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I totally can't understand this entry of P. 278 of FA. First it gives a winter's formula which I never saw before: Pco2 = 1.5 (Hco3-) + 8 +/- 2

then the 4 combination of acidosis and alkalosis seem to align wrong. but I'll just put them here in the way FA put it:
:arrow: metabolic acidosis: Pco2 increases 0.7 mmHg for every increase of 10 mmHg Pco2
:arrow: metabolic alkalosis:
:arrow: rspiratory acidosis: acute -- increase 1 mEq/L Hco3 for every increase of 10 mmHg Pco2; chronic -- increase 3.5 mEq/L Hco3 for every increase of 10 mmHg Pco2
:arrow: rspiratory alkalosis: acute -- decrease 2 mEq/L Hco3 for every decrease of 10 mmHg Pco2; chronic -- decrease 5 mEq/L Hco3 for every decrease of 10 mmHg Pco2

What does the Winter's formula mean? And how did they get those conclusions, can anybody explain for me?


hey bluestar check this out


thank you mash for the website. Now I know these are different formulas we can apply to diff conditions. But do you think we need to memorize them all? without these formulas, we can still judge what kind of acid-base abnormality there is, even though not so accurately shown in figures.


of course we can judge frm figures and dat is wat they test on usmle (this is wat i think )
coz i vent come across any ques where these formulae r reqd.....
wat do u say?


Any HCO3- under 15, you know you have a primary metabolic acidosis (possibly mixed also)

Any CO2 over 45, you know you have a primary respiratory acidosis (possibly mixed also)

I do not think you have to know the formulas, the clinical picture should mark the situation very clearly.


I agree with you both. btw, idiopathic, where does the figure 15 and 45 come from?


Just a standard that we were told by a clinician. He said it is a certainty.


Those are the bedside rules for assessment of acid-base compensation, and from what I remember, they are empirical. And Winter's formula is just as it says: the 1.5 + 8 rule.

Basically, as mentioned above, we compare the actual values obtained from the lab with the expected values in order to assess the nature of the compensation in the disorder.

I really doubt the utility of these rules.

I can explain them, but I'm pretty sure that you don't need to know them anyways.


thank you all very much! :P

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