I'm becoming all too familiar with heat stroke.  The bulk of our Emergency Clinic caseload increase this summer has seen dogs hit by cars and dogs with heat stroke.  We've lost two dogs in the ER, one about 45 minutes after arrival, the other a couple of hours later.  Both had temperatures too high to register on the thermometer so over 109F.  A few others have died before arriving at the clinic.  It's interesting to note that we get more cases when the air temperatures are upper 70s to upper 80s than when they're above 90.  My theory is that people are more aware of their pets' comfort when they themselves are uncomfortable.  I've suggested that the humane society make a public service message for TV next summer showing people throwing Frisbees, jogging, even lounging by the pool.... all while wearing fur or down coats!

One thing to remember is that heat stroke doesn't only occur with long exposures to heat and humidity.  It can occur through excessive activity in a short period when the animal isn't used to particular environmental conditions.  The first heat stroke case I worked on occurred in late November during an unusually warm spell of upper 60s, when a hunting dog was brought in.  Young and old dogs are more susceptible as are obese or dehydrated dogs.  (There are other disease or physical causes, not included here).

A dog is determined to have heat stroke when the rectal temperature is greater than 104.9F (40.5C).  Symptoms include excessive panting, excessive drooling, lethargy, muscle tremors, vomiting, diarrhea, unsteady gait, collapse, loss of consciousness, seizures, coma, and death.  The prognosis of recovery from heat stroke is guarded to poor.

Complications of heat stroke may include kidney damage, liver damage, cardiac arrhythmias and arrest, respiratory arrest, gastrointestinal ulceration, blood coagulation problems, nerve tissue damage, and permanent brain damage.  These signs can develop 3-5 days after the animal appeared to recover.  A vet can run various tests, though, to determine the extent of the physical damage caused by the heat stroke to include blood chemistry, complete blood count, urinalysis, and coagulation profiles.

The most important thing to do right away is to lower the core body temperature.  Get the animal into shade or indoors to a cool area.  Wet the coat down and then ideally fan it to help with evaporation.  Don't use ice and don't leave it in a tank or tub.  Both cause peripheral blood vessels to constrict and decrease the heat exchange from the blood to the atmosphere.  It's also possible to cool an animal too fast.  When the body temp drops below 102F/39C, the animal can start shivering and that produces more heat.  Massaging the animal after wetting can also help disperse heat because it increases blood circulation. 

In an ideal situation, while one person is wetting the dog down, another is calling the vet to let them know there is an emergency and getting the car for transport.  It's important not to delay arrival to the hospital.  If the vehicle is hot, leave the window down initially with the air conditioner blowing.  Once the air conditioner is blowing cold air, roll the windows up. 

At the vet's office, the personnel will continue to cool the animal and monitor the body temperature, making sure not to go below 103F.  If necessary, oxygen will be supplemented by a mask or intubation.  Once the temp is down, the animal may need to go into an oxygen tank.  Fluid support is given in most cases to reverse dehydration and support renal function.  Lab tests can be run to determine the extent of the damage.  Any complications will be treated.

The animal will be closely monitored during the cooling down period and should be watched for at least 24 hours.  It may need several days depending on complications.

Heat stroke is extremely serious.  It is also much easier to prevent than it is to treat.