Heatstroke in Cats and Dogs

Last week at the beginning of a routine feline wellness exam here at Chico Hospital for Cats, I removed the top of Ruby’s carrier, as is our standard way of beginning the exam without causing undue stress to a cat. Immediately upon removal of the lid, I could feel the heat emanating from Ruby, a domestic short haired, solid black female of–shall we say–rubenesque proportions. Like many carriers vets see in daily practice, this one was proportionately too small for its cargo, creating a “lunchbox” effect of limited free space and air movement within.

An immediate temperature reading from Ruby’s ear canal read 105.1. She was also panting. Cats are obligate nose breathers and panting is an activity only seen in times of fear, extreme exertion, hyperthermia, and serious impairments of the respiratory or cardiovascular systems.

Recently we have heard of several children tragically dying from prolonged heat exposure in cars. Ruby is a good reminder that pets riding in hot cars for even short periods of time can also overheat. Ruby was not left in a car alone; she was taking a routine ride in a cat carrier in a car without air conditioning. The temperature that afternoon was 90 degrees. It also made me think of our sister hospital, Chico Hospital for Cats. They have been part of a heat wave where the temperatures have been in the high 90s and even until the triple digits.

The ability of the cat and dog to cool the body is very limited. Their only sweat glands are on their feet. Their mouths, which can pant for cooling purposes, comprise a very small surface area compared to the rest of their heavily haired bodies. Add to these limitations the typical cat carrier which:

–Is often too small for the cat–in other words, lacks sufficient air flow and space for heat to dissipate,
–Lacks ample ventilation– in other words, a box with a few small holes and a small grate for a door,
–Consists of a material predisposed to trapping heat such as plastic, wood, and nylon.

When a cat or dog overheats, they will breathe faster and harder in an attempt to cool the respiratory tract and exchange more oxygen for carbon dioxide in order to satisfy increased tissue oxygen demand. All of that carbon dioxide is exhaled into a very small space, making the available oxygen lower, and creating a “catch-22″ of panting even harder and faster. A pet carrier made of plastic, with a large pet inside it, and with limited airflow on a moderately warm day can very quickly cause serious hyperthermia (overheating).

A dog left in a car with the windows rolled down even by a third can still overheat on a moderately warm day (70 to 80 degrees). Even with windows partly rolled down, the hotter the ambient temperature is, the hotter the inside of the car will be by several fold as heat is trapped and cannot escape. Lack of sufficient airflow, decreasing oxygen levels, increasing carbon dioxide levels from panting, lack of water, and the inability of the dog to cool down will very quickly escalate to heatstroke.

How can heatstroke be prevented when traveling with cats?
– Employ a coated metal, wide mesh kennel with a solid plastic bottom to transport the cat. These are often marketed as “dog crates” and have no solid sides or ceiling.
— Another option is to use a very oversized dog carrier; the cat should take up no more than 25% of the inside space.
— Put the cat in the direct line of the air conditioning vent, and feel the air flow to ensure it is reaching the cat.
— Use retractable car window shades to block direct sunlight from the crate if you are driving for more than a few minutes.
— Do not ever leave a cat in a car without the air conditioner running.
— Always feed your cat canned food (mixed with a little extra water) before and after the vet visit to ensure water is consumed, unless certain medical procedures prevent you from feeding.
All of the above also apply to traveling with dogs, but additionally:
– Do not be fooled into thinking it doesn’t feel that hot outside. Remember, you are not wearing a fur coat you can’t remove; you are able to sweat; your body temperature is not naturally two to three degrees higher.
— Do not leave dogs inside cars when the ambient temperature is above 70 degrees. If it’s 70 outside, it will be 80 inside the car within minutes.
— Always have water freely available at all times.

Luckily, Ruby cooled down quickly once she was removed from what I called her “greenhouse gasses” carrier. Rubbing alcohol was swiped on her ears and feet and she willingly drank tuna water. Within thirty minutes her temperature was 102.5.

Ruby was lucky but not all pets are. While working at a different practice, a distraught client dragged her 40 pound mixed breed dog into the lobby. The dog had been left in the car for an hour while she shopped; the car windows were only rolled down about two inches. The dog, in an attempt to free himself, had scratched up the backs of both front seats until all of his nails were torn. He had a rectal temperature of 108 degrees and died of hyperthermia. It was a preventable, heartbreaking tragedy that can happen to anyone, even the absolute best of pet owners.
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So remember: Ample Airflow with Air-conditioning Avoids Accidents!