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Hyperthermia in Dogs: It's Not a Fever

Posted November 03, 2014 in Dog Diseases & Conditions A-Z

Dog panting

Hyperthermia in dogs, which is defined as a temperature greater than 103.5°F (39.7°C), is semantically different from the definition of fever. Hyperthermia is typically an elevated body temperature secondary to exogenous (i.e., outside) causes versus the endogenous (i.e., internal) causes that cause fever. To clarify:

  • Fever is the body’s response secondary to cell mediators or signals that create an elevated body temperature; this is designed to create an environment in your body that is unsuitable for viruses and bacteria to survive.
  • Hyperthermia is different from fever; it’s often due to environmental factors or secondary accidental causes.

Causes of hyperthermia in dogs

  • Not being able to pant efficiently to blow off heat. This may be seen secondary to airway problems like laryngeal paralysis or brachycephalic syndrome. Dogs actually can sweat, but not very much; click here to learn more.
  • Factors that predispose to heat stroke including obesity, airway breathing problems (e.g., laryngeal paralysis), inappropriate exercise (in excess, in hot or humid weather conditions), dark-colored fur, etc.
  • Toxin exposure. Certain toxins cause tremors that result in secondary hyperthermia such as compost, moldy food, snail and slug bait, antidepressants, ADD/ADHD medications, chocolate, etc. Other types of toxins cause the body to develop inappropriate hyperthermia without the tremors – this can be seen with used hops poisoning (from homemade brewing kits).
  • Certain drugs. Rarely, certain veterinary anesthetic drugs can cause malignant hyperthermia in dogs. While this is very rare, it’s one of the reasons why we veterinarians so carefully monitor the body temperature after sedation or general anesthesia. Certain breeds such as greyhounds and Labrador retrievers may potentially be more at risk.

Treatment of hyperthermia in dogs
Prompt treatment for hyperthermia is necessary; if the body temperature exceeds 105-106°F (40.6—41.1°C), it can result in cellular injury to the body. Clinical signs of hyperthermia are similar to heat stroke and may include:

Untreated, hyperthermia can result in secondary complications such as disseminated intravascular coagulation (DIC) and organ failure. Prompt treatment is necessary in order to ensure survival.

Treatment includes:

  • Aggressive cooling down to a temperature of 103.5°F (39.7°C)
  • Thermoregulation
  • Cool intravenous (IV) fluids
  • Blood work monitoring
  • Anti-vomiting medication
  • Anti-diarrheal medication
  • Plasma transfusions
  • Antibiotics
  • Blood pressure and heart rate monitoring
  • Symptomatic supportive

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Justine has more than 18 years of experience in the veterinary industry and is a board-certified emergency critical care veterinary specialist and toxicologist as well as the CEO and founder of Vetgirl. She is also a founding member of IDEXX’s Pet Health Network team.