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When we have a metabolic acidosis or metabolic alkalosis, we should also consider if there is a secondary respiratory acid-base disturbance aswell.
If we have a metabolic acidosis, we then use the winter's formula (HCO3 x 1.5 + 8 +/- 2), that gives us an expected CO2 level for that given HCO3. If patient's actual CO2 is higher or lower than expected, there is a secondary respiratory acidosis (patient's CO2 is higher than expected) or secondary respiratory alkalosis (patient's CO2 is lower than expected).
On the other hand, if we have a metabolic alkalosis, we use this other formula: (HCO3 x 0.8) + 20 +/- 2.
And again, if patient's CO2 is lower than expected according to that formula, there's a secondary respiratory alkalosis, or if patient's CO2 is higher than expected according to that formula, there's a secondary respiratory acidosis.
First of all: is that correct?
Second of all: if that is correct, look at this case:
ABG shows pH=7.5, CO2 45, O2 86 & HCO3 36 what's the acid-base disturbance here?
answer: There is a primary metabolic alkalosis (too much HCO3 makes pH higher than normal), and now, if we apply the second formula given above, 0.8x36 +20 +/- 2 = expected CO2 should be somewhere between 48 and 50, but it's 45, therefore lower than expected for that given HCO3, meaning pt has a secondary respiratory alkalosis.
Is that correct? Because the thing is this is a question from Medquest, and in the video the teacher says that applying that fomula there is not a secondary respiratory disturbance
Thank you
If we have a metabolic acidosis, we then use the winter's formula (HCO3 x 1.5 + 8 +/- 2), that gives us an expected CO2 level for that given HCO3. If patient's actual CO2 is higher or lower than expected, there is a secondary respiratory acidosis (patient's CO2 is higher than expected) or secondary respiratory alkalosis (patient's CO2 is lower than expected).
On the other hand, if we have a metabolic alkalosis, we use this other formula: (HCO3 x 0.8) + 20 +/- 2.
And again, if patient's CO2 is lower than expected according to that formula, there's a secondary respiratory alkalosis, or if patient's CO2 is higher than expected according to that formula, there's a secondary respiratory acidosis.
First of all: is that correct?
Second of all: if that is correct, look at this case:
ABG shows pH=7.5, CO2 45, O2 86 & HCO3 36 what's the acid-base disturbance here?
answer: There is a primary metabolic alkalosis (too much HCO3 makes pH higher than normal), and now, if we apply the second formula given above, 0.8x36 +20 +/- 2 = expected CO2 should be somewhere between 48 and 50, but it's 45, therefore lower than expected for that given HCO3, meaning pt has a secondary respiratory alkalosis.
Is that correct? Because the thing is this is a question from Medquest, and in the video the teacher says that applying that fomula there is not a secondary respiratory disturbance
Thank you
0.7*rise in HCO3)+40 but the values turned out to be the same. 
