Heat stroke is a serious and potentially life-threatening situation that can affect both dogs and cats. It is especially common in dogs that have been left untended in cars. We all know it is not safe to leave an animal in a closed car when the outside temperature is extremely warm. However, even in temperatures as mild as 70-75°F, the temperature inside of a closed car can increase as much as 40° or more in one hour. That means the temperature inside of the car can increase to 110-115°F even when the temperature outside is mild.

Besides the car scenario, there are other situations in which heat stroke becomes more likely for our pets as well.

• Dogs (or other animals) left outside on hot and/or humid days without the availability of adequate shade and/or water are likely to suffer heat stroke.
• Animals that are exercised heavily on a hot and/or humid day may also suffer heat stroke.
• Brachycephalic (short-nosed) breeds of dogs and cats may be more likely to develop hyperthermia (an elevated temperature) and suffer heat stroke because their ability to pant effectively is hampered by their anatomy.
• Obesity can affect an animal's airways and make panting less effective at dissipating heat for the animal, predisposing the animal to heat stroke.
• Other diseases that hamper the airway can also alter the effectiveness of the panting mechanism that dogs and cats rely on to dissipate body heat, resulting in heat stroke.
• Animals exposed to forced heat, such as a hair dryer, may also suffer heat stroke.

Early symptoms seen with heat stroke include restlessness and excessive panting. The respiratory rate and heart rate will increase. Excessive drooling may also occur. Vomiting and/or diarrhea may occur. Dehydration and depression will occur as the symptoms worsen. As the situation progresses, the animal's gums may turn brick red in color or even purple or blue as oxygen saturation declines. The dog or cat may have difficulty breathing and may appear to be gasping. The pet will become weak and may stagger. Seizures may occur and the animal may become totally comatose. Petechial hemorrhages, small red areas that resemble bruising, may appear. As the pet nears death, the temperature may actually decrease to below normal.

A body temperature higher than 105°F is cause for alarm. It is important to remember that an elevated temperature can have many different causes and heat stroke is only one of those potential causes. However, often there are clues in the environment or the recent history of the pet that easily lead to the probability of a diagnosis of heat stroke. For instance, a dog found locked in a car that has symptoms consistent with heat stroke is likely suffering from heat stroke rather than another disease.

Any dog or cat suffering from heat stroke should be seen by a veterinarian as soon as possible. However, measures may be taken to begin cooling the pet before transport. It is important not to lower the body temperature of the dog or cat too much or too quickly. Cool wet towels can be placed around or over the animal. Towels soaked in cool water can also be placed between the legs, both front and rear. Placing cool water on the ears and paws may help cool the pet also. Naturally, the pet should be removed from the environment which caused the heat stroke. If possible, direct a fan toward the dog or cat.

Do not use ice or extremely cold water to cool a dog or cat suffering from heat stroke. Doing so may actually make the condition worse.

Though cooling the pet is part of treating for heat stroke, other procedures will also likely be necessary to save the animal's life and rapid evaluation and treatment at a veterinary facility is usually necessary. Heat stroke affects all body systems and causes thermal damage to numerous tissues.

• The kidneys are damaged, leading to acute kidney failure.
• The gastrointestinal tract is damaged and may lead to bacterial translocation from the intestinal tract into the blood stream.
• Damage to the liver and to the heart can occur due to thermal damage.
• There may be swelling within the brain and infarctions that cause further brain damage.
• Clotting deficits may occur, leading to bleeding abnormalities.

Treatment for heat stroke will vary depending on the condition of the animal, but intravenous fluid support is usually necessary. Blood transfusions may be required. Oxygen therapy may be necessary for animals suffering respiratory depression. Cerebral swelling (swelling within the brain) may require specialized medications, such as mannitol to reduce the swelling. Antibiotics may be necessary if there has been damage to the gastrointestinal tract to combat sepsis caused by bacterial translocation. Other therapies may be required. Severely affected may not survive despite best attempts at resuscitation.

In most cases, heat stroke is preventable by taking some simple precautions.

• Do not leave animals caged, tied or otherwise confined outside without adequate shade and water. At very high temperature, animals should be moved indoors rather than being kept outside for prolonged periods of time.
• Do not leave animals in closed compartments exposed to the sun, such as a closed car.
• Increased caution should be used with animals that are obese, have respiratory difficulties, are geriatric or are otherwise unhealthy.
• Be aware that some animals will lie in a sunny window long enough to become subject to heat stroke. Restrict access to these areas if necessary by closing blinds or draperies.
• Provide adequate water for animals that are performing strenuous exercises in warm temperatures. Be aware that animals performing arduous physical activities require more water, sometimes as much as twice the amount or more, than animals at rest.