Antifreeze Intoxication: What You Really Need to Know
Cold weather means snow, hot chocolate, and car problems. That puddle of antifreeze in the driveway could mean more than car trouble. Dogs can’t resist the sugary taste of antifreeze and consumption can lead to big problems for your pooch. Cats are less likely to lap up antifreeze but, if they do, the same fate awaits.
The main ingredient in antifreeze is ethylene glycol, an alcohol. Once ingested, ethylene glycol is rapidly absorbed in the GI tract, typically within 1-3 hours. The first 12 hours after ingestion pets will be intoxicated by the alcohol and therefore, may behave like they’re drunk. Ataxia (stumbling and falling), seizures, stupor, and coma can occur. Ethylene glycol is then broken down to glycoaldehyde → glycolic acid→ glyoxylic acid → oxalic acid, with different stages of disease occurring with the different metabolites.
Glycolic acid is highly toxic as it inhibits cellular energy metabolism and causes a severe metabolic acidosis. This can lead to cardiovascular collapse evidenced by high heart rate, pulmonary edema, and heart failure. If your pet survives these first two stages, it will contend with kidney failure caused by the end product of ethylene glycol metabolism, oxalic acid. Kidney failure typically occurs 24-72 hours following ingestion in dogs and 12-24 hours in cats. Oxalic acid causes kidney necrosis, or death, along with swelling. All three stages of toxicity can overlap making it difficult for the veterinarian to determine exactly where the pet is in the disease process.
If you suspect your pet has consumed antifreeze, you need to contact your veterinarian immediately. Diagnosis of ethylene glycol ingestion is made largely based on history and clinical signs as well as laboratory abnormalities. Metabolic acidosis, low blood calcium, and calcium oxalate crystals in the urine are typically diagnostic. These urine crystals can be present in the urine of nonaffected dogs and cats but should be held in high suspicion in animals with other symptoms. A blood or urine test exists for ethylene glycol, but is only available at certain laboratories and results may not be timely. Additionally, these levels are only detectable for up to 76 hours post ingestion.
Aggressive medical therapy is required. Aggressive diuresis with intravenous fluids is indicated. If ingestion recently occurred, the metabolism of ethylene glycol should be prevented by using compounds like 4-methylpyrazole (more widely used) or ethanol. Both compounds inhibit alcohol dehydrogenase, the main enzyme that begins the breakdown of ethylene glycol. In addition, drugs like thiamine and pyridoxine are used to prevent oxalate crystal formation. Urine output must be monitored closely. Some patients require hemodialysis or peritoneal dialysis.
Prognosis for animals treated in the early stage of ethylene glycol intoxication is guarded to good when appropriate treatment is instituted. Prognosis is poor for animals who have already developed kidney failure.
