Ethylene Glycol and Antifreeze Poisoning in Pets

When it comes to pets ingesting antifreeze, veterinarians are often left with more questions than answers. Ethylene glycol (EG) is a common antifreeze ingredient, and it can also be found in surprising places like snow globes.

Sources of Ethylene Glycol

Ethylene glycol is an alphatic polyalcohol that has a variety of uses:

• Automotive antifreeze
• Hydraulic brake fluid
• Aircraft deicers
• 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

Clinical Signs

Due to the alcohol component, pets may display these signs in the first few hours after ingestion :

• Emesis
• Ataxia
• Disorientation
• Depression
• PU/PD

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 1 to 6 hours post-exposure leads to the 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

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.