Ethylene Glycol Toxicosis in Cats
Ethylene glycol toxicosis is a type of poisoning that occurs after ingestion of antifreeze or other fluids containing the ingredient ethylene glycol. Ethylene glycol itself is not toxic, but it is metabolized in the animal's body to several extremely toxic chemicals that are responsible for its potentially lethal effects.
Potential sources of ethylene glycol in the environment include antifreeze (the most common source of ethylene glycol poisoning), air-conditioning coolants, brake fluid, heat exchange fluids from solar collectors, and fluids used in color film processing.
Ethylene glycol poisoning symptoms in the nervous system and severe kidney failure with almost complete cessation of urine output. Ethylene glycol poisoning can be fatal if not treated soon after ingestion (within 4 to 8 hours).
Cats that roam outside unsupervised are more likely to encounter ethylene glycol in antifreeze which has been disposed of improperly. Ethylene glycol has a sweet taste and cats will consume it readily. Unfortunately, many owners do not realize that their pet has consumed ethylene glycol and don't become aware of the problem until the pet shows non-specific symptoms of kidney failure like loss of appetite, lethargy and vomiting two to three days later. Treatment is often futile after severe kidney failure has developed.
Cats are more susceptible to ethylene glycol poisoning than dogs (i.e. smaller amounts are required to cause poisoning). The minimum lethal dose for a cat is 1.5 milliliters of antifreeze per kilogram of body weight. Therefore, a teaspoonful can be lethal for a 7 pound cat.
Definitive treatment should be started as soon as possible after consumption of ethylene glycol (within a few hours). If treated promptly and appropriately, pets that have consumed ethylene glycol will not develop kidney failure and have a good chance of survival.
What to Watch For
- Increased thirst
- Incoordination progressing to coma
- Pets may act as if they are intoxicated
These signs develop within 30 minutes to 12 hours after ingestion of ethylene glycol depending on the amount ingested.
Diagnostic test are needed to recognize ethylene glycol toxicosis, including:
- Complete medical history and physical examination
- Ethylene glycol test should be performed as soon after ingestion as possible
- Urinalysis to evaluate for characteristic calcium oxalate crystals (one of the metabolic end-products of ethylene glycol breakdown), casts, and other evidence of kidney damage
- Blood gas analysis to evaluate for the presence of severe acidosis
- Serum biochemistry tests to evaluate for electrolyte disturbances (including low blood calcium) and abnormally high kidney function tests (blood urea nitrogen, serum creatinine, serum phosphorus)
- Abdominal ultrasound examination to evaluate kidney size and appearance. Deposits of calcium oxalate crystals in the kidney result in a very bright (white on the ultrasound monitor) appearance within hours
- Kidney biopsy to confirm ethylene glycol poisoning if kidney failure is present
Treatment for ethylene glycol toxicosis includes one or more of the following:
- Induction of vomiting by oral administration of hydrogen peroxide if possible before transport of the pet to the veterinary hospital
- Hospitalization of the pet usually is necessary
- Induction of vomiting (if not successful before arrival) and gastric lavage (pumping of the stomach) to remove the poison before it can be broken down to its toxic end-products
- Administration of activated charcoal to bind ethylene glycol within the digestive tract
- Intravenous fluid administration to correct dehydration
- Treatment with sodium bicarbonate if acidosis is severe
- Specific drugs such as 20 percent ethyl alcohol that inhibits the breakdown of ethylene glycol to its toxic end-products if the pet is seen within several hours after ingestion of ethylene glycol
- Drugs to treat kidney failure and encourage urine production such as the diuretic furosemide and blood vessel-dilating drug dopamine. Unfortunately, these drugs are not often effective once severe kidney failure has developed and more than 80 percent of pets with kidney shutdown due to ethylene glycol poisoning die despite diligent medical treatment.
- Peritoneal dialysis or hemodialysis is necessary if severe kidney failure and shutdown of urine production are present. These procedures require referral to a veterinary specialist.
Remove your cat from the source of ethylene glycol immediately. Call your veterinarian immediately if you suspect your cat to have consumed ethylene glycol. Your veterinarian may recommend you induce vomiting in your pet by oral administration of hydrogen peroxide. Transport your pet to your veterinarian immediately.
Keep containers of antifreeze and air-conditioning coolant tightly closed and out of reach of pets. Clean up spills immediately and thoroughly. Antifreeze spills should be washed away with large amounts of water. Prevent access of pets to areas where ethylene glycol-containing products may be stored or spilled like the garage or driveway.
Use antifreeze products that do not contain ethylene glycol like Prestone LowTox® or Sierra®. Antifreeze products containing propylene glycol cause signs of drunkenness but are not fatal unless very large quantities are consumed, in which case death is the result of alcohol poisoning.
Most important: Do not allow your pet to roam unsupervised. Pets that are allowed to roam unsupervised are more likely to encounter a source of ethylene glycol and consume it. In many instances, owners are not aware their pets have consumed ethylene glycol until it is too late and severe kidney failure has developed.
Ethylene glycol toxicity is a life-threatening condition. The symptoms of ethylene glycol poisoning, however, are not specific for this disorder. Other diseases present symptoms similar to those observed in ethylene glycol toxicity. Examples of these diseases include:
- Garbage ingestion. Animals that have ingested garbage, especially garbage that contains moldy food, may shake and have muscle tremors, which helps to distinguish them from animals poisoned with ethylene glycol.
- Acute pancreatitis. Inflammation of the pancreas also causes vomiting, severe lethargy and, rarely, nervous system symptoms.
- Severe gastroenteritis or intestinal tract obstruction. These conditions can cause vomiting, lethargy, and progressive deterioration of the pet.
