Watch for Heat Stroke in Dogs and Cats

Heat stroke is defined as a state of extreme hyperthermia (high body temperature) resulting in thermal injury to almost all tissues in the body. Heat stroke occurs when heat generation exceeds the body's ability to dissipate heat. 

Normal body temperature for adult dogs and cats is between 99 and 102.5 degrees F.  Body temperature above 105 degrees constitutes a true medical emergency. 

Classically, heat stroke occurs when dogs are left in cars on a hot day without adequate ventilation.  A study from Sanford Medical Center found that on a warm day (70 degrees), the temperature inside a vehicle will increase an average of 40 degrees in one hour.  Imagine how hot the inside of your car is on a 95 degree day with high humidity - like an oven!  

While rare in cats, it occurs frequently in dogs. Heat stroke can also occur when an animal is outdoors on a hot, humid day without adequate water or shelter, or is exercised in hot, humid weather.  It can even occur when hot dryers are used after bathing.  

Heat stroke can occur more quickly in animals with certain medical conditions.  

- Short nosed breeds (Pug, Pekingnese, Japanese Chin, Bulldog, Shih Tzu, Lhasa Apso, French Bulldog, Boston Terrier, Brussels Griffon, as well as Persian cats) tend to have a facial conformation that results in breathing difficulties.  These animals have a much more difficult time dissipating heat through panting. 

- Animals with other respiratory diseases, as well as cardiovascular disease such as heart disease or high blood pressure are at greater risk as well. 

- Old, debilitated and obese animals are also at high risk. 

Heat stroke has effects on numerous body tissues:

- Enzymes vital for metabolism and other body functions become denatured (because they are proteins)
- Cell membranes are damaged resulting in cell death
- Kidney cells are damaged
- Intestinal lining is damaged, resulting in bleeding as well as bacteria from the intestines getting into the bloodstream, resulting in sepsis
- Brain swelling
- Clotting abnormalities resulting in bleeding as well as possible stroke
- Liver damage
- Heart muscle cell death

Early signs of heat stroke:

- Excessive panting
- Restlessness
- Vomiting
- Diarrhea

Will progress to:

- Severe respiratory distress
- Copious drooling
- Bright red or blue tinted mucous membranes
- Pinpoint hemorrhages
- Collapse
- Seizures
- Bloody diarrhea
- Decreased to no urine output
- Vomiting blood

EVERY pet owner should have a thermometer at home designated specially for their pet.  (I strongly recommend writing “rectal thermometer” on it with a permanent marker so you don’t confuse the pet thermometer with your own!!!)

WHAT TO DO if you suspect heat stroke:

1. Move your pet immediately to a cool environment.  Stay calm. 

2. Take a rectal temperature and record it.  

3. Call your veterinarian immediately and prepare to transport your pet to the nearest overnight care facility.

4. Initiate cooling immediately.  Place cool, wet towels on the back of the neck and between the legs (armpit and groin regions).  This is where the major blood vessels are, so your goal is to cool the blood in these areas.  Wet the ear flaps and paws with cool water and direct a fan on the wetted areas - this will increase cooling through evaporation.  

5. DO NOT USE ICE OR COLD WATER - this will cause the superficial blood vessels to constrict, effectively insulating the body core, keeping it hot.  Shivering will also result in more heat produced through muscle contractions.    

6. Offer fresh, cool water to drink, but do not force water into the pet’s mouth.  Have it nearby should the pet show an interest in drinking.

7. Continue to monitor the pet’s rectal temperature every 5 minutes and record.  Discontinue active cooling when the temperature reaches 103 degrees.  

8. Take your pet IMMEDIATELY to the nearest veterinarian or emergency center.  Just cooling your pet is not sufficient, they must see a veterinarian immediately.  They will almost always want to keep the pet overnight. 

Be sure there is someone who will be monitoring your pet overnight as the multiple organ complications from heat stroke do not always manifest immediately.  Urine production, heart rate, vomiting, diarrhea, bleeding and neurologic status will need to be monitored regularly to identify complications early. 

TO PREVENT HEAT STROKE:

1. If you love your pet, DO NOT EVER leave them in the car without ventilation, period.  Do not leave them in the car during the summer months, period.  

2. Do not cage animals outdoors without adequate shade or water.  Keep them indoors during very hot summer days.  Provide shade and fresh cool water to drink if they must be outdoors on a hot day.

3. Avoid strenuous exercise in hot, humid weather.  Very early morning or evening walks are better as the temperature tends to be cooler.  

4. Take extra precautions with short-nosed breeds, those with breathing problems, heart or blood pressure problems, sick, obese or geriatric animals.