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Overview:
Ethylene glycol is a common cause of poisoning in cats
& a leading cause of acute kidney failure.
It is a clear, odourless liquid with a sweet taste which is attractive to cats,
dogs & children.
It is most commonly found in antifreeze, but is also in many other products (see
end of article).
Once ingested the body starts to break down the
ethylene glycol quickly. Around 50% of the ethylene glycol is excreted by the
kidneys, the remainder is metabolised by the body into other
toxins including glycolate, glycoaldehyde, glyoxylate & oxalate. The oxalate
combines with calcium to form calcium
oxalate crystals inside the renal (kidney) tubular cells, causing blockage
& renal epithelial necrosis.
While ethylene glycol is relatively non toxic, the
metabolism causes by products which are highly toxic to the cat. Even as little
as a teaspoon or two is enough to kill a cat & ingestion of ethylene glycol is
always a medical emergency, and you should take your cat to the veterinarian
immediately.
What are the symptoms of
antifreeze poisoning in cats?
There are three stages to
poisoning. [1]
1) CNS Depression Phase
- Ethylene glycol is rapidly
absorbed from the gastrointestinal tract.
Within 30 minutes to 12 hours of ingestion the cat show the following symptoms:
These symptoms last for approximately 12 hours after ingestion. After
this, the cat may appear to recover.
2) Cardiopulmonary Toxicity
Phase - Approximately 12 - 24
hours after ingestion the following symptoms appear:
-
Tachypnea (rapid breathing)
-
Tachycardia (rapid heart
rate)
-
Metabolic acidosis (the blood
is too acidic)
-
Hypertension
-
Lethargy
-
Anorexia
3)
Renal Toxicity Phase
-
Kidney failure
-
Vomiting
-
Depression
-
Coma
How is antifreeze poisoning in
cats diagnosed?
Your veterinarian will take a
history from you, including possible exposure to ethylene glycol. He will perform a
physical examination of the cat.
A commercial test kit is available for
rapid identification of ethylene glycol in whole blood.
Urinalysis: To detect
the presence of calcium oxalate crystals in the urine & asses kidney damage.
Blood Gas: To detect the extent
of acidosis.
Ultrasound is performed to view
the kidneys & evaluate the extent of damage to the kidneys.
Serum biochemistry to
detect low blood calcium, as a result of calcium oxalate formation which
depletes calcium levels (hypocalcemia).
Some antifreeze products
contains the colourant fluorescein, which helps detect radiator leaks. This can
cause the cat's urine to glow a bright green colour when viewed under a woods
lamp. However, not all ethylene glycol products contain fluorescein, so the
absence of this doesn't necessarily rule out poisoning.
How is antifreeze poisoning
treated?
Successful treatment requires diagnosis & the
prognosis is always guarded. If treatment is not begun within 6 hours of
ingestion, prognosis is grave. [2]
Treatment is firstly aimed at blocking or
decreasing absorption ethylene glycol & preventing the formation of
toxic metabolites, removal of the toxin & treatment of the severe metabolic
acidosis. This includes;
-
Induce vomiting, lavage
stomach (washing out the stomach with
sterile water or a saltwater solution) or
both. -
Administration of ethanol.
This drug should be administered as soon as diagnosis is made.
-
Sodium bicarbonate is
administered to counter the metabolic acidosis. -
Supportive treatment to
include correction of fluid & electrolyte imbalances.
What other products contain
Ethylene glycol?
Photographic developing fluid, hydraulic brake
fluid, some cosmetics,
some plants, radiator coolant, decorative snow globes, air conditioning coolant.
References:
[1] C-Tech
Corporation
[2] The Feline Patient - Gary D. Norsworthy,
Mitchell A. Crystal, Sharon K. Fooshee, Larry P. Tilley. |
