00:01
When it comes to the management
of our patients
with hypotonic hyponatremia,
then it's really going to depend
on the underlying cause.
00:10
So in our patients who have
hypovolemic hypotonic hyponatremia,
what we want to do is correct
the intravascular volume
with isotonic fluid.
00:19
By doing that we will release
the stimulus for ADH.
00:23
So typically in that situation,
we want to give our patients
isotonic fluids
like 0.9% or normal saline.
00:30
Now, we have to be very careful
when doing so
because remember,
as you start to repeat that
patient's vascular volume,
you will turn off ADH.
00:39
And that patient will now have
a significant water diuresis.
00:43
So you will have to follow
their serum sodium very closely
so that you don't overcorrect
those patients.
00:49
In our patients who have
euvolemic hypotonic hyponatremia,
it's important to correct
the underlying cause,
so treating hypothyroidism.
00:56
Or having patients increase
their solute intake.
00:59
If they are tea and toast dieter,
or somebody who has beer potomania.
01:04
For SIADH, we strive to correct
the underlying cause
if it's identifiable.
01:09
But if not,
an ADH remains present,
there's a couple of things
that we have to keep in mind.
01:14
Number one,
we want to free water
restrict our patients.
01:17
So that means really reducing
water intake,
and that's all hypotonic fluids
to somewhere between
0.8 and 1.2 liters of water daily.
01:27
We want to increase
their solute intake.
01:29
Remember,
by increasing solute intake,
we increase our osmolar generation.
01:34
And the more osmoles we make
then the more water we can excrete,
because of that
obligate osmolar excretion.
01:43
We can give our patients things
like loop diuretics.
01:46
That's going to abolish
the medullary gradient,
and that will help us also
excrete more free water.
01:52
And then finally,
we can give our patients
V2 receptor antagonists.
01:55
Medications like
conivaptan or tolvaptan,
which directly antagonize
V2 receptors.
02:01
Now, they're available,
but they are costly.
02:03
And it's something that we can use
in our patient population.
02:06
In our hypervolemic hypotonic
hyponutrimic patients,
remember they have total body
sodium access or ECB access.
02:14
So we want to manage those patients
with diuretics.
02:16
And we also want to fluid restrict
them as well.
02:20
Now, there is something
I want you to keep in mind
when it comes to correcting patients
who have chronic
hypotonic hyponatremia.
02:26
That means that
they've been hyponatrimic
for greater than 48 hours
period of time.
02:31
That sodium correction
should never exceed
greater than 8 milliequivalents
within a 24 hour period of time.
02:37
If it does,
that patient can be at risk for
osmotic demyelination syndrome.
02:43
We'll talk about that
in just a moment.
02:45
Alternatively, what I do want
to tell you is that
if the patient is
symptomatic,
and they have life threatening
seizures because of cerebral edema.
02:52
It is okay to raise their
serum sodium rather quickly
by about
four to six milliequivalents
to get them out of the danger zone
with hypertonic saline.
03:00
Now, let's review what happens with
osmotic demyelination syndrome.
03:05
Just to remind us what happens
in the situation of hyponatremia.
03:09
Remember, water is going to be
primarily distributed to the
intracellular fluid volume.
03:14
Now that's fine, but when it comes
to our neuronal cells,
they are enclosed
by a rigid calvarium.
03:21
Therefore,
when they expand,
patients will experience
cerebral edema.
03:25
They might feel nauseated,
they might vomit or have confusion
because of that cerebral edema.
03:31
And our bodies being
elegant as they are
have that adaptive mechanisms.
03:35
So acutely, we will use things
like sodium, potassium, and chloride
to the extracellular fluid volume,
water follows and shrinks those
cell volumes
down to the normal size.
03:45
If this is happening chronically,
meaning greater than 48 hours,
then we start to lose
organic osmolytes
into the extracellular fluid volume.
03:52
Again, water follows.
03:54
So it brings our cells back
to the normal volume.
03:57
Now, let's think about what happens
if we all of a sudden
try to restore patient's
serum osmolality
back to the normal.
04:04
So if we have something
that is hypertonic
to their plasma osmolality,
then what's going to happen?
Water is going to move from that
intracellular compartment
to the extracellular fluid
compartment.
04:17
These cells remember,
already have lost
organic osmolytes.
04:21
So they start to shrink
even further.
04:23
And when that happens that
stimulates osmotic demyelination.
04:28
The way that patients manifest
is it can happen anywhere
from two to three days
after the event up to
two to three weeks.
04:34
And they oftentimes will have
severe debilitating
neurological symptoms,
including choreiform movements
or even locked-in syndrome.
04:42
So it's extremely debilitating.
04:44
And the people who are most at risk
are going to be
your malnourished patients
and females that are typically
middle to older age.