So first of all I've drawn here fluid movement and IV solutions. So there's
three different IV solutions that we have: isotonic, hypotonic and hypertonic.
Now I've drawn a blood vessel here and a cell right next to it so you can
see the difference of how the fluids will move. So first of all isotonic IV
solutions: they have the same concentration as the plasma so in a
beaker it would look the same. There would be the same concentration on
either side, hence there will be no fluid movement. The body will strive for
homeostasis but since the concentration of the IV
solution that we're giving the patient is the same as in the intracellular
space or as the serum osmolarity, fluids will not move. Hence, there's no fluid
movement and fluid stays in the intravascular space. Now two major or the two
only isotonic IV solutions are 0.9% sodium chloride, also called
normal saline, and lactated ringers solution. Now the difference is that 0.9%
sodium chloride or normal saline contains sodium chloride only, whereas
lactated ringers contains some more electrolytes as well as maybe some
bicarbonate and so forth. So depending on whatever the patient needs, the physician
or the provider will determine what kind of isotonic solution the patients will
receive. The indication for isotonic fluid
administration is typically fluid volume deficit. So if everything is too
concentrated in the patient, we want to kind of dilute it out a little bit and
we want to give the patient some more isotonic fluid in the intravascular
space. So indications will be dehydration that can be due to nausea, vomiting,
diarrhea, it can be due to fever, drains, such as from wounds or suctioning, such
as from an NG tube or so forth. Now the second principle or the second type
of IV solutions we have here is hypotonic IV solutions. And hypotonic,
meaning that the concentration is less than the serum. So if we give
the patient hypotonic solution, so you see I've only drawn three particles here,
so there will be more fluid than particles administered to the patient. By
the principle of osmosis as we have discussed earlier, osmosis will move
water in and out of the cell and because with the patient, we're giving the patient now a
hypotonic solution, meaning the particles are less than the fluids that we're
giving them, fluid will move inside the cell.
Because again the body is striving for homeostasis. So examples of hypotonic
solution is 0.45% sodium chloride, also called half-normal saline, makes
sense because normal saline is called 0.9% sodium chloride. So it is a hypotonic
IV solution. Another example is D5 1/2 normal saline. And D5 means that there is
5% of dextrose in the solution and then again the 0.45% sodium chloride.
Now keep in mind the dextrose here gets used up by the body right away and
therefore really as soon as this IV fluid hits the patient's veins, the D5 is
taken up, it's used by the cells for energy, and half-normal saline remains,
meaning that it is a hypotonic solution. Now hypotonic IV solutions you'll
see that a lot used in patients who might be going to surgery or just for
regular IV maintenance fluid. And as you can see here I wrote normal daily losses
such as from perspiring, sweating, GI tract, fluid losses through respiration
and so forth, they are hypotonic. So then if we
replenish the patient with hypotonic solution, everything will reach
homeostasis, just like the body wants to. Hypotonic solutions can also be used
at higher and a faster rate if there is intracellular dehydration. So if the cell
itself is dehydrated, it will need more fluid by us administering hypotonic IV
solutions, we'll give the patient again a lower concentration of particles, higher
concentration of fluids and that fluid, by principle of osmosis, will move
into the cell. One important principle here is to
remember just as we can only measure electrolytes in the patient's
intravascular space, the only way that we can control the fluid shifts is by
administering IV solutions into the intravascular space and then we know
by the tonicity, or by the concentration of the fluids that we give the patient
certain fluid shifts are going to occur. So now let's look at our third IV
solution here, which is a hypertonic IV solution. So hypertonic meaning more
concentrated. So now we're going to give the patient an IV solution that has
more particles, is more concentrated, than it has water. Again by
the principle of osmosis the body wants to equalize that. So now we have a higher
concentration in our intravascular space, hence the body is going to pull fluids
from the cell into the intravascular space to dilute the intravascular space
and make it again even. Now why would we want to dehydrate the cell? There's
really only two major indications as to why you would administer hypertonic IV
solution. Number one: severe hyponatremia. So if you have a patient who has sodium
level typically below 120, you will want to give
the patient a highly concentrated sodium chloride solution, which in our case is
3% sodium chloride. So that's much more concentrated. Remember that
0.9% is called normal saline, half of that so 0.45% normal saline, or
0.45% sodium chloride means half normal saline, and so 3%
sodium chloride is basically three times, or greater than three times
as much as that 0.9% sodium chloride. So we're giving the patient a very high
concentration of sodium chloride because their serum level that we have measured
is less than 120. Now being aware and knowing how the principle of osmosis
applies to this, we have to make sure that we monitor patient very closely
because as the fluid is being pulled from the cell, it causes cellular
dehydration. It can also mean that that fluid is being pulled in the
intravascular space and now all of a sudden we have extra fluid that's coming
from every single cell in the body that could accumulate in the lungs, hence we
have to monitor patients lung sounds very, very carefully. The other indication
for hypertonic IV solution administration would be head injury or
trauma or cerebral edema. So if a patient comes in with a severe head injury, let's
say there was a traumatic injury, there's a lot of bleeding and the cells in the
intracranial cavity swell, so there's a lot of swelling in
these cells, these cells swell and thus can cause mental status
changes, confusion, and it can even lead to a coma. So the one, and
typically the patient will need other treatments, but one thing that we can do
very quickly is administer hypertonic IV solutions to the patient so that we
can pull some of the fluid, that's caused from the trauma and the swelling, from
the cells so that hopefully the brain damage that the patient has is being
minimized. Another solution, another example of an IV solution, a
hypertonic IV solution would be D10, which is 10% dextrose. So that is a very
concentrated IV solution that again will have more particles coming into the
intravascular space. It would not necessarily cause any fluid shifts
because again the dextrose is used by the body. Now D10 usually gets
administered to patients who might have had an episode of hypoglycemia and
maybe they're NPO and we really can't give them any oral sugars, so we would
give them 10% dextrose and of course monitor their sugar levels, the mentation
status, and so forth very carefully. Now one more caveat: there is also, there are
several other types of IV solutions, but here are the most common ones. So there's
also an IV solution called D5NS, so dextrose 5% normal saline, which is
again 0.9% sodium chloride. This solution as it sits in your IV bag is hypertonic
because we have the normal saline and on top of that we have the D5 sitting in
there. We know normal saline is isotonic, but
the dextrose is sitting in the bag with the normal saline, so the concentration
is actually hypertonic, hypertonic in the bag, but as soon
as we start infusing this IV solution into the patient, that D5 again gets used
up leaving us with the normal saline, hence in the body it is an isotonic IV
solution. So keep that in mind. The nice thing is that all the IV bags that you
would administer to a patient have exactly labels of how many milliequivalents of whatever
electrolytes is contained in the IV solution that's there. And it will also
tell you the osmolarity of that IV solution. And keep in mind that we can
measure the serum osmolarity, so this would be showing up on a chemistry panel,
whether that's basic or a comprehensive chemistry panel, and that would also tell
you what that serum osmolarity is. Then you can see is the patient's
osmolarity normal, are they diluted, do they have fluid volume excess, are their
particles more concentrated, do they have fluid volume deficits and then does
the IV solution that I'm going to give the patient match whatever their lab
values say? Because we definitely always want to make sure
that we administer the right kind of IV fluids to the patients.
So thank you very much for watching. I hope this was a very brief and helpful
explanation of basic principles of diffusion, osmosis and how it applies to
our patient care, specifically IV fluid administration. Also watch the video on
fluid volume excess vs. fluid volume deficits and then the discussion of major
electrolytes and how the supplies to patient care.
Thank you for watching Nursing School Explained. Please leave any comments down
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