00:01
Students have always asked me "Dr. Raj, I am
having a hard time keeping straight and organized
the feedback mechanisms for water and sodium
pathophysiology." This is probably the most
important section here. You go through as
far as laying down the foundation of figuring
out the two compartments of ECF and ICF. What
kind of hormones would be involved and a little
bit of a clinical tag that I will be putting
in for you along with the physiology so that
you clearly know how to move on to in the
next lecture series of isotonic, hypotonic
and hypertonic fluid disorders. Let us now
begin. Basic definitions. Well, it comes down
to the kidneys, doesn't it really? Really. In terms
of being able to properly control and regulate
your fluids. Electroneutrality of body fluid
compartments become importance of back and
basic physiology when you are dealing with
action potentials and all. And you are dealing
with electroneutrality whenever you have a
positive ion such as sodium, of course, being
the most infamous of them all and along with
it must be a chloride so that you can have
proper electroneutrality as an example.
Composition between ICF and ECF is basically
what this line is saying. For example, when we talked
about total body water, you should
know that majority of your total body water
is where? Good. ICF. 2/3, isn't it?
Simple things that you knew and you
know that you keep repeating so that it becomes
part of your unconscious reflex. ECF, would
you tell me as to what is the most important
component clinically for us to measure in
your ECF. And you're telling me the vascular compartment,
isn't it? The plasma compartment. The effective
circulating volume compartment. All of this
is the same name. They are all synonyms for
your plasma compartment being a measly 1/4.
02:12
Now clinically most clinicians were used as
being 1/3, not saying that is wrong,
but at this point, I highly recommend that
you think of the plasma compartment being
1/4 and the interstitium being 3/4.
Body fluid compartments, we will take a look
at this. When we were dealing with the particular
box known as the Darrow-Yannet box, which is
being around for a long time and there is
a reason for that because it properly would
be one of the most effective measures for
you to clinically be able to see conceptually
in your head the shifting of fluids between
your ECF and ICF and there is a particular
chronological order that you should already
know, but we will then reinforce through clinical
examples. Regulation of water balance
and osmolality
will become the topic initially here before
we get into isotonic fluid disorders. At some
point, we have to have certain IV fluid definitions.
For example, the patient that was sweating
excessively coming in having low blood pressure,
what are you going to do with that patient?
Without even blinking, give that patient IV
fluids, of what type? Good. Normal saline at
0.9%. This we must talk about and give
you definitions of what saline is. What is
it? The electroneutrality component of sodium,
cation, anion, chloride, electroneutrality.
03:38
You see as to how everything is coming together
and then finally regulation of volume. Remember
the osmolality is an extremely sensitive indicator
in our body, isn't not?
Osmolality is extremely monitored closely
and as soon as there is any little change
in osmolality, then its the ADH that comes in. That
is the osmolality and at some point, we will
have to switch over to volume it may then
take priority especially if you are losing
volume in excess.