What is heat stroke?
Heat stroke occurs when there is an imbalance between heat load (heat produced in the body + environmental temperature) and heat dissipation. In dogs, heat dissipation is mainly via evaporation – both via the respiratory tract from panting and via the skin. Panting is the primary source of heat loss once the environmental temperature exceeds 32 degrees (or less for brachycephalic breeds). Heat stroke can occur due to high environmental temperatures, exercise in warm temperatures, or strenuous exercise alone. Humid conditions, confined spaces and upper respiratory tract dysfunction decrease the efficacy of heat loss via evaporation.
Heat stroke more commonly occurs after a sudden day of elevated temperature in Spring or early Summer. Dogs with normal heat exchange mechanisms can acclimatise to warm weather after 2-3 weeks, decreasing their susceptibility to heat stroke. The initial shock on the first few hot days is especially relevant in flat faced breeds.
Brachycephalic (or flat faced) breeds are unable to move air for heat dissipation as efficiently as other breeds. In addition, their increased work of breathing also contributes to heat generated. As a result, very mild increases in ambient temperature can trigger heat stroke or heat stress in any brachycephalic dog.
Symptoms of Heat Stroke
Affected animals will have a high body temperature and are often panting excessively with increased breathing noise or marked respiratory distress. High body temperature has effects on the body’s organ systems and can cause bloody diarrhoea, kidney failure and brain damage. As signs progress, collapse and seizures can occur, progressing to coma and even death due to multiple organ failure.
Initial first aid is aimed at cooling the patient. Place your dog on a cold surface, wet it down with cold water and then put it in front of a fan. Ice packs are not recommended as they cause peripheral vasoconstriction, which decreases heat loss. Wrapping your dog in wet towels is also not recommended as it will prevent surface evaporation. As soon as possible, transport your pet to a veterinary hospital. Patients often require intravenous fluid treatment, sedation to control distress and excessive panting, supplemental oxygen treatment and other management strategies.
Sadly, despite aggressive treatment, heat stroke can be a rapidly fatal condition.
How do I Prevent Heat Stroke?
The main advice here is awareness in warm weather – especially as it starts to warm up during Spring and the start of Summer.
- Exercise in temperatures over 32 degrees should be avoided or undertaken with care in any dog, but is especially important in brachycephalic breeds. Be careful on days as little as 20 degrees if it’s just starting to warm up, or 25 degrees right through Summer – especially if airway correction has not been done in your dog.
- Never leave your dog in an enclosed, confined space in warm weather conditions.
- Provide ready access to cool water.
Brachycephalic breeds are at a much higher risk of heat stress and heat stroke, both due to the effect of breathing harder than long nosed dogs (due to their restricted airways), and not being able to dissipate heat as effectively.
Outdated thinking was to only consider airway correction for brachycephalics that are really struggling to breathe, but this has been replaced with more modern advice that preventative surgery before symptoms become severe has multiple benefits. One of the benefits of early corrective surgery is the dogs ability to cope with warmer weather. From ambient temperatures of as little as 20 degrees, coming into Spring many dogs can struggle to cope. Hence 6-12 month correction allows for significantly improved lifestyles and even happier dogs, especially in warmer weather!