Medical Acid Base and ABGs Explained Clearly by MedCram.com | 7 of 8


so welcome to medical acid/base
part 7 we’re gonna go over some more questions and let’s just start off with
the next question which in this case is pH is equal to seven point two five $27.99 and a bicarb of 12 and the chem
seven shows a sodium of 140 a potassium of 4.0 a chloride of 96 and a bicarb of
12 so the first step again is to do the anion gap
what’s the anti gap so we add these two together and subtract from 140 so 96
plus 12 is 108 108 from 140 is equal to 32 definitely anion gap we now know
immediately that we have an anion gap metabolic acidosis and remember the
mnemonic for that as mud piles M for methanol you for your meid for diabetic
ketoacidosis but also alcoholic ketoacidosis and also starvation
ketoacidosis the P is paraldehyde eyes Ison eyes it or iron Ella’s lactic
acidosis is ethylene glycol or ethanol and SS salicylates so basically or and
the s could also stand for starvation ketosis as well if you wanted okay so
the anti gap is 32 which is a pretty sizable anion gap so what we need to do
next is calculate the Delta gap and the Delta gap is simply telling you above
and beyond 12 how much anion gap is there how
strong is this anion gap metabolic acidosis essentially so that’s simply 32
minus 12 which is equal to 20 what does that mean what is that 20 mean that
means there’s 20 units of conjugate base or conjugate anions floating around in
the blood that’s not accounted for here in the chem 7 and those 20 negatively
charged particles have to be balanced out we
the bicarb that was missing so essentially 20 units of bicarb had to be
taken away when they bound to the proton that came off of these 20 units in other
words what we could say is is if we took away the effects of this anion gap
metabolic acidosis and just took it away and see what else was there
we could add 20 to the bicarb and see what the bicarb would have been in this
case 20 plus 12 would have given us a bicarb of 32 what does that tell us
that means if we take away the known anion gap metabolic acidosis which we
already know is there what would the bicarb be while the
bicarb would be 32 and if the bicarb is 32 well let’s just write it down we
already know we have an anion gap metabolic acidosis we know we’ve got
that okay but if we were to take that effect away
since we know that Delta gap is 20 we know that that 20 sucked away 20 units
of bicarb let’s add back those 20 units of bicarb to the 12 that we have
currently and see what life would be like if we didn’t have that anion gap
metabolic acidosis what that would mean is our bike robe would be 32 and if our
bicarb was 32 that would mean that we also have a concomitant metabolic
alkalosis that could be like vomiting or Cushing’s disease or contraction
alkalosis or something like that so just by doing that we’ve already shown we’ve
already seen that we’ve we’ve identified two different metabolic processes that
are occurring okay so we know that so what’s the next step next step as we’ve
gone through is to look at the pH and the pco2 well we already know that both
are going down and we already have metabolic processes going so that’s
that’s easy we know that already the next thing is to do is to check to
see whether or not winters formula holds so obviously here we’ve got a metabolic
acidosis and a metabolic alkalosis which one do you think is stronger
well obviously the metabolic acidosis or in this case the anion gap metabolic
acidosis is stronger because we’re we’re acidotic
we actually acid emic okay so what we need to do is follow follow winters
formula for a metabolic acidosis and what does that say that says that for
every drop in the bicarb of one you should also get a drop in the pco2
of one and let’s see if that’s the case in our example here how much did our
bicarb drop by our bicarb went from 40 down to 12 how much of a drop is that
it’s about 28 actually it’s not from 40 down to 12
it’s actually from 24 down to 12 that’s the normal so if we went from 24 down to
12 that’s a drop of 12 how much did our pco2 go down by it went
from 40 down to 27 40 down to 27 is a drop of 13 and so what we see here is
that winters formula is followed perfectly for a metabolic acidosis okay
now let’s just say for some reason that the pco2 had dropped more let’s say it
had dropped 20 points for instance that would mean that instead of dropping just
13 points which it should have done if there was a pure metabolic acidosis
occurring or metabolic problem if it had dropped by 20 points that means there
would be an increased drop of the pco2 which would tell us that there must be
an additional respiratory alkalosis occurring and that would be an
additional diagnosis that we could put here
conversely if the pco2 had not dropped by 13 but it only dropped by 5 that
would mean that there must be a respiratory acidosis occurring because
the pco2 did not drop by the same amounts that it should have as predicted
by winters formula so basically when you’re doing this winters formula you’re
seeing if the pco2 drop is appropriate if it’s less than appropriate there’s a
additional respiratory acidosis if there’s an additional drop than what
should be predicted by winters formula then there’s a respiratory alkalosis
since in this case it fits winters formula pretty well then there’s no
additional respiratory component and what we’ve done is we’ve diagnosed
what’s happened an anion gap metabolic acidosis and a metabolic alkalosis okay
next question pH is equal to seven point two five $27.99
twelve chem-7 sodium 140 over 4.0 chloride is 118 and the bicarb is 12
first step calculate the anion gap 118 plus 12 is equal to 130 130 from 140 is
