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Posted on 06-24-2015

Heatstroke (hyperthermia) occurs when a dog’s normal body mechanisms cannot keep his body temperature in a safe range: that is, when heat gain exceeds his ability to dissipate that heat. Contrary to what we often think, dogs overheat more quickly than we do. Dogs do not sweat through their skin like humans, but sweat only through their nose and foot pads. Dogs primarily release heat by panting and blowing off the heat which is not as effective as in humans.

We cannot judge the comfort or safety level of our dogs through our own standards of how hot we are. This is particularly true for overweight dogs and for certain “flat-nosed” (brachycephalic) breeds (bulldogs, French bulldogs, pugs, Boston Terriers & others) who are more at risk because the very short muzzle limits their ability to cool themselves.

The prompt for progression from being hot to heat stress to heat exhaustion to heat stroke is most commonly, being a hot environment. (Certain types of inflammation can cause hyperthermia, but that isn’t what we’re talking about here.) If a dog cannot effectively expel heat, his internal body temperature begins to rise. Normal body temperature is 100° – 102.5°F, and a rise in body temperature of only 4° above that can cause damage to the body’s cellular system and organs, which may become irreversible. Once the process of heat stroke has begun, there is precious little time before serious organ damage or even death can occur.

High temperatures cause chemical reactions that break down body cells, leading to dehydration and thickening of the dog’s blood, placing extreme strain on the heart, causing blood clotting and subsequent death of involved tissue. Dramatic damage to liver, brain and intestinal cells can occur very quickly, followed by organ failure and death soon after. Even a dog who recovers from overheating can have organ damage and lifelong health problems. Walking a dog on hot pavement (especially asphalt surfaces) can initiate this process, or in areas without tree cover. One of the more common scenarios we see is from leaving a dog in a parked car. Even though we’ve heard the stories about these sad cases, people still leave their dogs in the car while they shop, dine, see a movie and all kinds of other activities. It doesn’t matter if you crack the windows or leave water for your dog to drink. It doesn’t matter if you park in the shade, there’s a breeze or if you’ve done this before. Even with the windows open or cracked, the temperature in the car can reach as much as 40 degrees warmer than the outside temperature in just a few minutes.

The signs of heat stroke can be subtle initially. Because our dogs want to be with us and don’t communicate distress or discomfort well, it’s important that we monitor them closely for any signs of heat stress.

Symptoms of heat stroke:

  • Rapid, frantic panting – Knowing how your dog breathes normally after walking on a cool day or when exercising in cooler weather, you can assess whether or not she’s comfortable.
  • Wide eyes
  • Thickened saliva, drooling
  • Bright red tongue
  • Dark red gums which progress to dry (tacky) gums and mucus membranes as he becomes dehydrated. Later the gums become pale then gray as circulatory failure occurs
  • Vomiting and diarrhea – often with blood or “coffee grounds” appearance
  • Disorientation. staggering, lying down & refusing to get up
  • Shock manifested as collapse and/or loss of consciousness. Seizures are possible

What to do if you suspect heat stroke:

If you have any thought your dog is experiencing any heat related stress, act immediately and don’t hesitate to ask others for assistance.  Contact us or a local pet emergency facility and bring your dog in as quickly as possible. This is potentially a life-threatening emergency. Here’s what to do if you can’t get her in immediately.

  • Move him out of the heat and away from the sun!
  • Begin cooling your dog by placing cool, wet rags or washcloths on the body – especially the foot pads and around the head. If you have a fan available, use it to blow cool air across her body.
  • IMPORTANT! DO NOT USE VERY COLD WATER as intense cold can cause the blood vessels to constrict, preventing the body’s core from cooling. This can actually cause the internal temperature to rise. If body temperature decreases too rapidly and hypothermia ensues, this can lead to organ failure too. Rectal body temperature should be checked every 5 minutes: when it reaches 103°, stop cooling.
  • Offer your dog cool water, but do not force water into your dog’s mouth and never put water in an unconscious or semiconscious dog’s mouth.
  • Even if your dog seems recovered: call or visit your veterinarian immediately for advice. In many cases of heat stroke, some organ damage will have occurred and your dog needs tests to help determine the extent of any damage and monitor the success of treatment. This damage may not be obvious immediately and without intervention could lead to permanent damage or even fatal complications.


Dogs with heat exhaustion or mild-moderate hyperthermia often recover without complications. Severe heat stroke can cause organ damage that might need ongoing care. It’s important to know that once a dog has had a case of hyperthermia, they are at increased risk of succumbing to hyperthermia in the future.

What the veterinarian does:

Initially, the veterinarian will work to cool your dog and lower the body temperature to a safe range while continuing to monitor her condition. She will be given IV fluid therapy and possibly oxygen as well. The veterinarian will monitor for shock, respiratory distress, kidney failure, heart arrhythmias, and any other complications. Any health issues will be treated accordingly. Blood and urine samples may be taken before and during the treatment as well as after treatment to monitor organ function, assess for clotting abnormalities, etc.

Preventing heat stroke:

Remember, any dog that cannot cool himself is at risk.

  • NEVER leave your dog alone in the car on a warm day. Cracking or opening windows or the sun roof or leaving water for the dog is NOT enough. Even if the weather does not seem extremely hot or you’re only “running in the store for just a minute”, the inside of the car acts like an oven: temperatures can rise to 140 degrees in a matter of minutes.
  • Dogs outside for any period of time need access to shade. Be sure if your dog is outdoors they have plenty of fresh, cool water and can get in the shade. Remember to check to see that there is shade available at all times of the day!
  • Dogs with predisposing conditions (heart disease, obesity, elderly dogs, or those with breathing problems): need extra supervision: even so-called “normal activity” for these dogs can be harmful.
  • Don’t jog with your dog on a day that is even moderately hot.  Avoid any exercise during the heat of the day, including hiking. Go before or near sunrise and around sunset when it’s cooler.
  • Avoid hot surfaces like sand and asphalt or areas lacking shade.  Remember, asphalt reflects heat upward–think of those waves of heat shimmering off the pavement.
  • Encourage your dog to drink frequently if she’s active.
  • Wetting down your dog with cool water, or allowing him to swim, can be beneficial. Don’t assume that a dog playing in water cannot overheat. When water temperature gets above 75°, vigorous play can lead to hyperthermia.
  • Be aware that certain types of dogs are more sensitive to heat: especially obese dogs and short-nosed breeds that can’t expel heat efficiently. In general, older dogs are less heat tolerant.
  • Keep your dog active year-round for his general health. If you want to exercise him on hot days, build up his tolerance for heat slowly and be sure to keep him hydrated.
  • If we’re having a heat wave, move your dog to a cool area of the house. If you don’t have air conditioning, keep her in the path of a safe and efficient fan. You can also fill and freeze water in soda or water bottles or plastic bags. Cover these with a towel and you can place these down for your dog to lay on or next to for cooling.
  • Put ice cubes in water to keep it cooler or give your dog ice cubes as cooling treats on a hot day. You can freeze a little chicken broth, juice, or Ice Pups to make staying hydrated and cool even more appealing.

Finally, practice what you preach–be safe in the heat for yourself and your dogs. They need you!

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