Ethylene Glycol is the principal ingredient in anti-freeze that is responsible for poisoning in dogs and cats. Antifreeze is colorless, odorless, and has a sweet taste that dogs and small children find appealing and will readily drink. As little as a teaspoon if antifreeze is sufficient to cause dearth in cats an tablespoon (or sometimes less) is all that is required to poison dogs.
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 the animal will appear “drunk” and consequently exhibit many of the classical signs associated with alcohol intoxication: staggering, stumbling, and in coordination. 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 owners rarely notice this
Unfortunately, most dogs and cats poisoned with antifreeze are not recognized until the third stage, when kidney damage becomes apparent and the kidney (renal) failure occurs.
Ethylene glycol is converted by the liver to more toxic substances (metabolites), that are responsible for the majority of injury to tissues including the kidney, liver, lungs, and heart. Signs of kidney failure include sever 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.
Early diagnosis of poisoning is often difficult because of an inadequate history and the nonspecific clinic 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 sent he pet exposed to radiator fluid, laboratory findings are often the key to making the diagnosis. Test 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 ethylene glycol or methods for directly removing the ethylene glycol and its metabolites from the body are indicated.
Ethanol (alcohol) and 4-methylprazole (fomepizole; Antizol-Vet) stop the metabolism of ethylene glycol; however, these drugs must be administered within several hours of poisoning and are effective when kidney damage had occurred, an effective dose of 4- methylprazole to stop the conversion of ethylene glycol has not been identified for cats, so its use is not recommended in cats. Peritoneal dialysis and hemodialysis are two techniques with which the poisons may be removed from the body.
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 hemo-dialysis 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 crippled kidneys.
The most common problem cause by anti-freeze is sudden kidney failure, and it is associated with a high death rate. The prognosis for animals to recover from the 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 condition. Prevention requires public awareness and responsible disposal of radiator fluid.
The even of less toxic antifreeze compounds such as propylene glycol will reduce the frequency of antifreeze poisoning in companion animals.