Rehab Cell

Physical Medicine and Rehabilitation

Hyponatremia Explained Clearly – Symptoms, Diagnosis, Treatment

Hyponatremia Explained Clearly – Symptoms, Diagnosis, Treatment

okay welcome to another MedCram lecture
now I’ve got a lot of requests out there to talk about a very difficult topic
we’re going to talk about hyponatremia okay low sodium now this is a very
complicated topic because we have to talk about water balance we’ve got to
talk about the difference between osmolality and tonicity and antidiuretic
hormone and aldosterone and compartments of fluids and the different types of
hyponatremia are the isotonic are they hypotonic hypertonic and then of the
hypotonic hyponatremia is is it hypovolemic hypervolemic a nice oval
emic and it just goes on and on and on but I think after you get done with my
series here in fact I know after you get done with my series you’ll be able to
work through how to deal with the different types of hyponatremia so to do
that we have to build a little bit of a foundation so you can understand what
we’re talking about so bear with me and go through these lectures and you’ll see
that it’ll build on one another just like our other series on acid-base okay
so the definition of hyponatremia is a sodium concentration of less than 135
milligrams per deciliter okay that is basically the definition anytime you
have any word that says amia at the end it’s relating to the concentration of
sodium in this case sodium or any other molecule in the blood so hypokalemia
alkyl emia acidemia all of that is related to the blood so let’s go ahead
and build the foundation the first thing that you should know is what is the
definition of osmolality so osmolality OS m o l al ity so that’s serum
osmolality as an equation and it’s two times the sodium concentration plus the
glucose concentration / 18 and that glucose concentration is
in milligrams per deciliter plus the B UN and please look at our acute renal
failure lectures to get a update on the B you win and that’s again in milligrams
per deciliter divided by 2.8 and the normal for that is 285 millimoles per
kilogram you can also say milligrams per deciliter as well so that is the
definition of serum osmolality 2 times the sodium plus glucose divided by 18 +
bu n divided by 2.8 and that’ll tell us if something has a basically a low
osmolality a normal osmolality or a high osmolality now something that’s very
similar to that is tonicity it’s a very similar concept and you’ll see it looks
very similar it’s two times the sodium concentration plus the glucose divided
by 18 once again so why is it missing the B UN component it’s missing the b1
component because B UN can go freely between the plasma membranes and so
therefore if b1 can go between plasma membranes it really doesn’t have too
much of an effect on the difference between the inside of the cell and the
outside of the cell so from now on what you’ll see is we’ll use tonicity and
osmolality interchangeably but just be aware that if they ask you to calculate
the osmolality of something this is the equation that you should use okay we’ll
come back to that again and again the other thing you should know about is two
major types of hormones one of them is ADH this is antidiuretic hormone
antidiuretic hormone is secreted from the posterior pituitary it’s actually
made in the hypothalamus but it’s secreted from the posterior pituitary
and if you could remember where this works it works at the collecting tubules
of the nephron and the presence of ADH at the
collecting tubules of the nephron causes water reabsorption and what’s that going
to do what’s reabsorption going to do it’s going to cause water not to go out
to the urine but to be reabsorbed into the blood and basically it’s going to
have the effect of diluting out a lot of your substances but specifically it’s
going to be used to retain water the this is a protein hormone and so it
works almost instantaneously as soon as it’s secreted the other hormone is
aldosterone you’ll if you look at our adrenal gland lecture you’ll see that
aldosterone is a steroid hormone it is secreted from the zona glomerulosa and
it works primarily at thee so we’ll put down here adrenal cortex
and it works primarily at the distal convoluted tubules of the nephron and
it’s action is to cause reabsorption of sodium and because of that water and it
causes excretion of potassium and excretion of protons so just be aware of
those things we’re going to talk about that obviously because water and sodium
are going to be intimately related to the discussion that we’re going to have
today okay so any discussion regarding intracellular extracellular fluid you’ve
got to know about the different compartments of the human body so let’s
get into a discussion of that and this drawing is going to be pretty important
so I want to make sure that you understand the difference nuances are
regarding this so this is a diagram essentially showing you the different
compartments of fluid in the human body okay so this is the intracellular fluid
so this represents this compartment here represents all of the all of the volume
inside of cells this is the entry vascular volume this represents all the
fluid insides arteries veins capillaries etc and this is the interstitial volume
so this is separated this intravascular volume is separated by the interstitial
volume by the capillary wall and we know the capillary wall is not a barrier to
the movement of electrolytes and fluid and I’ll represent that here by simply
drawing little openings in that so basically sodium and water can go back
and forth between these two and so basically this is effectively one
chamber for or one component or one container for electrolytes fluid things
of that in other words this wall does not separate their movement on the other
hand this wall here that separates if you will the extracellular fluid from
the intracellular fluid is separated and there is a a pretty tight barrier this
is basically the the membrane of the cell
now remember animals don’t have cell walls like plants do but yet this is a
pretty rigid wall when it comes to electrolytes water is able to move
