Friday, January 23, 2015

Q: Patient with history of hypertension and anxiety presented to the hospital with tachypnea.  Patient 

sodium  140meq/l,
potassium 3meq/l, 
chloride  94meq/l and 
HCO3  34.  

On arterial blood gas, 

ph 7.67
pCO2 30.  

What is the acid base disturbance?

A)  Respiratory alkalosis
B)   Metabolic  alkalosis
C)  Respiratory and metabolic alkalosis
D)  Hyperchloremic non-anion gap metabolic acidosis

Answer: C

Rationale: Patient HCO3 is high suggestive of metabolic alkalosis.

Patient expected CO2 should be (pCO2=HCO3x0.9+9;34x0.9+9=39.6); 
CO2 is 30, which is lower than expected pCO2,
suggestive of mixed respiratory and metabolic alkalosis.

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