Heat stroke occurs when a dog's internal body temperature rises to levels high enough to lead to death. For heat stroke to occur, a combination of factors must come into play: a confined space, poor ventilation, and high ambient temperatures, such as that produced in direct sunlight. Approximately 70 per cent of total body heat loss, in both dogs and man, occurs via the body surface. As a result, continual air changes (i.e. good ventilation) in the immediate surrounding area of the body are essential in order to remain cool.
In dogs, heat is also released through panting. You will note that a hot dog will have an enlarged tongue while panting. This helps to increase the surface area through which heat can be dissipated. Heat lost in this way can contribute to an increase in the ambient temperature in an enclosed space. Lack of ventilation increases the temperature without allowing the body to effectively remove the excess heat.
There are a number of other factors besides ventilation that can increase a pet's chances of getting heat stroke. Such variables as the amount of sunshine, humidity, color of car, type of seat covers, and wind factors all play some part. Health and weight of the pet, the thickness of the hair coat, availability of fresh water, recent feeding, and even a pet's own temperament can elevate body temperature. For example, a pet that is anxious, excited or frightened, or one that barks excessively, is more likely to get heat stroke than one that is calm or quiet. Brachycephalic breeds, such as Pugs, Pekes, Bulldogs, etc. are also more likely to have heat-related problems.
Heat stroke occurs when a pet has an extremely high body temperature, usually more than 41 degrees C (106 degrees F). Signs include rapid panting, warm dry skin, bright red gums, vomiting, and an anxious expression or staring appearance. Collapse, coma and death follow shortly thereafter. An animal with heat stroke must have its body temperature reduced quickly. Most effective is immediate immersion in a cold water. If unavailable, hosing it down with a garden hose may be effective. Ice packs should not be used because overcooling often occurs. The skin should be massaged gently, and the legs flexed frequently to encourage blood circulation. While this is being done, it is essential that the pet be transported to a veterinary hospital as quickly as possible.
Heat stroke can occur surprisingly fast, even when animals are left for only short periods of time in cars with the windows partially rolled down. Since prevention still remains the best alternative, animals are best not left alone in unattended cars or in a yard without shade and water in warm weather.