Summary: A St Bernard named Charlie is diagnosed with heat stroke. Dr. Julie Buzby recounts the emergency, shares symptoms and treatment, and explains why heat stroke in dogs is a life-threatening—potentially fatal—veterinary emergency. Keep your dog safe by learning how to prevent heat stroke.
Heat stroke in dogs: When the temps rise, so do the risks
Summer is fully upon us, and I love the long, sunny days and late nights to spend with my family. This year we have been blessed to travel to Israel for an extended working vacation. The heat here is intense; with high temperatures soaring to 110°F. I just read a post on a local Facebook group about a dog who suffered heat stroke in these conditions and was taken to a veterinarian. Many commenters lamented the dog’s fate but assumed he would just need IV fluids to recover.
Spoiler alert: I can’t stress enough that heat stroke is a life-threatening veterinary emergency which is complex and complicated. IV fluids will no doubt be a part of the treatment because of dehydration, but heat stroke can have a serious impact on multiple organ systems (including the GI tract, heart, kidneys, and central nervous system) and the body’s coagulation (clotting) cascade.
Heat stroke: when summer fun turns serious
Dogs who have experienced heat stroke will likely be hospitalized for aggressive and expensive treatment. Some of the serious complications of heat stroke will not manifest until after the initial episode, so the dog must be closely monitored.
As a mom, I love the summer, but as a veterinarian, it worries me for our pets. If the days are hot for us, imagine what it’s like to run around in a fur coat! Although I may be preaching to the choir, I am compelled to share the story of a St Bernard named Charles and beat the drum about the risk of heat stroke in our canine companions.
July in the south and Charles, a St Bernard, collapses in the heat
Charles was the first dog that I ever treated for heat stroke. Of course, I’d studied heat stroke in veterinary school. But studying about it in a textbook and seeing the suffering dog lying before me on a gurney were quite different.
It was July in the South. Need I say more? Picture humidity so thick that the mosquitoes were choking.
One of my favorite patients, Charles, was boarding at a local doggy daycare. He’d been outside, in the 90+ degree heat, frolicking with his friends when he’d suddenly collapsed.
The boarding facility called in a panic, letting us know they were bringing Charles straight in. I prepared my staff for his arrival.
Signs of heat stroke in dogs
When he arrived, Charles couldn’t walk. He looked melted in the back of the SUV, panting so heavily that I couldn’t understand how he was able to ventilate himself. His tongue lolled out to the side, and his eyes were panicked. I could feel the heat radiating from his body.
My staff jumped into action by carefully lifting him onto a stretcher and bringing him into the hospital. One vet tech began shaving Charles for an IV catheter to start cool intravenous fluids while the other technician took the St Bernard’s temperature and got his heart rate. (As an aside, knowing your dog’s vital signs just might save his or her life someday. To keep your finger on the pulse of your dog’s health, please check out my infographic and podcast: Learn Your Dog’s Normal Vital Signs.)
Charles’ temperature was an astounding 111°F.
Why a dog’s body temperature is critical
The canine body, just like the human body, is calibrated to function at a very specific temperature range. A normal temperature for a dog is between 99-102.5 degrees. It is controlled by a small part of the brain called the hypothalamus. Body temperature can be affected by both internal factors (bacterial and viral infections, for instance) and external factors (ambient temperature).
When a dog has a fever, the hypothalamus has reset the normal body temperature to a higher point. That’s why cooling a dog with a fever doesn’t actually help the fever. If you cool a dog with a fever, you bring the temperature down below what the hypothalamus has set as normal, and shivering sets in. Shivering is a compensation method to produce heat and bring the body temperature back up to the “new” normal.
In contrast, external factors do NOT reset the hypothalamus. An elevated temperature due to a hot environment is called hyperthermia rather than a fever. The temperature climbs and climbs, causing significant damage to the body. All of the organ systems run smoothest at the normal temperature range.
The body can tolerate fever for quite some time, and even overheating. It has built-in compensation methods. But once the body’s temperature exceeds around 108-109°F, systems begin to break down. This is when heat stroke becomes very serious!
Dogs rely on evaporation and convection to cool themselves
Did you know that dogs only sweat very little and only through their footpads? Unlike people, sweating is not an efficient means of cooling for canines. Instead, they rely on evaporation and convection to cool themselves.
Evaporation happens via heavy panting. Thus, one of the first signs of heat exhaustion in dogs is heavy, rapid panting.
Convection cooling occurs when a dog seeks a cold surface on which to rest, thus transferring heat from the body to the surface. In cases where there is no mechanism to lower the body temperature (such as a dog left in a car on a warm day), heat stroke happens quickly.
