NBME 20

nbme20/Block 2/Question#24

A patient with a 1-week history of diarrhea has ...

Decreased arterial Pco2

Login to comment/vote.

 +0  upvote downvote
submitted by hayayah(216),

Patient has chronic diarrhea leading to metabolic acidosis. Respiratory compensation will lead to decreased CO2 (respiratory alkalosis via hyperventilation).

usmleuser007  Aldo would increase b/c protons are anti-transported with potassium --> leads to hyperkalemia --> aldo activation ADH will also increase b/e of volume loss +  

 +0  upvote downvote
submitted by loopers(0),

Another quick way to think of this is through the formula: pH = HCO3/CO2. Since pH is low and HCO3 is low, CO2 must also be low.