Heat-Related Illness in Dogs

When outside temperatures increase, it is important to remember a few things to ensure that pets are comfortable and healthy.

Heat stroke is the most extreme and serious condition on the heat illness continuum, with heat cramps and heat exhaustion being less serious, but potentially still requiring medical intervention:

Heat stroke is a life-threatening condition characterized in dogs by a body temperature greater than 105.8°F (normal body temperature for a dog is between 99.5 and 102.5°F), neurologic issues, and organ problems. A body temperature greater than 106°F may cause permanent brain damage, and severe organ damage can occur when the body temperature exceeds 109°F.

Causes of heat stroke may be non-exertional or exertional. Non-exertional heat gain is the result of being in a hot environment, such as a hot car, or spending time outside in direct sun. Exertional heat gain is due to exercise, such as playing catch or running. It is important to note that increased body temperature due to heat stroke is not the same as fever, which is caused by the body’s reaction to an infection or other disease process.

Risk factors for heat stroke include:

• Body surface area/mass: Obese animals or those with thick hair coats have a harder time cooling their bodies due to increased insulation.
• External temperature and relative humidity: Spending time in a warm, humid environment can result in increased heat gain.
• Upper airway abnormalities: Dogs with shorter, flatter faces (brachycephalic) often have greater difficulties managing heat than dogs with longer faces.
• Poor acclimatization: Sudden increases in temperature can lead to heat stroke because animals are not used to hot environments. This is particularly a problem at the beginning of summer.
• Confinement/poor ventilation: Being in a small, poorly ventilated environment, such as a hot car, can increase the risk for heat stroke. It is important to remember that cars can quickly heat up to temperatures that exceed those outside.
• Health conditions: Health conditions, such as poor heart function, can increase the risk for heat stroke during hot weather.

Signs that may indicate your dog is experiencing heat-related illness:

• Panting and seeking a cool environment
• Fast heart rate and breathing rate
• Increased breathing noises (may be raspy)
• Wobbly, confused, having seizures
• Excessive thirst
• Vomiting and/or diarrhea
• Bruising on the abdomen (evidence of organ damage)

The outcome of treatment for heat-related illness is directly related to the temperature and duration of exposure. If you suspect that your dog is suffering from heat-related illness, contact your veterinarian immediately. They may recommend beginning to cool your dog before bringing them to the clinic or hospital. This can include wetting the dog with room temperature water and using a fan. Do not use ice water, as this shrinks the blood vessels in the skin and actually inhibits cooling. Also, do not cover the dog with wet blankets. This adds a layer of insulation, trapping heat under the blanket and stopping radiation of heat from the body’s surface. Cooling should be stopped when the body temperature reaches 103°F to ensure that the dog does not become too cold.

Many dogs with heat stroke recover without lasting issues. Those with severe illness may require aggressive medical treatment, especially in cases with organ or neurologic issues.

Here are a few things to consider during hot weather to avoid heat illness in your dog:

• Avoid exercise during the hottest parts of the day.
• As temperatures increase, decrease the length of walks until your dog becomes used to the heat. Bring water and take breaks in the shade.
• Never leave your dog inside a parked car.
• Make sure your dog has enough water and access to shade.
• Consider leaving your dog inside with air conditioning and/or fans on hot days, especially if they are older, obese, have breathing problems, or suffer from other medical conditions.

This information was presented as part of an Evening With Vet Med lecture in June, 2019, entitled “Summer Health Hazards for Dogs”. The full video can be viewed at: https://healthtopics.vetmed.ucdavis.edu/health-topics/canine/summer-health-hazards-dogs-lecture-video.

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