I just saw one of the biggest anion gap of my life and I don’t know the cause. Worse yet, the patient had this occur a few months ago, also with no explanation. So I want to figure out what is going on before admission number three.
Patient presented to the ED obtunded and was unable to give a cohesive history. The admission labs:
Looking at the numbers, the gap gets so large because not only is the bicarb so phenomenally low, but they have a pathologically low chloride and a sodium which is bumping up gainst the upper limit of normal. Additionally the potassium is a bit low, shrinking the other cations box.
We have an ABG done a few minutes after the chemistries were drawn:
- pH 6.94
- paO2 179
- pCO2 6
- HCO3 1
So with a massive metabolic acidosis and a ginormous anion gap, you should be itching to order a toxic alcohol screen. But first check for other causes of an anion gap metabolic acidosis:
- Aspirin: less than 2.0 mg/dl (works especially well with the concurrent respiratory alkalosis)
- Acetaminophen: less than 5 mcg/dL
- Lactic acid: 9 mmol/L
- Ketoacidosis: This hospital doesn’t do real time serum ketones. So we didn’t have data acetone, betahydroxybutyrate or acetoacetate levels. However the U/A showed ketones at 20 mg/dL
- A normal gap is 12 mmol/L
- Lactate is 9 mmol/L
- The phosphorus is 7 mg/dL. Four of that is included in the normal gap, the extra 3mg/dl converts to 1 mmol/L
- That comes to 22, leaving an unknown gap of 31. Some of this will presumably be filled by ketones, acetoacetate and betahydroxyburyrate.
- Acetone 31 mg/dl
- Methanol: not detected
- Ethylene glycol: not detected
- Isopropanol 12 mg/dL