Heat Stroke and Hyperthermia in Dogs

Hyperthermia due to fever is a symptom of an illness and is typically accompanied by additional symptoms, such as inflammation while non-fever hyperthermia and heat stroke occur when dog’s natural ability to regulate temperature through panting cannot keep up with elevated external temperatures. These conditions are most likely to occur when a dog is in a small, hot space without ventilation, such as a car, or outside for too long on a hot day without access to shade and water. Dogs with restricted airways, such as brachycephalic (flat-faced) breeds of pug, boxer and bulldog, dogs that are exhausted from exercise or excitement, and dogs that are wearing a muzzle are more likely to develop these conditions than others.

Hyperthermia, is the condition of elevated body temperature, occurring if your dog’s temperature is above 103°F. Heat stroke is more severe, occurring when a dog’s body temperature is above 106°F, putting your dog in danger of organ failure and death.

Fever Hyperthermia occurs when inflammation due to a bacterial or other infection raises a dog’s body temperature.

Non-Fever Hyperthermia occurs when a dog is unable to cool down by panting and overheats due to a combination of external temperatures, physical activity, hormonal or chemical response and/or dehydration. Types of non-fever hyperthermia include:

• Heat stroke due to excessive external heat and humidity. Excessive heat alone or exacerbated by dehydration due to lack of access to water, lack of fresh air and physical exercise can cause the extreme hyperthermia known as heat stroke. Additional factors that contribute to an increased risk of heat stroke are a long coat, a dog not acclimatized to a hot environment, obesity, any condition or physical feature that inhibits breathing (dogs of short-faced breeds or dogs with upper respiratory tract complications), voice box paralysis, and heart, nervous system or blood vessel disease.
• Heat stroke due to excessive exercise alone.
• Overheating due to excessive exposure to a grooming dryer.
• Malignant hyperthermia, an uncommon reaction to substances, such as anesthesia and caffeine. Also known as “canine stress syndrome,” malignant hyperthermia can be a chemical reaction to stress. Malignant hyperthermia is a disorder to which some dogs are genetically disposed, particularly Labrador Retrievers, and can recur throughout a dog’s lifetime.
• Hyperthermia due to elevated thyroid hormones.
• Hyperthermia due to lesions in the hypothalamus, the temperature-regulating area of a dog’s brain.

Hyperthermia and heat stroke are serious medical emergencies, and swift identification of the conditions is the key to recovery and avoidance of serious complications or death. If your dog is exhibiting any of the above symptoms due to environmental factors, immediately begin to cool the dog down by offering water to drink (not forcing your dog to drink water). Continue this effort by spraying or immersing the dog in cool water, applying rubbing alcohol to the foot pads, and/or utilizing fans to provide fresh air. If symptoms occur as a result of exercise, calm your dog in order to get it to rest, finding a shady spot to utilize cooling techniques.

Always use cool and not cold water, and never ice, to lower your dog’s temperature, in order to avoid shivering and blood vessel constriction, both of which can raise the temperature, as well as to avoid drastically lowering temperature.

The next step is to seek veterinary attention, whether symptoms have dissipated and the temperature is stabilized or not. You will need to provide a thorough report of your dog’s symptoms, and anything you think may have caused them. Always mention any relevant medical history in addition to the events leading up to the episode. Your veterinarian will determine by taking your dog’s temperature if she requires treatment in order to stabilize temperature. If the veterinarian determines temperature to be stable, your dog will then check for serious complications that may have occurred. A urine sample will be taken and analyzed in order to assess kidney function, a blood sample will be evaluated for blood chemistry and complete blood count, a blood clotting test will be performed, and an electrocardiogram, or EKG, may be taken in order to monitor the patterns of your dog’s heartbeat.

Your dog’s recovery will depend upon the type and severity of the heat stroke and/or hyperthermia. If diagnosis determines that hyperthermia or heat stroke was not severe enough to cause complications, your dog will have a swift return to health, provided you follow instructions to avoid heat and any type of exercise for a 3 - 7 full days, which will allow your dog time to rest.

Your veterinarian may advise you to make changes in you and your dog’s lifestyle in order to prevent future episodes. Changes may include grooming your long haired dog in the summer, placing an obese dog on a healthy diet, monitoring or changing exercise habits to adapt to your dog’s physical ability and weather conditions, adapting your dog’s living space to assure access to shade, water, fresh air, etc. Never leave your dog in a hot room or unattended in a parked car.