Beautiful table here for
us to truly understand.
Do you remember those wheels of life? And by that
I mean, we took a look at two circles, one
circle was dealing with tonicity and the other
circle was dealing with volume. Do you remember
that? And I told you at that time with the circles
that you wanted to pay attention to the tonicity
first because that becomes of upmost priority
and importance within our body on a day-to-day
breath-by-breath moment, With that said,
tonicity, what was the hormone that was responsible
for properly monitoring or regulating your
tonicity? I believe it is ADH. That is correct.
And osmoreceptors, remember all of that also
plays a role as we discussed in the very
beginning of this lecture. Let us take all
this into consideration. I want to set up
this graph. You see it first and then we are
going to walk through the verbiage, not vice
versa. I want you to see it first, then we
will walk to the words. Otherwise, I am wasting
your time. On the X-axis is your percentage
change. On your Y-axis, actually says plasma
ADH. So as you move up the Y-axis, you are
increasing your plasma ADH and the X-axis
represents the percentage change that is occurring.
Now, that is just the parameters. Let us now
make sense of all this, what I really need
to also pay attention to is the actual terminology
here, that yellow golden lines solid and linear
fashion that you are seeing there is your isotonic
osmotic increase. I would like for us to work
on that first, please. That linear relationship
that you see on the golden line there represents
for every percentage increase in tonicity.
You find a linear increase of your ADH. So
even a little bit of increase of your osmolarity
tells your osmoreceptors and signals the release
of ADH. That is how important as I said plasma
osmolarity is to you and how important it
is to regulate that. Okay. If that is the
case and that is your osmotic line, what is
the green curve that we are seeing? Well
go up to the key and in the key, you'll noticed
that this is isotonic volume depletion.
Do you see as to how I emphasize depletion? So the
percentage change here on your X-axis is representing
volume loss percentage. What is that magic
number? Do you remember when you had a crossover?
What crossover? What does that even mean?
Dr. Raj, I don't remember anything that you
are saying. Yes, you do. The wheels, the tonicity
was one wheel and that was dealing with ADH
and the other wheel in the circle that I showed
you was dealing with aldosterone and volume
and then I told you that tonicity is measured
and regulated all of the time, volumes when
need be with aldosterone. At some point in
time, when you have enough volume loss
of ten percent of the effective circulating
volume, you will then have a crossover
effect of one circle to another. In other
words, you will have the angiotensin II from
the wheel of the volume, which is then going
to trigger the release of ADH, which is then
going to do what? Now keep in mind what the
heck is going on here clinically? You have
lost greater than ten percent of volume. Do
you understand the significance of that?
Let us back up, big picture. Your patient just
lost greater than ten percent volume. What
does that mean? Massive hemorrhage. So what
do you think is the most important thing to
do in your body? It is to replenish what?
The volume, isn't it? So, therefore, the osmolarity
will then be sacrificed for the replenishment
of the volume. That is a lot of information
for you to interpret in this graph and all
of it is here, but the only way that you make
sense of it is by listening to my previous
discussions that we have had about regulation.
And if you weren’t paying attention there,
that is okay, there's a lot of information.
Go back and review those wheels real quick for me. Take
a look at that crossover effect. You pay
attention to that ten percent that I refer
to there and you will notice that here. Take
a look at the red box now. That red box as
you move from zero on the X-axis, 0, 5, 10.
That's ten percent. Now for volume, that means
that you have lost up to or greater than ten
percent. I want you to move up now, the Y-axis
you will notice. Please notice between
0 and 10 percent was there much of a change
on your Y-axis? Look. Once again between 0 and 10
were there much of a change on your Y-axis?
No there wasn't. It was pretty flat. It means
the ADH remained at a relatively constant
level maybe it increased a little bit, but
my goodness you go beyond 10 percent loss
of your volume, you almost find not just a
linear, but hyperbole type curve in which
you have a massive release in ADH because
the volume must be replenished because your
patient is in severe hypovolemic shock. With
all that said, let us now walk you through
the verbiage that we see here. They're controlled
by the hypothalamic osmoreceptors. Who is?
ADH secretion. That is the theme of this slide.
ADH secretion stimulated by plasma osmolarity.
Plasma hypovolemia. Stop there. That is the
big deal now, isn't it? When do you have hypovolemia
that finally releases ADH? That is the big point.
That is the green line. That is the
green curve. It is only when you lose greater
than 10 percent in which plasma hypovolemia
will release ADH. Apart from that, on a homeostatic
control mechanism in which everything is normal,
it is plasma osmolarity that truly regulates
your ADH, as I said on a minute-to-minute basis.
This crossover effect meaning who is it that
comes from the volume circle that then is
going to release ADH to then control or
should I say release your ADH? And that is going
to be angiotensin II. Remember the angiotensin II
was on the wheel of your volume and that
was dealing with sodium and company. You only
have that crossover effect with angiotensin II.
So, therefore, that also becomes extremely
important. Let us move on ADH inhibition.
So if hyperosmolarity within the plasma, therefore,
released ADH, you will notice you have hypo-osmolality.
In other words, your plasma is diluted thus
you are going to inhibit ADH and plasma hypervolemia,
the opposite. They are also though, would
be, well we will take a look at a graph in
a little bit where 10 percent becomes interesting.
So at this point though, your focus should
be on volume loss and only after you have
understood everything that I have said, you
will go into hypervolemia, but not before
that, please. Now, overall physiologic
range of effective
circulating volume, what that represents is
from 0 to 10 percent X-axis and you don't
have much of a change in ADH with volume.
In general, only volume depletion now here
is the point. Take a look at where now we
have had a blank from 0 to 10. The 10 has
now been boldened and look at the verbiage.
The words are saying here depletion of
greater than 10 percent has a severe stimulation
of ADH release and hence you find that the
green curve is now taking a drastic increase
on your Y-axis. What happen here? Hypervolemic shock