Ethylene Glycol
Well, Labor Day was this past weekend, which means summer is unofficially over. As a good southerner, I am ok with that. To quote John Ward, the voice of the Tennessee Volunteers for over 30 years, who passed away this summer (may he rest in peace), “It’s football time in Tennessee!” The leaves will soon be changing colors in the Smokies, and if the Vols have an away game, all of the UT students will head to the mountains to hike the Chimneys or their favorite trail. Such great memories!
As fall approaches, we all start thinking about “winterizing.” So, today’s blog is written as a reminder of the dangers in preparing for cold weather.
Now almost all pet owners know that antifreeze contains ethylene glycol, but did you realize that methanol, which is present in windshield washer fluid, is toxic as well? The “safer” forms of antifreeze contain propylene glycol. This is 3 times less toxic than ethylene glycol, but it can cause liver and kidney damage, too.
Ethylene glycol (EG) is also present in caulking agents to protect against leaks around windows. It can be found in household paints, floor polish, and household hard surface cleaners (liquid). The ink in refillable ball point pens contain EG. Ink pads and other stationery items, including finger-moistening compounds, contain EG. The post bases for portable basketball goals contain EG, and some imported snow globes contain high levels of EG.
Once EG is ingested, it is rapidly absorbed within 40-60 minutes. After absorption, EG is metabolized by alcohol dehydrogenase, and it enters the CNS (Central Nervous System) where is causes depression. As EG is further metabolized, it causes severe metabolic acidosis, and the final product in this metabolism, oxalic acid, binds to serum calcium, forming calcium oxalate crystals. These precipitate in the kidneys, causing kidney failure, which leads to death.
Peak levels of EG are reached within 1-4 hours after ingestion. The diagnosis is often made based upon a history of exposure along with compatible clinical signs and clinical laboratory abnormalities. There are also commercially available test kits for EG toxicity, but the kits may not be sensitive enough to diagnose toxicosis in a cat, as they are more sensitive than dogs.
Ultrasound can also provide useful information when diagnosing EG toxicity, as the kidneys exhibit classic sonographic changes. The outer surface and the inner region are brighter than normal, and the region between the two is darker than normal.
Antidotes are available to treat EG toxicity. Fomepizole (4MP) is the treatment of choice, as it inhibits alcohol dehydrogenase, preventing EG from being metabolized. If this is unavailable, ethanol can also be used, as it has a high affinity for alcohol dehydrogenase. Ethanol can enhance the alcohol-related clinical signs such as depression, nausea, vomiting, and metabolic acidosis.
Therapy for EG toxicity is otherwise supportive with IV fluids, correction of metabolic acidosis, and antiemetics to prevent vomiting. Patients can be given B vitamins (thiamine and pyridoxine) to help metabolize glycolic acid to a non-toxic end product. Patients may need help maintaining their body temperature, and good nursing care is a must to keep them clean and dry.
Intensive monitoring is required for several days, and the prognosis for survival is dependent on the amount of EG ingested, the time lapse from ingestion until treatment is initiated, and the severity of clinical signs/degree of kidney compromise. Patients treated with 4MP within 5 hours of ingestion have the best chance for survival. If therapy is delayed for more than 8-12 hours, EG toxicity is often fatal, and patients that have significant elevations of kidney values at the time of admission are unlikely to survive.
The real take home message here is pretty easy – keep your pets away from EG. Clean up antifreeze spills immediately. Store EG-containing products in areas that are inaccessible to pets. If you think your pet has ingested EG, take them to the nearest emergency hospital immediately. Let’s all get ready for winter safely this year!
