Hi. Welcome to our video series
on interpreting lab values.
In this one, we're going to take a
look at the complete blood count.
Now, we usually shorten that to CBC.
So when you see a physician's order,
it will say "CBC" because we shorten
everything in healthcare.
So, a complete blood count
or CBC is a lab test.
You'll have to get a blood
sample from your patient,
but it's going to give us
a ton of information
about the types and numbers
of cells in the blood.
So you can learn a lot about
your patients' health,
right then and there from when
the blood sample is drawn.
So let's take a look at what's
involved in a CBC.
Now, we've got a great picture for you there.
This tells you kind of the
percentages of these cells.
Look that -- 45% is your
packed red blood cells.
1% is the Buffy coat that your white
blood cells and your platelets,
and 55% is plasma volume.
So that kind of gives you a feel for it.
There's three types of cells in the blood.
There's red cells, white cells, and platelets.
So take a look at that test tube right there.
Kind of start to get set in your mind,
what you have there and what our
percentages are because
we talk about white cells, but
look what a tiny percentage
of an average healthy blood sample they are.
55% of that plasma volume can
also change with your dehydration.
Looking at the packed red blood cells,
when you hang a unit of blood for a patient,
that's what you're hanging,
ecause we want to get that oxygen-carrying
component in the red blood cells,
besides adding all that extra volume.
Okay, now that we've kind of looked at that,
let's go back and take a look
at the different types of cells.
We've got red cells, white
cells, and platelets.
Now the job of the red blood
like we said, is to carry oxygen.
That's why we want to look closely
at another value on a CBC,
the H&H or the hemoglobin and hematocrit.
So when you hear someone refer to an H&H,
that's what they're talking about --
hemoglobin and hematocrit.
Now why we care about that is
because hemoglobin is
the oxygen-carrying protein in
the red blood cells.
Now, adult has four of those with
each red blood cell.
Babies have six.
That seems kind of weird, doesn't
it? But when they're first born,
they've got extra hemoglobin-
The hematocrit tells us the proportion
of red blood cells
to the fluid component or the
plasma in your blood.
So if I have somebody who's bleeding out,
their H&H will go lower.
So keep that in mind. If I have a
patient who's experienced a trauma
and they've lost a lot of blood, that
H&H will be lower than normal.
Okay, so we've looked at the first cells,
the red blood cells. We know their
job is to carry oxygen.
Now the white cells, these are the infection
fighters. That's what they do.
And the platelets help with blood clotting,
and that's a good thing. Remember
our trauma patient?
Well, we want their blood to be able to clot
because we want them to stop the
bleeding and the hemorrhaging,
so we can hang on to their blood volume.
So when you're looking at this slide,
let's go back and make sure you
have it kind of set in your brain,
before we move forward to look
at these in more detail.
55% of your blood is plasma.
45% is your packed red blood cells,
and 1% is your white blood
cells and platelets.
So think through in your mind.
What should make up the largest
percentage of your blood volume?
About the other half of your
blood volume is made up of
packed red blood cells.
Good. And the tiniest percentage, >1%,
is your white blood cells and platelets.
Now, one more thought before
we move forward.
Think through, do you kind
of have in your mind,
what's the purpose of red blood cells?
Don't look at your notes.
Just see if you can pause and reflect,
what's the purpose of red blood cells,
what's the purpose of white blood cells,
and what's the purpose of platelets?
Okay, ready? Let's keep going.
Remember that the CBC facilitates
us identifying anemia,
infection, or leukemia.
And we're going to talk about
how those lab values are
particularly unique to each
one of those things.
So if I look at a CBC, it might give
me a clue if a patient is anemic,
meaning they don't have enough oxygen-
carrying capacity because they have
low red blood cells.
Maybe they have an infection. You're
going to see those white cells go like crazy,
or a disorder like leukemia.