Ethylene glycol (EG) is a highly toxic ingredient in antifreeze products that causes poisoning in dogs when ingested. Ingestion of a toxic dose of EG is an emergency. The prognosis is poor once symptoms develop.
Antifreeze toxicosis symptoms include sudden onset of severe vomiting and incoordination with rapid deterioration. Clinical findings suggesting antifreeze toxicosis may show up on routine blood and urine tests, and a specific EG detection test is available. Management of life-threatening symptoms takes priority during treatment. The antidote (ethanol or fomepizole) is administered intravenously. Intensive care is usually required for several days. The prognosis for antifreeze poisoning is poor.
Ethylene glycol is highly toxic and ingestion presents a life-threatening emergency. Treatment initiated prior to the onset of symptoms has a better chance of a good outcome.
Antifreeze poisoning is caused by the ingestion of ethylene glycol (EG). EG’s sweet taste is appealing and the lethal dose is small, so the potential for dangerous ingestions is high. Vehicle engine coolant is the most common source of EG, but it can be found in many other common products such as:
• Hydraulic brake fluid • Ink, especially stamp pads • Antifreeze for recreational vehicle toilets • Ballpoint pens
• Solvents • Paint • Cosmetics
The main symptoms of antifreeze poisoning include:
• Vomiting • Excessive thirst and urination (polyuria/polydypsia) • Difficulty walking and incoordination (ataxia)
• Collapse• Seizures• Coma
Dogs with antifreeze poisoning usually deteriorate rapidly.
The clinical signs of antifreeze poisoning vary with the dose, but symptoms are divided into three stages:
(I) 30 minutes to 12 hours after ingestion:
• Vomiting • Lethargy • Incoordination • Stumbling • Excessive thirst
(II) 12 to 24 hours after ingestion the dog may seem to be in remission. In this stage, the body is metabolizing the ethylene glycol.
(III) 36 to 72 hours after ingestion the kidneys fail, resulting in:
• Abdominal pain • Appetite loss (anorexia) • Vomiting • Diarrhea • Lethargy • Seizures • Coma • Death
Diagnosis is simplified when ingestion is known, but dogs presenting with symptoms of antifreeze poisoning typically undergo the following diagnostic procedures:
• Physical examination • Routine blood tests• Urinalysis
Characteristic findings during this initial workup may suggest antifreeze poisoning. Antifreeze fluoresces under black light, so evaluation of the dog’s mouth (or fur if it has vomited) can suggest ethylene glycol exposure. When antifreeze poisoning is suspected, a specific EG detection blood test may be performed, if available.
The prognosis for antifreeze poisoning is poor. Initial treatment efforts focus on addressing life-threatening symptoms like seizures and heart arrhythmias.
Specific treatment for antifreeze poisoning is directed at lowering the absorption rate of the ingested ethylene glycol, namely:
• Gastrointestinal decontamination: In cases where the dog is hospitalized during the first 2 hours after a small ingestion, gastric lavage or induction of emesis may be utilized in an effort to prevent additional absorption of EG.
• IV administration of an antidote to EG, such as:◦ Fomepizole, also known as 4-methypyrazole or 4-MP ◦ Ethanol
Activated charcoal is not helpful for ethylene glycol ingestion because it does not bind to EG.
Dogs with antifreeze poisoning require aggressive intensive care and monitoring for several days. Where available, peritoneal dialysis or hemodialysis can be utilized to remove EG from the bloodstream. IV fluid therapy helps address electrolyte imbalances and dehydration. Antiemetics are given to relieve nausea. Nursing care to keep the dog clean, dry, and warm is critical for recumbent or comatose dogs.
Hasty care is crucial, as dogs treated within 8 to 12 hours have a better chance of survival. Animals treated with 4-methylpyrazole within 5 hours of ingestion have a higher probability of survival. Once kidney damage occurs, the prognosis is extremely poor. The kidney damage that results from ethylene glycol toxicosis is permanent and treatable only with a kidney transplant.
Antifreeze poisoning is not contagious. It is preventable by eliminating the possibility of exposure to EG through environmental controls. Strategies include:
• Frequent inspection of automobile radiators to check for leaks
• Supervision of the animal in areas where ethylene glycol could be present (driveways and garages)
• Diligent storage and waste disposal of antifreeze containers
• Immediate clean-up of any possible spills. If a spill does occur, covering the area with an absorbent material, such as sawdust, to discourage the animal from licking any residue
• If possible, choose propylene glycol products over ethylene glycol as a less toxic alternative. Propylene glycol is also less attractive to animals as it does not have such a sweet taste.
EG ingestion is common and makes up nearly 10% of calls to pet poison hotlines every month, all year round.
Treatment of EG ingestion may include:
• Intravenous administration of the antidote: ethanol or fomepizole (4-methylpyrazole, 4MP)
• Aggressive management of life-threatening symptoms: ◦ Antiarrhythmics ◦ Anti-seizure medications
• Intensive monitoring and supportive care: ◦ Fluid therapy ◦ Peritoneal dialysis or hemodialysis
◦ Kidney transplant
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