Okay well welcome to another MedCram video we're going to talk about
vasopressors today so vasopressors are those very short acting medications that
we give via an IV or more likely a central line or PICC line to patients
who are in the intensive care unit who need to get their blood pressure
elevated or their heart stimulated we're going to talk a little bit more about
how do they compare and how do we use them what's the strategy that we use for
vasopressors when do we use vasopressors and why so let's talk about them now so
the first thing that you've got to understand when we talk about
vasopressin is what's going on in the circulatory system and I have here a
very generic and cartoonish cardiovascular system so I can describe
what it is that's going on so we've got the heart here and it's pumping blood
through the arterial system and it gets to some point here where it branches off
and I've made up some end organs here like the brain the liver and the kidneys
and that blood is distributed amongst those organs and we take the blood
pressure here which is basically upstream of where the regulatory
mechanisms occur and those regulatory mechanisms occur here at the arteriolar
level in these areas here okay now there are different types of receptors here
that auto regulate that now in sepsis or in septic shock where there is an
overwhelming infection you get vasodilation these are the areas where
we get vasodilation and that can cause hypotension and mal distribution of
blood which is when sometimes we use vasopressors vasopressors basically
constrict using different receptors which we'll talk about to get these
areas constricted so it increases blood pressure but as you can already see if
we constrict these areas it may reduce blood flow to the target and organs so
we'll talk a little bit more about that also as part of this are receptors on
the heart that make it beat harder and stronger so let's talk about some of
those receptors the first receptors we want to talk about are alpha 1 receptors
alpha 1 receptors basically do one thing and one thing only and that is that
alpha one receptors cause constriction okay constriction is the name of the
game that's what they do that's the only thing that they do and so when you
stimulate these alpha one receptors you will cause the narrowing of these blood
vessels which will then cause a back pressure here which will cause the
pressure in this vignette ometer to go up and that will allow the pressure to
go elsewhere in the body so alpha one receptors will cause
generalized global vasoconstriction which will cause your blood pressure
reading to go up but also notice that they could cause problems with flow to
the end organ if it is significant enough now the other type of receptor
that's in the same area our beta receptors and I'll make those green here
so beta receptors specifically beta 2 receptors and beta 2 receptors are in
generally the same area and they caused this smooth muscle relaxation so if you
stimulate a beta 2 receptor it's going to cause vasodilation it's going to
allow more blood flow to go to that target organ but since it's allowing
more blood to go through we could also get a drop in pressure so here at the
Swick manometer beta 2 receptors could cause a drop whereas alpha 1 receptors
would cause an increase in blood pressure that brings us to our third
type of receptor beta 1 receptor the beta 1 receptor basically is on the
heart and it causes the heart to beat faster so you get a higher heart rate
and you also get a stronger heart rate and so we'll say here in o trophy so it
beats faster and harder therefore basically more blood flow let's go ahead
and make sure we have that beta 1 receptor is going to cause increased
heart rate it's basically a cardio stimulant again let's review if I
stimulate the alpha 1 receptor I'm going to get vasoconstriction the beta 2
receptor phase of dilation and the beta 1 receptor more cardiac output
faster heart rate more blood flow okay so now what we're going to do is we're
going to talk about specific drugs and of course the drugs have cross
reactivity with different receptors and so it's kind of like a fruit salad so
let's go ahead and talk about some of these receptors on the top so the first
column is going to be talking about the alpha 1 receptor the second column or
the third column actually is going to be talking about the beta 2 receptor and
finally the second column is going to be talking about the beta 1 receptor and
the one at the very end which we're going to add just for clarity is the
dopamine receptor and we'll talk about that in a little bit but what we will be
talking about here are vasopressors the first one that we want to talk about is
a very unusual vaso repressor and that is actually called vasopressin now
vasopressin is made in the hypothalamus and it is secreted from the posterior
pituitary in the form of ADH but it can be given exogenously in the form of
vasopressin the typical dose that you'll see is 0.01 units to 0.04 units per
minute and the vasopressin molecule will actually stimulate a receptor that we
haven't talked about called the arginine vasopressin receptor 1a the reason why I
bring that up is because it doesn't actually hit any of these receptors but
what it does do is it causes pure basal constriction now if you think about that
that's basically good it cause pure vasoconstriction it's going to
definitely elevate your blood pressure but it could do so at the risk of
