Sometimes we forget how quickly the temperature can rise inside a car and we’re aware of the danger of children in cars, particularly the very young, and the danger can be magnified for the dog in a locked car.
When a dog becomes hot, the body gets rid of the heat by panting, by moving the air very quickly through the mouth, where the warm or hot blood travels to allow the heat to escape. You may recall that dogs actually do not sweat, which is the major method of heat loss in people.
You see, when we get hot, our body secretes a watery substance called sweat, onto our skin and the air moving across the moist skin causes evaporation which allows the heat to move away from the body. This is what produces the cooling effect.
Dogs however do not sweat, so their method of cooling is to move air through the mouth where the hot blood is traveling through the mucous membranes – that’s the name for the tissue in lining of the mouth and throat. As the air moves back and forth, the moist warm tissue cools by evaporation, just as we do over all of our body by sweating.
However there is a limited area in the throat and mouth for a dog to have this effect of cooling, so they have a limit to the amount of heat that they can dissipate into the environment. Inside the sealed car, the temperature rises rapidly escalating the danger to the dog.
The dog becomes agitated because they’re separated from their owner, starting to pant from anxiety and moves around the car, increasing their body temperature and building up the temperature inside the car. Now we are in a vicious cycle with a body producing heat, the air is warming up, and yet there’s no air movement and the heat lost through evaporation cannot occur.
Once this spiral of heat retention and heat production occurs, things rapidly progress and the dogs body temperature moves from the normal of 38.5°C to greater than 42°.
At this level the proteins in the dogs blood are affected and denatured, such that they don’t work, and so the dogs blood fails to clot. This leads to a condition called disseminated intravascular coagulation (DIC).
The other major organ system affected by this heat retention is the gastrointestinal tract. The cells lining the gut are very sensitive to heat and they start to die off causing protein loss, blood loss and fluid loss, and allowing bacteria to walk through the wall into the bloodstream. This process of gut damage and the resulting bacteraemia (bacteria in bloodstream) causes sepsis and multiple organ failure, which can rapidly progress to death.
In heat stress, other organs affected are the brain, the heart and lungs, and the kidneys, as muscles break down, flooding the kidney with the toxic myoglobin.
Treatment of a dog in this scenario can be very difficult and the message as always is prevention is far greater than the cure. So make sure this summer to look after your pets and children you keep them out of locked cars.