through it very freely of course because it’s a not ionic compound but in terms
of sodium sodium cannot go through this it is not permeable to sodium if sodium
is going to go through it’s got to go through channels and so this is very
well regulated sodium is not gonna be able to go through however water can go
through all of this okay so water can go through here and water can go through
here and so because of that because sodium is able to freely go through here
and water is able to we’ll call this simply this whole thing the extra
cellular fluid compartment so this is intracellular fluid extracellular fluid
and generally if you want to look at a compartment this is about four liters
this is about 10 liters and this is about 28 litres of fluid so the key here
is that there are three compartments the intravascular and the interstitial
combined to form the extracellular fluid this is where sodium and water mix water
is able to go across this semi permeable membrane but sodium is not and that’s it
that’s a key there so when we’re talking about drawing blood with needles
okay this is the fluid compartment that we’re talking about when we’re talking
about hanging IV fluids okay it goes into the vascular and extracellular
fluid compartment so the question is going to be is what happens to these
fluid compartments when there are perturbations in sodium and fluid
management and we’re going to talk about that so the way we’re going to represent
this from now on in the lecture to simplify it is basically two
compartments and remember this is going to be the intracellular fluid and this
is going to be the extra cellular fluid now why do I have it drawn this way as a
vertical and as a horizontal well the way I’m going to represent this if you
can imagine these are X and y axis is the x axis is going to represent volume
so how much so simply this dimension here represents how much volume is in
there and the y axis is going to demonstrate the sodium concentration so
the higher this is on the y axis the higher the concentration of sodium or
the lower the concentration of sodium and the farther out this goes on the x
axis the more volume there is or consequently the less volume this is now
because of that you’ll note that the area then is simply represents the
number of sodium molecules let me give you an example if I were to add water to
this just straight out water what would that do the water would add volume
to this compartment but at the same time it would cause the sodium concentration
to go down so instead of it instead of it being these dimensions we would have
something more along the line of this dimension but you could see that the
area in the box would be the same because the number of sodium molecules
wouldn’t change but the way this is depicted on the graph would change
because we have a lower sodium concentration and a bigger volume so
that’s how we’re going to depict this just to finish up the analogy if I did
by the way add h2o to this you would see what would happen here the first thing
that you would see will happen is that the sodium concentration would go down
and that the volume would get bigger that would be if there was absolutely no
transport of water across this membrane but we know that that’s not the case
because as soon as this sodium concentration would go down remember
this is a permeable membrane to water and if water is on both sides of this
and the sodium concentration goes down on this side water is going to go to the
side of the higher concentration that’s the law of osmosis so you would have
water going across from the extracellular fluid into the
intracellular fluid and you would see that would happen until what would
happen until this would be diluted down to a similar level well in fact what
would happen is is that this would go down and then this would go down to meet
this until this was equal but because this has a much larger volume in fact
it’s probably twice the volume of this that about twice the volume of water
that we’re putting in here would go into the intracellular fluid chamber and so
you can see here that when you give pure water or in medically speaking dextrose
d5w when you give water to somebody you can see why this
not expand the intra the intravascular volume it’s because the majority of this
volume as soon as it goes into the extracellular fluid is going to go
across the membrane and basically fill up the intracellular volume rather than
the extracellular there will be some left in the in the extracellular volume
but because this is a larger volume more of this is going to go into the
intracellular varm so to review free water goes in it causes a reduction in
the sodium concentration because of that the law of osmosis means that water will
keep going across this membrane until the sodium concentration in the cell
matches that in the extracellular fluid which means that most of the water that
you give the patient if it’s in the form of free water is going to go into the
intracellular fluid compartment now that’s as opposed to giving someone
normal saline or as we like to say 0.9% okay or 0.9% normal saline so normal
saline when is given it’s basically as if you’re just adding it on to the edge
and why is that because the fluid concentration that is being added to the
extracellular volume is already at exactly the same concentration or very
close to the same concentration of the fluid that’s already there because of
that that will simply be added on to the volume there is no change in the
extracellular fluid concentration of sodium because of that there is no shift
of fluid over into the intracellular fluid and that is why normal saline is
the best type of fluid to give if your primary purpose is to expand the
extracellular fluid compartment and that’s how that is represented here we
see that the volume has gone up but the sodium concentration in that
extracellular fluid is the same okay so with these basics we’re going to move on
and talk about the different types of hyponatremia the hypotonic hyponatremia
the hyper Tomic hyponatremia and the hypotonic
hyponatremia so isotonic hypertonic and hypotonic we’ll talk about those in the
next lecture thanks for joining us

