Canine Heat Stroke: What Symptoms to Be Aware Of

Canine heat stroke is a body temperature above about 41 degrees that panting can no longer bring down. Early signs are heavy panting that does not settle, thick drool, bright red gums and a dog that wants to stop. Advanced signs are vomiting, staggering, pale or purple gums, seizures and collapse. Wet the dog with cool water, get air moving over the coat and drive to an emergency vet. It is always an emergency.

Canine heat stroke happens when a dog's body temperature climbs past the point where panting can bring it back down, usually above 41 degrees, and the heat starts damaging the gut, the kidneys, the liver, the brain and the blood's ability to clot. It is one of the emergencies we see most through a Western Sydney summer, and one of the few where what the owner does in the first ten minutes makes a real difference to what we can do when the dog arrives.

The early symptoms are easy to wave away as a dog who is just hot. The later ones are not. Here is how to tell them apart, what to do on the drive, and what happens once your dog reaches us.

Why are dogs so vulnerable to heat?

Dogs barely sweat. They have a few sweat glands in their paw pads, and that is about it. Almost all of their cooling comes from panting, which evaporates moisture off the tongue and airways, and evaporation needs air that is cooler than the dog and moving. On a 38-degree afternoon in Rouse Hill, with the dog on hot concrete and no breeze, panting just moves warm air in and out.

There is a second problem. A dog does not decide to stop. A kelpie chasing a ball at 2 pm in January will keep chasing it until it falls over. The Royal Veterinary College's VetCompass program looked at 1,259 heat-related illness events among more than 905,000 UK dogs in a single year. Where a trigger was recorded, 74 per cent were set off by exercise, 13 per cent by hot weather alone and just 5 per cent by a car. The hot car gets the publicity. The afternoon walk does most of the damage.

Symptoms of heat stroke in dogs: early signs and advanced signs

Heat exhaustion in dogs is the early stage of the process that ends in heat stroke. There is no line between them you can judge at home, so treat the early list as your cue to act, not to watch.

Early signs (heat exhaustion)

• Heavy, fast panting that does not ease after five minutes of rest in the shade

• Thick, ropey saliva and drooling

• Bright red tongue and gums

• Restlessness, seeking out tiles or shade, or lying down and refusing to move

• A racing heartbeat, and ears and belly that feel hot to the touch

Advanced signs (heat stroke)

• Vomiting or diarrhoea, sometimes with blood in it

• Wobbling, staggering, bumping into things or seeming confused

• Gums turning pale, grey, blue or purple

• Pinpoint bruises on the gums or belly, a sign the blood has stopped clotting properly

• Tremors, seizures, collapse, or an unresponsive dog

A rectal temperature above 40 degrees in a dog that has been exercising or sitting in the heat is enough to start cooling and start driving; above 41 is heat stroke by definition. But do not go hunting for a thermometer you do not own. The signs above are enough.

Which dogs are most at risk?

Can a dog have a heat stroke on a day that does not feel especially hot to you? Yes, and the dogs below are the ones that do.

• Flat-faced breeds. Pugs, French bulldogs, British bulldogs and boxers have narrowed airways, so panting moves less air. In the VetCompass data, they had more than twice the odds of heat stroke from hot weather and three times the odds from a car.

• Overweight dogs. Fat insulates, and a heavy dog works harder for every step. Dogs above the average weight for their breed had higher odds of exercise-triggered heat stroke.

• Senior dogs. Dogs aged 12 and over had about three times the odds of heat stroke from hot weather compared with dogs under two.

• Thick or double coats. Huskies, border collies, golden retrievers and Samoyeds carry a winter jacket they cannot take off.

• Any dog left in a car. The NSW Department of Primary Industries measured it: on a 29-degree day, a parked car reaches 40 degrees inside in ten minutes and 48 in thirty, shade and cracked windows included. RSPCA Australia puts the time it can take a dog to die in a hot car at six minutes.

Dog heat stroke treatment starts in the car: first aid on the way to the vet

Every minute above 41 degrees does more damage, so cooling starts the moment you notice the signs and continues while someone else drives. Call ahead so we are waiting.

• Get out of the heat. Shade the house, or the car with the air conditioning on. Stop all exercise.

• Wet the dog with cool water, not ice. Tap water from a hose, a bottle or a bucket over the whole body, especially the belly, groin, armpits and paws. Ice makes the surface blood vessels clamp down and can trigger shivering, both of which slow the heat getting out.

• Move air over the wet coat. A fan, the car air conditioning on full, or open windows while driving. Wet fur with no airflow does very little.

• Do not wrap the dog in wet towels. A towel over the back traps heat within a couple of minutes. Pour, do not wrap.

• Offer water, never force it. A wobbly or drowsy dog can breathe water into the lungs.

• Stop active cooling at 39.5 degrees if you can measure it. Overshooting causes its own problems. Without a thermometer, keep cooling gently until you reach us.

A dog that perks up after cooling still needs to come in. The organ damage shows up over the following 12 to 48 hours, and the dogs that worry us most are the ones that looked fine at hour two.

What happens when you arrive at VECA?

