Jessica Zelnik, DVM
Ethylene glycol is the active ingredient commonly known as antifreeze for automotive radiators, but can is also found brake fluids and de-icers. Other sources of ethylene glycol include condensers, heat exchangers, home solar thermal units, toilet winterizers, and the post bases for portable basketball goals. It’s an odorless, colorless, syrupy, sweet-tasting liquid. Dogs and cats are attracted to the sweet taste of ethylene glycol which makes them at risk for toxicity. It only takes a small amount of ingestion to cause severe damage and death as it is absorbed very rapidly. Once ingested, the body metabolizes the ethylene glycol into glycoaldehyde, which in turn, is oxidized to oxalic acid, which is toxic to the kidneys. Within 45 – 60minutes after ingestion, pets are already poisoned.
Glycoaldehyde, one of the first metabolites of ethylene glycol, enters the central nervous system and alters glucose metabolism and neurotransmission. Pets appear inebriated anywhere from 30 minutes up to 12 hours after ingestion.
Oxalic acid, the final metabolite of ethylene glycol, binds to calcium in the blood to form calcium oxalate crystals. These crystals cause the majority of kidney damage by mechanically obstructing the renal tubules. Kidney failure may occur 24 – 72 hours after ingestion of ethylene glycol.
Ethylene glycol is extremely poisonous. Cats are twice as sensitive to the poison as dogs. Diagnosis of poisoning is based upon history of exposure or compatible clinical signs. During a physical examination, the kidneys are palpated to be large, soft, and painful. A blood panel would show dehydration, high phosphorus, low calcium, high potassium, and elevated blood urea nitrogen (BUN) and creatinine. A urine sample would show low concentration, casts, renal epithelial cells, and red and white blood cells. Calcium oxalate crystals may appear in a urine sample 6 hours after exposure, but the absence of crystals does not rule out ethylene glycol poisoning.
Cats and dogs may appear disorientated and ataxic at first. They can be nauseous and have vomiting and diarrhea. They progress to show increased thirst and urination, inability to stand, decreased righting ability, and decreased reflexes. Rarely, with very large ingestions, coma and/or seizures may occur.
Immediate treatment involves administration of fomepizole or ethanol, which are antidotes to ethylene glycol. They must be given within 3 hours or less after ingestion or the poisoning will be fatal. Fomepizole and ethanol prevent ethylene glycol from being metabolized. Fomepizole is preferred as it does not contribute to CNS depression or diuresis. Other treatments include intravenous fluid therapy, dialysis, antiemetics, Vitamin B, and intensive nursing care. Prognosis for survival depends on the quantity ingested, time after ingestion to when an antidote is administered, severity of clinical signs that develop, and degree of compromise to the kidneys.
Prevention is the only secure way to prevent ethylene glycol poisoning. Products containing ethylene glycol should be clearly marked and stored appropriately. Spills should be cleaned up immediately. Choose products that contain propylene glycol instead whenever possible.
Dr. Zelnik has been a practicing veterinarian in the Salt Lake valley since 2009. She practices at the University Veterinary Hospital and Diagnostic Center. She has received advanced training in dentistry, soft tissue surgery, and pain management. Dr. Zelnik enjoys running and hiking with her dogs: Kami, a Boxer, and Jake, a Schnauzer mix.