I put together these medical challenges. The cases are hypothetical and do not necessarily represent actual or typical presentations of medical diseases. Disclaimer is at the bottom of this page.
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?
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).
Yes, and it signals chronic compensation rather than acute.
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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.