Death due to heat stroke is a real risk in hot weather, and even on moderate days for some dogs and in some conditions. What can you do to protect your pet from this terrible condition?
Heat stroke (hyperthermia) is a very serious, potentially fatal condition, which unfortunately, is seen commonly in veterinary practice. Dogs rely mostly on panting to cool themselves, as, unlike humans, they’re unable to sweat. When the ambient temperature is similar to body temperature, evaporative cooling via panting is not very efficient. The muscular work associated with panting can actually generate more heat than that lost by panting and the associated salivation can lead to dehydration and worsening hyperthermia.
The following are factors that predispose to heat stroke
– Brachycephalic (“flat faced”) breeds such as Bulldogs or Pugs have abnormal upper respiratory tract conformation and cooling via panting is less effective. Their breathing can be so inefficient that they are still at risk of heat stress on a hot day, when they have access to shade and water or are travelling in an air-conditioned car.
– Having a respiratory disease such as laryngeal paralysis or a heart condition that interferes with effective breathing
– Debilitated (e.g. sick, aged, arthritic) animals may be unable to seek shade
– Being confined in an area with no shade or water
– Confinement in a car, even if the windows are open a little
– Exercising in hot, humid weather
– Previous heat stroke episodes (it’s thought that heat stroke damages the hypothalamus, the area of the brain responsible for thermoregulation and increases the risk of recurrence of heat stroke in the future)
We have seen near fatal heat stroke in a black bulldog just sitting in the sun on a hot day, another bulldog after a 10 minute walk on a warm day, and fatal heat stroke in a pug travelling in the back of an air-conditioned station wagon. The dog died while travelling in the car with its owners. Other examples include a golden retriever who ran everyday with its owner, but on this day he ran one extra kilometre, and two kelpie type dogs whose owner had stupidly put them in the car boot after they swam in a muddy river.
Symptoms of early heat stroke include severe panting, agitation, weakness, incoordination, a fast heart rate and bright red mucous membranes. They will feel hot to the touch and their rectal temperature will be > 40°C.
Signs of late heat stroke include depression, coma, weak pulses, difficulty breathing, vomiting, diarrhoea and haemorrhage. Muscle tremors and seizures may also occur.
Consequences of heat stroke can include brain damage, multiple organ failure and cardiac arrest.
If you suspect your animal is suffering heat stress, measure their rectal temperature if possible. Then spend 5 minutes cooling them with cold water – the normal temperature from the cold tap. Do not use ice baths or ice packs because it causes constriction of peripheral blood vessels and reduces cooling. Offer water if the dog is able to drink. You can also place a fan in front of them. Then telephone your veterinary hospital to arrange for emergency treatment. Always telephone before going to the vet – your vet can be getting ready for the emergency or, if your vet is unavailable, you will be directed to an available emergency service, rather than wasting time driving around. Dogs which are actively cooled by their owners and presented for veterinary care within 90 minutes have a better prognosis than animals with delayed presentation or no active cooling at home.
Written by Dr Kim Cleary