Heatstroke, and the first ten minutes
3 min read · Updated
Twenty-two of the breed profiles here warn about heat, and they are the flat-faced breeds, the thick-coated Arctic ones and the animals that cannot sweat at all. Heatstroke is one of the few emergencies where what an owner does in the first few minutes changes the outcome more than anything a vet does afterwards.
Why animals overheat so easily
Dogs and cats barely sweat. A little through the pads, and that is all. Cooling is done by panting — moving air over the wet surfaces of the mouth and airway — which works well until the air itself is warm and humid, and then stops working.
So anything that restricts the airway restricts cooling. A brachycephalic dog is trying to pant through a narrowed nose and an overlong soft palate, and the effort of doing it generates heat of its own.
Anything that traps heat has the same effect: a thick Arctic double coat, obesity, a black coat in sun.
And some animals have almost no defence at all. Rabbits cannot pant effectively and lose heat mainly through their ears; they are in trouble above the mid-twenties Celsius. Chinchillas evolved in the high Andes and are at risk above roughly 25°C. Guinea pigs, likewise.
The signs
Heavy, frantic panting that does not settle, and a change in its sound.
Thick, ropey drool.
Gums that are brick red at first, then pale or bluish as things get worse.
A racing heart, unsteadiness, stumbling, glazed eyes.
Vomiting or diarrhoea, sometimes bloody.
Collapse, seizures, unconsciousness.
A rectal temperature above about 40°C in a dog is heatstroke, and above 41°C is critical. But do not spend time on a thermometer if the animal is obviously in trouble — start cooling.
Cats hide it better and are seen less often, which means a cat that is open-mouth breathing is already a serious emergency. Cats do not pant casually.
What to do, in order
Get the animal out of the heat, into shade or air conditioning.
Cool it with water immediately, and do not wait until you reach a vet. The evidence here has changed: cold water immersion is now supported as the most effective method, and the old advice to use only tepid water because cold causes shock has not held up. In the large study of working dogs, cold water was associated with better outcomes. Pour or hose cold water over the whole body continuously, or immerse the animal up to the neck if you safely can.
Keep the water moving. Water that sits on the coat warms up and then insulates.
Air movement helps: a fan, or an open car window while driving.
Offer small amounts of cool water to drink if the animal is conscious and can swallow. Never pour water into the mouth of an unconscious one.
Do not cover it in wet towels and leave them there — a towel that has warmed up is a blanket.
Then go to a vet, even if the animal seems to recover. Heatstroke causes organ damage and clotting problems that appear hours later, and the collapse afterwards is often what kills.
Preventing it
Never leave an animal in a parked car. On a warm day the interior passes lethal temperatures in minutes, and a window cracked open makes almost no difference.
Walk dogs early and late. Test the pavement with the back of your hand for seven seconds — if you cannot hold it there, it is too hot for paws, and if it is that hot the air is too hot for a walk anyway.
Use a harness rather than a collar for any flat-faced dog, so nothing presses on an already compromised airway.
Shade and airflow for hutches, runs and aviaries, checked through the whole day as the sun moves. A hutch that is shaded at nine can be in full sun at two.
For rabbits and guinea pigs, frozen water bottles wrapped in a towel to lie against, and ceramic tiles to lie on.
Do not shave a double coat to help. It removes the layer keeping sun off the skin and does not make the animal cooler.
And swimming is not a universal answer: many bulldog-type dogs cannot swim at all, and drownings in garden pools are well documented.