At this time of year, as temperatures drop, vets will begin to see specific issues arising in our pets. One of the most dangerous and scary to see is antifreeze poisoning. Antifreeze is something that many of us will have around the home or garage and even if not, it can be found in every car engine. Animals can be exposed to it through spillages of a product or leaks from a car’s cooling system and once ingested, the effects are rapid and severe. Here, we will look at why antifreeze is such a problem, how to recognise an affected animal, any first aid you can take as an owner and how vets will try to treat it.
What is antifreeze and why is it harmful?
Antifreeze is a substance that does what it says – when added to the cooling system of a car, it will prevent the engine from freezing. It does this by lowering the freezing point of the water in the system, but in higher temperatures, it will also raise the boiling point to prevent overheating. It is usually comprised of ethylene or propylene glycol and it is the ethylene glycol versions that are the most toxic. The ethylene glycol antifreeze solutions have a sweet taste to them which is attractive to animals, especially cats. Unfortunately, it doesn’t take much to be ingested – only around 1-2 teaspoons – to have toxic effects. For dogs, the toxic amount is 3-4 teaspoons.
Once ingested, the ethylene glycol is metabolised by the liver into two main compounds – glycolic acid and oxalic acid – both of which are highly toxic to the body. They cause a state of severe acidosis which will affect the central nervous system and create crystals of calcium oxalate in the kidneys which lead to blockages and damage to the kidney tissues. The severity of the impact of antifreeze occurs because of its rapid onset of toxicity (within 30 minutes of ingestion) and the fact that the kidneys do not recover well from damage. Because of this, very sadly, the effects are not reversible.
Clinical signs and diagnosis
The clinical signs of antifreeze poisoning are widespread, will start very shortly after ingestion and continue to progress over time. Within an hour of ingesting antifreeze, the animal may appear ‘drunk’, with symptoms including
- vomiting
- increased thirst and urination
- in-coordination
- lethargy
If left untreated, after 12-24 hours in cats and 36-72 hours in dogs, further symptoms can occur such as
- inappetence
- depression or stupor
- seizures
- irreversible kidney damage
- rapid breathing
- coma
Unfortunately, these symptoms can occur with a wide range of illnesses and other toxicities, so unless the animal is actually seen to drink a solution containing ethylene glycol, it can be hard to diagnose it as such.
Because the toxic dose of antifreeze is so low, any amount of ingestion ought to be treated, so if it is witnessed, they must be taken to a vet straight away. Without a witnessed event, all we will have to go on are the symptoms and associated diagnostics.
Blood work in a symptomatic animal is likely to show acute kidney failure, though in the very early stages, it may not be present yet. A urine sample can be very useful and if calcium oxalate crystals are seen, then it is as close to a definitive diagnosis as we can get. Interestingly, some antifreeze solutions contain a dye that fluoresces in UV light so using a Wood’s Lamp (usually used for detecting ringworm!) can also give us an answer. Beyond this, a blood sample will typically show evidence of dehydration, high potassium, high phosphorus and sometimes low glucose and low calcium.
First Aid
If you see your dog or cat ingesting antifreeze, it is vital that you get them to a vet immediately so treatment can begin. However, spending two or three minutes trying to prevent further exposure can be highly beneficial. Immediately remove them from the source of the toxin and carry out simple decontamination – rinse or wipe out the mouth and around the muzzle, clean any liquid off their feet and fur but do not attempt to make them vomit.
If you have access to the container of antifreeze, bring it along (securely sealed and in a plastic bag) to the veterinary clinic as this can help the veterinary team determine the toxicity level and how best to treat your pet.
Treatment of antifreeze poisoning
The sooner treatment is started, the better. If an animal presents with known antifreeze ingestion and it is within the first hour or so, then the vet will attempt to make the animal vomit to reduce the chance of absorption. However, it isn’t safe to do this if the animal is showing neurological signs and there is a risk they may choke. Because of the rapid absorption of antifreeze, there are also questions around how beneficial this may be.
Beyond this decontamination, treatment needs to be aimed at maximising the excretion of the ethylene glycol. This is best achieved by providing the animal with intravenous fluid therapy to correct dehydration and ‘flush’ the kidneys, increasing urine production and attempting to protect renal function.
Ideally, an antidote to the antifreeze will be given. A substance known as 4-methylpyrazole, or fomepizole, can be highly effective in dogs but this is a human drug which is very difficult to obtain. In the majority of veterinary practices, a much more common method is to use ethanol itself, most often found in alcoholic drinks. In fact, in UK practice, known antifreeze toxicity cases are often treated by given intravenous vodka. This prevents the ethylene glycol from being broken down to the toxic substances of glycolic acid and oxalic acid.
However, this is potentially high risk, as ethanol itself is also toxic to cats and dogs. As a result, treated animals will need to be hospitalised for a number of days on continued fluid therapy. They may have a feeding tube placed help maintain their nutrition during their inappetence and will require intensive nursing care, especially if they are showing neurological signs.
Unfortunately, by the time most cases are presented, kidney failure has already occurred and the chances of a full recovery are slim.
Prognosis
Antifreeze poisoning is a perfect storm – most incidents are not witnessed, toxicity occurs incredibly quickly, causing often irreversible damage, and there is very little chance of specific treatment. Therefore the prognosis for these cases is highly guarded. The best chance of a successful outcome is to act quickly – do not delay treatment, even if there is only a suspicion of poisoning.
Prevention
The only way to prevent antifreeze poisoning is to prevent animals from having any exposure to it. This means keeping any solutions containing ethylene glycol in sealed containers and out of the reach of children and animals. If a spillage occurs, clean it up immediately and thoroughly rinse the area with water to dilute any possible remains. It is also a good idea to cover the area with sawdust or wood shavings to discourage any animal licking at it and to help absorb any remaining product.
If you need to have antifreeze solutions at home, consider using those containing propylene glycol instead of ethylene glycol. Although these are also considered toxic, the toxicity is much reduced compared to the tradition ethylene glycol preparations and therefore treatment is often much more successful. Propylene glycol also doesn’t carry the sweet taste that ethylene glycol does, so it isn’t as attractive to pets.
Thankfully, antifreeze toxicities are not a common occurrence but it is useful to know the potential clinical signs so that action can be taken quickly if required. As always, speak to your veterinary team if you have any concerns and keep your pets safe over the winter.
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