The problems with cars…

The average car is a metal box with glass windows. Metal is an excellent conductor of heat, meaning heat can pass through metal easily, think of your kitchen saucepans. Glass is a poor heat conductor but allows sunlight to pass through. This means that light energy from the sunlight enters the car through the windows but then gets trapped as heat by the glass. Some of this heat will be lost through radiation and conduction into the surrounding air, but if sunlight continues to fall on the car, it will continue to heat and in summer, this happens far quicker than heat can be lost to the environment; the reason greenhouses are so effective.  The net result is your classic summer hot car.

The typical British summer is an unpredictable affair. Whilst temperatures regularly reach 20^oC or more, often we have consistent cloud cover, intermittent rain or high winds to keep things feeling fresh, and stop cars turning into ovens.  Last summer, we experienced one of the first prolonged heatwaves of this century, with temperatures regularly hitting 30^oC and endless blue, cloudless skies.  We have become complacent. Our dogs are typically part of our family, so we like to take them with us, whether we are taking them for a walk, for a day out, or travelling somewhere. The problem is, on a typical sunny day of 21^oC, your average family car will reach temperatures of 31^oC in 10 min. As the outside temperature climes to 31°C, the internal temperature of the car can reach 54°C. 80% of that temperature rise happens in the first 30 minutes.

We’ve all seen the adverts, surely no one would be so stupid…?

Since 2016, summer has been heralded by the “dogs die in hot cars” campaigns supported by a number of charities to increase awareness of the risk of leaving dogs in cars in the summer, and yet last year (2018) the RSPCA received 8290 calls, an increase from around 7800 calls concerning heat exposure in animals 2017. In a single weekend, over the 2018 May Bank holiday weekend, 217 calls were made by people concerned about dogs left in hot cars. One London police force was even offering a ‘free ventilation service’ if dogs were left in cars during the hot weather (by breaking the window).

So why do people leave dogs in hot cars? A two-minute trip into the shop for a couple of forgotten items can easily become ten minutes. When questioned, owners gave a range of excuses, from “My dog is white, he’ll be fine” to “We feel bad leaving him at home on his own all day.” “We didn’t think we’d be long.” “It’s OK, I’m a vet”. No doubt, the vast majority of people do not want to harm their dog, but simply do not think. When leaving the car, the air con or open windows from travelling can make the car feel relatively cool. However, left in the sun for any length of time, even with the windows cracked slightly, it will get hot. Shade can help to keep the car cooler, but as the sun moves round, the shade can quickly disappear.

A human in a similar situation would begin to sweat to try and lose heat. Dogs don’t have the ability to sweat, they will pant, but as the temperature continues to rise, panting becomes less effective, and once the car temperature exceeds body temperature (around 38^oC) there is nothing the dog can do to cool down. Unless the dog is actively cooled (see below) their body temperature will rise with the car temperature, and once they exceed 41^oC, they are likely to develop heatstroke.

Heatstroke – the problem

Heatstroke isn’t the same thing as sun stroke, or heat cramps, or heat exhaustion.  These conditions can often be treated with cooling, plenty of fluids and rest. True heatstroke causes multi-organ failure. Picture an egg in a frying pan, you crack the egg, the yolk is yellow but the egg white is clear and jelly like.  Once the egg starts to heat, the chemical structures of the proteins start to change, the egg white becomes firm and changes colour. Now imagine this happening to the proteins within the body. As body temperature exceeds 41^oC the stomach and intestines stop functioning, so the dog may vomit or pass bloody diarrhoea. The kidneys stop working, so despite fluid therapy the dog is unable to flush out the toxins from all the cellular damage taking place around the body. If the dog’s brain overheats, they may start fitting, or fall into a coma. The mortality rate for dogs with heatstroke is up to 63%.

Don’t risk it.

Don’t keep your dog in the car and never leave them unattended. Even in the shade, car temperatures can increase quickly, and shade may disappear. Leaving windows partially open has little effect on car temperature. If you are stuck in traffic or travelling, have the air conditioning on to keep the car cool and make sure windows are shaded from direct sunlight. Don’t assume your dog in the car boot area is fine because you are, check them regularly, your air conditioning may not reach the boot. Ideally, leave your dog at home in hot weather. Car shields and shades may help to keep the car cool by reflecting the sun’s rays, but some may also act as an insulator, particularly if the car is already hot inside. If you have no alternative other than to keep your dog in the car, open all windows, open the boot, try and maintain airflow, park in shade, and don’t leave your dog. Stay with them so you can be absolutely sure they are OK.

If you see a dog in a hot car, the advice is to phone the police. Heatstroke can kill quickly. A dog that is suffering from heatstroke needs to be actively cooled and taken to the vets. Active cooling is key. Even before setting off to the vets, use water to splash the dog’s legs, belly and throat area, get them out of the sun and into the shade, and if possible move them somewhere with good air flow – this might be in a car with the air conditioning already blowing. To give you an idea, the army have been known to use the downdraft from helicopter rotor blades to create airflow over soldiers with heatstroke. Next, getting to the vets as quickly as possible is the current best advice. Avoid using ice or very cold water, as this can do more harm. When your skin is cold, the blood vessels constrict, which can make it harder to cool the dog, and increase the risk of them going into circulatory collapse (shock).

There is no guarantee any dog will survive heatstroke, so the best way to keep your dog safe is to prevent it.