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?

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)