Antifreeze is commonly used in colder climates in automobiles and other equipment. Many antifreeze formulations contain ethylene glycol, a substance that has a sweet taste that makes it attractive to curious dogs and cats. Unfortunately, ethylene glycol is a poisonous substance for both dogs and cats. Ingestion of antifreeze containing ethylene glycol can very easily be fatal to dogs and cats that ingest the substance.
How Much Antifreeze Is Necessary to Poison a Dog or Cat?
Very little antifreeze is necessary to cause a serious and life-threatening toxicity.
- For a cat, walking through a puddle of antifreeze and then licking the feet can produce a toxic dose.
- For a medium sized dog, as little as four to five tablespoons can be poisonous.
Remember that antifreeze has a sweet flavor that many pets, especially dogs, find pleasant tasting.
Mechanics of Antifreeze (Ethylene Glycol) Poisoning in Dogs and Cats
When ingested by a dog or cat, the unmetabolized portion of antifreeze (ethylene glycol) enters the spinal fluid and causes depression of the central nervous system. This depression may result in lethargy, incoordination, paralysis, seizures and even coma.
At the same time, ethylene glycol is metabolized by the liver into various metabolites, including glyoxylic acid and oxalic acid.
- Glyoxylic acid causes metabolic acidosis, which in turn will affect both the respiratory and cardiac systems.
- Oxalic acid binds to calcium, causing a decreased blood calcium level (hypocalcemia). It also forms calcium oxalate crystals that damage the kidneys, causing kidney failure and uremia (an increase of nitrogenous waste products in the blood stream). Uremia further contributes to the metabolic acidosis. Hypocalcemia makes seizures more likely.
Stages of Canine and Feline Antifreeze or Ethylene Glycol Toxicity
There are three stages that occur in antifreeze poisoning in the dog and cat.
- Stage one of ethylene glycol toxicity occurs very quickly after ingestion of antifreeze and can last up to 12 hours. Symptoms include an increase in thirst and an increase in urination. As the ethylene glycol affects the central nervous system, signs of intoxication will occur and may include lethargy, incoordination, partial paralysis and extreme sleepiness. Seizures and coma are other possible central nervous system symptoms that can be seen with antifreeze poisoning.
- Stage two usually begins within 12-24 hours of ingestion of antifreeze. Symptoms are primarily a result of metabolic acidosis and usually involve the heart and the lungs. An increased respiratory rate and heart rate are commonly seen. The lungs may also become congested or filled with fluid and breathing may become difficult as a result.
- Stage three typically starts 24-72 hours after ingestion of the toxic dose of ethylene glycol. Dogs and cats in stage three exhibit signs of kidney damage and kidney failure. These signs include lack of appetite, vomiting, depression, oral ulcers (sores in the mouth) and seizures. In the later stages, kidney failure will cause the kidneys to produce only small volumes of urine. This is termed oliguric renal failure. Eventually, urine production may cease altogether.
Often, pets suffering from antifreeze poisoning will appear to get sick, recover for a time and then have the symptoms return in a more severe manner.
Prognosis of Antifreeze (Ethylene Glycol) Poisoning for the Dog and Cat
The prognosis for a dog or cat that has ingested antifreeze containing ethylene glycol depends on several factors:
- the dose ingested
- the size of the animal
- the stage at which medical intervention occurs
Medical intervention is most successful when it occurs immediately after ingestion of the antifreeze. Generally, pets that receive adequate medical intervention within five to eight hours after ingestion have a much higher survival rate than those that receive medical attention later.
Once symptoms of kidney failure have developed, the chances for survival are poor and only the most aggressive medical attention (such as peritoneal dialysis, hemodialysis or even kidney transplantation) will give the pet any chance of survival.
Antifreeze poisoning is a common problem in dogs and cats and occurs because many types of antifreeze contain ethylene glycol, a toxic substance for both the canine and feline species.
Join the Conversation