00:01
So in managing our
hypernatremic patients,
we have to target not only
the underlying cause,
but we also want to do interventions
that limit further water loss.
00:10
So in targeting
the underlying cause,
we want to correct
the hypertonicity.
00:14
by administering dilute fluids
and free water.
00:17
We can actually calculate this
by looking at the water deficit.
00:20
So that means we can take our
patient's current total body water.
00:24
We multiply that
by their serum sodium
divided by their desired
serum sodium,
which is typically normal
at 140.
00:30
And subtracting one from that.
00:33
Now, in addition to correcting
just their water deficit,
you also want to make sure
that you are targeting
any ongoing water losses.
00:41
So that means insensible losses
just breathing or sweating.
00:44
In addition to any
urinary losses or stool losses
that that patient
might be incurring.
00:50
Now, what kind of interventions
can we do
to further limit water loss?
Well, in the case of somebody
who has, for example,
central diabetes insipidus,
then we can actually administer
Desmopressin, an ADHD analog
in order to correct
their water deficit,
and help them to retain water.
01:09
So, I do want to just take a moment
to talk about
administering parenteral fluid
in the management of
hypernatremia patients.
01:15
So remember,
we talked about being able
to correct their water deficit.
01:19
Now, if a patient's thirst
is intact,
they can do that by drinking,
or taking oral intake.
01:24
But if a patient has
impaired thirst,
or if they're in a situation
where they don't have
free access to water,
then we can use
things like parenteral water.
01:34
And we do this in our
critically ill population,
perhaps who are intubated,
and in the intensive care unit.
01:41
So how about our patients who are
hypovolemic and hypernatremic.
01:45
Remember, those are patients who are
both volume depleted and dehydrated
because they have both
sodium and water losses.
01:52
If they don't have
free access to water,
we can give them something like
half normal saline,
which is going to both restore
their vascular volume
and at the same time
replace their water deficit.
02:03
And our patients who are
euvolemic and hypernatremic.
02:07
This means that they're dehydrated
only due to water losses,
then we can use if need be
parenteral free water.
02:13
And that's given in the form of
5% dextrose in water.
02:17
Remember, we can't get
pure water IV
because the hypotonicity
will cause lysis of cells.
02:23
Now, if thirst mechanism
that is intact,
and the patient
can take oral intake,
then we want to provide access
to free water.
02:30
Similarly, if a patient has an
NG tubing or a do tubing
then we can provide
enteral free water as well.
02:38
So, I do want to mention
that you have to be cautious
with correcting hypernatremia
in the chronic state.
02:43
So if somebody has been
hypernatremic
for greater than
48 hours duration,
then it's important not to correct
that serum sodium
greater than 10 mEq
over a 24 hour period of time.
02:53
Otherwise, that patient
may be at risk for cerebral edema.
02:57
So just to remind you both
hyponatremia and hypernatremia,
serum sodium needs to be monitored
and followed very closely.
03:05
Meaning that
you need to check it
somewhere between
two and four hours.
03:08
And therapy should be modified
accordingly
so that you avoid
too rapid of a correction.
03:15
So let's review again
the effects of hypernatremia.
03:17
And what happens if we correct
our patients too quickly.
03:20
Just to remind ourself
in the hypernatremic state,
where our patients have a
high osmolality,
those neuronal cells are actually
decreased in size and cell volume.
03:31
Now, remember what
happens adaptively.
03:33
Initially, you have movement of ions
into those neuronal cells,
water will follow
restoring the cell volume
back to the normal state.
03:40
In the chronic situation,
meaning that if it's been
greater than 48 hours,
then we have organic osmolytes
that move from the ECF
into that cell volume
and water will follow.
03:49
Again, restoring those cells
back to the normal cell volume.
03:52
Now what happens
if all of the sudden
we provide hypotonic fluid?
We're going to lower
that serum osmolality
and guess what happens,
where's that water
going to go?
It's going to move to the
intracellular compartment
because two-thirds of water
distributes to that
intracellular compartment.
04:09
When that happens,
remember what happens
with those neuronal cells,
they're enclosed
in a rigid calvarium
and therefore those
patients are at great risk
for actually having
cerebral edema.
04:19
So we have to be cautious
about correcting patients
too quickly
in the hypernatremic state.