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?
The patient has a chronic respiratory acidosis with metabolic compensation. I cannot remember the calculations, so I found a calculator online.
2. What is the second day disorder?
This disorder goes by the name post-hypercapnic metabolic alkalosis. I sometimes use the phrase “revealed metabolic alkalosis”. It occurred because the patient had an appropriate compensation for a chronic respiratory acidosis, and then we successfully improved ventilation – lowering the pCO2 faster than the kidneys can adjust.
3. What would you do now?
We gave the patient acetazolamide to lower the HCO3 . Here are the subsequent ABGs:
| ABG | Day 3 | 5 hrs later | Day 4 |
|---|---|---|---|
| pH | 7.63 | 7.41 | 7.36 |
| pCO2 | 40 | 59 | 62 |
| pO2 | 56 | 83 | 74 |
| HCO3 | 42 | 37 | 35 |
We give the acetazolamide to add stimulation to ventilation.
