Hypertension Explained Clearly by MedCram.com | 2 of 2

Hypertension Explained Clearly by MedCram.com | 2 of 2


welcome to part 2 of hypertension
we’re going to talk about the others in the last lecture in part 1 we talked
about the ABC DS which was the ACE inhibitor ARB for a the beta blockers
for B the calcium channel blockers for C and the diuretics for D I don’t want to
get into the other medications that we use for hypertension maybe not first off
the bat but further on down we’ll talk about them one by one and so the others
is what we’ll be talking about today the first one we’ll talk about is the
alpha blockers so alpha blockers and they do exactly what they say they block
the alpha receptor particularly the alpha 1 receptor so in the peripheral
vasculature you’ve got two things that can happen you can have vasoconstriction
or you can have vasodilation and the vasoconstriction is mediated by an alpha
1 receptor whereas the vasodilation is mediated by the beta receptors now you
should know just as a way of reminding you that there’s a medicine out there
called dobutamine just this wave reminder of if you want to have more
information about this look back at our septic shock lecture dobutamine is pure
beta which is great for the heart is it will make the heart rate go up and be
more strongly contractility goes up but it also stimulates the beta receptor
which causes vasodilation so that’s why dobutamine is not really known as a vaso
constrictor or vasopressor but more of a positive inotrope but yet I digress so
let’s go back to our alpha blockers so if you’ve got alpha receptors on this
peripheral vasculature which is causing vasoconstriction that’s obviously going
to increase your blood pressure if I were to block those I wouldn’t get this
vasoconstriction in other words I could cause vasodilation which would reduce
your blood pressure so typically these alpha blockers end in Osen or o s I and
so process into R as a sin all of these things are alpha blockers
so the thing to remember about alpha blocker the thing that they will test
you is indications obviously it’s used as a blood pressure medication but it’s
never really been shown to reduce mortality in congestive heart failure in
myocardial infarction so really there’s no indication for reduction in incidence
of my carbon for a congestive heart failure but it does reduce blood
pressure so if you just want numbers to reduce blood pressure it may be
effective the other thing that you should remember about alpha blockers is
sometimes it can actually as an alternative also be used to prevent
nightmares in PTSD so they may ask you that on boards the other thing to
remember probably the biggest thing to remember is this thing is a side effect
called first dose hypotension now the thing to remember about first those
hypotension is if your body is not used to taking it you could really impair
your body’s ability to vasoconstrict and this is important if for instance you’re
standing up if you stand up you need vasoconstriction
so that all of the blood doesn’t rush to your feet not to your head and you could
pass out so that’s really what you’ll see is first those hypotension or first
those orthostatic hypotension as a result of this we’d like to have the
first dose taken right before bedtime so take it what we call pio orally qhs that
means every night before bed so that most of that first dose hypotension
occurs while you’re already laying down asleep now the other thing you should
know about these alpha blockers is really where they’re mostly used they’re
not really used a lot in hypertension they’re usually usually used in
prostatic hypertrophy or b ph benign prostatic hypertrophy it’s benign in
terms of the fact that it’s not cancer however it can cause neuropathy
obstruction and kidney failure if it’s not treated adequately and the reason
why does this is for it’s very same principle that it causes relaxation
of not only in this case the blood vessels but also the smooth muscle right
before the urine it comes out through the urethra
okay the next medication I want to talk about is different class although it
sounds very similar and that’s the alpha-2 agonist now you just said that
well alpha one blockers are going to reduce high blood pressure why would an
alpha agonist reduce blood pressure well it’s because of where it is it’s an
alpha 2 the key there is alpha 2 and the probably the best example of this one is
clonidine now whereas the alpha that we were talking about before works on the
blood vessels the alpha 2 that we’re talking about those receptors are
actually in the brain okay there’s my there’s a little bit better
picture of a brain okay and so in the in the central brain stem
there are alpha 2 receptors that are actually feedback mechanisms and if you
can stimulate those it’ll actually ramp down the sympathetic tone so if you want
to know the more pathophysiological explanation basically clonidine
stimulates these alpha 2 receptors in the brain which reduces cardiac output
and peripheral vascular resistance lowering blood pressure so it
specifically binds to these presynaptic alpha 2 receptors and so when you’ve got
this synapse basically down here okay and there’s little alpha 2 receptors
here when you stimulate those it actually reduces the calcium in the pre
synaptic cleft and it inhibits the release of norepinephrine which causes
low blood pressure okay so that’s the that’s the mechanism so what do you need
to know about these things well clonidine is a medication because of its
central action it also in addition to lowering blood pressure it also can be
helpful in opioid withdrawal okay so that’s something that it’s also
