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


welcome to another MedCram lecture
we’re going to talk about hyperkalemia hyperkalemia like anything else that
ends in e mia has to do with the blood and the k if you remember from the
periodic table has to do with potassium so we’re going to talk about high
potassium in the blood and that generally speaking is greater than 5.0
but of course the higher it goes the worse the symptoms can become so the
normal range for potassium is about 3.5 to 5.0 this is an extremely well
regulated system potassium has to be very well regulated in the blood and the
reason is is because the conduction system in the heart
specifically and also in the muscle depends heavily on potassium going
through the membrane and so the conductivity to potassium is very high
so that if there is a problem with the concentration of potassium outside the
cell it’s really going to affect the depolarization of those cells and so
potassium abnormalities are really going to hit the heart quite hard and cause
arrhythmias and that’s why the body is so keen on protecting the level of
potassium so we’re gonna talk about the causes of hyperkalemia the
manifestations of hyperkalemia and the treatment of hyperkalemia okay so let’s
talk about the causes the first cause is excessive tissue release or trans
cellular shifts okay so you can think about for instance diabetes remember
what happens in diabetes is there’s a lot of glucose around the cells so
you’ve got a cell here and you’ve got glucose outside the cell and that causes
water to leave the cell and for it’s something to do something called
coronation shrinks basically and when that happens the potassium concentration
which is already high in the cell is actually going to go up and this causes
leakage of potassium outside the cell and the fact in diabetes is insulin
which especially in type 1 diabetes is rare and insulin is responsible for
putting potassium back inside the cell okay so that’s an important note is that
insulin causes potassium to shift back into the cell and in a patient with
diabetes the glucose is high that causes eventually potassium to leak outside the
cell since there’s no insulin it cannot be put back inside the cell another
corollary to this is something called HH or hypo Ren anemic hypo aldosterone ism
okay so that’s hypo renin the renin is the thing that this should be
stimulating the adrenal cortex to make aldosterone but as a fact that it
doesn’t you get hypo aldosterone now remember aldosterone works on the
distal convoluted tubules right about there and remember what it
does it causes potassium excretion and sodium reabsorption at the distal
convoluted tubules so if you don’t have enough aldosterone
being secreted from the zona glomerulosa of the adrenal cortex you’re gonna get
an accumulation of potassium inside the serum the reason why I bring this up
together is this hypo Renick hypo aldosterone ism can be seen together
with diabetes so that’s just one cause of hyperkalemia
the next cause is kind of obvious and that’s just increased intake of
potassium so you got to kind of know what has potassium in it and some of the
things that have potassium in it our salt substitute so instead of having the
cation sodium that has the cation potassium the other thing that you can
see is the excessive intake in renal failure these people who are in renal
failure typically are the ones that are on salt substitutes and this potassium
cannot be cleared the other one that we kind of talked about if the zona
glomerulosa of the adrenal cortex is not secreting aldosterone is you will see
adrenal failure this is otherwise known as Addison’s disease however if it is a
problem with the pituitary not stimulating the adrenal cortex the
aldosterone still is secreted in sufficient amounts that you may not see
hyperkalemia however if there is a direct attack on the adrenal cortex
where antibodies are destroying all three layers then your aldosterone
levels will be low and you will see hyperkalemia in addition to all of the
other things that you would see in adrenal failure for instance
hypoglycemia hyponatremia and metabolic acidosis the last thing that you would
see is of course in a potassium sparing diuretic so some examples of this would
be spironolactone or a miller ID incidentally other medications that
could also increase your potassium are things that can also affect shifting of
the cells or affect the other areas that we’ve already talked about the ones that
you should know about our ACE inhibitors so remember ace inhibitors inhibit a
switch is angiotensin converting enzyme which is in the lungs and that’s going
to affect the ability to make aldosterone the other thing that can do
this is beta blockers we’ll talk about treatment with beta agonists later but
beta blockers can affect shifting of potassium and actually caused it to go
out of the cell another cause is something that’s interesting and it’s
called pseudo hyperkalemia and it’s really based on the fact that all cells
in the body have high concentrations of potassium in it so where you see this is
if you have a patient with many cells that are drawn in a test tube so if you
have marked leukocytosis or thrombocytosis so they’ll be in
platelets as well and you get coagulation in the test tube that causes
these cells to lyse and release their potassium
when you put this through the laboratory equipment you’re gonna see elevated
potassium and they’ll sometimes tell you if they see this and they’ll say
hemolysis and if you get hyperkalemia and they say by the way hemolysis was
three plus then you may have to take that with a grain of salt so to speak
and maybe repeat the test again to see and redraw the blood actually because if
once there’s human lysis you really need to get a new blood draw on that specimen
okay let’s talk about manifestations of hyperkalemia
what would happen really has a lot to do with the heart and the reason is is
because the conductance of potassium in the depolarization of cardiac conduction
cells is quite high such that potassium is always leaving the cells and so what
happens is you have a positive charge leaving the cell okay what’s that going
to do that’s going to generally make the inside of your cell negative and that’s
exactly what we see here down to close to negative 90 millivolts you’ve got
this negative the problem here is is that when you have an abundance of
potassium in the solution in the serum in other words when you have
hyperkalemia these potassium ions are not going to leave the cell as quickly
and so whereas you would have a very negatively charged cell it’s not going
to be so negatively charged you’re going to get something called depolarization
so these cells are more excitable and as a result of that not only is it
depolarized but instead of having a nice sharp
uptick it’s going to come up more slowly and the repolarization is going to be
somewhat dampened okay as a result of that when you look at a nice QRS complex
instead of having a discrete P wave q r s t what you’re actually going to see is
the P wave is almost going to be non-existent the R wave is going to sort
of come up slightly you’re gonna have this s depression and then this T wave
and it’s almost gonna look sinusoidal and of course the higher the potassium
and the faster the potassium has gotten high the more quickly you’re gonna see
this if somebody is camping out at five to six and they go up to seven you’re
not gonna see those changes because the body has a chance to adjust perhaps but
if someone is living in the 3s two fours and then jumps up to seven you’re more
likely to see that the first thing that you’ll see with hyperkalemia is you’ll
actually see peaked t-waves okay that’s the first thing that you’ll
see and then eventually you’ll just see this thing go sinusoidal so it’ll just
kind of go like this and you’ll just go into cardiac arrest so what should you
know about manifestations you will have depolarization due to low potassium
conductance lower than normal and then after that you’ll get hyper polarization
due to inactivated sodium channels you’ll have this reduced phase zero
velocity okay and you’ll have decreased membrane excitability and then you’ll
get increased potassium conductance and accelerated repolarization okay so what
should you know what would they actually test you on a test about hyperkalemia I
think the thing that they would test you on is number one no that peaked t-waves
is the first sign that you’ll see number two if it eventually gets high enough
you’ll get this sinusoidal wave and number three hyperkalemia in general is
going to affect the heart and all of this is an emergency now in the next
video we’re going to talk about the treatment of hyperkalemia and some of
the reasons why this treatment works you


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