Medical Acid Base and ABGs Explained Clearly by MedCram.com | 4 of 8


welcome to Part 4 of Medical acid-base I
wanted to just review what we had just talked about before and that we’ve got
two different types of metabolic syndromes metabolic acidosis metabolic
alkalosis and that we’ve got for respiratory and the reason why there’s
twice as many respiratory’s is because you have to deal with the situation
where respiratory has no compensation from the kidney and then or very little
compensation from the kidney and then chronic compensation from the kidney
same on the respiratory alkalosis side as well and the key point that we
discovered here is that when the pco2 and the pH are going in the same
direction either up or down the primary pathology is metabolic and
then the opposite is true for respiratory when we see the pco2 and the
pH here for respiratory acidosis is going up and the pH is going down and
for respiratory alkalosis the pco2 is going down the pH is going up again
that’s a respiratory process and what I want to do is kind of put this together
for you in a nice graph especially for those people who are spatially inclined
let’s go ahead and clear this and I want to kind of draw a graph for you and it’s
going to be a graph that hopefully you’ll take with you and you’ll kind of
see the utility in this so it’s just a regular graph with specifically pco2 on
the y-axis and we’ll put you know a middle here which is about 40 and here
pH with the middle of 7.40 okay and we said that there were six different types
of acid-base disorders so let’s talk about let’s put some lines in here so we
can kind of get an idea about what we’re talking about okay so that’s that and let’s go ahead and put a line right
about here and we’ll put one more line and right about here okay so here’s our
graph now we already said that if we had a situation where the pco2 and the pH
were going in the same direction that had to be a metabolic and so let’s go
ahead and label these this one here would have to be what well this line
would have to represent that of a metabolic process because the pco2
as it’s going up so is the pH so we know that this is down here
in metabolic acidosis and why is it acidosis because the pH is low so at
metabolic acidosis tend to push things down in this direction whereas this must
be a metabolic alkalosis okay let’s talk about these other ones so these must be
respiratory the question is which one is a respiratory acidosis so which one’s a
respiratory alkalosis well we know that these two up here must be acidosis
because again they’re lower than the pH and are lower than pH of seven point
four oh and these must be respiratory alkalosis because they’re higher than a
pH of seven point four Oh notice though that this one here has less play in
terms of the pH and so if you were to conclude that this must be a chronic
line here and this must be the acute you’ll be right because again the
chronic allows for kidney compensation and there’s less shift so this would be
a chronic respiratory acidosis and this would be a chronic respiratory
alkalosis and if we go to this one this would be acute respiratory acidosis and
this one down here would be acute respiratory alkalosis and you can kind
of see what this is going to look like now let’s talk about this so as we go
down here let’s talk about the metabolic acidosis first remember what’s going on
in metabolic acidosis bicarb is falling and as the bicarb Falls the pco2 is go
to also fall and when they both fall remember the bicarb is going to fall
further than the pco2 and you’re going to get a low pH so how do you know
you’re dealing with a metabolic acidosis well we have something called winters
formula or winters rules and let me put this in terms of an equation and I’m
going to be talking about these equations so that you could figure this
out now we all know that and I’m just going to sort of right over here off to
the side that we look at the henderson-hasselbalch equation in terms
of hco3 over co2 or the P co2 and we know that things either go up or they go
down or what-have-you and so what I’m going to do is I’m going to tell you for
every single point that one goes up what does the other one do so we know that
down here they’re both going to be going down okay they’re both going to be going
down how much does the bicarb go down well I’ll tell you for every one point
that the bicarb goes down the pco2 should also go down by one point and
that’s how you can tell that what you’re dealing with there is a metabolic
acidosis what about a metabolic alkalosis
well things up here are actually going up and in fact the bicarb is
going up the ratio for up here is for every two points that the bicarb goes up
the pco2 should go up by one point and that’s how you’ll know so what do I mean
remember everything starts off with a 24 and a 40 so here what would this speed
if things were to drop by let’s say four points it would be 20 over 36 okay
alternatively it could also be 14 over 30 so in other words for every point
that the numerator drops the denominator should also drop from this going to