Veterinary treatment for heat stroke in dogs
Back to Charles. As we started his treatment, the worried daycare attendant told me that it had been exceptionally hot, and Charles was romping very actively with his friends. As a St Bernard, he had a heavy, thick coat and was a little overweight. (These two factors alone made Charles more prone to heat stroke.) Fresh water with ice cubes, as well as kiddie pools, were placed around the play area to keep the dogs cool, but Charles still overheated.
The first sign that the attendant noted was that Charles was panting too fast and struggling to get up. By the time he arrived at our hospital, he couldn’t lift his head.
What happens to a dog’s body systems when it overheats
Heat stroke affects every single system in a dog’s body. But what is actually happening?
Let’s look at a dog left in a hot car. The temperature is initially tolerable, but then it quickly begins to go up. The dog starts to pant and seeks a cool place to lie down. There is no cool place, and the panting gets faster and faster but cannot effectively bring down body temperature. The blood vessels supplying the skin dilate, another mechanism for cooling. This pulls blood to the skin and away from the core.
The downward spiral begins. Central blood pressure starts to drop. The body compensates by increasing output of blood from the heart. It does this by speeding up the heart rate. Due to the high ambient temperature, the body cannot continue to compensate, and it becomes overwhelmed. Once the temperature is 109°F, body systems shut down quickly.
Charles receives cooling treatments
My hospital doesn’t have overnight care, so our goal was to stabilize Charles before transferring him to the local 24-hour specialty clinic. He would need days of critical care; and even with all that modern veterinary medicine has to offer, his prognosis (expected outcome) was “guarded.”
We started by cooling him. There is some controversy in veterinary medicine over how best to cool patients, especially the big, shaggy ones. In Charle’s case, we opted for hosing him down with cool water while a fan blew on him. We wrapped ice packs in towels and placed them along his belly and in his armpits. The goal was to cool him to about 103.5°F and stop, allowing the body to slowly bring the temperature down the rest of the way.
If cooling is too aggressive, then a rebound hypothermia will occur, and body temperature will be too low.
Another way we cooled Charles was with IV fluids. These serve several purposes. A dog having a heat stroke is in shock. This means blood pressure is low, heart rate is high, and circulation is poor. With poor circulation, oxygen delivery to tissue is decreased. Oxygen is essential for normal body function. IV fluids bring temperature down while restoring circulation.
Yet a third way to cool this gentle giant was to use oxygen. We placed a face mask (filled with ice chips) over his muzzle. This served two purposes. It provided cooling with the cold oxygen flowing over his face, and it increased oxygen delivery to his tissues to improve their status in his state of shock.
Red spots pop up and the patient needs a plasma transfusion—stat
As we worked on Charles, I noticed red spots starting to pop up on his gums and belly. Uh-oh. Those red spots are called petechiae. This is a common consequence of heat stroke.
At temperatures over 109°F, the clotting system in the body starts to break down. Clotting factors are made in the liver, and like the rest of the body, they are sensitive to internal temperature. At 109°F, they no longer function. One of the earliest manifestations of this is red spots on the skin called petechiae. As those spread and merge into large patches, they are called ecchymotic hemorrhages.
Charles needed a plasma transfusion. Plasma is one component of blood. It contains important proteins including clotting factors. Most general practices do not keep plasma on hand. It is expensive and requires careful storage and handling. As a result, I knew we had to get Charles to the local referral hospital where they would have it, stat. But he had to be stable first!
We continued the fluids. My technicians checked his temperature regularly, as well as his blood pressure. Normal blood pressure in a dog is about 100, just like people. Charles was hovering around 75, so we still had work to do.
Nausea, vomiting, bloody diarrhea—side effects of heat stroke
After we started cooling him, I noticed that he seemed nauseated. The poor dog was licking his lips and drooling. The gastrointestinal tract cells are extremely sensitive to heat damage.
With heat stroke, the cells lining the stomach and small intestines start to die. This is a problem for two reasons. First, that lining is critical in maintaining a barrier between the intestines (full of bacteria) and the bloodstream (sterile—no bacteria!). Second, absorption of nutrients through the gut is critical.
When those cells are damaged by heat, nausea and bloody diarrhea often result. As the barrier breaks down, bacteria can enter the bloodstream. This leads to life-threatening systemic infection (called sepsis or septicemia).
Antibiotics, anti-nausea meds, and all hands on deck for the St Bernard
It was all hands on deck for Charles. I reached for antibiotics and anti-nausea agents. The antibiotics were critical for treating sepsis, and the anti-nausea medication would help Charles feel better.
