Heat stroke is a common form of hyperthermia in dogs, caused by inadequate heat dissipation in an environment with high ambient temperatures and poor ventilation (a typical example is inside a car with the windows closed and exposed to direct sunlight). More specifically, heat stroke occurs when the body’s heat gain from high environmental temperatures and poor ventilation exceeds the heat dissipation that normally occurs through panting, vasodilation, postural changes, and perspiration. It’s important to remember that dogs primarily dissipate excess heat through panting—a sudden increase in respiration rate from about 30–40 breaths per minute to approximately 300–400 breaths per minute—while sweating plays a minimal role.
Heat stroke is more common in larger breeds, brachycephalic breeds, and obese dogs due to their reduced ability to dissipate heat compared to other breeds and normal-weight dogs. The harmful effects of hyperthermia are mainly due to high cellular metabolic activity caused by increased body temperature, leading to high cellular oxygen consumption that exceeds the oxygen delivered by the blood flow. This imbalance between oxygen consumption and delivery causes cell damage. Cellular damage typically begins when body temperature rises above 42°C, and its severity depends on the extent and duration of the temperature increase. Heat stroke can affect nearly all organs and systems in the body. Life-threatening complications of heat stroke include acute renal failure, dehydration, a severe systemic coagulation disorder called disseminated intravascular coagulation (DIC), hepatic failure, damage to gastrointestinal mucous membranes with the entry of enteric bacteria into the bloodstream (sepsis), and cardiovascular shock.
Heat Stroke Can Be Life-Threatening
This explains why heat stroke is a life-threatening condition that requires immediate and aggressive treatment, as death can occur in less than an hour. The affected dog should be immediately placed in a cool, shady, and ventilated area, and total body cooling should be initiated as soon as possible. Body cooling is most effective through water baths and rinses with cool water—avoid using cold water. If the water is iced or too cold, it can cause peripheral blood vessels to constrict, which inhibits heat dissipation through vasodilation and slows the cooling process. Total body cooling should be started immediately and continued during transport to the veterinarian, and should be stopped once the dog’s body temperature approaches normal (about 40°C or lower) to avoid hypothermia. Other methods to promote heat dissipation include gastric lavage and enemas with cool water, although their effectiveness has not been proven to be greater than cool water baths.
In addition to total body cooling, treating dogs with heat stroke involves appropriate medical measures to manage or prevent shock and multiple organ damage. Oxygen and fluid therapy are often necessary, especially in severe or prolonged cases of hyperthermia. Antibiotic therapy can be helpful if sepsis is suspected, while the use of corticosteroids to reduce systemic inflammation remains controversial due to their renal and gastrointestinal side effects. It is crucial to note that treating dogs with heat stroke does not involve the use of antipyretics (such as non-steroidal anti-inflammatory drugs or NSAIDs), which are ineffective. The mechanism behind the elevated body temperature in heat stroke is entirely different from that which causes fever, which responds to antipyretics. Additionally, NSAIDs, like corticosteroids, have renal and gastrointestinal effects that contraindicate their use in heat stroke treatment.
In summary, therapy for treating dogs with heat stroke should begin immediately, if possible, with the owner initiating body cooling measures and continuing them until the dog reaches the veterinary clinic. Once at the clinic, the veterinarian will determine whether to continue or discontinue cooling treatment (depending on the dog’s core temperature) and whether additional treatments are necessary. The key is not to waste time—start emergency total body cooling and get the dog to the veterinarian as quickly as possible to avoid a fatal outcome.