metabolic alkalosis for every two points that the bicarb goes up so let’s pick a
number here let’s say oh I don’t know 30 it went out by 6 points and so the by
the vco2 should go up by 3 points so this would be 43 ok so let’s go and look
at the chronic respiratory situations let’s first of all look at acute
respiratory acidosis so what’s happening in acute respiratory acidosis remember
the lungs are not breathing the pco2 is going up if the pco2 is going up then
here our fraction is going to start from the bottom and here the pco2 is going up
by a lot and we’re not expecting a huge increase in bicarb why is that because
it’s a cute we haven’t had the kidneys the chance to kick in so here the ratio
is 10 for every 10 points that the pco2 goes up the bicarb only goes up by one
point and so what would be a good example here a good example here would
be for instance if this was 50 on the bottom and this would be 25 that would
be acute respiratory acidosis what about in chronic respite
really dosis again same situation we have a fraction however because the
kidney is now kicking in we are expecting to see less of an increase in
co2 without the the kidney kicking in and here it’s for every three points
that goes up on the pco2 the bicarb goes up by one point so
something that we would see here let’s let’s say we had the same kind of ratio
let’s say we had 49 okay that would be nine increase for every three that would
be three of those and so we would add three to that that would be 27 okay
because for 249 that’s nine points 9 divided by 3 is 3 3 times 1 is 3 we add
3 to the 24 we get 27 and that would be the new ratio and that’s how we can tell
let’s go down to these again chronic respiratory alkalosis here the ratio
actually let’s go to acute respiratory as alkalosis remember here what’s going
on the lung is blowing off a tremendous amount of co2 and the kidney has not had
a chance to kick in so for every 5 points that the co2 drops by the pco2
drops by the bicarb is going to drop by 1 point and so let’s look here let’s say
that a good example would be lets say that the pco2 dropped to 30 okay that
would mean that the bicarb would drop down to 22 okay if you’re doing your
mouth right and then similarly over here chronic respiratory alkalosis here the
kidney has been allowed to kick in so we’re not going to get as much co2 drop
per drop in bicarb and so here the co2 is dropping again but for every two
points that it drops the bicarb goes down by one point and so what would that
would mean again if we had a ratio an example where the pco2 had dropped down
to 30 that’s a out going from 40 down to 30 for every
two of those would be five so we drop by five that means that our bicarb would
then be about nineteen so again these are ratios for every one that the the
bicarb or sorry for every one of the bicarb drops here are the pco2 drops by
one and so these ratios here the ones that I’m circling these here are ones to
know for each of these different types of categories because it will help us
later identify if something else is going on okay these are the
characteristic signatures of these type of processes and there are six processes
these are sometimes known as winters formula these are ones that I’ve kind of
made up for the for the six here we got metabolic acidosis metabolic alkalosis
we’ve got acute respiratory acidosis chronic respiratory acidosis chronic
respiratory alkalosis and acute respiratory alkalosis and so those are
the rules great so I think the basic points here
were understood this is concludes part four we’re going to put everything to
come together and show you how to attack an acid-base problem and put it all
together through a systematic step in part five so please join me for part
five and we’ll kind of review everything there Thanks

25 thoughts on “Medical Acid Base and ABGs Explained Clearly by MedCram.com | 4 of 8

  1. DR S. you are the best…I teach nursing and you have helped me understand this elusive subject so much better..thank you

  2. Hi, can you please explain how the maths work at the end of the video? I don't quite get the method :/

  3. who  can  tell  me  about   the   winters rules,where  i  found  them,i  want  to read  some  article.I  dont  understand  why in  acidosis  the   HCO3 is down by 1  and  the  compensatory  drops  1 by  Pco2.WHy   not HCO3  drops 2  and  Pco2  by  3    ,this  i  want  to  understand.

  4. Help!!!! Can I find the lecture and notes to purchase under pulmonary??? I need to get my hands on the notes for this lecture soon please, I'm a nursing student and I have an exam soon.

  5. Thanks for such a great explanation. I wonder as doctors we use our reasoning and creative mind to a minimum compared to majority of professions who use is to the maximum, what we mainly do is cramming. All we require is a good memory.

  6. Hi Dr, i read that for every 1 meq/L fall in HCO3 the CO2 will decrease by 1.2 for metabolic acidosis and for every 1 meq/L rise in HCO3 the CO2 will increase by 0.7 for metabolic alkalosis. Is this correct?

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