Monday, August 17, 2015

Big anion gap or biggest anion gap?

One night that I was on call, I received an interesting patient from the ED.

The patient was confused but walked into the ER and was able to give at least a partial history. They did some initial chemistries and called me with the following results:
This is the kind of lab that grabs your attention.

With that glucose the first thought should be, "Is this DKA?"


Beta-hydroxybutyrate: 6 mmol/L

I try to account for the anion gap. So I look at all the anions I measure and see how well they explain the gap. And if I can't account for the majority of the gap I have difficulty sleeping. This patient's gap was 51, 12 is normal which leaves 39 to account for. Only 6 can be accounted for with beta-hydroxybutyrate.

"Is there a lactic acidosis?"



That still leaves 17 mmol/L of unexplained anions.

Next step, look for an osmolar gap.

Measured osmolality 348
Ethanol level 0



An osmolar gap of 32 is a profound osmolar gap. We ordered fomepizole and started hemodialysis for presumed toxic alcohol poisoning. 

The alcohol screen came back the next day:

ETHYLENE GLYCOL, SERUM = 0 mg/dL (Reference Range: 0.0-5.0 mg/dL)

PROPYLENE GLYCOL, SERUM = 8.1 mg/dL (Reference Range: 0.0-5.0 mg/dL)

Propylene glycol is normally due to the solvents used to dissolve IV drips. So usually we see problems in patients who have been in the ICU for awhile.
Arroliga AC

Propylene glycol is also found in antifreeze and hydraulic fluids. 

The molecular weight is 76, so the 8.1 mg/dl represents only about 1 mmol/L, however it may explain the severe lactic acidosis and by stimulating the production of D-lactate it may explain even more of the gap.
Kraut, JA
Dialysis removes the parent compound and metabolites. Whether patients need to receive fomepizole is less clear. Kraut and Kurtz suggest fomepizole would be beneficial, while others feel less strongly.

In this N=1 case, our patient did well without receiving fomepizole. 

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