88 thoughts on “Hyponatremia Explained Clearly – Symptoms, Diagnosis, Treatment

  1. BUN: Blood Urea Nitrogen. It is a measure of the amount of nitrogen in the blood in the form of urea, and a measurement of renal function

  2. Please correct the units of sodium in 135 mg/dL to 135 mmol/L or meq/L from 1:35 onwards. That is the unit that the Clinical Chemistry laboratory provides you with.

  3. Thank you for catching this mistake. An annotation at 2:37 has been added to correct it.

  4. I've read so many books and attended so many talks but never like this. Many thanks Roger,you have no idea how many people you have had helped. I'm still waiting for hypernatremia.

  5. Glad you found the series useful. We'll put Hypernatremia on the slate for a future lecture. We are doing a vote on our MedCram Facebook page for the next topic to be covered. Take a look if you get a chance.

  6. Unbelievable that after two years of nursing school, I don't think I ever COMPLETELY understood WHY 0.9% NS was what you used. Thanks so much!

  7. Many Thanks for video lecture. I would really appreciate if you could kindly post the video related with NIV, BiPAP, CPAP and the mechanism involved in these modalities.

  8. Thank you so much! I told some friends about Med Cram and appreciate your help. I would love to see more topics in the future.

    I also appreciated your videos on Hypoxemia/Hypoxia.

    You should work for Kaplan or come out with your own series covering all subjects from Pharm to Path to Microbiology and so on.

  9. this might have been mentioned before, but you said 0.9% saline, but .09% was written at 14:30.

    Also thanks many times for this lecture series – easily one of the best on youtube!

  10. Thanks so much; you do an excellent job on these. I'd love to see you handle all the electrolyte disorders commonly found on Step 2, etc. as well as renal tubular acidoses. Great work!

  11. Very clear video, great job! Thanks for creating these series!
    One thing I'd like to bring to your attention: from your video it might be incorrectly assumed that intracellular and extracellular sodium concentrations are equal, which they are not (12 mmol/L vs 140 mmol/L respectively).

  12. Hyponatremia and fluids are one of the hardest concepts to grasp–at least in my view–and thankfully you have clearly explained this concept in a way I visualize it and understand it! Thank you SO much! I'm a pharmacy student on a critical care rotation in a burn unit and was told to look up how to to workup/assess and treat hyponatremia and after watching & taking notes on these videos I feel absolutely confident to explain this concept!

  13. Wow, It's amazing to learn from teachers who teach with passion. Thanks. "if you can't explain it simply you don't understand it well enough", you've made ir pretty simple. <3

  14. thanks dr for the amazing series! i have a presentation on hyponatremia and ur lectures are the best reference!

    i hv a suggestion: could u plz do lectures on antiarrythmics and explain the physiology underlying them.. this is a vry tough topic fr me and i would appreciate that so much.. thx 🙂

  15. this happened to me a few days ago.. it was absolutely hands down the worst experience in my life. i thought i might die or else i would end up permanently brain damaged. i think i was VERY close to having a full on seizure and becoming unresponsive.. luckily i got an iv with sodium drip and it managed to fix it (albeit after many more hours of pain). they were giving me valium and morphine and it barely touched the pain i was feeling. i couldn't hold still. my limbs were just jerking all over the place. even the valium didn't really stop it.. just slowed my twitching down a little

  16. See the whole series at along with other top quality videos including reviews in pulmonary, cardiology, infectious disease, and hematology!

  17. I drank 2 16.9 oz of water within 1 hour and by the time i have posted it has been about 13 hours. I am 15 and I'm afraid I might die, I haven't told my parents because my mom has warned me before. I was not doing any exercise within that time and I want to know what the possibility of me dying rn is. Please help

  18. would you say y axis is na concentration instead of na? so the area is (na/h20)xh20 which make more sense? good video btw, thnk u!

  19. When you add normal saline at 15:16, the read line is supposed to stay at the vertical level of the purple line right? Because the Na+ concentration doesn't change, right?

  20. hi i was just wondering if you have any links to the references that you have used? i would like to use this for my assignment but i need to include review papers too!
    (hopefully you see this in time)

  21. I drank 1.25 litres of water in the space of 30 seconds and woke up a few hours later and started vomiting. I have the worst stomach pain I’ve ever experienced, and can’t sleep. Do I have this condition and will I die 😥😓. I am actually so worried someone pls tell me if that amount of water is enough to kill me

  22. All these videos explaining hyponatremia and SIADH for trainee medicos and other health professionals.

    Great. But what about the patient??? How does the patient find out what to do on a new diagnosis??? When I exercise in a warm climate do I just not drink. and become dehydrated. Or do I drink and take a salt tablet?

    Do I just give up on a healthy exercise regime???

    Where's the information for the layperson and patient???

  23. I went to the doctor and when I got there, I got out of my car and my legs got so weak I was shaking and could barely walk. I had to have help into the doctors office. I had a headache that wouldn't go away. They did blood work and my sodium was very low. I was told to go home and eat alot of salt. Nothing is working. I'm losing my balance and scared I'm going to fall. My legs and feet cramp like crazy. When my legs get weak, I go down and it's like I have no control of my legs at all. I'm scared and don't know what to do

  24. For all the med students here: know that consumption of mdma can lead to Hyponatremia. So if you have a patient coming from a nightclub, don‘t forget that it could be Hyponatremia and you may save a life.

  25. How can it be cured??? Please advise

    My aunt is going through hyponatremia.. She is hospital… It seems like it got cured and under control but again severe symptoms of hyponatremia are showing… There is no permanent treatment and cure for this desease?!!

    Please advice

Leave comment

Your email address will not be published. Required fields are marked with *.