Heat Stroke in Dogs: Symptoms and Treatment

by: Laura McLain Madsen DVM

What is heat stroke in dogs?

Heat stroke in dogs is the final stage on a spectrum of heat-related illness, and can be rapidly life-threatening. The first stage is heat exhaustion, in which the blood vessels in the skin dilate to try to release excess heat. This diverts blood away from the internal organs and brain and causes weakness and dizziness. When heat exhaustion progresses to heat stroke, the dog loses its ability to compensate and can rapidly go into multiple organ failure.

How does it happen?

Dogs don’t sweat like humans, so they dissipate heat primarily by panting. When the moisture of the tongue evaporates it takes body heat away. Minor ways a dog can dissipate heat are through radiation (radiating heat from the skin, although the fur tends to block this), conduction (resting on a cold surface) and convection (a breeze).

Anything that decreases their ability to dissipate heat can lead to heat stroke in dogs. Factors include hot weather, high heat index, high humidity (making the evaporation of panting less effective), being muzzled, being locked in a hot car, strenuous exercise, lack of acclimation to hot weather, or dehydration.

Which dogs are at risk?

Various factors can make a dog more susceptible to heat stroke. Flat-faced dogs, like English and French bulldogs, pugs, and Boston terriers, have trouble breathing in even the best of circumstances and aren’t able to pant as effectively as other dogs. Dogs with laryngeal paralysis (paralysis of the muscles in the throat) or collapsing trachea (windpipe) also can’t pant as effectively. Dogs with thick hair, dark-colored fur, obesity, pre-existing heart or lung conditions, or old age are also at higher risk.

What happens to a dog with heat stroke?

In heat stroke, the body temperature can get very high, above 108 degrees F. (The normal body temperature for dogs is 100.0-102.5 degrees F.) When the body temperature rises above 107, many changes occur in the body including cell death. Damage to the cells of the organs and brain leads to kidney failure, sloughing of the intestinal lining, heart muscle damage, liver failure and brain damage. The heat also inactivates proteins like clotting factors, leading to uncontrollable bleeding. A serious complication is DIC (disseminated intravascular coagulation), in which there are both blood clots and hemorrhage.

Unfortunately, death can occur very rapidly in heat stroke. If a dog is trapped in a closed car death may occur within 30 minutes to an hour.

What are symptoms of heat stroke in dogs?

Early symptoms of heat stroke in dogs are rapid heart rate, excessive panting, vomiting, diarrhea and weakness. When you lift the dog’s lips, the gums will be hot, dry and dark pink or red. If your dog is showing these symptoms, immediately move him to a cool location out of direct sunlight.

If heat stroke worsens, later symptoms include mental depression, stupor, collapse, pale or gray gums, bruises on the gums or belly, bloody vomit, bloody diarrhea, raspy breathing, seizures, coma and death.

In humans, the definition of heat stroke includes altered mental status. Fortunately, dog brains are more resistant to high heat than human brains, so the mental state may be normal in a dog with heat stroke.

How is heat stroke diagnosed?

Heat stroke in dogs is diagnosed on the basis of exposure to a hot situation, symptoms, and laboratory testing. The body temperature is always elevated initially, but may decrease to normal or even below normal if the dog is going into shock. Your veterinarian will likely recommend blood and urine tests to look at liver and kidney function, white and red blood cell counts, blood sugar, electrolytes, and clotting factors. These tests will usually need to be repeated throughout treatment to assess response.

What is the treatment for heat stroke in dogs?

Treating Heat Stroke in DogsIf you suspect your dog may be suffering from heat stroke, immediately hose him off with cool water and get him to a veterinarian as soon as possible. It’s crucial that treatment begin rapidly, because the dog’s condition will quickly deteriorate. Even if the dog seems to improve after cooling off, it’s still very important to take him to a veterinarian, as there may be damage to the internal organs that will continue to worsen.

Depending on the severity of heat stroke, treatment can be very intensive and prolonged. The body temperature needs to be brought back down by bathing the dog in tepid to cool (not cold) water. Some veterinarians will also use a cool water enema or even cool sterile fluids infused into the abdominal cavity. The cooling process needs to be done carefully, monitoring body temperature frequently. Cooling measures are stopped when the temperature reaches 103 degrees to prevent “overshooting” hypothermia. Cold water or ice baths should not be used because the extreme cold causes the skin vessels to constrict, which actually slows heat loss.

Most heat stroke patients will require:

* Oxygen to help the dog breathe more easily. Supplemental oxygen is delivered via a special cage, mask or nasal tube.

* Intravenous fluids to treat shock and prevent kidney failure.

* Stomach protectants due to the significant damage to the lining of the stomach and intestines: famotidine (Pepcid®), sucralfate (Carafate®).

* Antibiotics. When the intestinal lining cells are destroyed, bacteria from the intestines can enter the bloodstream and lead to septic shock. Typical antibiotics used are ampicillin, enrofloxacin (Baytril®), and metronidazole (Flagyl®).

Other treatments that may be needed on a case-by-case basis include:

* Anti-nausea medications: maropitant (Cerenia®), metoclopramide (Reglan®).

* Mannitol, a drug to prevent swelling in the brain.

* Medications to enhance kidney function if kidney failure is present: furosemide (Lasix®), dopamine. In addition, a urinary catheter may be placed to monitor the exact amount of urine being produced to make sure the kidneys don’t shut down.

* Liver support if liver failure is present: SAMe (s-adenosyl-methionine, Denosyl®, which promotes liver cell regeneration and detoxification).

* Blood transfusions if the dog is anemic from blood loss.

* Plasma transfusions if the clotting factors have been destroyed or used up.

* Hetastarch, a synthetic protein to support blood pressure and cardiovascular function.

* Oxyglobin®, a modified hemoglobin to increase oxygen delivery to tissues.

Heat stroke patients will typically be hospitalized for at least 24 hours to monitor vital signs (temperature, pulse, respiration, blood pressure), blood sugar, electrolytes, kidney and liver function, and coagulation parameters.

What is the prognosis?

The prognosis with heat stroke is guarded. One study found the overall mortality to be 50%. Even with prompt treatment, some dogs will deteriorate and die. The prognosis is better for dogs who are quickly removed from the hot situation, cooled at home with cool water, and promptly transported to a veterinarian. If the dog is already showing evidence of low blood sugar, kidney failure, seizures or bleeding when it arrives at the veterinary hospital, the prognosis becomes much worse.

How can heat stroke in dogs be prevented?

If your dog will be outdoors in warm weather, make sure he has access to shade and water. Don’t ever leave a dog alone in the car, even just for a few minutes. Temperatures inside a closed car in the summer can quickly reach over 130 degrees F. In hot weather only exercise your dog in the cooler mornings or evenings, not in the afternoon. Acclimate your dog to exercise. Keep smush-faced dogs like bulldogs in a cool environment.

If a dog has recovered from an episode of heat stroke it can reset the body temperature “thermostat” in the brain, making the dog more prone to future episodes of heat stroke, even at less extreme temperatures. For this reason, any dog who has survived heat stroke should be monitored very closely and kept out of hot environments life-long.

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