lots of fluids
and not usually taking much in.
And in severe diarrhea, you're losing a lot of
fluid in your stool that you normally would not.
So, these 3 things can make
you extremely dehydrated.
Most at risk population for dehydration
would be our very young and our very old.
They can become dehydrated even quicker than
an average, middle-aged, healthy adult.
So, I'm going to always watch a patient
who I think is severely dehydrated
for signs of low blood pressure.
Now, if you live in my state,
it's really hot where I live,
and when those kids are out doing
2-a-day football practices,
they have to be on them like crazy to make sure
that they're replacing the
fluid that they're losing
because of the heat and because of the exercise.
Otherwise, they're going
to end up with heatstroke,
which definitely involves
a very low blood pressure
because they have low volume on board.
On top of that, we've talked about diuretics.
Those are drugs that encourage fluid loss,
and that's usually for a good reason.
We use diuretics often…remember, those
are drugs that encourage fluid loss.
We use diuretics for people
with high blood pressure.
Because think back to what you know about
blood pressure, cardiac output and SVR.
If I have less volume on board, I have a lower
cardiac output and a lower blood pressure.
So using an appropriate amount of diuretic is a
really good way to bring blood pressure down.
But sometimes, if that ratio gets off a little
bit, that can really drop their blood pressure.
Now, there's medications…other medications
that can cause low blood pressure.
If we have you on a blood pressure medication,
an anti, against, hypertension medication,
that may drop your blood pressure too low.
So I always say, anything a drug can
do well, it can also do over well.
So we put you on an antihypertensive and
now you end up with low blood pressure.
Nitroglycerin is a vasodilator.
Now you may know someone who's on nitroglycerin.
Sometimes, they have patches that they wear.
They take them off at night, so
they don't build up tolerance.
They have little tiny pills that they carry
with them in little brown glass bottles,
so the light doesn't get to them, and
they put them…underneath their tongue.
But that's a vasodilator.
Anytime I make the diameter of the
vessels bigger, you've got some issues.
Now, this doesn't go after arteries.
Nitroglycerin goes after your veins.
And what happens is blood kind
of pools and hangs out here,
and not as much blood comes back to my heart.
So it makes your body feel
like there's less volume.
So when someone takes nitroglycerin,
it should lower their blood pressure.
Other vasodilators will do the same thing.
You end up with more blood staying out
here, less is coming back to the heart,
so that's why you end up
with a lower blood pressure.
So there are medications that can cause
your patient to have low blood pressure.
There's another term, orthostatic hypotension.
That's where a person who…either low volume
or they're on a blood pressure medication.
If they're lying down and they sit up too quickly,
or if they jump up and stand up too quickly,
they're going to…the room starts to spin.
That's orthostatic, depending
on their position, hypotension.
It takes our body a minute to kind of readjust.
So when you're having patients that
are on antihypertensive medications,
kind of want to recommend to them,
"Hey, if you're laying down, sit up
slowly and wait for a couple seconds
just to make sure you're acclimated,
and then stand up slowly and
give yourself a couple seconds
just to make sure that you're not dizzy
because of that orthostatic hypertension."