Tuesday, March 24, 2009

Methanol and Ethylene Glycol

Today we discussed a patient who presented in a Hyperosmolar Non-Ketotic state secondary to hyperglycemia. You can read more about the precipitants and management of DKA and HONK here.

We also discussed poisoning with methanol and ethylene glycol - either by intentional or unintentional ingestion.

These get metabolized in the liver first by Alcohol Dehydrogenase, then Aldehyde Dehydrogenase. They have toxic byproducts - Formic Acid in methanol poisoning, and Calcium Oxalate in ethylene glycol. Formic acid causes renital edema and destruction and can also lead to ischemia in the basal ganglia. Calcium oxalate can cause irreparable renal damage.

What to do? Firstly, "intoxications" have to be on your differential diagnosis - if you don't think about it, you will never diagnose it. Also consider other co-ingestions with prescribed or non-prescribed drugs/toxins.

Clinical Hints: Patients may have a decreased level of consciousness and those with methanol intoxication may complain of blurry vision. Look for evidence of renal failure, a raised anion gap, and an elevated osmolar gap. Note that it is possible to have methanol/ethylene glycol poisoning with a normal osmolar gap. Also note that if patients co-ingest alcohol, this will delay the presentation of methanol/ethylene poisoning. Send off blood levels for these alcohols.

Plan: Basically we want to get rid of the methanol or ethylene glycol - and dialysis is the fastest and most effective mechanism to do this. We also want to prevent the formation of our toxic byproducts (formic acid and/or calcium oxalate). How do we do this?
  • Ethanol: best given intravenously. The alcohol dehydrogenase will work on ethanol rather than methanol/ethylene glycol - preventing the formation of toxic byproducts. It is cheap, but difficult to dose.
  • Fomepizole: this will directly inhibit alcohol dehydrogenase. Easy to use, very effective, very expensive.
Links:

Dion Phaneuf of the Calgary Flames (smoking the Ottawa Senators) pictured left.

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