Hypernatremia Explained Clearly – Pathophysiology & Treatment
22
August

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


welcome to another MedCram lecture
we’re going to talk about hypernatremia not hyponatremia but hypernatremia and
this is defined as any sodium concentration that is greater than 145
that just as a reminder anything that ends in the word or the letters emia
refers to something that is in the blood so we’re talking about an elevated
sodium concentration that is in the blood now if you want to know about
hyponatremia please refer to our hyponatremia lectures now if you may
recall when someone has hyponatremia the first thing that you need to do is you
need to figure out whether it is hypertonic isotonic or hypotonic and
then you need to figure out if it’s hypovolemic hypervolemic or iso bulimic
with hypo with hypernatremia however almost all of these issues with
hypernatremia are also hypertonic which means that the tonicity of the serum is
high so the next thing you need to figure out when you have someone that
has a high sodium concentration on their blood test is to figure out what it’s
due to is you’ve just got to figure out what the volume is of the patient what
is the volume and that simply is is the volume too high or hyper valley mech is
it too low from hypovolemia or is it the same what we call ice oval emia the
first thing we’ll talk about is actually going to be hypovolemic hyponatremia
then we’ll talk about hyper voli m’q hyponatremia and then we’ll talk about
ISO vole emic hyper natrium iya so I’m going to divide the screen into three
areas the first one is going to be hypovolemic hyper Nate remya so we can talk about that one
the next one we’ll talk about after that is hyper bulimic hyper tree Mia and
let’s pick a nice blue color here then we’ll talk about ISO Philemon hyper tree
Mia okay so basically we’ve got people who have high sodium’s who look like
they don’t have a lot of fluid we have people with high sodium’s that look like
they have a lot of fluid and we have people with high sodium’s that look like
their volume status is about the same by far the most common is the hypovolemic
hyponatremia these by definition are people who have lost salt and water but
they’ve actually lost more water than they have salt and as a result of that
their sodium concentration in their body goes up so the key here is they’ve lost
lots of water and sodium but they’ve lost more water than sodium and the way
I want to kind of show that is through a graph now this is kind of the graph a
similar graph that we used in our hyponatremia talk and I’m going to kind
of use the similar status now this is a graph here which graph sodium
concentration on the y-axis and volume on the x axis this area is the intra
cellular fluid and this is the extra cellular fluid so what first happens
here is that the patient is losing water and soda
in both and as a result of that when they’re losing water and salt both all
you’re going to have is a reduction in volume okay but because the patient is
losing more water than salt their sodium concentration is going to go up now when
the sodium concentration goes up on the extracellular side what’s going to
happen is water is going to go from the intracellular side to the extracellular
side to offset that high sodium concentration and as a result the sodium
concentration in the intracellular fluid will also go up and it will lose some of
its volume and so this is what you will have yellow meaning the pathological
process white being the normal ok so again you lose volume and water and as a
result of that sodium concentration goes up and of course the sodium
concentration in the intracellular side and the extracellular side should always
be the same because water can freely go through that permeable membrane and as a
result you lose intra cellular volume as well now there’s two reasons why this
could happen okay there is the non renal reason non renal and of course there is
the renal now why would what would be the non renal reason why someone would
lose this well if they were having sweating or diarrhea or probably the
most common reason that I see is they’re elderly they’re in a nursing home and
they have these insensible losses but they can’t get up to get a drink of
water and so I see these patients coming in from the nursing home with high
sodium’s and they look very dry and they fit into this category and the most
likely reason is is because they’re just becoming the
hydrated so how do I know what’s the hallmark of that well you know that if
the kidney is not getting enough blood flow it’s going to want to hold on to as
much sodium as possible and so therefore the telltale sign that this is a non
renal hypovolemic hyponatremia is that the sodium concentration is going to be
less than 10 in the urine okay now what about renal what are some renal causes
for a hypovolemic hyponatremia well you could have an osmotic diuresis and what
would be the reason for that well if you have a bleed in the brain patient and
they’re on mannitol okay so we give a man at all that’s going to cause a
diaeresis getting rid of free water through this osmotic diuresis through
the kidney and that’s going to cause the sodium concentration to go up what’s the
telltale sign well obviously if you know the patients on mannitol that’ll explain
it but here the urine concentration of sodium is going to be greater than 20 so
what’s the treatment for this the treatment for a hypovolemic hyponatremia
is what do you think if you’re losing salt and water the treatment is going to
be normal saline so we have these patients coming in from the nursing home
that are dehydrated and their sodium is high we don’t want to just give them
water we want to give them salt and water and this is kind of paradoxical
