Antifreeze Poisoning in Dogs and Cats

Poisoning by antifreeze is one of the most common small animal toxicities, particularly in cold climates. Every year do-it-yourself motorists get out the gear needed to winterize their vehicles, including antifreeze. Unfortunately, this poison is colorless, odorless and has a sweet taste that dogs and small children find appealing and will readily drink. Spilled or leaked antifreeze is lapped up by many dogs and cats in quantities sufficient enough to cause severe sickness and even death. Learn more about antifreeze poisoning in dogs and cats below.

Signs and Symptoms of Ethylene Glycol (Antifreeze) Poisoning

Ethylene glycol is the principal ingredient of radiator fluid that is responsible for antifreeze poisoning in dogs and cats. Antifreeze poisoning is most common in the fall and spring, when radiator fluid is inadvertently abandoned in streets and garages after automobile radiator fluid is changed.  Signs of antifreeze poisoning depend upon the time after ingestion but symptoms can include:

  • Depression
  • Staggering
  • Seizures
  • Excess water consumption
  • Excess urination
  • Vomiting
  • Kidney failure

Poisoning classically proceeds through three stages. Absorption after ingestion is rapid and initial signs occur within 30 minutes to 12 hours. Ethylene glycol is an alcohol, hence during the initial phase of poisoning the animal appears "drunk" and consequently exhibit many classical signs associated with alcohol intoxication: staggering, stumbling and incoordination. Vomiting, nausea, extreme thirst and frequent urination are also observed. Some animals simply sleep through this period and owners are not aware that poisoning has occurred.

At the end of the first phase, the clinical signs resolve and the animal appears to have recovered. The second phase of intoxication occurs 12 to 24 hours after poisoning. The heart rate and breathing rate are rapid, but this is rarely noticed by owners. Unfortunately, most dogs and cats poisoned with antifreeze are not recognized until the third stage, when kidney damage becomes apparent and kidney (renal) failure occurs. Signs of kidney failure include severe depression, vomiting, and diarrhea. The kidneys stop producing urine and toxins normally excreted by the kidney build up in the body, resulting in a life-threatening situation.

Cats are less likely to drink unknown fluids and it is suspected that cat poisoning occurs after cats have walked through anti-freeze and ingest it when they clean their feet. As little as a teaspoon of antifreeze is sufficient to cause death in cats and a tablespoon is all that is required to poison dogs. Although the poison affects both the animal's neurological and kidney function, the most severe damage usually involves the kidneys.

Diagnosis and Treatment

Early diagnosis of poisoning is often difficult because of an inadequate history and the nonspecific clinical signs, which can mimic those of many other conditions. A high index of suspicion is vital for rapid diagnosis and it is important not to rule out ethylene glycol poisoning because the owner has not seen the pet exposed to radiator fluid. Laboratory findings are often the key to making the diagnosis. Tests that support a diagnosis of ethylene glycol poisoning are available to your veterinarian.

Treatment involves preventing absorption from the stomach, increasing removal from the body and preventing the alteration of ethylene glycol to its more toxic components. If poisoning is witnessed, vomiting should be induced immediately and the stomach cleaned out with activated charcoal. Your veterinarian will need to give intravenous fluid solutions. Additional treatment depends on the stage of the disease. If the animal is not in kidney failure, drugs to stop the metabolism of ethylene glycol or methods for directly removing the ethylene glycol and its metabolites from the body are indicated.

If the animal is in kidney failure, techniques to support kidney function are required. Medications to encourage the kidney to produce urine are administered but are often futile and advanced techniques such as peritoneal dialysis or hemodialysis that replace the function of the failing kidneys may be necessary. Both of these procedures require referral to a specialty center. Support must be provided until the kidneys can heal, which may take several weeks to months, and in some animals the damage is too severe and recovery is not possible. In these patients, kidney transplantation may be indicated to replace the kidneys. The prognosis for animals to recover from acute kidney failure is poor; however, the prognosis has improved with the advent of hemodialysis, which provides support until the kidneys can regenerate. Antifreeze poisoning is a deadly disease. Prevention requires public awareness and responsible disposal of radiator fluid.

The best way to combat antifreeze poisoning is by preventing the animal from having the opportunity to drink the poison. Keep all containers tightly closed when not in use and clean up spills immediately. It should be noted that this toxin affects people as well as pets and that small children are also at risk for ethylene glycol poisoning.

There is currently a new product on the market (one trade name is Sierra) which claims to be safer than other brands of antifreeze. This product contains propylene glycol as its active ingredient. If ingested, it can still cause the nervous system injury, resulting in incoordination and possibly seizures, but does not cause the more frequently fatal kidney damage. It is clear using such a product would pose less of a health hazard. The best advice remains, however, to always use any potentially toxic product carefully to prevent accidental poisoning in the first place.

Article submitted by: © Roger Ross DVM

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