used for it comes it comes in two different forms it can come in an oral
form Pio and it can also come topically as well which may be helpful in patients
who can’t swallow pills or patients are in the intensive care unit things of
that nature climbing patch be aware of course that
the clonidine patch is dosed q week whereas the p o– is dosed tid three
times a day okay now as a result of all of this you’ve got to remember that
because it acts centrally you have a big problem
with withdrawal withdrawal of the medication think about this on exams
where you’ve got a patient that came in with clonidine and it wasn’t continued
and as a result the patient becomes what would they become they would become
hypertensive and also tachycardic so be aware of that so that’s clonidine it can
be it’s got a number of uses it can also be used for as I mentioned opioid
withdrawal heroin withdrawal all those sorts of things but it’s also used in
hypertension so just be aware of it I think those are the the key points that
you should know okay let’s talk about nitrates I’m sure you’ve heard of
nitrates before nitrates are pretty cool so let me kind of draw what we’re
talking about what nitrates are used first of all they are used for blood
pressure of course but they cause vasodilation and specifically they cause
more and this is the key here veno dilation although they do cause
vasodilation too why is this important this is important because of perfusion
to the myocardium let me explain so what you have here is you’ve got
myocardium okay and here you have the arterial side and it’s going in to feed
the myocardium okay and then where does it come out comes
out to the veins and it collects into the coronary sinus
and it dumps into the right atrium so if you want to get more oxygen profusion to
the myocardium it’s going to be dependent on the flow to the myocardium
so this myocardial tissue and that’s going to be the difference in pressure
between the arterial supply and the right atrium anything we can do to
increase the pressure in the coronary arteries with respect to the right
atrium is going to improve myocardial oxygen supply so when you give nitrates
because it’s a vino dilator because remember the veins also dump in to the
right atrium so if we reduce the pressure in the veins it’s going to
reduce the pressure in the right atrium and as a result of that it’s going to
increase the difference in the pressure and that’s going to give more flow to
the myocardium this is the major reason why nitrates are used in ischemia and
cardiac ischemia so yes nitrates are great at what we call preload reduction
and as a result of that they can increase myocardial oxygen perfusion the
other thing they do is they reduce afterload that’s very important as well
especially in patients with congestive heart failure let me explain you’ve got
the thoracic cage in that thoracic cage sits your heart then you’ve got the
aorta coming out and going down into your body if you’ve got very very high
afterload the heart has to pump against that after load and as a result of that
there’s a there’s a big back pressure and so let me demonstrate that using a
graph here is the after load here is where the
heart sits in terms of pressure in the chest and here is where the aorta is and
the heart has to take blood at that level and pump it up to this level
before it’ll jecht through the aorta this difference is known as afterload
okay if we give somebody a nitrate yes it does reduce preload but it also
reduces after load and so instead of the pressure in the aorta being up here it’s
now moved down to here that reduces after load and now there’s less pressure
that the heart has to pump against and therefore this can help in someone with
congestive heart failure who has pulmonary edema so we see nitrates used
in myocardial infarction congestive heart failure ischemia and it also
reduces blood pressure the other thing I should tell you is that in patients who
cannot tolerate beta blockers we have already said that they are key in
patients with congestive heart failure an alternative to beta blockers is
nitrates plus hydralazine we’ll talk about hydrolyses next but if you can use
these two together if you cannot use beta blockers in congestive heart
failure alright so those are nitrates typically
the thing you should know about nitrates is that it’s absolutely contraindicated
in patients with right ventricular heart attack or right reticular myocardial
infarction or RV failure they call it so don’t do it in RV failure the other
thing you should know is every day there should be a nitrate free interval that
means if you continuously use nitrates the patient becomes used to it and you
need to have a moment during the day where the patient is not on nitrate so
usually we’ll do it for the greater part of a day and then take it off take the
patch off or have a nitrate-free interval okay
let’s talk about hydralazine hydralazine is simply a vasodilator and that’s
obviously going to cause the blood pressure to go down so it reduces a
blood pressure by causing vasodilation more than it does vino dilation the the
problem I guess that you should know about hydralazine is it needs to be
given four times a day qid it can be given IV or Pio and it
can’t be given in combination with nitrates as we mentioned in congestive
heart failure patients especially in african-americans seems to do pretty
good the one thing that you should know is that if you give it for too long you
can get a lupus like condition which goes away with withdrawal so it does go
away they may test you for that on boards if you’ve got a patient who’s got
hydralazine so the thing about hydralazine is is that a vasodilator you