because you’re saying to yourself well this patient’s sodium is elevated well
that’s true their sodium is elevated but they’re also volume deficient and so in
these cases even though they’re sodium’s maybe in the 150s
I give normal saline because I know that they are behind in volume and it’s only
once you correct that volume if their sodium is still high then I will go
ahead and give them free water but I will never give them free water first
because what happens when I give free water free water will only correct
the concentration of sodium that’s elevated it will not correct this volume
because remember free water gets distributed throughout the entire system
and this is what I want to correct first is the volume deficit and that’s why I
give normal saline okay let’s talk about hypervolemic hyponatremia it’s kind of
rare don’t see it much wouldn’t jump to the conclusion that that’s what it is
when I see it in a patient but what’s going on here is you’re getting lots of
sodium retention in fact your retaining salt plus water but guess what you’re
retaining more of you’re retaining more sodium than you are water and a lot of
things can happen here you could get what are some reasons why you could do
this over resuscitation with IV fluids okay so IV fluids could do it or in a
code situation if you’re giving a lot of sodium bicarbonate in a code situation
you’ll I’ve seen that before so that’s that’s predominantly how that
happens now in terms of why this could be caused this would be a what we call a
non renal reason or a excess of fluids but what else could happen well before
we get to that let’s actually draw a picture and show what’s going on so
let’s draw our normal situation here’s our intracellular fluid here’s our extra
cellular fluid is our intracellular fluid so we said here that we had
retention of sodium and water but more sodium than water so what’s the first
thing that’s going to happen the first thing that is going to happen is we’re
going to have sodium and water giving us a larger volume but because we’re also
retaining more salt than water our extracellular fluid compartment is
going to go up in concentration now as a result of that higher concentration
intracellular fluid is going to shift into the extracellular fluid water is
going to go that semi permeable membrane and as a
result of that water leaving the sodium concentration is going to go up in that
intracellular fluid compartment and it will have less volume so this is the
shift that we will see now what’s another reason in addition to IV fluids
and sodium bicarbonate well there’s another thing that could cause it and
that is mineral corticoid excess we see this in things like Cushing syndrome remember in our adrenal cortex in the
zona glomerulosa there is a hormone called aldosterone aldosterone causes
sodium reabsorption and potassium excretion in the distal convoluted
tubules this excessive mineral corticoid secretion could cause elevated sodium
levels and exactly this sort of a state so what’s the treatment well if we’re
retaining too much sodium and water in this situation then diuretics should
work especially those that cause salt wasting and of course giving free water
will not hurt either okay let’s talk about ice oval emic so
here we’re not losing volume that’s the key there is ice oval emic means no loss
in volume but what we are seeing here is loss of free water just simple free
water is being lost so what would be the non renal reasons why this would be well
if we’re losing free water it could be simply that we’re no longer retaining
that free water the other possibility is is that if we’re losing that free water
it’s because we no longer have the antidiuretic hormone which as you recall
works on the collecting tube you’ll to reabsorb free water from the collecting
tubular the Efrain looks like this loop of Henle and
then you have the collecting tube you’ll remember that the ADH works here to
reabsorb free water if for some reason the brain is not secreting ADH this
would be the opposite of the syndrome of inappropriate ADH this would be like
what we call a diabetes insipidus the other possibilities you could get
nephrogenic diabetes insipidus nephrogenic diabetes insipidus is where
the kidney is not responding to the antidiuretic hormone okay so there’s a
number of reasons why either you not you’re not secreting enough antidiuretic
hormone from the posterior pituitary and not we’re not making it in the
hypothalamus or the collecting tube you’ll is simply not responding to it
and you get a nephrogenic diabetes insipidus the treatments in all of these
situations is simply free water replacement just free water so how is
that going to look in terms of our diagram again here is our extracellular
fluid compartment extracellular fluid and then intracellular fluid okay
so again here we are simply losing free water and so what is that going to look
like well we’re not actually changing volume here the volume is the same so
all we see is since free water is being lost the concentration of the
extracellular fluid is going to go up now as a result of the extracellular
fluid going up what’s going to happen water is going to go from the
intracellular fluid over to the extracellular fluid and as a result of
that you’re going to lose intracellular fluid compartment space and in a lot of
cases here this volume line doesn’t really move much from where it started
you notice how it doesn’t move much it might move a little bit but it’s not
going to move very much and that is the reason why it’s called ISO polemic again
the treatment is free water so I would recommend that if this doesn’t make a
lot of sense to you go ahead and review our hyponatremia lecture also review our
adrenal gland lecture and make sure that you understand what it is that’s going
on there thanks for joining us you


