Pets have several physiologic mechanisms that normally help them to dissipate heat and maintain a normal body temperature. Although dogs and cats don't have many sweat glands in their skin, their primary cooling mechanisms are through panting and dilation of blood vessels in their paws. 

Heatstroke occurs when an animal loses the ability to dissipate heat from their body - resulting in a dangerously high core body temperature. Whereas the normal body temperature for dogs and cats ranges between 100-102 degrees F, pets with heatstroke may have body temperatures that exceed 105 degrees F. This can occur due to environmental conditions or physical exertion.

Environmental risk factors include high ambient temperatures and high humidity. Additionally, the temperature inside of a parked car, even with windows cracked or in a shaded area, can quickly rise and be deadly to pets. In as few as 10 minutes, the temperature can rise almost 20 degrees F - which means that even a comfortable 70-degree day can quickly approach 90 degrees - inside of a car. Strenuous physical exercise can also lead to heatstroke.

In spite of these well-known facts, many animals die from heatstroke every year.  Well-intending pet owners may think that leaving a car running, with the air conditioning on, is the solution to keeping their pets safe. Although it may sound like a good idea, sadly that's not always the case. VetVine's Emergency and Critical Care expert, Dr. Elisa Mazzaferro explains:

Risk Factors

Heavy exercise on a hot day or in high humidity can cause a dog to develop exertional hyperthermia (dangerously elevated body temperature), in as few as 30 minutes. Another cause for hyperthermia in dogs would be from their inability to get away from a heat source, such as pets left in a parked car.
 

Additional predisposing factors include:

• Obesity
• High ambient humidity
• Exercise without acclimation
• Lack of available drinking water
• Airway disorders - laryngeal paralysis, upper airway obstruction
• Brain (hypothalamus) abnormalities
• Breed predisposition - "Brachycephalics" such as Pugs

Dangers of Heat Stroke

If the core body temperature rises to a dangerous level (104.9 - 109.4 degrees F) as in hyperthermia, it can quickly lead to tissue damage (kidney, liver, and central nervous system), organ failure, and possible death of patient.

Signs of Hyperthermia

• Panting
• Vomiting
• Hypersalivation
• Bleeding (from the nose or in the gums)
• Diarrhea 
• Tremors
• Listlessness
• Loss of consciousness
• Seizures

Treatment of Pets With Heat Stroke

• Move the animal to a cool area - with air conditioning or fans
• Spray with cool (NOT cold) water - DO NOT immerse them in ice or cold water
• Ice or cool packs in the groin or armpit area