reducing perfusion and oxygen delivery to your end organ tissues ok so that can
cause anaerobic metabolism and it could also cause issues with lactic acidosis
etc so that's vasopressin we'll talk about what order to use these in
and the next one that I want to talk about is a medication called phenol
Ephraim and there's a reason why I'm going in this order I'm starting with
the most constrictive and then going to the least constrictive the other name
for this is Neos in Ephraim and the typical dose for Neos a nephron is
anywhere from 20 to 200 micrograms per minute now just like the other one this
is almost pure alpha so I'm gonna kind of draw circles here to visually show
you how powerful this is by giving it five dots okay
so it's highly stimulates the alpha 1 receptor and really it doesn't do much
else so it's basically pure alpha the next one that we want to talk about is
norepinephrine the other name for that that you'll see is Levophed and Levophed
can be dosed anywhere between 5 and 30 micrograms per minute whereas phenol
Efrain is pure alpha Levophed or norepinephrine does stimulate the alpha
receptors there's no question about it but it also stimulates the beta receptor
and also a little bit of the beta 2 receptor so because it stimulates the
alpha 1 receptor more than the beta 2 receptor you're going to get
vasoconstriction but in addition to that you're also going to get stimulation of
the beta 1 receptor so you're gonna get a little bit of increase in cardiac
output as well the next one that we're going to talk about is dopamine dopamine
can be dosed anywhere between 1 and 20 micrograms per kilogram per minute and
at lower doses you're going to get less alpha and beta and at higher doses you
get more alpha and beta let's just say for kind of mid-range doses you're only
gonna get about 3 on the alpha 1 you're actually to get about 4 on the beta 1 so
you get a little bit more cardiac contractility
again only about two on the beta 2 so you get a little bit of vasodilation and
of course because this is dopamine you're going to see quite a bit of d
receptor activation so dopamine receptor activation works predominantly in the
kidneys there has been a lot of controversy about whether or not this is
beneficial for renal perfusion and the answers have come back fairly certain in
the last number of years which shows that there is no benefit to low-dose
dopamine so don't even bother the next one we want to talk about is epinephrine
not norepinephrine but epinephrine the other name that this goes by is
adrenaline both norepinephrine and adrenaline are made in the adrenal
medulla and the typical dose is anywhere from 1 to greater than 5 micrograms per
minute you'll notice here there's a pattern all of these are in micrograms
per minute except for those that begin with the letter D dopamine which is
weight-based micrograms per kilogram per minute so epinephrine again is one of
those ones that's going to hit the alpha receptor pretty hard so I'll give it
five circles for that however it hits the beta one also pretty hard with four
and the beta two only with about three okay so you're going to get probably
some more vasoconstriction here since alpha is greater than beta two but
you're also gonna get quite a bit of cardiac stimulation and no dopaminergic
as well the next one we're going to talk about is dobutamine and like we alluded
to because it begins the letter D it's gonna be weight base so to 220
micrograms per kilogram per minute and here there's only a small component of
alpha one stimulation where this is really big is in beta one so here this
is really good to stimulate the beta one receptor so dobutamine stimulates the
beta one so if you want cardiac stimulation dobutamine is the thing for
you and also a modest amount of beta 2 stimulation so you gonna get
vasodilation so if you think about this dobutamine is going to increase cardiac
output and it's also going to cause vasodilation it's going to cause more
contraction and more vasodilation so if there's one medicine that's going to
increase cardiac output tremendously it's dobutamine although you may not see
the effect in a higher blood pressure so this is a situation where you may
actually start W to mean the blood pressure may actually go down slightly
but your cardiac output is increased tremendously and then there's one more
medication that I want to talk about here which kind of takes it to its
extreme and that is a medication called isoproterenol doesn't begin with the
letter D interestingly and anywhere from 0.5 to 30 micrograms per minute so once
again those vasopressors that begin with the letter D are micrograms per kilogram
per minute micrograms per kilogram per minute the other ones are all mics per
minute mics per minute mics per minute mics per minute except for vasopressin
of course which is measured in units per minutes but isoproterenol believe it or
not is just nothing but pure beta so here we've got five out of five in terms
of beta one and we have five out of five in terms of beta two and so here you're
really going to get just the tremendous amount of beta stimulation both in the
heart and vaso dilatory that's basically the vasopressin us for the next video
where we actually get into the clinical aspects of what medication we're
actually going to use for what and where for sepsis for congestive heart failure
and for pacing and things of that nature thanks for joining us
you