Heat stroke patients go to the front of the queue. A triage nurse takes a temperature and checks gum colour and heart rate at the door, and active cooling continues on the treatment table while the vet starts the rest: an intravenous line and fluids, oxygen if the dog is struggling, and bloods in our in-house laboratory to check the kidneys, the liver, blood sugar, electrolytes and, most importantly, clotting, because the clotting system is often the first thing to fail.

Then monitoring, usually for 24 to 48 hours, because the complications of canine heat stroke arrive late: Kidney injury, damage to the gut lining, abnormal heart rhythms, brain swelling and a clotting disorder called DIC. We have mechanical ventilation and our own blood bank on site at both hospitals for the dogs who need them.

We will not promise you an outcome, because heat stroke does not allow it. What we can say is that the dog cooled in the car and seen within the hour starts from a very different place than the dog left to sleep it off.

Preventing canine heat stroke in a Sydney summer

Western Sydney is a different climate from the coast. Bureau of Meteorology records from 1968 to 2017 show Western Sydney averaging 12.4 days a year over 35 degrees against 3.7 at Observatory Hill in the city, and in extreme heat events the west runs 6 to 10 degrees hotter than the eastern suburbs. Camden, next door to Campbelltown, averages 11 days a year over 35. A plan that works for a dog in Manly does not work in Rosemeadow or Kellyville.

• Walk before 8 am or after 7 pm on hot days. Skip the walk altogether above 35 degrees. A dog can go a day without one.

• Check the ground. Back of your hand on the footpath for five seconds. If you cannot hold it there, the pads will burn, and the heat coming off it is cooking the dog from below.

• The car rule is simple: never. Not for five minutes, not with the windows down, not in the shade.

• Shade that moves with the sun, and two water bowls. A kennel in full sun at 3 pm is an oven, and one bowl always gets knocked over.

• Flat-faced and senior dogs inside with the air conditioning on days over 30.

• No fetch, no agility, no running beside the bike in the heat. Exercise is the trigger in three out of four cases. And do not shave a double coat; brush out the undercoat instead.

Care Tip: Keep a two-litre bottle of water in the car boot from November to March. If your dog starts to flag on an outing, you can wet them down at the roadside and drive straight to us rather than losing fifteen minutes finding a tap. If your dog is panting hard and not settling, call VECA on 02 4089 4638 (Campbelltown) or 02 4089 4630 (Norwest). We are open 24/7.

Frequently Asked Questions

Can a dog have a heat stroke in the car with the windows down?

Yes. Open windows and shade slow the heating but do not stop it. The NSW Department of Primary Industries' measurements show a car interior reaching 40 degrees within ten minutes on a 29-degree day, and flat-faced breeds had three times the odds of car-related heat stroke in the VetCompass data. If you cannot take the dog with you, leave them at home.

My dog was panting hard but seems fine now. Do I still need to see a vet?

If the panting settled within a few minutes of rest and water, and your dog is bright, eating and moving normally, watch closely for two days. If the panting went on longer, or there was any drooling, wobbliness, vomiting or a change in gum colour, call VECA and come in. Organ and clotting damage can take 12 to 48 hours to show, and bloods pick it up before the symptoms do.

Should I give my dog ice or ice water to cool down?

No. Cool tap water poured over the body and air moving across the wet coat cool a dog faster than ice. Ice and iced water constrict the blood vessels in the skin, which keeps the heat inside, and can set off shivering, which generates more heat. Offer cool water to drink if your dog wants it, but never force it, and never wrap a hot dog in wet towels.

If your dog is panting hard and not settling, do not wait to see how it goes: wet them down, call Campbelltown Clinic or Call Norwest Clinic, and start the car.

Reviewed and Approved By

Dr Phil Hayton, Emergency & Critical Care Veterinarian at VECA

Dr Phil Hayton is an Emergency and Critical Care Veterinarian, working in Client Relations at Veterinary Emergency Care Australia (VECA). He has experience across emergency medicine, critical care and veterinary diagnostics, including a professional background in veterinary virology. He is passionate about clear communication, client advocacy and helping pet owners navigate difficult decisions about their animals' care.

Sources

References for statistics and claims cited in this article.

1. Hall EJ, Carter AJ, O'Neill DG. Dogs Don't Die Just in Hot Cars: Exertional Heat-Related Illness (Heatstroke) Is a Greater Threat to UK Dogs. Animals, 2020 (Royal Veterinary College VetCompass) | https://pmc.ncbi.nlm.nih.gov/articles/PMC7459873

2. NSW Department of Primary Industries, Dogs in Hot Cars fact sheet | https://www.dpi.nsw.gov.au/__data/assets/pdf_file/0011/1495316/Dogs-in-Hot-Cars-fact-sheet-FINAL.pdf

3. RSPCA Australia, 4 ways to keep your dog cool this summer (2022) | https://rspca.org.au/blog/2022/4-ways-keep-your-dog-cool-summer

4. The Australia Institute, Western Sydney HeatWatch, 2020 (Bureau of Meteorology climate data 1968 to 2017) | https://australiainstitute.org.au/wp-content/uploads/2020/12/Western-Sydney-Heatwatch-WEB.pdf

5. VECA, 24 Hour Emergency Vet Clinic in Campbelltown and Norwest | https://www.veca.com.au/emergency