Goals of Treating Antifreeze Poisoning
The goals of treating a dog with antifreeze poisoning are to try and prevent absorption of ethylene glycol (EG) from the gastrointestinal tract, prevent the conversion of EG to its toxic metabolites, increase the excretion of EG and its metabolites and prevent the development of acute renal failure. Treatment must be implemented very quickly after a dog ingests antifreeze for the outcome to have even a remote chance of being successful.
If a dog is presented for treatment very shortly after it ingests antifreeze, it may be possible to limit gastrointestinal absorption by inducing vomiting (emesis) and/or through a procedure called gastric lavage. These techniques usually are only valuable when they are performed within an hour or so following ingestion of the toxin. Vomiting can be induced by administering activated charcoal, syrup of ipecac or hydrogen peroxide orally. The dog’s veterinarian should be consulted about the appropriate amount and procedure for administering these products. Gastric lavage involves passing an orogastric tube through the dog’s mouth and esophagus, and ultimately down into its stomach. The contents of the stomach can then be evacuated by the flow of gravity, by siphoning or by suction. After the dog’s stomach has been emptied, isotonic fluids can be infused into the stomach to bathe the gastric lining; they will also be removed by gravity, siphoning or suction. This process is usually repeated several times in an attempt to remove as much of the antifreeze or other toxic materials as possible before they are absorbed into the dog’s blood stream.
Several antidotes are available to treat antifreeze toxicity, including ethanol and fomepizole. Authorities recommend that only one of these antidotes be used in any given dog; they should not be used together. Fomepizole currently is the antidote of choice, as long as it can be given intravenously within the first 8 hours after the dog has swallowed antifreeze. Fomepizole inhibits the transformation of EG into its most highly toxic metabolite, oxalic acid. Administration of fomepizole can have adverse side effects, although these are generally fewer and less severe than the side effects associated with the administration of ethanol as an antifreeze antidote. Ethanol must be given within the first few hours after antifreeze ingestion for the treatment to have a chance of being effective. Generally, dextrose is added to ethanol to prevent the dog from becoming hypoglycemic (having abnormally low levels of glucose in its blood). Ethanol is also usually administered intravenously in antifreeze poisoning situations. Intravenous fluids usually are necessary as part of the treatment for a dog poisoned by antifreeze.
If appropriate, gastrointestinal protectants can be administered to soothe the stomach and relieve the intestinal irritation that frequently is associated with antifreeze poisoning. Kidney transplantation is slowly becoming a potential option for pets that have developed acute renal failure following ingestion of antifreeze. This surgical procedure is extremely expensive and is only available at a very few veterinary teaching hospitals and specialty referral centers. It has been best described in cats and is not considered to be a realistic treatment option for dogs at this time.
Dogs suffering from antifreeze poisoning are usually very, very sick. If only the renal tubules of their kidneys are affected, the damage may be reversible, although recovery can take weeks to months to years. Dogs that are treated with an ethylene glycol antidote within a few hours of ingesting antifreeze have an excellent prognosis; those treated within 8 hours of ingestion usually will recover, as well. However, as each hour passes, the prognosis worsens, especially if a large amount of antifreeze was ingested.
Ethylene glycol and its metabolites are usually excreted out through the kidneys within 24 to 48 hours. If the dog survives that long, the long-term consequences of antifreeze toxicity may be minimal, and the animal may have a good prognosis. Unfortunately, once a dog develops oliguric kidney failure – in other words, once the dog’s kidneys have shut down and are no longer able to produce urine - the prognosis is poor to grave.