When it comes to antifreeze ingestions, we are typically left with more questions than answers. A biggie in the antifreeze realm is ethylene glycol, and it’s in surprising places (snow globes, for example).
Sources of EG
Ethylene glycol is an alphatic polyalcohol that has a variety of applications:
Hydraulic brake fluid
Home solar units
Portable basketball goal post bases
Industrial solvent in paint and plastics
Printer's and stamp pad inks
Ballpoint pen and ink
Some snow globes
Some eye masks
Initial signs in the first few hours after ingestion are largely due to the alcohol component and can include:
These signs may be mild enough to go unnoticed or severe enough to be life-threatening.
As the course of the intoxication progresses, you may see progressive metabolic acidosis, calcium oxalate crystaluria (only present in 40% of cases), hypocalcemia, hyperphosphatemia, hyperkalemia, increased osmolal gap, hyperglycemia, azotemia, polyuria, moderate to severe dehydration and hypoperfusion, high anion gap, oliguric or anuric renal failure and death.
Testing for Ethylene Glycol
Human hospital: A quantitative test at a human hospital is the gold standard for ethylene glycol testing and eliminates potential false positives. A time frame of serum and urine within one to six hours post-exposure creates best results in most cases.
Dog: Test run at a human hospital with EG levels < 50 mg/dl is considered negative.
Cat: Test run at a human hospital with EG levels < 20 mg/dl is considered negative.
Benchtop tests: There are both semi-quantitative test and qualitative tests available for use in hospital settings. In-house testing is less sensitive and specific than in a human hospital.
Treatment is aimed at preventing the parent compound (ethylene glycol) from being metabolized, as it is the metabolites that cause acute kidney injury. Treatment is best started as soon as possible to minimize production of these toxic metabolites.
In cats, treatment should be started within four hours post-exposure to maximize the chance of a positive outcome.
Treatment with Fomepizole (4 MP or 4-methylpryrazole) inhibits alcohol dehydrogenase. Unlike ethanol, it does not induce hyperosmolality, CNS depression or diuresis. Adverse effects of 4-MP are uncommon and may include hypersalivation, gagging, tachypnea and anaphylaxis.
Ethanol acts as a competitive substrate for alcohol dehydrogenase. Ethanol can add to CNS and respiratory depression, dehydration and metabolic acidosis. Acid base status should be monitored carefully in patients receiving ethanol.