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Reference Desk

Preventing Heat Stress and Injury in Pets

by Dennis Chew, DVM, DACVIM

    SILVER SPRING, Maryland, August 13, 2012—It always amazes me when, every year as the temperatures rise, there are still reports of animals being left alone inside hot vehicles, despite the fact that the dangers of doing so are well-known. Animals that exercise too vigorously in the heat or cannot seek relief from it are at risk for illness and injury as well. Not too long ago, I had a concerning experience like this with my own dog when I took him out for a little fun in the dog park. That’s why, as the dog days of summer arrive, I thought it might be helpful to review some simple facts about how the heat can affect our pets.

    Balmy Weather? Still Deadly

    It’s important to realize that dogs and cats can develop heat-related injury quickly when they stay inside a parked car or other vehicle. This can happen even when the windows are partially lowered, the vehicle is in the shade, or the outside temperatures seem relatively moderate. Many people do not realize just how quickly the interior temperature of a car can increase to deadly levels, even with some airflow provided by cracked windows. For example, on a 90° day, the temperature inside a closed car can climb to 109° within just 10 minutes. In less than 50 minutes, temperatures in that same car can rise to above 130°. On even a comparatively balmy 70° day, temperatures inside a vehicle can reach triple digits within 30 minutes. (TABLE)

    Heat toxicity can also occur in dogs that exercise too vigorously during periods of high heat, especially if the humidity is also elevated. Even dogs that are in good athletic shape and used to regular exercise can develop heat injury when out and about in extreme conditions. Heat toxicity, or heat injury, can run the gamut from heat exhaustion (which occurs in the early stages of a heat-related event) to heatstroke, which is a full-blown emergency that requires immediate veterinary intervention.

    What Happens to a Heat-Stressed Pet?

    During heat stress, the animal’s internal body temperature can increase rapidly, and fatal organ failure can follow. Since dogs and cats do not sweat (except on footpads and the nose) the way humans do, they cannot use this as a method to lower body temperature. Instead, dogs and cats try to regulate their body temperature by panting to help body heat dissipate. This response, however, is limited and easily overwhelmed under extreme conditions.

    Signs of Heat Stress

    Initial signs of heat toxicity include:

    • Panting
    • Excessive salivation (which is often thick and ropey)
    • Weakness
    • Collapse
    • Bright red membranes of the mouth, tongue, eyes, and sometimes skin in light-pigmented dogs
    • Vomiting and diarrhea can also occur due to damage to the gastrointestinal tract

    Multiple organs can fail if the excessive heat retention is not relieved soon enough. These organs include the gastrointestinal tract, kidneys, liver, heart, muscles, brain, and bone marrow. Heat retention causes the blood vessels to dilate, and a form of shock develops as the condition advances.

    If the animal is in a state of collapse when found, it is imperative to get him to a veterinarian or an emergency clinic immediately. Quickly cooling the animal for the trip with cool water from a garden hose may be helpful but do not immerse your dog in cold or ice water as this could lead to shock. If shock does develop, intravenous fluids and other medications may be needed for a few days upon arrival at the hospital.

    Preventing Heat Stress

    Never assume that it is okay to leave your dog or cat in a car unattended during warmer weather, and carefully monitor and limit strenuous exercise periods for your dog in high temperatures. Reduce the time you allow your dog to walk, run or jog with you, or to follow you during bike rides. If it’s hot enough, you may need to postpone the activity altogether. Keep in mind that obese dogs or ones that only exercise occasionally are particularly vulnerable to overheating.

    Even on a reduced exercise schedule, take frequent rest breaks in the shade. Remember to take water and even ice cubes along for your dog to drink when outdoor temperatures are above 80°. Towels that can be wet with cool water and placed over your dog can help bring his body temperature down following exercise bouts—but be sure to remove the towels once they become warmed from body heat. Exercising in dog parks early in the morning or later at night when outside temperatures are lower will also reduce the risk for heat-related injury. Restrict exercise when outside temperatures are above 80°, especially in locales with high humidity. Finally, dogs with long hair may benefit from being clipped or shaved for the summer months.  

    My Own Personal Experience

    Recently, my own dog was vigorously exercising in the dog park—running around with two other dogs and having a great time. The ambient temperature was about 92°, and the humidity was quite high. He was fine for about 5 minutes but then started to salivate a lot and was panting very rapidly. We removed him from the park and walked back to the car. He could not jump into the car on his own, and I had to lift him into the vehicle. He was extremely quiet and didn’t move during the 5-minute drive home. I kept the air-conditioning on high with the vents directed his way. Upon arrival at the house, I hosed him down for 5 minutes with cool water from the garden hose. He revived over the next 10 minutes. Had he not come around right away, we would have been on our way to the emergency clinic for IV fluids. This incident underscored for me just how easy it is for a dog to get into trouble in the heat—even with a watchful veterinarian as an owner. If you see any potential signs of distress in your dog, be sure to take prompt steps to cool him. And if you have any doubt about how serious the situation may or may not be, call your veterinarian immediately.

    Dennis Chew, DVM, Diplomate ACVIM, is a board-certified Veterinary Internal Medicine specialist, a vetstreet.com board member, and a frequent lecturer and author of numerous scientific books and publications. He is a Professor Emeritus of The Ohio State University College of Veterinary Medicine where he taught for many years. He has a special interest in nephrology and urology in small animals and pioneered many of the diagnostic procedures used today for urinary endoscopy in dogs and cats.

    Source: Vetstreet


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