Now the clinical application of creatinine
is pretty much what this entire lecture series
is about. Do we use creatinine clearance?
Yeah, but rarely. So what does that mean?
You really are thinking about your patient
suffering from renal disease. In the process
of renal failure. What is the number one cause
of renal failure? Diabetic nephropathy. So
if your patient over a long period of time
has diabetic nephropathy, then you can pretty
much predict that your patient is going to
go into renal failure and you want to truly
assess as to what the functionality of the
kidney is and that can be the threshold, the
critical point at which the patient is then
necessitated or is required to go on dialysis
and vary from patient to patients so we are not
going to get into actual kidney function
or percentage that then takes you into dialysis,
but it is important for you to understand
how to correlate the creatinine that you will
get in which say you go from one and will
keep it simple. Remember from the blood, if
you get 0.6 to 1.2 for learning purposes,
we are going to say 1.0 we are going to repeat
all this upcoming. All I am doing here is introduction
and then when we actually see it, then it
will be a positive reinforcement. So if we
say that blood creatinine is 1.0 and we keep
our GFR simple as well with the rate of 100,
we are going to use those values so that we
can use creatinine in a clinical application.
So we are clear about what is happening.
If your creatinine moves up from 1.0 to 2,
is that good or bad, that is your first question?
Keep it simple. Bad. How bad? If your creatinine
that you are measuring in blood moved up from
1.0 to 2, guess what happened? You weren't
filtering, why? It is kidney disease. That is no joke.
What do you mean no joke? How dramatically would you lose
kidney function when you move from 1.0 to
2.0? Fifty percent. That means 50 percent
of the kidney function has been lost because
the creatinine is stuck in the blood. Now
we will reinforce that very fact as we
move on, but I want to make sure that I make
an impact now. So because it requires timed
urine collection, generally considered a nuisance.
What is the creatinine clearance? Instead,
what we do. Understand this point versus the
points that I just made, which is here you
as a clinician are quickly going to assess
the functionality of the kidney by checking
the creatinine in the plasma. It is a surrogate
marker. It is the perfect marker. Of course
not, why? Because it is slightly secreting.
Keep that in mind. So if there is a huge change
taking place in the kidney that creatinine
that you are going to measure in your plasma
is not going to be the best indicator. I hope
that is clear. So at what point would you
perhaps recommend creatinine clearance. If
you know for a fact that let us say that your
patient came in and the creatinine levels
in plasma were 2.0 and an approximate assessment
of GFR sure, but then how do you get a better
assessment? Why not recommend a creatinine
clearance? That is all about next step of
management. This whole thing that I have been
talking to you about with creatinine and its
assessment of your kidney. Let us go into
little bit more detail.
Lets say that this is plasma creatinine
and it is inversely proportional to GFR. What
does that even mean Dr. Raj? How do you use
this with the patient? That's a lot of math
granted. Let us do an example. Let us say
we give creatinine. May I ask you one more
time normal levels of creatinine approximately
0.6 to 1.2. If you use that you will be in
good shape. Trust me. So now you got a creatinine
level 1.0. What does that mean? That means
you are within normal range of GFR and we
will use GFR here for learning purposes as
100 and I want to harp on the units here.
Milliliters per minutes,allow my voice and
what I am telling you to haunt on you forever
more. The units of GFR milliliters per minute.
Are you hearing me in your dreams? Now, what
if your creatinine moved up to 2? If it moved
up to 2, what is this? what kind of creatinine is this?
Plasma. So what happened? Oh no! GFR has dropped.
How much? By fifty percent. So if normal GFR
was 100, the GFR now dropped down to approximately
50 milliliters per minute. That is the biggest
drop in percentage as you go from 1 to 2.
Now let us say your creatinine moved up to
3, where is my creatinine? This means plasma.
What is normal? 0.6 to 1.2. I'm going to keep repeating
this. If you moved up to 3, then you lost,
well, now you have moved down to 33. And as you go
from 3 to 4, it is 25. Now you tell me where
is the biggest drop? As you went from 3 to 4 or
1 to 2. What am I referring to? The creatinine.
Where? In your plasma. If your creatinine
goes from 1 to 2 in the plasma, you have dropped
by 50 percent. As the creatinine goes from
3 to 4, you have dropped down by 8 percent.
But the point is this. Once you get past 2
and it keeps rising just because the drop
is not as dramatic as you go from 3 to 4,
it doesn't mean that the kidney is not in bad
shape. Thirty-three percent is horrible kidney
function, approximately 25 percent is even
worse now. As I said for learning purposes,
this is not a nephrology course. This is an
introduction nephrology in just enough detail
so that when you walk on the ward and you
take your boards, you will be successful as
what objective is. So 25 percent is quite
low. Now in terms of is that patient required
to go on dialysis well that depends on the
overall well-being of your patient and that
can differ from patient to patient here.
I hope that is clear and only if it is are you
permitted to move on. Next.
Clinical application further. That's everything
we just talked about. So let us go and read
here a little bit. We have a GFR and as we
go from 1 to 2 that is much more of a significant
drop as opposed to your creatinine go from
4 to 5. Is that clear? What does that mean
to you again? Close your eyes. Where is this
creatinine? In the plasma compared to creatinine
clearance. This is plasma. What is normal?
0.6 to 1.2. We are going to use 1. As we go
from 1 to 2, how much did your kidney function
drop? By 50 percent, much more significant.
Now, if it goes from 4 to 5, my goodness the
drop is not going to be as dramatic, but both
are really bad and how do you assess this
further? Well. We will walk into that right
now. I truly want to make sure that we lay
down the foundation for creatinine. Now as
we get older, understand that maybe perhaps
our GFR drops naturally. But before move on also
keep in mind with the creatinine, it is slightly
secreted. What does that mean to you? One
more time. Tell me the relationship between
the clearance and GFR. GFR is filtration.
Clearance is what is actually being evacuated
and the creatinine it is slightly secreted
thus your clearance is greater than GFR. Understood?