Heatstroke is the decline in mental status and damage to internal organs that happens when the body temperature rises too high. A dog suffering from heatstroke will often pant rapidly, drool, vomit and become weak or mentally un-responsive. Body temperatures of 105-106, if sustained, have been reported to cause permanent organ damage; if body temperature rises to 109, direct thermal damage to internal organs occurs quickly. This can begin a cascade of organ malfunctions that is fatal.
When humans' body temperature rises a mere 1/10 of a degree, we begin to perspire to cool ourselves. Our canine friends only perspire minimally from the pads of their feet and from the tip of their nose. The only meaningful way they actively cool themselves is by evaporating water from the inside of their noses and mouths by panting. While this is adequate under most circumstances, it is not as efficient as perspiring, and therefore puts dogs at risk during prolonged exposure to hot weather.
Dogs with shorter noses and mouths (pugs, bulldogs, etc.) are at the greatest risk because, in part, of the smaller surface area inside their noses and mouths to evaporate water when panting. One of the tragic aspects of this condition is that dogs that are active and healthy, and even acclimated to exercising in hot weather, can still become stricken unexpectedly when exposed to hot temperatures.
Veterinarians can only speculate the reason this occurs unpredictably is due to a dangerous combination of high ambient temperature, sufficient humidity, and a dog's state of hydration, which can vary from day to day. It may be that the active, healthy dog that succumbs one day to heatstroke while on a routine hike has simply been the victim of a "perfect storm" of temperature, humidity and dehydration.
Please do not be lulled into a sense of security about your dog's ability to handle hot weather based on past successful outings. There is no precise outdoor temperature above which heatstroke can be predicted to occur. Your best guide is common sense: If it's a hot day for you, it's an even hotter day for your furry friend who can't sweat.
The most tragic example of heatstroke is when a dog is inadvertently left outdoors on a hot day without adequate shade and water or is left in an enclosed area (a garage or car) without adequate ventilation. Temperatures inside a parked car rise quickly to over 100 degrees in the sun, even with the windows partly down. And a car that is parked in the shade right now may not be in the shade soon. Never, ever, ever, leave your dog in a parked car.
What can happen to a dog suffering from heatstroke? Just for starters: liver failure, kidney failure, brain damage, muscle damage, damage to blood vessels throughout the body, massive intestinal hemorrhaging, blood clotting crises and death. It is complicated and difficult to treat if severe.
I don't want to scare everyone into locking their dogs indoors all summer, but on the other hand I really DO want to scare people enough to be conscious of this serious, sometimes fatal condition any time you take you dog outdoors for an extended period of time in the next few months. If you must take your dog out during the heat of the day, be sure they are well hydrated before hand. Be sure they have had plenty of opportunity to drink before going out, and have water supplies for them while you are out. I also recommend carrying a spray bottle so you can "mist" them in the face frequently.
If you think your dog may be suffering from heatstroke, immediately get them out of the sun and to a veterinary office adept at emergencies. Douse them with cool (not cold) water. Place a fan in front of them. Applying cold packs in a dog's groin area and under the arms will help cool the blood that is returning from the limbs on its way back to the interior of a dog's body.
However, soaking them COMPLETELY in very cold water is not recommended for fear that this would cause the blood vessels throughout a dog's skin to constrict (in a natural reaction to try to prevent further loss of heat through the skin) and thereby trap the heat inside the body's core - exactly what we don't want to have happen.
This summer, walk your dog in the early morning or evening, and be sure they have plenty of shade, water and ventilation if they are outside. Heatstroke is an unpredictable occurrence, and one that can have tragic consequences.
--Dr. Franklin Utchen, shown with his dog Tory, has been practicing veterinary medicine in the San Ramon Valley since 1989 and currently co-owns Bishop Ranch Veterinary Center & Urgent Care. For questions or comments e-mail firstname.lastname@example.org.