equal to 10 that means there’s no anti get metabolic acidosis
step number 2 go ahead and look at the pH and the pco2 are they going in the
same direction or in opposite directions in fact they’re going in the same
direction and they’re both going down therefore it’s a metabolic process and
it’s a metabolic acidosis because the pH is low therefore there must be something
pushing it down so it’s a metabolic acidosis the question is is there an
additional respiratory component and for that again we need to look at our
winters formula and that simply states that the drop in the pco2 and the bicarb
must be very similar again so if we have a drop in the hco3 minus and the pco2
that’s a drop of 1 to 1 let’s see if that occurred here so how much of a drop
in bicarb did we have again 24 is the normal number and it dropped from 24
down to 12 so therefore we had a drop in 12 points here we went from 40 down to
27 that’s a drop of about 13 again winters formula for metabolic acidosis
predicts that the pco2 went down exactly as it should have to compensate and
therefore there is no other respiratory component remember if the pco2 had gone
down even more than what was predicted by winters formula that would be an
additional respiratory alkalosis if the pco2 went down but went down by
less than predicted so let’s say it only went down by 5 points instead of 13
then that would be a respiratory acidosis in addition to the metabolic
acidosis next question pH is equal to seven point five zero 4890 bicarb 38
chem seven sodium is equal to 135 by car sorry P or potassium is three point six
chloride is 85 and as we mentioned bicarb is 38 first step measure anion
gap 85 plus 38 it’s 123 123 from 135 is 12 so the anion gap is equal to 12 the
Delta gap zero we do not have an anion gap metabolic acidosis step number two
look at the pH and the pco2 and see what the direction is here we have a pH going
up here we have a pco2 going up so it must be a metabolic problem and since
they’re both going up it must be in alkalosis question let’s do winters
formula again for every increase in the hco3 and an increase in the pco2 there’s
a two to one ratio in a metabolic alkalosis let’s see if that holds up
here how much that our bicarb go up by 24 is the normal number therefore it
went up by 14 points how much did our co2 go up by it went up
by 8 points is that ratio pretty consistent I would say so remember now
if the pco2 went up by more than 8 points then I would say there is a
concomitant respiratory s dosis if it went up by less than 8
points then I would say there’s a concomitant respiratory alkalosis but in
this case it looks like it’s about the same therefore we can say the secure
metabolic alkalosis okay next question pH is equal to seven point one five
forty 55 and a bicarb of 15 here we have our chem seven sodium is 140 potassium
4.0 chloride 98 bicarb is 15 first step calculate anion gap 98 + 15 is 113 113
240 anion gap is 27 that’s elevated okay so the Delta gap must be 27 minus 12
which is 15 we know right off the bat that we have an anion gap metabolic
acidosis okay so mud piles again mu dpi le s must be one of those and what do we
know we know that there are 15 units of the conjugate base or negative charge
hanging around that protons were released those protons were bound to
bicarbonate which we lost we lost that bicarbonate and so if we could just wave
our magic wand and say if we were to eliminate this and I get metabolic
acidosis what would our bicarb e and we simply
add this anion gap to our current bicarb level and we get 30 that’s what would it
be and if we saw a bicarb level of 30 we would say that means there must be a metabolic alkalosis occurring at the same time so we have
two different processes occurring at the same time so let’s look at our pH and
our pco2 okay remember we do that next pH pco2 obviously we’re dealing with a
metabolic acidosis so it’s going to be low and we look at our pH the question
now is since we have a metabolic acidosis and a metabolic alkalosis the
question is which one is stronger we need to know which one is stronger
because we need to know which winter’s formula to use do we use the metabolic
acidosis winters formula or do we use the metabolic alkalosis winters formula
and we see here that the metabolic acidosis must be the stronger of the two
so we’ll use the metabolic acidosis winters formula which states that the
drop in hco3 and the drop in p co 2 must be equal to 1 over 1 so let’s take a
look at that how much did our bicarb drop our bicarb dropped by 24 to 15
that’s 9 points okay how much did our pco2 drop by however our pco2 did not
drop at all it’s still at 40 how much should I have dropped it should have
dropped by and at 9 points right and the reason why is because winters formula
would predicts that if this were metabolic acidosis that were occurring
the bicarb drop of 9 should mean the pco2 drop should be 9 but it didn’t drop
low enough so if the pco2 did not drop low enough there must be a respiratory
acidosis because the pco2 did not drop enough so what we actually have here is
we have an anion gap metabolic acidosis we have a metabolic alkalosis and we
have a respiratory acidosis so we have a triple acid-base disorder that we could
figure out just based on the blood gas and also the chem 7 why don’t you join
me for part eight for a couple more questions Thanks

39 thoughts on “Medical Acid Base and ABGs Explained Clearly by MedCram.com | 7 of 8

  1. Thanks for explaining. Was a little hard to understand for me at first, since we get the abg listed with different units here (kiloPascale and mmol/L) and also we get the base excess listed, which I guess is equivalent to the anion gap. .

