Heat Stroke – Expanded Topic

Last Thursday, I put up a post about the horrible heat and obesity related deaths of two dogs. One of our readers, David, asked if I could put together a post about distinguishing normal cooling behavior of dogs from dangerous overheating. It was a great suggestion, so I’ve done a bit of research.

We need to define some terms and some normal values first.

Hyperthermmia = higher than normal body temperature
Dogs have a body normal body temperature between 99.5F and 102.5F (37.5C-39C)
Hyperthermia is a temperature above 103F (39.4C).
A body temperature over 105F (40.5C) is generally considered dangerous/serious.

Cooling Mechanisms

Dogs and cats will pant, which means that they open their mouth and rapidly breathe to move air back and forth over the tongue and in the trachea.
Dogs and cats do sweat, but only a little, and it’s confined to their feet.
Blood vessels in the surface area of the skin will expand, allowing more blood to flow to the skin surface, where it may be cooled by the ambient air.

Tolerances

Dogs can tolerate fairly high rises in their body temperature for short periods of time. Some informal data collection I came across looked at German Shepherd working dogs and found that many of them had temps of 105-106 F (40.5-41.1C) after an hour of exercise in air about 75F (23.9C). I suspect that this is fairly common across breeds during intense activity. The lower outside air temps helps the dogs cool down by panting and losing heat through the skin to the environment. In warmer temperatures, it gets harder and harder for dogs to get rid of heat with their normal mechanisms.

Increased Risks

Dogs at higher risk for overheating include: brachycephalic (short-nosed) breeds, thicker coats, and working dogs.
Higher environmental temperatures and higher humidity.
Strenuous activity.

This is where things get more difficult. How do you, as an owner, know what normal cooling is compared to a dog that’s about to be in trouble from overheating? I couldn’t find a sign to watch for that would give you a specific clue. The tipping point between “He’ll be ok” and “He’s going to die from overheating” can happen in an incredibly short time — mere minutes — and some of the signs of heat stroke are profound and sudden.

Signs of heatstroke can include:
Panting
Brighter red mucous membranes.
Excessive drooling.
Weakness, lethargy, or collapse
Vomiting
Diarrhea (may be severe and bloody)
Shock
Coma
Seizures
Bruising of the skin

Remember, panting is normal. Brighter pink mucous membranes (gums, inner lips) are also normal. Some dogs will drool a little. After those signs, the list gets far more serious far more quickly. The rest of the signs in that list indicate severe damage to the body. Heat stroke can cause an inability to clot the blood, brain damage, kidney failure, blood infection, and death.

So, how does an owner know where the true danger is? Unfortunately, you can’t readily tell just by looking at your dog. What I’d like to encourage is for you to use common sense.

If it’s hot out, avoid strenuous activity. Or do so in the coolest parts of the day (early morning, late evening). If your pet is outside, take cold water and give small amounts frequently. Panting is normal. Panting and refusing to be more active is a big red flag. If your pet is even a little bit slower, or lethargic, or won’t move, COOL HIM DOWN.

If you think your pet is suffering from overheating, here’s what you should do:

Wet your pet down with cool (not ice cold!) water.
Apply rubbing alcohol (isopropyl) to the top and bottom of the feet.
Apply a cold wet cloth to the armpits and groin. (Several sources I looked at disagreed about whether you should use an ice pack or not. In practice, I do, but I wrap it in a wet towel.)
****GET YOUR PET TO THE VETERINARIAN ASAP!****

You will also need to stop trying to cool a pet down when the temperature gets down to about 103F (39.4C). If you keep cooling after this point, hypothermia will occur, and that has its own host of dangers.

Prognosis for Overheating
The prognosis for a pet that’s been overheated is extremely variable. It will depend on how high the temp got, and for how long it stayed there. The higher and longer, the worse the damage is. Kidney failure, shock, blood infection, damaged and sloughing GI tract, blood clotting disorder, and brain swelling can all occur. These cases need care at an emergency-level practice for 24-hour monitoring. Treatments include IV fluids, antibiotics, blood plasma transfusions, medication for brain swelling, and other symptomatic management. The prognosis is always very guarded. The best prognosis seemed to be for dogs that were cooled some by the owner and brought to the vet hospital as rapidly as possible.

Take-home message:
Use common sense. If you wouldn’t run around in a heavy fur coat, don’t make your dog do so.
Protect dogs from themselves during hot weather: they’ll run until they collapse.
Shade, cool water, and take it easy!
Know where your emergency veterinary facilities are.

One final note. If you see a dog left in a car in sunny bright weather, call the police. There should be ZERO tolerance for this. A car sitting in the sun with the outside temp at 75F (23.9C) will rise to about 115F within an hour. That’s WAY too hot for safety.

Here are couple of links to articles and info on heat stroke in dogs:
Pet MD
VIN Partner

As always, thank you for reading. Enjoy the spring and summer! 🙂

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4 Comments

Filed under exercise, safety, summer, weather

4 responses to “Heat Stroke – Expanded Topic

  1. This is such helpful information to distinguish the line between overheating and heat stroke.

    I keep an extra car key with me for emergencies. Once I had to stop at a drugstore for my mom on a hot summer day while my dog was with me. I locked the doors and left the car running with the air conditioner on while I ran into the store. Not an ideal situation, but better than the alternative, even for a quick stop.

  2. This poses an interesting quandary.

    While the risk is lessened by the AC, there’s still a risk that the AC won’t be enough or could fail. Interestingly enough, the Police dogs Ft Lauderdale/Miami are left in the police cars with the AC running.

    The risk is still more than I’d recommend taking. 🙂

    Thanks for bringing up a good situation to test our theories and strategies!

  3. David

    “Protect dogs from themselves […]” —

    So dogs don’t have reliable thermal self-regulation, and even minor signs of overheating count as a potential emergency!

    I’m going to be a lot more cautious with Mischa than I have been in the past. Thank you for the advice!

    Evolutionary musings: I can’t imagine dogs’ evolutionary ancestors often run themselves to death in hot weather, and dogs still survive in some scaldingly hot climates (think Indian pariah-dogs). So I find it curious that our household mutts are so susceptible to overloading themselves. I have to wonder if the self-regulation has been unintentionally bred out of them, or if it’s a skill that dogs can learn by experience, but which our pampered pets never have to pick up.

    Or perhaps wolves just do get heat-stroke once in a while. Maybe we should ask David Mech to look into it. 🙂

  4. They do have thermoregulation to a point, and they can acclimate to higher temperature locations…to a point. It’s just so damned hard to figure out where that fine line is between “I’m hotter than normal” and “I’ve denatured the proteins that clot my blood and make my kidneys work.”

    Dogs’ evolutionary ancestors had the luxury of living in packs, which helps spread the workload during high temps. I’d guess they also spend more time hunting during early and late hours of the day when the heat isn’t as bad. I’ve got no good way to support my agreement that we’ve bred a lot of hardiness out of our domestic dogs.

    If you do happen to come across any info on thermoregulation (from David Mech or anywhere else) please let me know!

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