Introduction and Causes

Every year, thousands of dogs suffer from heat stroke, which is defined as the elevation of body temperature above normal levels due to the production of excessive heat, exposure to excessive ambient temperatures or failure of the body properly to lose heat. Heat stroke is not the same as “having a fever.” Heat stroke, also called non-pyrogenic (non-fever-based) hyperthermia, occurs when the animal’s heat-dissipating mechanisms cannot accommodate excessive heat. In many cases, owners are not aware that their dogs are developing this condition until it is too late to reverse the damage. Immediate emergency medical treatment is necessary to prevent multisystemic organ damage, and death. Early recognition of the common signs of heat stroke is critical to saving the dog’s life.

Contrary to popular belief, heat stroke does not only happen when a dog is confined in a small enclosed place during high temperatures and with poor ventilation, although certainly this is a common cause of the condition. Many dogs develop heat stroke when they are moved from a cold to a warmer and more humid climate, during seasonal temperature fluctuations or after vigorous exercise (including play) in hot weather. As a dog’s body temperature starts to rise as a result of these conditions, it cannot release the excess heat naturally produced by metabolism and other bodily functions. This, in turn, leads to the dangerous physical effects of heat stroke which, if not immediately treated, are usually fatal.

Symptoms of Heat Stroke in Dogs

The initial symptoms of heat stroke in dogs are characterized by unanticipated restlessness. They include physical signs such as excessive or fluctuating panting, which may start, stop and then start again. Other physical signs are excessive drooling (hypersalivation), foaming at the mouth, dry tacky gums and labored or difficult breathing (dyspnea). Among common behavioral changes are agitation, whining, barking and other signs of anxiety. As the dog’s core body temperature becomes dangerously elevated (called hyperthermia), the initial signs normally progress to include vomiting, diarrhea, confusion, lack of muscular coordination (ataxia), very red gums and uncontrolled tremors. In the end stages of heat stroke, a dog will become listless, dull, weak and recumbent. It may try to move to cool places but be unable to rise, will have increased difficulty breathing and ultimately will have seizures, collapse, lapse into a coma and die.

Very young and older dogs are at higher risk of heat stroke. Brachycephalic breeds, obese animals and long haired and dark-colored dogs are also predisposed. Dogs with hyperthyroidism, cardiopulmonary disease or thick hair coats are also at increased risk of developing heat stroke. If you notice these signs in your dog, take your dog to a veterinary clinic immediately.