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Heat Stroke

Heat stroke can occur when body temperature rises to 104-106 degrees F (greater than 40 degrees C) and usually involves exposure to high environmental temperatures.

Exertional heat stroke occurs when internal heat generated by exercise cannot be adequately dissipated, with body temperature rising to a dangerous level.


Causes can be split into two groups. Those that decrease the dog’s ability to lose heat and those that increase heat production.

External factors that decrease heat loss include confinement in a poorly ventilated space (eg locked in car), high environmental temperatures, increased humidity, and limited access to water. Internal factors include obesity, thick coat and jackets, and upper airway and heart disease.

Factors that increase heat production include prolonged seizures, exercise and fever.

Clinical Signs

Panting and high temperature (hyperthermia) are most common, but can progress to weakness, collapse, coma or convulsions.

Breathing may be very noisy and the gums can become bright red or blue.

Some dogs may have vomiting and diarrhoea.

Delayed signs may develop 3-5 days after apparent recovery due to damage to internal organs and can include reduced volumes of urine (kidney damage), jaundice (liver damage) and sudden death from heart failure.


Diagnosis is based on finding an extremely high body temperature, a history of exposure to heat, and consistent clinical signs.

Often lab tests will aid in assessing damage to internal organs and degree of dehydration and electrolyte imbalance.


This is an emergency! The goals of treatment are to lower body temperature, treat shock and other organ damage and correct any predisposing factors.

As soon as you realize your dog has heat stroke soak him in cool water, wrap in a cool, wet towel and get into air-con and to a vet as soon as possible.

Cooling methods at the vet include immersion in a lukewarm bath, applying ice packs to feet and groin (hairless skin) and using fans. Care must be taken to avoid body temperature dropping too low (hypothermia)

Treatment for shock may involve intravenous fluids, oxygen therapy, and treatment for seizures or brain swelling.

Follow Up and Prognosis

Most animals with heatstroke require intensive monitoring for several days after the incident, and prognosis depends on the severity and duration of the hyperthermia, and how much damage has been done to internal organs.

Sadly comatose dogs have a poor survival rate, and animals that have an episode are prone to recurrences.

Whilst most pet owners in Hong Kong are aware of this condition, many forget high air humidity is a risk factor. Dogs only sweat from their pads and rely on evaporation by panting to lose heat. In high humidity evaporation is of course compromised. At Acorn we would strongly advise caution on too much exercise on very sunny or humid days, or if possible choose the beach over the Twins!