Thursday, June 23, 2011

Heat Stroke: What Happens In The Dog's Body?

by Jennifer Coates, DVM

Every summer, veterinarians warn about the dangers of excessive heat for dogs.  

Heat stroke, which is characterized by a body temperature between 106 and 109°F (normal is 101.5°F give or take a degree), is most likely to develop when one or more of the following conditions is met:
  • hot and humid weather combined with exercise and/or a lack of shade and access to water
  • being confined in a car or other location where heat can build up
  • obesity
  • advanced age
  • heart disease
  • upper respiratory disease (e.g., laryngeal paralysis or brachycephalic airway syndrome)

But what exactly happens when a dog’s body temperature reaches 106°F or above, and why is it so dangerous?

IMG_2918
Photo Lindsey Kone

First, as a dog’s temperature begins to climb, the body cools itself via panting, drooling, and dilating blood vessels on the surface of the body (vasodilation).

These mechanisms are sufficient up to a point, but if there is no relief from high external temperatures, the dog’s excessive panting, drooling and vasodilation leads to dehydration and low blood pressure. 

These conditions inhibit the body’s ability to cool itself, setting up a vicious cycle wherein the hotter the body becomes, the less effective are its mechanisms to deal with the situation.

When body temperatures reach the danger zone, proteins break down, cell membranes are damaged, and the body can no longer produce energy at the cellular level.   

As tissues degrade and blood clotting abnormalities develop, the kidneys and liver begin to fail, the lining of the gastrointestinal tract dies, and heart and brain damage occurs.

If a body temperature of 110°F is reached, a dog can die within just a few minutes.

Early symptoms of heat stroke include extreme panting, a rapid heartbeat, red mucous membranes, vomiting, and diarrhea.

As his condition worsens, a dog may suffer from difficulty breathing, abnormal bruising, bloody vomit and diarrhea, blue or pale mucous membranes, collapse, seizures, and paradoxically, a lower than normal body temperature.

If you suspect that a dog is suffering from heat stroke, thoroughly soak him with cool water (do not use ice though) and transport him to the nearest veterinary clinic in a car with the air conditioning on or with all the windows open.

Heat stroke has a mortality rate of around 50%, but with prompt and intensive treatment, many dogs can survive!

***

Jennifer Coates, DVM graduated with honors from the Virginia-Maryland Regional College of Veterinary Medicine in 1999.  In the years since, she has practiced veterinary medicine in Virginia, Wyoming, and Colorado.  She is the author of several books about veterinary medicine and animal care, including the Dictionary of Veterinary Terms: Vet-speak Deciphered for the Non-veterinarian

Jennifer also writes short stories that focus on the strength and importance of the human-animal bond and freelance articles relating to a variety of animal care and veterinary topics.  Dr. Coates lives in Fort Collins, Colorado with her husband, daughter, and pets.

Articles by Dr. Coates:
When Is It An Emergency?
The Other Side Of The Coin: The Cost Of Defensive Medicine 
Common Misdiagnoses (Part 1) 
Common Misdiagnoses (Part 2)
Dog Allergies: Common, Commonly Misdiagnosed, or Both? 
The Perplexities of Pancreatitis 
Don’t Forget the Physical Therapy
Picking the Right Dog to Breed 
To Neuter Or Not To Neuter… That Is The Question 

Related articles:
Signs, Symptoms And Treatment Of Heat Stroke In Dogs
Know Your Dog's Enemies: Heat Stroke Is No Light Matter! 
Hypo- Versus Hyperthermia

Further reading:
Overheating in Dogs
Heat Stroke in Dogs and Cats: Signs, Symptoms and Treatment
Hyperthermia (Heat Stroke, Heat Prostration)

10 comments:

  1. My 5-year-old dog died today of heat stroke and we are all just so devastated. She was not outside more than 10 minutes at a time and we have a cool, air-conditioned house. I did notice she was panting but just thought she was hot (it is 100 degrees here in Kansas City). She had plenty of water and drank a lot. The vet thought her hypothalamus could have been damaged but he wasn't sure. I can't help but feel 100% responsible for her death and am just beside myself. I should have recognized that she was hotter than usual. Ignorance is no excuse and I will have to live with this. It is just horrible. I never post comments but just want others to learn from this. Take your dog panting and acting differently seriously. She died within a very short amount of time. She was the best dog in the world and we loved her so much. We rescued her 3 years ago and she was truly the best. We love you, Toffee....

    ReplyDelete
  2. OMG, that is so terrible! :-( I'm so sorry. 100 degrees IS quite hot. Still, though, it would depend on other factors - the amount of exercise she got while out, whether it was in the shade or on the sun ...

    ... I think your vet might be right that the heat was not the only issue. Hypothalamus is the temperature "control center". If not functioning properly, the body wouldn't cool itself properly.

    Though of course mild to moderate exercise in hot conditions causes an increase in core temperature and heat dissipation become inadequate to expel the heat load and eventually can lead to heat stroke.

    It could be that in Toffee's case it was a combination of the two factors.

    There are other signs of dangerous body temperature besides panting, such as gum and tongue color. Dogs can pant from exercise and excitement also. While I watch the level of panting, I keep a close eye on the gum and tongue color also. (you can check the Signs, Symptoms And Treatment Of Heat Stroke In Dogs article for all the signs one can watch for.

