Ethylene Glycol (Radiator Fluid) Toxicity

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. Antifreeze is
colorless, odorless, and has a sweet taste that dogs and small
children find appealing and will readily drink.

Cats are less likely to drink unknown fluids. 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.

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 animals appear “drunk” and consequently
exhibit many of the 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.

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 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.

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.

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
ineffective 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 hemodialysis
that replace the function of the failing kidneys may be
necessary. Both of these procedures require referral to a
speciality center. Support must be provided until the kidneys
can heal, which may take several weeks or 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 caused by antifreeze poisoning is sudden
kidney failure, and it is associated with a high death rate. 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 advent of less toxic antifreeze compounds such as propylene
glycol will reduce the frequency of antifreeze poisoning in
companion animals.

The above is general veterinary information. Do not begin
any course of treatment without consulting your regular
veterinarian. All animals should be examined at least once every
12 months.