By Adem Lewis / in , , , , , , , , , , , , , , , , /

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

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