  2. Sorry bout that!. Actually the base excess is not the anion gap but is related to the amount of HO3 in the serum. (i.e. 0 means normal).

  3. Yeah you're right, I went on to study it some more and realised you use the base excess (normal range -2 to +2) to determine wether there is a metabolic component to the pH, ie. renal compensation or metabolic alkalosis/acidosis through HCO3.
    By the way I had my exam in acute medicine yesterday and was presented with 5 different abg's and everything went smooth. Got a B, I didn't get an A because I missed something on an X-ray hehe. So thanks again for the videos, I appreciate them. 🙂

  4. Man, this is so amazing. I did not truly understand the utility of delta gap and Winter's rules before this. Amazing.

  5. I've been using the formula pCO2 = (1.5 x HCO3) + 8 for Winter's formula to find the expected pCO2 b/c I can calculate this faster than comparing the ratio of the delta HCO3 and delta pCO2. Does this work in all cases (never breaks down)?

  6. 12:28 what is the difference here between using the formula pCO2 = 1.5 x HCO3 + 8 and doing your method? I am curious because it seems the formula above suggests there would be a concomitant resp alkalosis with the met alkalosis, but that is not the conclusion you reached? So are both answers possibly correct? (as your fraction was also not as close as usual..)

  7. Final example: will we ever need to differentiate between acute and chronic if the resp disorder is the 2nd concomitant problem?

  8. there are several way of doing it. Another way is to simply at 15 to the bicarb and see what the CO2 is. if the actual co2 is higher then (bicarb + 15) you have a resp acidosis, if the actual co2 is lower then (bicarb + 15) you have a resp alkalosis. – works most of the time.

  9. Hi, could you explain how you were able to tell in the first example that the additional bicarb was due to metabolic acidosis and not renal compensation?

  10. This was the hard part – to understand the additional respiratory process that goes on with the metabolic process.  Thank you for explaining it so well that anybody can understand.  I cannot thank you enough for this lecture.  Thank you.

  11. mecram for president of WHO 
    actually no 
    he would be too busy and neglect us and wouldnt make vids anymore 🙁

  12. For the first example in this video, why  does the Winturn's formula hold for AG Met Acidosis? Shouldn't the pC02 be higher since it has to compensate for Met Alkalosis as well?

  13. Would it be correct ( or more appropriate ) to say in the first example that you have a AG metabolic AcidEMIA and a metabolic AlkalOSIS?

  14. How did you determine in 16.28 that there is a respiratory acidosis when the rule for that is 1/3 or 1/2 when we have 9/0 ?

  15. You are awesome, you should consider partnering with a rph who is just as knowledgeable in their field and understands the needs for naplex. This way we get both the med side and in depth pharm side. Although you do provide some info its not as in depth as we need.

  16. @7:34 – At what point would this shortcut break down? In this case, we assumed that 12/13 is close enough to 1/1, but exactly where can we draw that line? 12/14 is pretty close too but as we get further and further away, 12/15, 12/16, 12/17, where can we say that we are beginning to break away from a pure 1/1 ratio? In the Winter's formula, 1.5[HCO3]+8, there is a component of +/- 2 to account for this range. I like the method that you use but I need to be convinced that it won't miss any respiratory acid/base disturbances just because I assumed that the ratios were "close enough" to 1/1.

  17. Damn. I finally understand this crap. Its still complicated but systematic approach helps to organize thoughts when solving these numbers. Thank you soooo much. My next issue is ECG. Will definitely buy the course. This guy kicks ass!!!

  18. Hi
    Thanks for your great lectures. Unfortunately the 8'th video is not available. I wonder why it's shown as a private video?

  19. hi there thanks aot.. i have a patient of mine can help me ot for this confused with winters formula…
    6.98/64.5/243/14.4 chem 7: 132/3.4/98/14.4
    hope u can help
    thanks again

  20. Dear sir, Thank you and your team very much for all sharing these medical lectures.
    I could not find part 8 ! How could i have it please?

  21. This is the most helpful video about ABG I've ever watched. Though I think the 3rd example was wrong in application of Winters formula. Maybe a review would do wonders. Thanks anyway.

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