Low Bicarbonate and High CO2; Acid Base Balance! - USMLE Forums
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Old 12-02-2011
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Question Low Bicarbonate and High CO2; Acid Base Balance!

I want help here please
for example if HCO3 is low e.g. 12
and CO2 is 80

How do we know it is metabolic acidosis or respiratory acidosis or both??
for me it looks like both but I don't know why

please please help
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Old 12-02-2011
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Hey Dr. Muhamad usually when the CO2 and the HCO3 move in opposite direction there is a combined respirator and metabolic alkal.or acidosis , so both parts of the acid base system have a disbalance.
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Quote:
Originally Posted by Glomerulus View Post
Hey Dr. Muhamad usually when the CO2 and the HCO3 move in opposite direction there is a combined respirator and metabolic alkal.or acidosis , so both parts of the acid base system have a disbalance.
thx my friend
but i got a choice for the same numbers i mentioned above that says
it is uncompensated respiratory acidosis or both respiratory and metabolic acidosis
so i am confused how can we figure out the difference
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My answer would be it is a metabolic and respiratory acidosis. In a noncompens. respiratory acidosis there is a high CO2 and a normal HCO3.
Compensated respr. acidosis high Co2 but also elevated HCO3
Metab. and respiratory acidosis High co2 but low HCO3. Hope it helps!
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Quote:
Originally Posted by Glomerulus View Post
My answer would be it is a metabolic and respiratory acidosis. In a noncompens. respiratory acidosis there is a high CO2 and a normal HCO3.
Compensated respr. acidosis high Co2 but also elevated HCO3
Metab. and respiratory acidosis High co2 but low HCO3. Hope it helps!
thanks a lot i was thinking in this way too
thanks for help
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Old 12-02-2011
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Respiratory disorders change Pco2.

Metabolic disorders change HCO3.

When the compensatory mechanisms drive the pH back to normal,then it is a mixed disorder.

When the compensatory mechanisms just compensating for the cause who created acid - base disturbance but not driving pH back to normal,then it is not a mixed disorder.
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Default Winter's Formula

Whenever you have this dilemma, You should go for Winter's formula

Solve it like that >>>

1st: It's clearly a case of metabolic Acidosis as HCO3 is low

2nd: A respiratory compensation must compensate for such a metabolic acidosis and to cacluclate how much PaCO2 should go down to compensate for the metabolic acidosis we have to use the Winter's formula like that >>

Expected PaCO2 = 1.5(HCO3) + 8 = 1.5X12 + 8 = 26

Meaning that PaCO2 here should be 26 to compensate for the current metabolic acidosis ,, and hence it's above 26 (Actually it's 80 now) >> then this is a case of mixed metabolic and respiratory acidosis

N.B: Your presented case here is clear as PaCO2 is 80 but when it's within the normal range for PaCO2 for example = 40 , this will be problematic as you don't know if it's normally compensating for the current metabolic acidosis properly or not in spite of being within the normal range , Here Winter's formula would be of great help for you.
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Acid-Base-, Electrolytes-, Physiology-, Respiratory-

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