When Charles first arrived and we placed the catheter, my forward-thinking technical staff had obtained blood samples from his catheter. We ran two tests on the in-house bloodwork machines—a complete blood count (CBC) and a chemistry panel. A complete blood count is exactly what it sounds like! The blood components—red and white blood cells and platelets are counted.
In dogs with heat stroke, alterations in these numbers happen fast. As expected, Charles’ platelets were low (the first step in the clotting cascade discussed above), and his white blood cell count had fallen as well. This is because of heat damage to the bone marrow, where those cells originate, but also because of the body’s overwhelming inflammatory response to heat stroke “tying up” those cells.
A chemistry panel evaluates the organs and electrolytes. Already, Charles had alterations in his kidney values—BUN and creatinine (elevated)—and his liver enzymes. His blood sugar was also dangerously low at 50 (normal range is 75-120). All of these changes are to be expected in dogs with heat stroke, as every organ in the body is damaged. Electrolytes (like sodium and potassium) can also be deranged, although Charles’ were normal.
I added dextrose, a synthetic sugar, to his IV fluids to bring his blood sugar back to normal. His temperature was down to 103°F, and my technicians had removed the fan and ice packs. It was time to transfer him to the referral hospital.
Five days of TLC and a full recovery
I strive to tell you stories of hope and happy endings, and Charles is one of those stories. Under our care and then the care of a 24-hour hospital, he survived. He received three units of fresh frozen plasma and remained hospitalized for five days on IV fluids, antibiotics, and GI protectant medications for his damaged gastrointestinal tract. His blood sugar levels fluctuated, and he needed dextrose supplementation to fuel is cells. His veterinary bill for the incident was several thousand dollars.
He could have died, and it’s a miracle that he didn’t.
There are two uplifting takeaways here: Charles survived AND heat stroke (in all but the rarest cases) is absolutely preventable. When the temperatures rise, there’s no need to risk it. Preventing heat stroke means avoiding risky situations in the first place, being mindful of your dog’s limitations, and knowing whether your dog is prone to heat stroke.
Which dogs are prone to heat stroke?
There are certain types and breeds of dogs that are more prone to heat stroke than others. If your dog falls into any of these categories, please take heed:
- older dogs that are overweight
- dogs with “flat” faces (called brachycephalic) like Boxers and Bulldogs
- dogs suffering laryngeal paralysis
- breeds that are not suited to hot environments such as Huskies
Keeping dogs cool, safe, and happy
Whether your dog falls into one of these at-risk categories or not, here are more important facts and helpful tips to keeping your dog cool, safe, and happy:
- In the summer, at-risk dogs should NEVER be exercised in the heat. Walks should be in the early morning, before the heat of the day, and at twilight or after dark.
- It goes without saying that dogs kept outside in the summer should always have access to shade and fresh, cold water. But, seriously, dogs in hot climates need to be brought inside to cool off!
- Never, never leave a dog confined in a car with the windows rolled up. Truthfully, it is safest never to leave a dog in a car, even with the air conditioner running. Recently, a colleague reported a client leaving two of their dogs in a running RV with the air conditioner blasting. They left for a few hours, and when they returned, the A/C had failed. Both dogs suffered heat strokes, and only one survived. Air conditioners break! It is always best to leave your dogs at home when running errands, unless you are visiting dog-friendly establishments.
- Dogs with laryngeal paralysis are also uniquely prone to heat stroke. This occurs because of upper airway obstruction. Since they cannot pant well and ventilate appropriately, they quickly become distressed. This is one of the most common reasons for a dog to have a heat stroke, second only to being left in a hot car.
- Overweight dogs can also overheat rapidly. This is because of excess body fat, which acts as an insulator and traps heat within the body.
- Arctic breeds such as Huskies and Malamutes are not suited to hot environments, yet they are frequently seen in places such as the deep South. This was part of Charles’ problem. He was a big, shaggy dog suited to the snowy mountains of the Alps, not in sweltering South Carolina in the summer! Knowing your dog’s limitations is a very important part of dog ownership.
- By simply keeping your dog cool, not exposing him or her to hot or humid conditions, and knowing your dog’s limitations, heat stroke is preventable. When in doubt, the best approach is to keep your canine companion safely at home in the air conditioning with plenty of fresh water!
As I said, I’m sure this is preaching to the choir, but please share this article to help educate other dog owners. With knowledge and information, we won’t need a stroke of luck to prevent heat stroke in dogs.
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