00:02
Approach to acid base.
Well, now we get into specifically
metabolic acidosis.
00:07
Keep that in mind.
00:08
So for metabolic acidosis,
you will calculate the anion gap.
00:11
This is what you will know
clinically.
00:13
And this is what you stick with,
and do not, I repeat,
DO NOT, for the sake of time,
use anion gap for
metabolic alkalosis
That will drive you crazy.
00:21
Metabolic, and it's really no need.
00:23
A metabolic acidosis. I'm gonna
explain what this anion gap means.
00:27
I'll show you graphs and pictures,
and then we'll go one step further.
00:30
We already discussed
where it's your cation,
sodium,
do not use potassium,
negligible.
00:38
3.5 to 5.0
potassium negligible,
And you have your anions,
chloride and bicarb.
00:44
Normal anion gap
10 to 14.
00:48
You can use 10
as a point of reference.
00:51
Next, what do you have to do
clinically?
You know, so many conditions
in which your patient
could actually present
with hypoalbuminemia.
01:01
So many? Yes, you do.
You know, nephrotic disorders.
01:05
And you also know about
liver damage
As a pretty major
in terms of society?
Sure it is.
01:12
Now, what type of charges
and protein have?
Negative charge.
01:17
So, therefore,
for every 1 g/dl below 4
you will subtract 2,5 mEq/L
to "normal anion gap".
01:26
By normal anion gap
we mean approximately 10.
01:29
So, you have to clinically then
correct for hypoalbuminemia,
if need be,
if that is a patient who has
something like cirrhosis,
something like nephrotic disorder,
and the question is asking you
about metabolic acidosis,
and to please figure out
the anion gap.
01:48
What else do you want to do?
Well, this is the
unmeasured anions,
and the unmeasured cation,
the sodium.
01:55
You rearrange the formula,
you end up getting your anion gap.
01:59
What's your normal?
Approximate 10.
02:02
What does it all mean?
Let me set this up for you.
02:05
On your left,
all cation that you will use.
02:10
Should I say, the only cation
that you use clinically,
is a sodium of 140-145.
What have you?
Okay, so that's my cation.
02:19
What must always exist in your body
as a measure of homeostasis?
Electroneutrality.
02:25
So whatever
positive charges you have,
you have to be able to equate
that to negative charges.
02:31
It is that simple?
So opposites will attract.
02:35
So let's add this up, shall we?
Say of 140 of sodium.
What does that? Cation.
02:40
We have chloride between 95 to 105.
We have an anion of 105, chloride.
02:46
So now we have a difference
of how much? 35.
02:49
So, if you add up all the anions
well, now you have 25.
02:53
And what are you anions
in the formula? Take a look.
02:56
Chloride plus bicarb.
02:58
Well, that then adds up to, what?
Well, we have at 130.
03:02
Which anion gap?
10.
03:05
Is that normal? Absolutely.
03:07
Absolutely. So the unmeasured
anions of 10 is perfectly normal.
03:12
So what are they?
That's your proteins.
03:14
By proteins, I don't mean albumin.
03:15
And so therefore, they will be like
sulfates and phosphates,
organic anions.
03:19
So some of these will then
contribute to that an anion gap.
03:23
In other words, excess anions.
03:26
Normally, about 10.
03:28
What does this mean
in terms of moving above 10?
We'll take a look.
03:32
Say that you have a patient
who's exercising.
03:35
And when they exercise excessively,
is it possible that you
start feeling cramps and pain
in your muscles? Aw.
03:42
Well, what does that mean to you?
That means
that you are now shifting
from aerobic
to anaerobic glycolysis, aren't you?
As you shift into
anaerobic glycolysis,
then would you produce
more of and less of?
A less of ATP
and you produce more lactic acid.
03:58
To lactic acid buildup in your
muscles then gives you that cramp.
04:02
Doesn't it?
Sure it does.
04:03
Another big topic as well is if
there's just straight up ischemia.
04:08
Anytime there's ischemia.
04:09
You know that there's an
increase in lactic acid.
04:11
To begin with, when would you
even consider doing anion gap?
Metabolic acidosis.
04:16
What is lactic acidosis?
The metabolic acidosis.
04:20
So now you do anion gap.
04:22
You find your cation of 140.
04:26
Lets do your anions
while the board's give you
something like your bicarb of 10
and a chloride of 105.
04:33
What do you get?
You get a measly 115.
04:37
So you get 115.
