heatherspetblog

All about pets

Why Short-Nosed Dogs Can’t Take The Heat

By Dr. Tony Johnson:

Mother Nature usually does things pretty economically. Basically, she’s trying to get genes passed on from one generation to the next with a minimum of fuss. Everything else is just details. Even when something natural seems flashy and unnecessary, like a peacock’s feathers, for example, it is usually rooted in this overarching goal of gene shuffling. The more colorful a peacock’s feathers are, the healthier the bird and the better the chances of a genetically superior mate who can garner more resources. This is also why I typically wear very colorful (and, I am quite certain, stylish) shirts every day.

When people step in and start mucking about is usually when the troubles begin. When we breed for a particular look (rather than for a purpose intended to maximize chances of passing on genes), function gets tossed out the window at the expense of form and things can get bogged down pretty quickly.

Lots of different dog breeds suffer from problems due to overzealous breeding, but perhaps none so much as the short-nosed, or brachycephalic breeds such as pugs, English Bulldogs and the like. As the weather turns warmer, we see lots more of these type of dogs in our ER at Purdue suffering from heat stroke than at any other time of year. I want to say, right off the bat, that I am not slamming these breeds or the folks who love and breed them, but they do have some medical differences that I think people who own them, or are thinking of owning them, should be aware of. I have owned some of them in my life, and I think they can make wonderful companions.

Dogs are largely unable to sweat. Maybe a little around the feet (sometimes my more nervous patients will leave cute little paw-shaped sweat prints on the exam table), but not through their skin like people can. They regulate their body temperature largely though panting, which dumps heat from their bodies through evaporation of water from their tongues rather than their skin. I don’t know why, but Mother Nature decided that for people, we should thermoregulate by sweating and not panting. Sometimes, just for kicks, I will try and regulate my body temperature by panting instead of sweating, and I just get weird looks. Then I go back to sweating, usually in my colorful shirt.

In order to keep cool through panting, dogs need a good airway. They need a good-sized trachea (windpipe), and this is one of the weak spots that is common amongst brachycephalic dogs. They almost all have smaller tracheas (in terms of cross-section) relative to other dogs of comparable size, a condition known as tracheal hypoplasia. Bulldogs often have a trachea that would keep a Yorkie quite happy, but for the bulldog it must be like breathing through a coffee stirrer. When we have to intubate brachycephalic dogs for surgery (which involves placing a soft, plastic tube into their trachea to deliver oxygen and anesthetic gases), they will often wake up with the tube in place after the procedure and seem quite happy to have an open and bigger airway for the first time in their lives.  Most other dogs can’t wait to get the dang tube out!

Brachycephalics also have a few other quirks that make the path from their lungs to the outside world a little more harrowing than for the rest of the doggy universe; they can have little blobs of tissue in the back of their throat (known as laryngeal saccules) that can turn inside out and block the airway, and they often have teensy weensy little nostrils that look cute as a button but don’t move too much actual air. Together this constellation of tiny tracheas, lumps of flesh and wee nostrils is known as brachycephalic airway syndrome, and it makes life miserable for the poor snub-nosed breeds. Surgeons can fix a few of the problems and provide for a better life for some of them, but the threat of heat exhaustion always remains.

When they try and dump excess body heat through panting, brachycephalics have to work so hard to move enough air through their tiny tracheas that they actually end up generating more heat and making things worse. It would be like having a coal-fired air-conditioner in your house; when the house gets warm, the A/C kicks on, but the heat from the coal fire would make the house warmer. (I majored in Crappy Analogies in college. Minor in balloon animals, if you must know).

When the weather turns warm and humid, these dogs need to stay in a carefully controlled and cool environment to avoid overheating. The last thing they need is to be out in the sunshine and heat running about. It may seem like the most natural thing in the world to take your dog our for a run when the weather turns nice, but even a few minutes of play in the heat can be too much for some dogs.

Signs of heat exhaustion (which is the last step before heat stroke) include bright red gums, inability to get up, and loud, raspy panting.  Dogs that are going into full-on heat stroke often vomit, become severely lethargic and can have explosive diarrhea. Once heat stroke develops, cooling them down is job #1, but it often is not enough.  Some dogs will go down the slippery and tragic slope into multi-organ failure and be unable to be saved, even with days of ICU-level care.  Prevention is the key with this disease, so remember to always watch out for heat exhaustion if you share your home with a short-nosed breed, although it can happen in any breed of dog.

If you do have a dog that you think is suffering from heat stroke or exhaustion, douse them in cool water, get them out of the heat and calmed down and head for the nearest veterinarian without delay. Even a few minutes can make all the difference in the world.

June 21, 2011 - Posted by | Uncategorized

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