So I thought about the problem overnight. The key here was the persistent respiratory acidosis. The patient clearly did not have COPD. I did mention his weight, and then I decided he must have obesity hypoventilation syndrome.
So we go into the room the next morning and he is now alert and his wife is in the room. I turn to her and ask if he snores – and then the floodgates open. He had a history of sleep apnea, and was supposed to be using CPAP, but his mask had broken.
When he came to the emergency department, he had altered mental status, and thus the history was incomplete. We initially blamed his hypoventilation on the hyperosmolar state. However, the hypoventilation persisted after his blood sugar came down to normal and he awoke to normal mental status.
My family medicine interns put it best. They related that this patient re-emphasized the importance of continuing to take history. History taking does not end during the intial evaluation. We should take cues and clues and revisit the history regularly.
To restate the presentation:
41 year old man with left hemipareis s/p right brain aneurysm surgery in the past. Now presents with increasing obtundation, increased urination and abdominal discomfort. Labs follow:
On 2l nasal oxygen:
| ABG | |
|---|---|
| pH | 7.41 |
| pCO2 | 47 |
| pO2 | 95 |
| Electrolyte panel | |||||
|---|---|---|---|---|---|
| Na | 128 | Cl | 83 | BUN | 8 |
| K | 4.2 | HCO3 | 24 | creat | 0.7 |
| Blood Sugar | 742 |
The patient is a large man (110 kg) who now admits to 4 weeks of increased urination and recent constant thirst with a marked increase in water intake.
Now for the hard part, figure out the acid-base problem. Next I will give you his labs 2 days later, then my interpretation.
At this point I see:
- anion gap of 21 – therefore anion gap acidosis
- pCO2 = 47 – hypoventilation thus respiratory acidosis
- Delta gap supports bicarbonate of 33 (add 9 to 24 – the 9 being the difference between the observed anion gap and the expected anion gap)
- Thus when first presented I assumed a mild ketoacidosis (or possible mild lactic acidosis), a respiratory acidosis and a metabolic alkalosis
- I wondered if his obtunded state was causing hypoventilation
- I assumed significant volume contraction (and probably total body potassium depletion) from his glucose induced osmotic diuresis
The next day we have these numbers:
| ABG | |
|---|---|
| pH | 7.35 |
| pCO2 | 48 |
| pO2 | 68 |
| Electrolyte panel | |||||
|---|---|---|---|---|---|
| Na | 139 | Cl | 106 | BUN | 5 |
| K | 4.4 | HCO3 | 26 | creat | 0.6 |
| Blood Sugar | 321 |
Related Posts B
- AMS – an acid-base problem II
- Another hyperkalemia – my explanation
- Part 2 of the acid-base problem
- Acid base answer
- 17 days at the VA – day 12
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