04:39
So what is the anion gap
at this point?
140 minus 115. I do believe
that that is your 25, isn't it?
Okay. So you get a 25 there
has been anion gap.
04:48
What's normal?
Approximate 10.
04:50
What accounts
for 15 additional anion gap?
The lactate.
04:57
An example, here you go,
of anion gap metabolic acidosis,
in fact, is lactic acidosis.
05:03
Can you replace that
lactic with ketones?
Sure you can.
05:07
Will you end up getting
diabetic ketoacidosis, don't you?
Keep this picture in your head,
as far as the electrolytes
that are responsible for
contributing to anion gap,
because we will have to go
one step further.
05:18
And another step further,
and another step further,
so that you get
every single perspective
of anything that's thrown
at you absolute correct.
05:27
The more knowledge that you have,
the more aware
that you know things exist,
the less you'll be confused, right?
But be careful though, you also
have to have a firm understanding.
05:35
Let's move on.
05:36
So elevated anion gap refers
to increase in unmeasured anions.
05:41
These include ketones, or lactate.
I just sent you a new picture.
05:47
Step four. Read this.
05:50
For elevated anion gap
and metabolic acidosis.
05:55
AG stands for anion gap.
05:57
MA? When would you only
use anion gap, please?
Good, metabolic acidosis.
06:02
So when you're using this step,
if you need to?
Remember,
every step of the way,
you're asking yourself
this question,
"Have I answered the question?
Have answered the question?
Have I come to the proper
conclusion about my patient?"
If you have, then step away,
you've done your job.
06:18
Let's move on to the next one.
06:20
Here says, that you haven't.
06:21
And you do an
anion gap metabolic acidosis.
06:24
That's what you have.
Give yourself an example such as
lactic acid or DKA.
06:28
We'll go through differentials.
Big time.
06:30
We've talked about some
of that, the mnemonic
that you may use such as
MUDPILES.
06:35
Right, we talked about Methanol,
we talked about Uremia,
so on and so forth.
06:40
So those are your differentials.
06:41
Check urine ketones, and if not
present, check renal function,
lactate, toxin screen,
and osmolal gap.
06:50
What does that mean?
Please give me two ways
in which a patient
can develop metabolic acidosis.
06:56
Two ways. Keep it simple.
06:59
Endogenous within the body.
Exogenous you're consuming it.
07:04
Endogenous, I just talked to you
about exercise.
07:07
What are you producing?
Good, lactic acid.
07:10
What is that?
An anion gap metabolic acidosis?
What about diabetic ketoacidosis?
That is also, what?
An anion gap metabolic acidosis.
07:20
Where is the origin of that?
Good, endogenously.
07:24
What if you were consuming an acid?
What do you mean? Such as
ethylene glycol, such as methanol?
Such as, ah, salicylate.
07:34
So, exogenous sources?
And what can you possibly do
mathematically, clinically,
so that you,
if you can figure out
how is it that the patient
has developed
an elevated anion gap
metabolic acidosis?
Understand something here.
07:50
Whenever you're given a piece
of information of anion gap
that automatically puts
in the realm of above 10,
maybe 25, maybe 30.
07:59
What if it says non-anion gap?
That means normal, which is
not our discussion yet. Not yet.
08:04
Keep in mind the big picture.
08:06
So, what is the osmolal gap?
It is the measured osmolality,
subtract this from the
calculated osmolarity.
08:13
For example, let's say that
you calculated osmolarity was
approximately 300.
08:17
So, now, let's say that your
osmolal gap is greater than 10.
08:21
If your osmolal gap
is greater 10,
guess where this anion gap
is coming from?
Possibility of ingestion of cause
of anion gap metabolic acidosis.
08:31
So if you find that the
osmolal gap is increased
between the
measured and calculated,
guess what, you have most likely
confirmed or highly now suspect
that there's going to be
an ingestion
of anion gap metabolic acidosis.
08:47
Interesting, isn't it?
So this might then give you
a differential of well, huh,
exogenous?
Now you're looking for sources?
What exactly did
your patient consume?
Was it ethylene glycol?
Was it methanol? Was it alcohol?
Was it type, some type of drug,
so on and so forth?
Let's continue.
09:05
Now, I'm going to go
through this efficiently.
09:09
It's just enough where you have
enough information.
09:12
So at this point,
you have absolutely diagnosed
elevated anion gap
metabolic acidosis.
