Heatstroke/Overheating in Dogs and Cats

As warmer weather draws nearer, we tend to spend more time outside with our pets. Because of this, there is an increased risk of our pets experiencing overheating and/or heatstroke during the spring and summer months.

Heatstroke occurs when a pet is not able to dissipate heat effectively. This results in a significantly elevated body temperature which can lead to multiple organ dysfunctions and failures. In cats and dogs, this occurs when their internal body temperature is greater than 105.8°F (41°C). Heatstroke can occur from exposure to a hot and/or humid environment, as well as strenuous exercise. While we typically think of heatstroke occurring directly because it is hot outside, heatstroke is also caused by seizures, ingestion of certain toxins or medications, and even cancer.

In the spring and summer, pets are more susceptible to heatstroke when the temperatures rise quickly. This can also occur in cooler climates if the ambient temperature rises so quickly that a pet cannot adequately acclimate. Increased risk for heatstroke include poorly ventilated housing/vehicles, heart disease, brachycephalic breeds (breeds with short noses i.e. pugs, bulldogs, Persian cats), dark coat colors, older age, obesity, laryngeal paralysis, and other respiratory conditions.

Heatstroke is different from fever. With fevers, the thermoregulatory center in the brain raises the temperature set point, leading to elevated body temperature. With heatstroke, these pets have a normal set point, but their body temperature is elevated because they cannot release the excess heat effectively.

Elevated body temperature can cause inflammation and reduced blood flow to multiple organs. This can cause problems with the kidneys, lungs, gastrointestinal tract, central nervous system, and coagulation (the ability to clot blood). As a result, pets can suffer from kidney failure, respiratory failure, sepsis, GI bleeding, swelling of the brain, cardiac arrhythmias, and spontaneous bleeding.

Signs at home can include extreme lethargy, collapse, seizures, drooling, vomiting, and diarrhea. They may pant heavily at first, but it is important to note that as heatstroke progresses, they will not always display panting.

Treatment is initially focused on cooling the pet. Evaporative cooling is the most efficient way – misting with cool or room temperature water and placing them in front of a fan are good options. Do NOT use ice or cold water – this can constrict blood vessels and further damage organs.  At the hospital, pets are placed on intravenous room temperature fluids to help cool them as well. Active cooling is stopped once the body temperature is around 102°F to prevent hypothermia, as their temperature can continue to drop after cooling has been discontinued.

Other treatments are focused on the individual organ damage. This may include intravenous fluids, oxygen supplementation, anti-arrhythmics, antibiotics, GI protectants, and blood transfusions.

Prevention is aimed at avoiding hot environments if possible – do not leave pets in a vehicle or other enclosed spaces (garage, shed, cages, etc.). Keep animals inside during hot days and walk them early and late in the day when the sun is not as strong and the temperatures are cooler. Do not let them exercise strenuously during hot days and always ensure they have access to shade and water if they are outside.

Heatstroke can be very serious, and the prognosis can vary depending on the duration, severity, and response to therapy. Many times, heatstroke can require multiple days of hospitalization. If you suspect heatstroke, contact a veterinarian as soon as possible.