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#1
06-03-2013
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anion gap?

Hi,
If anion gap equation = Na - (Cl + HCO3)
How come the anion gap will INCREASE if we add new acids?
It is supposed that the net anion gap is decreased if we add new acids (as the sum of Cl + HCO3 will increase)
Thanks

#2
06-03-2013
 USMLE Forums Addict Steps History: CS Only Posts: 195 Threads: 28 Thanked 283 Times in 70 Posts Reputation: 293

Quote:
 Originally Posted by melboghdady Hi, If anion gap equation = Na - (Cl + HCO3) How come the anion gap will INCREASE if we add new acids? It is supposed that the net anion gap is decreased if we add new acids (as the sum of Cl + HCO3 will increase) Thanks
Anion gap formula uses measured cations (Na) minus measured anions(cl+hco3). So in metabolic acidosis the acid is an unmeasured cation and when it increases, the measured cations decrease to compensate. Hence a rise in the CALCULATED anion gap.

Note: The actual gap stays the same.

Hope that helps!
 The above post was thanked by: melboghdady (06-03-2013)
#3
06-03-2013
 USMLE Forums Addict Steps History: CS Only Posts: 195 Threads: 28 Thanked 283 Times in 70 Posts Reputation: 293

Also note in Hyperchloremic Non Anion gap Metabolic acidosis Chloride rises to compensate for a a loss of Bicarb hence there the calculated anion gap stays the same in this case.
 The above post was thanked by: melboghdady (06-03-2013)

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