09:17
You have now figured out that
this patient has exogenously taken
some kind of acid.
09:23
So therefore,
you got an increase in osmolal gap.
09:27
Is there a possibility
that your patient
has an anion gap
metabolic acidosis,
along with a mixed non-anion gap?
True.
09:37
So therefore, this brings us
to an interesting concept
called the delta gap.
09:41
All that I wish to point out to you
based on feedback that I've gotten,
making sure that I give you
everything that you need
for proper tools. Let's begin.
09:52
Calculate patients anion gap.
09:54
But we already know the patient has
an anion gap metabolic acidosis.
09:58
So that will be given.
You'll know or you've calculated.
10:01
And then from this,
you subtract your normal anion gap,
that literally means
your delta gap.
10:07
What the heck does that even mean?
That means if the change in bicarb,
remember that picture
that I just showed?
I asked you to please conceptualize
and keep that bar graph
of sodium on one side, of 140?
What are the two anions
on the other side?
You buy carbon chloride,
which gave you the original?
Well, there, that gave you
approximately, 125.
10:30
And so therefore,
should I say, 130.
10:34
And we had a
normal anion gap of 10, right?
So everything equaled out.
That was normal.
10:38
And I told you, in our next figure,
that if that
well, you started adding in lactate,
you're taking away, what?
Bicarb.
10:47
And you already know,
a metabolic acidosis,
that your bicarb has decreased.
10:51
My point is this.
Is that changing bicarb?
Is that changing bicarb
enough or sufficient
to properly explain
the change an anion gap?
This will then give you
a Delta gap.
11:05
Let's take a look.
Compared to change in bicarb.
11:09
What does that mean?
Once again,
who's your patient so far?
Metabolic acidosis anion gap.
11:15
Where that anion gap come from?
The osmolal gap would
tell you most likely,
if it is going to be
exogenous, or endogenous
and greater than 10, exogenous.
Stop there.
11:26
So now we have anion gap
metabolic acidosis.
11:30
And now you want to see
as to whether or not
there's an underlying issue.
11:34
So underlying issue here
is going to be,
well, is the change in bicarb
equal to the change in anion gap.
11:42
If those two equal out,
then you know that your patient
has normal change.
11:47
and it is strictly a
anion gap metabolic acidosis
with no mixed underlying issue.
11:54
Let's take a look at a few.
11:55
Example, a bicarb of 16,
stop there.
12:00
Normal bicarb. About 24.
We'll use 24.
12:04
Dropped down to 16.
12:06
So far, very clear that we
have metabolic acidosis.
12:10
Remember, this entire topic is
anion gap metabolic acidosis.
12:13
So, all I want to do is make sure
that we're on the same page.
12:17
There is an anion gap of 20.
12:19
Either they gave it to you
or you figured it out.
12:22
How did you do that?
Sodium minus your anions.
12:26
Okay. Normal anion gap is 10.
12:30
But here we have 20.
12:32
So this is definitely an
anion gap metabolic acidosis.
12:35
Next, let's say your
normal anion gap is about 12.
12:39
Now, we take the difference, the
absolute difference of 20 and 12.
12:46
We get 8,
unmeasured anions.
12:48
Okay, let me stop you there.
12:51
If there's a change of
8 unmeasured anions,
and you're thinking about
that graph,
the bar graph that I showed you
with cations,
obviously,
we're on the side of the anions.
13:03
And if there's a change of 8,
what can it change
should we find in bicarb?
Eight.
13:10
If both of these are equal,
then it is a pure anion gap
metabolic acidosis.
13:16
What is this called? A delta gap.
13:18
Now, before any of this, obviously,
you did your degree of compensation.
13:23
And by that we mean,
if it was metabolic acidosis,
and that respiratory compensation?
What was it
respiratory compensation,
and metabolic acidosis?
A decrease in bicarb should equal
a decrease in carbon dioxide.
13:35
So that step was already
done by you,
and that's in the initial stages.
13:39
So, normal bicarb 24.
13:42
The patient's bicarb 16.
13:44
What's the absolute difference?
Eight.
13:48
It is the change in bicarb
equal to the anion gap change.
13:52
Yes, it is.
13:52
So therefore, what's my diagnosis?
A pure anion gap,
metabolic acidosis.
13:59
Now, if the change is
greater than changing bicarb,
it's a concomitant
metabolic alkalosis.
14:08
Let me show you something as you
move through here as an example.
