Antifreeze causes many deaths each year mostly because, by the time the animal is presented to the veterinarian, irreversible damage has already occurred and treatment only serves to put off the inevitable. One of the problems is that the fact your cat has consumed the poison goes unnoticed until signs of intoxication develop. A lethal dose for a typical 10-pound cat is only one tablespoon of 50:50 radiator fluid.

The toxic ingredient in antifreeze is ethylene glycol, a type of alcohol linked to a sugar so that it tastes sweet. It is not the ethylene glycol itself, but rather the breakdown products of the metabolism that cause the irreversible kidney and organ damage and eventual death to almost all animals ingesting the poison.

After ingestion, ethylene glycol is rapidly metabolized in the liver into glycolic acid by the enzyme alcohol dehydrogenase (the same enzyme people use to metabolize alcohol). The glycolic acid is then slowly metabolized into oxylate, oxalic acid and formic acid. The slow conversion rate allows large concentrations of glycolic acid to build up and causes severe irreversible damage to the kidney.

• Clinical signs of Stage I are similar to those of a person drunk on alcohol-- stumbling, knuckling, vomiting, drinking water and excessive urination.
• Stage II begins 6-12 hours after ingestion as the high concentrations of glycolic acid build up, causing a severe acidosis or drop in the pH of the body. The acidosis effects the heart, lung and kidney functions as well as altering the blood chemistry balance. Brain damage and seizures can occur from 12-24 hours after ingestion.
• Stage III occurs 24-72 hours after ingestion, when the kidneys shut down and the animal enters renal failure. The kidney failure is due to the combination of the severe acidosis and direct damage to the kidney by high concentrations of glycolic acid (from phase II) and oxylate. The animal eventually dies of kidney failure.

1. Drunk gait (ataxia)
2. Vomiting
3. Urination
4. Hyper-excitability
5. Stupor/coma
6. Seizures
7. Disorientation

1. Depression
2. Anorexia
3. Vomiting
4. Stupor/seizure
5. Weakness

1. No urine (renal failure)
2. Coma
3. Death

Diagnosis:

Diagnosis will be based on the above clinical signs and laboratory tests. Blood work shows severe metabolic acidosis early on, and kidney failure later in the course. A positive test for ethylene glycol in the blood is diagnostic. The test is most sensitive during the first 2-8 hours, but positive results can be seen even 12-24 hours after ingestion of a very large amount of antifreeze. Any animal even suspected of intoxication should have a blood test run.

After inducing vomiting, the animal is put on a IV infusion of alcohol (usually vodka) to slow down the conversion of ethylene glycol to glycolic acid in the liver. Vodka works by competing with the ethylene glycol for alcohol dehydrogenase, the enzyme needed for metabolism of both compounds.

Unfortunately, treatment must be initiated almost immediately after ingestion and before high levels of glycolic acid have been formed. The remainder of the therapy is based on aggressive fluid therapy to flush out the kidney, and supportive care, including seizure control, maintenance of blood pressure and correcting acidosis. If the animal is already exhibiting signs of kidney failure, therapy will be of no assistance and euthanasia is recommended.

The prognosis will be guarded (less than 25 % survival) if caught early (within 6 hours), and it will be poor to grave if caught after 12 hours or beyond, depending on the amount ingested.