Monday, December 26, 2011

Open Ended Question

You are working in the clinical laboratory and get an arterial blood gas: pH 7.27, PCO2 70 mmHg, serum HCO3 31 meq/L.

Challenge: Your mentor asks you to interpret. Is the patient compensating for the acid-base disturbance?

2 comments:

Reflex Hammer said...

Yes, and it signals chronic compensation rather than acute.

Craig Chen said...

yep
-
Open Ended Question

This is a respiratory acidosis. If it is acute hypercapnia, then the 30mmHg rise in PCO2 should increase serum HCO3 by 3 meq/L; if it is chronic hypercapnia, then the 30mmHg rise in PCO2 should increase serum HCO3 by 11 meq/L. The observed value of 31 meq/L could represent several scenarios: (1) chronic respiratory acidosis with a superimposed metabolic acidosis (ie. COPD + sepsis), (2) acute respiratory acidosis with a superimposed metabolic alkalosis (overdose leading to vomiting and respiratory depression, (3) acute respiratory acidosis superimposed on mild chronic respiratory acidosis (COPD + pneumonia), or (4) acute respiratory acidosis evolving into chronic respiratory acidosis (between 1-3 days).

Source: UpToDate.