This is a classic ABG sequence:
| ABG | Admission (on 2 L O2) | Day 2 (Bipap 100%) |
|---|---|---|
| pH |
7.28 |
7.52 |
| pCO2 | 89 | 52 |
| pO2 | 60 | 373 |
| HCO3 | 42 | 42 |
Your tasks are to understand and explain the course of events for this woman having a COPD exacerbation.
1. What is the initial acid-base disorder?
2. What is the second day disorder?
3. What would you do now?
{ 3 comments… read them below or add one }
I would comment, but the only thing I know about acid is acid reflux!
Initially a chronic respiratory acidosis, converted to a chronic respiratory acidosis with an acute respiratory alkalosis.
I would cut down, or cut out, the BIPAP and put her on controlled flow oxygen (Venturi Mask in the 28% range). It is possible that with controlled flow oxygen she might have avoided ventilation to begin with – low flow nasal cannula should not be the primary approach with a significant CO2 retainer who comes in unstable. That should be reserved for when their ventilation and cardiovascular status are stable. This is because the amount of oxygen they are getting is uncertain with a nasal cannula and it makes a difference early on..
She started with a chronic respitory acidosis which was compensated with a metaolic alkalosis. However her COPD worsened for whatever reason and she retained more CO2 so she became more acidotic quicker than the kidneys could retain HCO3 to compensate so she is now acidotic. She was probably a member of the 60/60 club to begin with(pCO2/PO2) so when the BiPap drove the CO2 lower she actually became alkalotic as the HCO3 takes time to return to baseline.
You have a couple of options: Diamox to pull off extra HCO3 or reduce the BiPap as mentioned above.