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Old 07-08-2010
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Question Acid Base Disorders in USMLE Step 1

Do we need to know the exact calculations for the compensations of all the disorders?
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Old 07-09-2010
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Question What do you mean

Do you mean the formulas that let you calculate how much pCO2 should decrease in the face of how much bicarbonate is elevated and stuff like that.
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yeah i mean those
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Old 07-10-2010
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Arrow Perhaps on the Winter's Formula

No, I don't think you need to know the exact equations and numbers to calculate the various changes in an acid base disorder.

It's important however that you know (by heart) the normal values of the PH, CO2, and Bicarb so that then you can judge what is the problem.

See the PH first then look at the CO2 then see the bicarb.

Do practice questions as much as you can. This is a very high yield topic.

There's one exception (I think) which is the Winter's formula that you need to memorize.

Winter's Formula

Expected pCO2 = 1.5 X HCO3- + 8
this is to measure the adequacy of respiratory compensation in cases of metabolic acidosis (specially in DKA cases).

Example:
Patient with DKA and his bicarb is only 8, then his pCO2 should be 20 if it's higher than that then he's not adequately compensating (respiratory fatigue or ensuing coma) then you need to think of assisting his ventilation.
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Awesome thanks a lot, btw where did u get winter's formula is that in FA?
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Arrow I just know it

Am not sure if it available in FA or any other book.
I just know this formula by heart and I remember there were practice questions that needed it to solve the problem.
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Old 07-10-2010
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Yeap, Winter's formula, as well as the rest of compensations (which are unmemorizable, btw!) are all included in FA.
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Quote:
Originally Posted by ath.pantelis View Post
Yeap, Winter's formula, as well as the rest of compensations (which are unmemorizable, btw!) are all included in FA.
yah they are unmemorizable hopfully none show up on the exam!
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Old 12-07-2011
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i was reading goljan, and i think FA makes it very easy to understand. Plus you need to read kaplans physiology to get davenport and add it to FA.
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Old 08-16-2015
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Wink Winters Formula

PaCO2 = (1.5 x Bicarb)+8 +/- 2

I`ve just do a question about this in UWorld.
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