    My heart goes out to you, not only for Toffee, but also because you're blaming yourself. This makes the pain 100x worse. (((hugs)))

    If you'd like to write up Toffee's story as a feature article, please let me know. It might save lives of many other dogs.

    Love,
    Jana

    ReplyDelete
  3. Thank you, Jana. Your words of support do help. I would be happy to write up Toffee's story. My husband and I have been over it and over it. When we rescued Toffee (3 years ago), she was positive for heartworms. We ran her through the aggressive Heartgard treatment and she tested negative after that course of treatment. We cannot help but wonder if she had an underlying heart issue that may have contributed to this issue. Although, she was active and always had good energy levels.

    She was a Chow/German Shephard mix that had a rough start in life (heatworms, neglect, surgery to remove an embedded pinch collar, mange). We adopted her despite her problems because we just had a good feeling about her. She had a great life with our family until the end. I'm still so sad and will be for a long time.

    I never heard of or knew to check their gums, tounge and other signs and I like to think that I am a fairly intelligent person. For that, I think it is important to get the word out to others to stress the importance of signs and symptoms - and that they don't have to be outside for a long time to suffer death!

    Thank you for your words and let me know if you would like me to write her story and how to go about it.

    ReplyDelete
  4. You know, it could well be, the heartworm itself can cause heart damage and the treatment is also very hard on the system.

    Oh, wow, embedded pinch collar, that's so sad.

    Having a great life with you is what it is all about. You gave her all you could. At the end that's all that matters.

    Understanding what heatstroke can do to a dog's body and what signs to watch for is important. That's why this information can never be repeated enough. Having a real life tragedy as an example might be just what is needed to open people's eyes.

    Yes, I'd love it if you wrote up Toffee's story. There are a number of real life stories on my blog already, you can take a peak how they're done.

    Generally it includes an introduction about the dog and your relationship, and then an account of what happened, including all symptoms noticed (or missed), what had been done to treated and the outcome.

    My email is in the About Me section.

    My heart really goes out to you. But you gave Toffee couple great years full of love she wouldn't have had otherwise. Without you she might have had been long gone.

    (((hugs)))
    Jana

    ReplyDelete
  5. My dog, a 13 year old Golden Retriever, got heat stroke last night after taking a walk at 5 pm in Raleigh, NC. The whole country is going through a heat wave, and stupidly I thought if I walked the dogs in the shade and on grass they'd be ok. The younger ones were, but obviously you can't avoid the sun everywhere and when we got home he collapsed. His panting was extreme, and he couldnt drink water. We covered him with wet towels and called the vet. The had me take his temp, which was 107.3, so we raced him to the animal hospital where they immediately hooked him up to fluids, sprayed him with cool alcohol and fans, and he stayed overnight while they ran tests. He was released today and will stay inside except to go to the bathroom, and be on a diet of i.d. meatballs and prilosec and pepcid. We are extremely lucky - what saved him was getting him immediate attention.

    ReplyDelete
    Replies
    1. So sorry about your guy, wow, 107.3 is very high. Glad he made it. Heat is treaturous, one cannot be too careful.

      Delete
  6. My heart goes out to Toffee's family, it is so hard to lose our furry kids, but thank you for posting so that more people can learn from your story.
    I found your posts because I was looking for information online. I think I have a rescue who has a problem regulating temperature. (We live in South Africa and are swiftly moving into summer.)
    Years ago I picked up a dog looking lost at the side of the road. I took it home and called the number on it's collar ... but it wasn't looking good. Was panting way too much for normal behaviour. Fortunately I decided to hose the dog down (gently) to cool him down and as the owner called about 15 minutes later and relayed his condition ... that he couldn't regulate temperature and could overheat ... well I'm glad that I did. We rushed the dog to the vet where the owner met us and fortunately all was well.
    But it's this memory that now comes to the forefront with Goldie my new rescue and latest furry kid. She seems to be struggling to regulate and process the heat so I think after having read all your posts ... that I'm gonna have to be ultra careful with her.
    Thanks for sharing.

    ReplyDelete
    Replies
    1. I would want to look into the cause behind the poor temperature regulation.

      What bread is it? Brachycephalic breeds, such as Bulldogs, Boxers ... typically have harder time with temperature regulation and can overheat easier.

      What is the dogs' body condition? Overweight dogs also have a harder time.

      Dogs with hormone issues (thyroid, adrenals) can also have difficulty regulating their temperature.

      I'd want to look into a cause.

      Delete
  7. Hi Jennifer, My name is Lindsey Kone. I see that you have used one of my photographs of my dog Bongo from my Flickr account. All of my photos are licensed under the Creative Commons License, which means they are free to be used as long as a) they are not manipulated in anyway and b) there is clear acknowledgement of credit to the artist. I won't ask you to remove my work if you credit it back to it's owner under the photograph. Thank you

    ReplyDelete
    Replies
    1. Hi Lindsey. Thank you for your note. The credit actually was embedded with the photo (if you roll over you can see it and it has a link to your flickr.)

      However, I added the credit underneath as well.

      Great photo!

      Delete

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