I sometimes wonder how the Dingos of Australia and the wild dogs of Africa get around the issue of heat exhaustion. They are built on the same game plan as all other successful canines, but they live, run and hunt in a much less temperate climate. Do they mostly hunt at night? I should be a better naturalist, I guess.
Dogs in general have pretty poor mechanisms for getting rid of excess body heat. People perspire for evaporative cooling. "Horses sweat, men perspire, and ladies feel the heat." Dogs only perspire on their nose and footpads, which is not nearly enough to cool them off. Panting exchanges hot inside air for cool outside air. When the outside air is 100 degrees Fahrenheit, that doesn’t cool you off much. You can lose heat by simple radiation, as in walking around in the cold with your coat off. Again, that doesn’t work so well when the heat index tops 100. Also, the bigger the dog, the fewer square inches per pound. Square inches radiate heat, and pounds generate and retain it. This means the big dog seldom is bothered by the cold, but is miserable in the hot summer time. Generally, this goes double for the weird-looking dog, especially the brachycephalic ("smashed face") breeds.
Conduction is another way to get rid of heat. Lie down on or in something cool. You might try a dip in the pool, and you’d have evaporative cooling when you got out. Then there’s the ever popular expedient of digging a big hole in the yard. This exposes cool, moist earth which you can lie on and wick away some of that excess heat. Of course, after a while the dirt dries out and gets as hot as the rest of the yard. "Hey, I need to dig another hole, here." You might call this the mine-field crater method.
If you’re a big dog, you generate a lot of heat just by being alive. The chemical reactions that carry out your basic metabolism all generate a little waste heat. If you get up and move around some, you generate more heat. Since you can’t "work up a sweat", you just get really hot. Eat a big meal and you generate more waste heat in processing your fuel. It’s not uncommon for big dogs to lose weight during extremely hot weather; they just don’t want to do much or eat much. My own dog usually won’t eat untl after ten PM, and then she only eats a big meal about every two days. Think about your own point of view: if you’re working hard outside, would you rather have a cold sandwich or a big steaming bowl of hot chili?
If you generate too much heat, and can’t get rid of it, bad things start to happen. You can get anything from an irregular heartbeat to a profound state of shock, where your circulatory system collapses. This can be followed by the sloughing of the gut lining, kidney failure, and even death.
With dogs, this most commonly happens when the animal is tied up and gets his tether tangled up. He can’t reach his water and shade, or he just panics because he’s caught and begins to struggle violently. Choke collars (which should NEVER be left on an unattended dog — they are strictly for training use) are worse, but even a broad, flat, well-fitted collar won’t protect a struggling dog in high temperatures. My most recent patient was on a chain long enough to enable him to hop over the fence…but not quite long enough to make a landing on the other side.
Only once have I seen heat-stroke in a dog who wasn’t tied. He was running alongside while his owners rode their four-wheelers by the borrow pits (big holes full of water where he could swim, for you city folks). You’d think that when he felt hot and tired he would have just stopped and taken a quick dip. He was a Labrador Retriever, a water dog, after all. Of course, if you talk to people who have suffered heat exhaustion, they will tell you that one minute they’re feeling okay, working like they have so many times before, and the next minute things are going south in a hurry. I guess you couldn’t expect the dog to be any smarter; he was having fun running with his people. He had so much fun that he ran himself into a heat stroke and collapsed… and died. His folks brought him directly to the clinic, but he was already pouring blood from his rectum and he did not respond to treatment.
Speaking of treatment, if you fear that your dog may have become overheated, start cooling him with cool (NOT ice-cold) water, and using the hose is fine. Cool large areas, rather than concentrating on a spot. Don’t use ice, don’t use alcohol, don’t use extreme measures (like cold-water enemas — you can push him too far the other way). DO get him to your veterinarian, as he needs support with intravenous fluids, antibiotics, and intestinal protectants. Realize that he may appear to be responding rapidly to treatment and still take a nose-dive later. A lot depends upon how bad he gets and how long he stays that way. Getting those I.V. fluids going as soon as possible may save his kidneys (and he does need his kidneys).
You know that your dog needs shade and plenty of water, and a fan would be nice, too. If it’s over 80 degrees outside, be your dog’s conscience. Unlike the Dingo or the wild dog of Africa, your dog may not know when to quit. Never tie a dog out with a choke chain, or leave a choke-collar on an unsupervised dog. Avoid chaining the dog in the first place: aside from being dangerous, it makes them crazy — they hate it. If you MUST chain your dog, be double-sure there is nothing to get the chain wrapped and tangled around. Just assume that the dog will do the goofiest thing possible and be sure he can’t get into trouble. Put that chain on your own neck and see if you can get into trouble.