Hello everyone welcome to Nursing School Explained. Today we'll cover the basics
of fluid and electrolyte balance and how it applies to patient care as well as
the administration of IV fluids and patient care. To get started, let's start
by reviewing some very basic concepts that I'm sure all of you have learned in
pathophysiology but we'll just go back to review these principles to make sure
that we have a basic understanding of why things work in a certain way in the
body. So first of all the principle of diffusion. Remember pathophysiology class
or physiology class? It's a concept of where you have a container and then we
have a semipermeable membrane in the middle. Now on one side we have a higher
concentration of particles and on the other side of the
semipermeable membrane we have a lower concentration of these particles. By the
principle of diffusion, the particles will move from the area of higher
concentration to the area of lower concentration.Reason being that the body,
as diffusion applies to the human body, the body always strives for homeostasis
or balance.So the seminary permanent membrane here always tries to equalize
both sides of the fluid compartments and we'll talk later and how this applies to
the patient and intracellular/ extracellular fluids.
So remember diffusion - particles move. In osmosis, if you see the beaker down there
that I drew, again on one side, on the left side here we have a higher
concentration of particles, then we have our semipermeable membrane
and on the other side we have a lower concentration of particles. Now see
the difference here? The green and the blue. And in osmosis the water moves, not the
particles, but the water. Again the body strives for homeostasis
but in osmosis, the water here moves from the concentration of higher on the right
side here to the lower concentration on the left side. Something that I like to
remember this by is: osmosis - H2O, okay so keep that in mind as we move on. So just
a brief review principle of homeostasis: the body always strives to have the same
amount of fluids or particles on each side of the semipermeable
membrane. Now let's move on to reviewing the major electrolytes. So keep in mind
there is basically two but really three fluid compartments in the body. First of
all, we have our ICF - intracellular fluid. Major intracellular electrolytes are
potassium, magnesium, sulfate, and phosphorus. Intracellular fluid makes up
about 65 percent of our total water in the body. So there's a large percentage
sitting in the cells of these electrolytes and fluids. Then when it
comes to the extracellular fluid, it gets divided into the intravascular fluid,
and I've drawn a blood vessel right here, and then intravascular fluid we have
mostly sodium, chloride, bicarbonate, and calcium. Total body fluid in the
intravascular space makes up about 7% of our total body fluid. Then in
between we have what's called the interstitial space. And that's about
28% of fluid. So the interstitial space is the space between
the intravascular fluid and the intracellular fluid, where fluid kind of
tends to shift and kind of sometimes accumulate when there's certain disease
processes. And we'll review that at a later point. So keep in mind:
extracellular fluid - everything outside the cell, intracellular fluid - everything
inside the cell with the major electrolytes of how we typically find
them. And then extracellular fluid: intravascularly that means in the serum.
And think about the only thing that we can measure in a patient is what's going
on in their intravascular space by taking a blood sample from one of their
veins and sending it to the lab for analysis. So we really can never analyze
a patient's intracellular fluid and electrolyte components because we really
don't have access or the technology to do that. So really what the only thing we
can do is take blood from the patient's vein, analyze the sodium, chloride, and so
forth components of that, and then come to conclusions as to what's going on in
the intracellular fluid because we know that things typically shift back and
forth. And we also know which major electrolytes are typically in the intravascular
versus the intracellular space. Now
moving on: another concept that applies here is osmolarity or also serum
osmolarity. Now whenever I say serum, it applies to the intravascular space
because that is the serum, that's the only thing that we can measure. Now
typically serum osmolarity is anywhere from 280 to 295, depending on your
textbook or the hospital that you might be doing clinicals at or that you're
working at. Now every lab might have different values but in general this is
a pretty good range so refer to your textbook or your professors to make sure
that you have the right range so you don't memorize the wrong range here. Now
serum osmolarity, you might have known or heard about it before, it's basically the
concentration of solutes in the serum, in the patient's intravascular
space. Now this is basically the concentration of particles that we have
here as it applies to the patient's intravascular space. Now if the
concentration is less than 280, then that means that would be basically over here,
on this side of the semipermeable membrane, so the patient would have less
concentration there and that's usually also called hemodilution. Let me write
this in red so that we distinguish here.
And this is also called fluid volume excess. Now when the concentration in the
serum, when the osmolarity gets above 295 that means that everything is much more
concentrated, much like we have over here on this left side of the semipermeable
membrane. And this is called hemoconcentration,
also called fluid volume deficit. This also you might have heard about this
principle before with urine. So urine specific gravity measures the
concentration of solutes in the urine and the higher the number, the more
concentrated the urine is and the more dehydrated the patient typically is.
For urine specific gravity the same principle applies: the lower the number,
that means that there's more water than solutes, much like on the right side of
this principle right here, and therefore there's more dilution going on. So
there's something going on as to where the patient, pertaining to the urine now,
the electrolytes and the particles that are being filtered by the kidney are
more diluted and there might be certain reasons for that. So moving on: now how
does this apply to our patient? How does the fluid movement apply to the
administration of IV fluids?