- Acute kidney failure. This may result from other types of toxins, trauma and infection. These causes of kidney failure are distinguished from that caused by ethylene glycol by laboratory tests, abdominal ultrasound and kidney biopsy. Treatment of acute kidney failure depends on the underlying cause.
Veterinary care should include diagnostic tests and subsequent treatment recommendations.
Diagnostic tests are needed to recognize ethylene glycol toxicosis. These include:
- A complete medical history and physical examination to determine if exposure to ethylene glycol or other toxins has occurred. Unfortunately, in many cases the owner is not aware that the pet has consumed ethylene glycol and first recognizes the non-specific signs of severe acute kidney failure such as lethargy, loss of appetite, vomiting.
- An chemical test to detect ethylene glycol in the blood. The test is only accurate if performed within 6 to 12 hours of ingestion.
- Urinalysis to evaluate for dilute urine, casts, and calcium oxalate crystals, which appear in the urine within 3 to 5 hours of ethylene glycol ingestion. Failure to identify calcium oxalate crystals in the urine does not rule out the possibility of ethylene glycol poisoning because crystal formation may cease within a few days of poisoning.
- Venous blood gas analysis to identify severe acidosis (low blood pH) characteristic of early ethylene glycol poisoning.
- Serum biochemistry tests to evaluate for low blood calcium concentration (hypocalcemia) that may occur soon after ethylene glycol ingestion. Abnormal kidney function tests, like high blood urea nitrogen, serum creatinine, and serum phosphorus, will be observed if acute kidney failure has developed between 12 and 72 hours after ingestion of ethylene glycol. Serum biochemistry tests also help identify electrolyte disturbances, like abnormal blood sodium, potassium, and chloride concentrations, and help evaluate other organ systems, for example liver function and pancreas function, which will help your veterinarian eliminate other diagnostic possibilities.
- A calculation called the "osmolal gap," if your veterinarian suspects recent ethylene glycol poisoning. A high osmolal gap raises suspicion that a large amount of ethylene glycol metabolites are present in the blood.
- An ultrasound examination and ultrasound-guided kidney biopsy for diagnosis if the pet is presented in kidney failure. The ultrasound examination typically shows very bright kidneys with ethylene glycol poisoning. A biopsy is recommended to confirm the diagnosis of acute kidney failure due to ethylene glycol poisoning because of the extensive treatment required and the poor prognosis.
Therapy is often successful if the pet is seen by the veterinarian within a few hours after ingestion of ethylene glycol and before kidney damage has occurred. Such pets never develop kidney failure and are discharged from the hospital after a few days of treatment and observation. If kidney failure already is present (based on observation of high kidney function test results and lack of urine production) the prognosis for recovery is very poor. Treatment is difficult and hospitalization may extend for weeks. More than 80 percent of pets with severe acute kidney failure due to ethylene glycol poisoning die despite intensive treatment.
Your veterinarian may recommend any of the following treatments for ethylene glycol poisoning:
- Induction of vomiting is indicated if your pet is seen within a few hours of ethylene glycol ingestion. Induced vomiting eliminates poison that had not yet been absorbed from the stomach. Call your veterinarian immediately if your pet has consumed ethylene glycol. Your veterinarian may recommend you give your pet hydrogen peroxide by mouth to induce vomiting before you transport the animal to the hospital.
- Gastric lavage (pumping the stomach) also is indicated if your pet is seen within a few hours of ethylene glycol ingestion.
- Activated charcoal is administered via a stomach tube or by syringe to the animal to prevent further absorption of ethylene glycol from the digestive tract. Activated charcoal binds ethylene glycol in the stomach and allows it to pass through the digestive tract to be eliminated in the stool. A cathartic may be given with the activated charcoal to speed its movement through the digestive tract.
- In cats, only 20 percnt ethanol (ethyl alcohol) is used to prevent the breakdown of ethylene glycol to its toxic end-products. Twenty percent ethanol produces nervous system signs of "drunkenness" but can be used both in dogs and cats. 4-methylpyrazole (4-MP or Antizol®) does not produce "drunkenness," but at this time, it is not recommended for use in cats. Ethanol must be used within 6 to 8 hours after ingestion of ethylene glycol. Treatment requires 2 to 3 days.
- Treatment with sodium bicarbonate may be required if the pet has severe acidosis (low blood pH).
- Fluids are administered intravenously to correct dehydration resulting from vomiting and to help prevent damage to the kidneys. Intravenous fluids often are continued 24 to 48 hours after treatment with 20 percent ethanol has been completed.
- Thiamine (vitamin B1) may be administered to aid in the conversion of the toxic by-products to non-toxic metabolites. This treatment is adjunctive only.
- Furosemide (a diuretic) and dopamine (a blood vessel-dilating drug) are used to try and increase urine production when kidney failure is present. Often it is impossible to increase urine production despite intensive treatment.
- Peritoneal dialysis and hemodialysis are available for animals that have developed severe kidney failure and are not producing urine despite intravenous fluid, furosemide and dopamine administration. This treatment is very expensive and is only available at selected specialty referral hospitals. Some animals with severe kidney failure due to ethylene glycol poisoning die despite dialysis support.
- Metoclopramide and the antihistaminic drugs cimetidine, ranitidine, and famotidine are examples of drugs that may be used to treat the gastrointestinal complications of severe kidney failure such as vomiting and gastric hyperacidity, respectively.
- Phosphorus binding drugs such as aluminum hydroxide may be given to bind phosphorus in the digestive tract.
- Blood transfusions and intravenous nutritional support, called "total parenteral nutrition," may be required from animals that survive yet have prolonged hospitalization times.