Westbury Animal Hospital
713.723.3666 · 4917 S. Willow Dr. Houston, Texas 77035 

 The Heat is On!

by: Dr. Alex Betzen

The (somewhat) cooler temperatures this week are welcome for Houstonians, but it’s still worthwhile to discuss heat prostration (heat stroke).  Heat stroke is seen in typically warm and humid environments.  Heat stroke is common in dogs, but rare in cats.  Basically, heat stroke occurs when the body creates more heat than it can remove.  Dogs with heat stroke often have temperatures greater than 106 F.  High temperatures can cause potential life-long injuries to organs (brain, heart, liver, and kidney).

            Veterinarians have two ways to categorize heat stroke.  The first category is the inability to remove heat.  This most often occurs in dogs with medical conditions (laryngeal paralysis, congestive heart failure, obesity, upper respiratory diseases) or dogs confined in small and hot environments.  A recent study from Stanford showed that on a 70 F day (pretty cool by Houston’s July standards!) found that the temperature inside of a car increased by an average of 40 degrees in the first hour!  With no air circulation, and usually no water, these dogs overheat extremely quickly.

Upper respiratory disease is especially important to consider in our “smushed-face” friends.  These dogs (French Bulldogs, Pugs, Bulldogs, Boston Terriers, etc.) have a more difficult time adequately panting than other dogs.  They can be very prone to heat stroke and need to be carefully monitored. 

The second category is called exertional heat stroke, which occurs from the excessive creation of heat.  This occurs most commonly in active dogs that push their bodies beyond the limit, but also occurs in dogs with seizure disorder, toxicities, or severe muscle spasms.

 

Signs of Heat Stroke

            Unfortunately, heat stroke can have a slow onset, can be difficult to detect and can show many different signs.  The degree of heat stroke typically correlates with the duration of the temperature elevation and degree of temperature elevation (i.e. the hotter and longer the animal is overheated, the worse the signs).  The most common signs of heat stroke are panting and elevated body temperatures.

            In the initial period, many dogs show some form of neurologic disease.  Affected dogs often have a “dull” or dazed attitude (mentation), appear weak and wobbly, collapse, have seizures and convulsions or even coma.  Dogs will have high respiratory and heart rates, and sometimes have changes in the sound of their pant.  Their gums may appear bright red or blue (cyanotic) and pulses are often weak.  Dogs that are in “shock” will have vomiting and diarrhea, often with blood.

            Bleeding can occur in other places as well, with small bleeding noted on gums and skin or in the urine.  If the dog has exertional heat stroke, the urine could be a very dark brown color.

            Several days (typically 3-5) after recovery, dogs can show signs of organ failure.  This typically manifests as decreased urine production (kidney failure), jaundice (liver failure), infections or sepsis, severe respiratory disease, widespread bleeding, or even sudden death from arrhythmias.

 

Diagnosis and Treatment

            If you suspect heat stroke with your pet, they need to see a veterinarian immediately.  This is a life-threatening medical emergency!  With a good history, and supporting clinical signs, your veterinarian will be suspicious of heat stroke.  Sometimes we can get tricked though, as dogs with severe heatstroke may have normal or below normal temperatures by the time we see them.

            We will often run blood chemistry profile to determine if there is any liver or kidney damage, or changes in electrolytes which help guide our therapy.  A Coagulation profile to determine if the body is clotting blood adequately is usually done as well. 

            If you suspect heat stroke, soak a towel in cool (not cold) water and wrap your dog with the towel.  Ice water can cause shivering (which raises the dog’s temperature) and also causes the blood vessels in the skin to constrict.  These blood vessels should be open and dilated during heatstroke.  This allows the blood to cool as it crosses the skin.  Ice water would prevent this very important function! 

Transport your dog to a veterinary hospital immediately!  Once there, we’ll recheck a temperature and continue the active cooling, typically with IV fluids, wetting the fur, and placing the dog in an area with fans to allow for evaporative cooling.  We need to be very careful though, because these dogs are very prone to hypothermia from overzealous cooling.

            If your dog is in shock, it may need a breathing tube, oxygen, supplemental electrolytes, glucose (sugar), medications for seizures or arrhythmias, and medications for the edema (swelling) that can occur in the brain.  If the clotting tests are abnormally high, a plasma transfusion may be considered.

            Dogs are typically hospitalized for 2-3 days for monitoring after a successful recovery for us to monitor blood pressure, pulse quality, gum color, blood oxygen levels and other vital parameters.  Repeat blood work or radiographs may be performed to monitor for organ damage.

            The prognosis for heat stroke is dependent on the severity and length of time in the heat.  Dogs with mild signs of heat stroke often recovery very well.  Unfortunately, comatose dogs, or those with liver or kidney failure or unresponsive bleeding, are very difficult to save.

 

Conclusion

Heat stroke can occur in any dog, but there are certain medical conditions and breeds that make it more likely to occur.  In Houston’s humid and warm environment, it is important to remember that heat stroke can occur without much warning and is life-threatening.  However, warm and humid environments aren’t all that is required for heatstroke.  Dogs showing signs of heatstroke should see a veterinarian immediately, and if you are suspicious, start active cooling at home!

While working in San Diego, I saw two dogs come in for heat stroke on days with temperatures in the mid-70’s.  One dog was playing ball at the beach and doing lots of swimming, while the other dog was running with his owner.  While both dogs did very well, they serve as important lessons.  As anyone who’s done competitive swimming, triathlons, or laps in a pool can tell you, swimming in a pool will raise your body temperature and you’ll be hotter than you think when you get out of the water.  Dogs that are swimming are still prone to heatstroke.  And even with temperatures in the 70’s, dogs going for prolonged jogs can still get heat stroke.

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