can expect if it’s going to cause vasodilation what’s the body going to do
as a result of that it’s going to see that there’s more volume so you might
notice that your heart rate will go up and you also may notice that you retain
fluid so some things that you may need to add to the patient who you’re
starting them on hydralazine is something that will slow heart rate down
like a beta blocker and if the retaining fluid you may need to add something like
a diuretic okay so just be aware of that okay so
let’s talk about minoxidil minoxidil is a vasodilator it actually hits potassium
channels causing the hyper polarization of the cell making it less likely to
vasoconstrict what you see there in minoxidil is also
hair growth so it’s used topically so just be aware that if it’s used as a
blood pressure medication that it can cause hair growth especially
if it’s used topically obviously it’s it’s indicator for male pattern baldness
but it’s going to drop blood pressure I find that it’s very helpful in some my
end-stage renal disease patients if we can’t get the blood pressure under
better control however I would I would not go to minoxidil without a
nephrologist involved and just be aware that minoxidil is kind of one of the
last things that you would go for I don’t see it being tested that much just
be aware of its other indication so last one I want to talk about which is a nice
medicine is spironolactone now spine relax own is a diuretic and as such we
probably should have talked about it during the the first lecture that we did
and if you haven’t seen that lecture I would recommend that you look at it the
reason why I left it here is it kind of stands on its own a bit as you recall
the nephron the proximal convoluted tubule you’ve got the loop of Henle
collecting tube you’ll remember in the distal convoluted tubule you have a
sodium potassium pump where you’ve got sodium being reabsorbed and potassium
being dumped and that would be stimulated by a hormone called
aldosterone if you don’t remember that look at the adrenal gland lecture that
we’ve done i remember just go to med cram videos and you can see all the
lectures that we’ve done but remember aldosterone is a steroid hormone
secreted from the zona glomerulosa of the adrenal cortex spironolactone is a
very similar-looking structure that blocks that and therefore inhibits this
kind of action in the distal convoluted tubules and it’s a diuretic in that case
it’s a potassium sparing diuretic as well so you’re going to get not
potassium necessarily going up potentially but not going down as much
as the other diuretics would now the thing you should remember about
spironolactone is that it is indicated in CHF in patients with New York Heart
Association class three and four who have an ejection fraction
of 35 percent or less okay so they did a trial back in 1999 that was reported in
the rails trial the trial was actually discontinued early due to the unexpected
benefits there was actually a 30% reduction in the risk of death and a 35%
reduction in hospitalization for the patients that were receiving
spironolactone and so it’s it’s good to use this in a patient with congestive
heart failure and this kind of goes along with everything else in congestive
heart failure seems as though everything that raises
potassium is good so beta blockers raise potassium are good ACE inhibitors raise
potassium are good spironolactone raises potassium it’s just kind of a nice way
to remember everything so congestive heart failure now what about the side
effects obviously hyperkalemia is something
you’ve got to watch for the other thing that they looked for and we’ve got to be
careful of especially in these patients with congestive heart failure is the
creatinine so if these patients have a crack knee that’s worse than you know
three three and a half things of that nature you’ve got to be very careful
with that so acute renal failure is something you’ve got to watch for
there’s also something else that you’ve got to watch for and that’s gynecomastia
okay so if they’ve got gynecomastia that could be a result of the spinal a stone
again probably because it is a steroid hormone blocker and so when you when you
block those hormones you allow the gynecomastia to occur
well now fortunately there’s a new medicine that’s sort of a new version of
Spira lactone called EPL e r e and o and a pleura known this doesn’t cause the
gynecomastia the sexual side effects because it’s a little bit cleaner it’s
specifically this a player known is specifically indicated for the reduction
of cardiovascular death in patients with heart failure and congestive heart
failure dysfunction within three to 14 days I’m going to acute myocardial
infarction so post mi with congestive heart failure in the Ephesus trial
this lowered the risk of death and never needed to treat of 41 to save one life
which is pretty impressive so that’s something else to think about and keep
in the back of your head that if you’re looking for spiral lactone without the
gynecomastia think of a player known it’s relatively new medication but also
indicator for congestive heart failure so we’ve talked about in a hypertension
we’ve talked about what defines it what the indications are for treating it and
again I want to emphasize that all of these things can reduce blood pressure
but you want to match up what the patient’s diagnosis are with the right
type of medicines to use so that you can maximize the benefit and minimize the
side effects and I think that’s what they’re going to be testing you on on
the test and knowing the side effects so please go ahead and look at some of the
other lectures and we will continue makes very much for joining us you you