14:10
If the change in anion gap
is less than bicarb,
and it's a concomitant non or normal
anion gap metabolic acidosis.
14:19
Stop there.
Now, I'm going to show you something
so this makes better sense.
14:23
For example, let's do this one.
14:26
Bicarb of 10. Normally, by 24.
14:30
So we have metabolic acidosis.
14:33
Okay. Anion gap of 20.
14:36
Either you calculate it
or they've given it to you,
and so therefore we have,
what's my diagnosis?
Obviously,
anion gap metabolic acidosis.
14:43
That's the change in anion gap.
We get 8.
14:48
Stop there. Now, what?
Well, we should find
a change of bicarb being 8.
14:54
Let's see whether or not
that is taking place.
14:57
Normal bicarb of 24
and the patient's bicarb is 10.
15:01
What's the absolute difference?
14.
15:04
Uh-oh.
15:06
The unmeasured anions,
anion gap,
does not add up
to the change in bicarb.
15:13
Do you see this?
Wow, so what's happening?
There's a difference of
how much there?
The difference of 6,
isn't there?
8 and 14.
15:22
So the six means what?
It's accounted for.
15:26
So the fact that you
do not find an anion gap,
which explains this,
there must be an underlying issue.
15:33
What is the underlying issue?
Here, you'll notice that
go back to the previous discussion,
that we just had about
anion gap being less than.
15:42
If the anion gap,
the 8
is less than
the change and the bicarb,
than this to you
gives you a combined,
combined the diagnosis of
anion gap and non-anion gap
metabolic acidosis.
15:57
This is as tricky as they will get,
I wish to introduce
the concepts to you.
16:03
If I were you, I would go through
the first few steps
where you figure out the pH.
16:08
You forgot the primary, you figure
out the degree of compensation.
16:13
If need be, for metabolic acidosis,
you do an anion gap.
16:18
With anion gap, you then figure out
if it's exogenous or endogenous.
16:22
It would behoove you to make sure
you pay attention to the
osmolal gap.
16:26
Once it get as far as that
maybe perhaps
you take a look at delta gap,
if need be.
16:32
Most of your questions
will be answered
as far as
what I've taken you.
16:37
Now, if it is respiratory,
and it's renal compensation,
what did you want to know
about that?
It can have an
acute and chronic change.
16:45
Continue.
16:48
So for a normal anion gap
is the only thing
that we're left with now.
16:51
With the normal anion gap,
what do you want to do?
This is interesting as well.
16:56
With a normal anion gap
metabolic acidosis,
you know,
that there is no anion gap.
17:03
I mean to say that,
or in other words, really,
it's within normal limit.
17:07
Okay.
So what does that mean to you?
Well, check urine anion gap.
Why?
Because you don't know
as to whether or not that bicarb
is being lost through the urine,
or if the bicarb is lost, where?
Through the intestine.
For example, think diarrhea.
17:26
When you have diarrhea,
what happens?
You lose bicarb.
17:30
It has nothing
to do with the urine.
17:32
So you're non-anion gap
metabolic acidosis,
by using clinically,
a urine anion gap
will then give you
how your patients lost their bicarb.
Is that beautiful?
Well, not so much for the patient,
but for you.
17:46
Urine sodium + urine potassium.
17:50
From this, you subtract your
urine chloride. Stop there.
17:53
The first time that
we're seeing potassium
in the urine, it is significant.
17:56
And when I bicarb,
why isn't bicarb here?
Because that's what you're
trying to figure out.
18:00
If the urine anion gap is positive,
think of it as being positively
getting rid of bicarb.
18:08
You want to think of
potential causes such as
renal tubular acidosis, type 2.
18:13
And type two wasn't a problem.
What was it?
Two lines to make an X.
18:19
Proximal convoluted tubule
is type two RTA.
18:22
What could be a potential problem?
Oh, carbonic anhydrase inhibition.
18:27
So therefore, your anion gap
will be positive for bicarb.
18:31
What if you do the formula and
that urine anion gap is negative?
And how would you get?
Well this means that the bicarb is
not being lost through the urine.
18:41
In fact, it's being lost, where?
Through the GI tract.
18:45
Welcome to diarrhea.
18:46
This is for non-anion gap
metabolic acidosis.
18:50
This is all for what?
A metabolic acidosis.
18:54
You see as to how important it is
for you to absolutely do
the anion gap.
18:57
So put you into two major
families of differentials.