70 thoughts on “Hypernatremia Explained Clearly – Pathophysiology & Treatment

  1. JUST took my renal block final. Your videos regarding hyponatremia were awesome. Thanks! These help out so much with the boards. Keep em coming!

  2. I love your lectures! Very good review. I wish the teachers in Nursing School would teach the way you do – so much simpler to understand.

  3. thanks…pl also upload hyper and hypokalaemia , hyper and hypo calcaemia , respiratory and metabolic acidosis and alkaloids.
    love your videos. upload on a daily basis. 🙂 

  4. Brilliant dr. Roger, thanks 🙂 I have one question: why in case of isovolemic hypernatremia does the volume stay the same? isn't the patient losing free water? thanks again sooo much ^_^

  5. Thank you so much for these videos. I'm a student nurse and have never had this explained properly. This makes so much more sense than my god forsaken nursing book. Again please keep it up this is great.

  6. I just want to thank you for your videos. You helped me pass nursing school and the NCLEX! More importantly, I understand and can function past those trick tests and actually provide safe and proficient care to patients. Thanks so much!

  7. Dear Dr. Seheult,

    First off, thank you for the fantastic videos that you make on YouTube. I have question regarding Conn's Sx and Secondary causes of Hyperaldosteronism such as CHF, Cirrhosis, Nephrotic Sx etc.

    I am confused as to why Conn's Sx results in a Hypernatremia while secondary causes of Hyperaldosteronism results in a Hyponatremia.

    Thank you

  8. I'm currently rotating at a burn unit that uses a lot of ½NS..your videos on hypo- & hypernatremia have really helpe dme understand these concepts but I'm having a hard time with figuring out where ½NS fits in to this picture?

  9. As always, thank you so very much. This seems like simple stuff to simply read about, but when the brain starts to fatigue, these videos always give me the kick start that I need. Thank you, thank you, thank you. BTW, for the Hypertonic/Hypernatremia… shouldn't we have discussed the importance of 0.45% NS in this patient? Just throwing that out there if you ever reapproach the topic. And in case I didn't convey it- thank you.

  10. Excellent but how can we diagnose the volume status? I have a patient with Na concentration 152 and is on lasix 20mg and is in good health; his blood pressure is 150/80 but having bigiminy on ECG . He is 80 years old.

  11. Wonderful explanation of Hypernatremia and Hyponatremia. I've spent the past couple of days trying to figure this out and these videos finally made it click!

  12. so the saying that hypernatremia is always a sign of the intracellular dehydration, is correct. but my question is when and how to fit corrected hypernatremia, and how is that helpful in the treatment settings? thanks

  13. Thanks for the nice video! What I can't understand is the urine concentration in hypovolemic hypernatremia. In non-renal causes, when we have lost more water than salt, shouldn't the kidney try to compensate, reabsorbing more water?

  14. in hyovolemia hypernatrema:The drawing confused me
    why when the fluied goes from ICF to ECF the volume in EC not increase?

  15. When you talk about a loss of volume, is it the cellular fluid that has a loss of volume, or what exactly is it that losses volume?

  16. Hello there! I have a patient who is recovering from AKI and now he's making a lot of urine (post AKI diuresis), and his Na is going up. Would he be classified as Isovolemic Hypernatremia? Because his recovering kidneys maybe cannot respond to ADH and thus is loose a lot of free water ?

  17. I have palpitations. Dr told me i have Hypernatremia even though my Na was only 141. She told me to reduce salt intake. She told me that the palpitations were caused by Hypernatremia. Is it true?

  18. Great videos!!!! I have a question. The y axis refers to the osmolality not to the sodium concentration [Na+], right? The Sodium concentration can not be the same between intracellular and extracellular volume. (at 5:28)

  19. Hello- I have a question.. I just watched the Hyponatremia lecture and it said that Mannitol would cause Hypertonic Hyponatremia,,, how come now you are saying, it will cause Hypotonic Hypernatermia? Which one is it? Thanks

  20. hi …i have a question …but please answer me…i have seen a new patient with the following clinical picture :coma 92 years old history of alzheimer …B.P 100/60 Lab. showed : Na 190 !!! K 5.3 BUN 300 Ht 44 Creat. 6.8 Albumin 2.5 Liver enzymes normal WBC normal …i have diagnosed the case as a one of severe dehydration and hypertonic hypernatremia …i gave the patient 0.45 normal saline one liter Q 8 hours and observed the gradual decrease in her Creat and Na and BUN and only occasionally i gave her D/W 10%after few days her Lab improved gradually and SLOWLY and the patient improved markedly.My question is that i have given her 0.45% saline and not 0.9% normal saline while you proposed to give 0.9% normal saline …what is your opinion? Is it better to give 0.45% or TO give 0.9% saline especially in my case the patient has severe hypernatremia and it is risky to add on Na since Na is 190 which is very very high

  21. Great and simplified illustration ..
    I wanted to ask regarding the rest of electrolytes if they have any clue regarding finding the cause of hypernatremia or the treatment as I have one patient with Na:171 and k:2.9 Mg:0.6 Po4:0.8 mmol
    Clinically:dehydrated with Cancer larynx with secondaries and tracheostomy,feeding via Gastrostomy tube and hypotensive

  22. Shouldn't diarrhoea cause a dilutional hyponatraemia due to the volume depletion stimulating ADH release and water retention without additional Na retention?

  23. Sir, this was well explained.. I mean it's not new for me to feel like this way because your every lecture is meant to build basic foundation in Medicine..

  24. I'm studying for med-surg nursing certification and this is an excellent review, with a little extra considering it's for medical students.

  25. Sorry, you explained very well and i got most of it.
    But what really makes no sense to me is to take Diabetes Insipidus into Isovolemic.
    You clearly loose volume by polyuria (Low ADH or ADH resistance) and this should make my body hypovolemice. We're talking in terms of tonicity and volume about the ECF, which is lost here. And if you argue it is replenished from the ICF, how and when? By osmosis, which drive need to be hypovolemia/hypertonicity of ECF, right?

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