The patient is a 69 year old woman admitted with abdominal pain and nausea. She may have lost weight. She has no known past medical history and is taking no medications. Her labs give many clues:
| Electrolyte panel | |||||
|---|---|---|---|---|---|
| Na | 142 | Cl | 113 | BUN | 106 |
| K | 6.5 | HCO3 | 11 | creat | 9.1 |
| Blood Sugar | 79 |
Alb 3.2; Calcium 5.1
ABG on room air
| ABG | |
|---|---|
| pH | 7.23 |
| pCO2 | 23 |
| pO2 | 80 |
| HCO3 | 10 |
So please address these questions:
1. What is the acid-base disorder?
Here is my approach. Anion gap = 18. Therefore, the patient has an increased anion gap acidosis by definition.
The expected gap is approximately 9 (note the albumin).
The delta gap is 9; adding to 11 (the HCO3 ) gives an estimated prior bicarb of 20.
pH shows acidemic and according to the Winter's equation the respiratory response is perfect.
Therefore, I assume a combined normal gap and increased anion gap acidosis.
Given the high BUN and creatinine I asked for the PO4 level – I predicted around 7-8. There is not simple equation for the amount of anion gap increase for elevated PO4 . The patient's phosphate was 7.9. Thus, the patient had an increased anion gap secondary to uremia. The normal gap acidosis might have been a type IV RTA, but at least is associated in some way with the CKD.
2. Predict other laboratory testing?
I predicted an elevate phosphate. The high phosphate and low calcium predicted secondary hyperparathyroidism.
3. What would you do at admission?
As noted in the comments, I would address the hypoxemia – note the elevated A-a gradient. They appropriately checked an EKG that showed normal T waves.
Nephrology dialyzed her the next morning and all the abnormalities improved. Her A-a gradient was due to volume overload
{ 4 comments… read them below or add one }
But how did he do with the surgery?!? You know, the sex change operation that must have occurred between admitting a “69 year old woman” whose labs give many clues, and “dialyz[ing] him the next morning.” (Apologies for being a gender Nazi.)
touche – I changed it back!
One more:
Nephrology dialyzed her the next morning and all the abnormalities improved. His A-a gradient was due to volume overload.
(Unless this patient’s volume overload increased someone else’s A-a gradient.)
How can you tell what the patient’s A-a gradient is unless you provide the FIO2?
I assume this patient is on room air, 21%. so there is a mild A-a gradient, actually not much for a person that age.
But the point is no arterial blood gas is complete without providing the oxygen the patient is breathing.
I have dealt with more than one malpractice case where a patient had a pO2 of 100 and the issue was whether the FIO2 was 21% or 100%.
the first person is probably not sick. The second may be an hour away from dying.