Hyperthermia is an elevation in body temperature that is above the generally accepted normal range. Normal ranges do vary in dogs, but generally speaking, this means a body temperature above 39°C (103 °F). 

Hyperthermia is semantically different from the definition of a fever. Fever is the body’s response secondary to elevated body temperature and is designed to create an environment in which viruses or bacteria can’t survive. Hyperthermia, on the other hand, is often due to environmental factors or secondary accidental causes. For example, exercises your dog on a warm sunny day. 

What causes hyperthermia in dogs? 

Hyperthermia can affect any breed of dog but is more frequent in longhaired dogs and short-nosed, flat-faced dogs (also known as brachycephalic breeds). It can occur at any age but tends to affect young dogs more than old dogs. 

Causes include:

• Excessive environmental heat and humidity (hot days, inadequate shade or being enclosed in an unventilated room or car)
• Upper airway disease that inhibits breathing (includes the nose, nasal passages, throat, and windpipe)
• Underlying disease (e.g. paralysis of the voice box or larynx; heart and/or blood vessel disease; the nervous system and/or muscular disease; previous history of heart-related disease)
• Poisoning (e.g. strychnine and slug and snail bait)
• Anaesthesia complications
• Excessive exercise
• Inadequate drinking water

What to look for in your dog 

Hyperthermia can be categorized as either fever on non-fever hypothermia’s; with heatstroke being a common form of the latter. Symptoms of both types include:

• Panting
• Dehydration
• Excessive drooling
• Agitation/restlessness
• Increased body temperature (39 degrees celsius)
• Lethargy/weakness 
• Small amounts of urine or no urine
• Rapid heart rate
• Reddened or pale gums and moist tissues of the body
• Bright red tongue
• Black, tarry stools
• Changes in mental status (delirium)
• Irregular heart rate
• Muscle tremors
• Seizures
• Wobbly or drunken movement
• Sudden breathing distress
• Shock
• Vomiting blood
• Blood in stools
• Unconsciousness 

Preventing hyperthermia in dogs

Dogs can’t respond to heat in the same way that we humans do. We have sweat glands all over our bodies that help us to regulate our temperature but dogs only have a few in their feet and nose. That’s why dogs rely on panting and external cooling to lose heat. 

Pup Junkies advise: “Because dogs can’t cool themselves down as well as us it’s important that you be extra careful to provide them with a cool, well-ventilated and shaded environment with access to clean, fresh drinking water. Dogs are very susceptible to hyperthermia (especially in summer) and it can happen a lot faster than you may think.” 

As well as good ventilation, shade, and water you should:

• Never leave your pet in a car (temperatures rise extremely quickly even on cooler days)
• Avoid exercising your dog in hot weather
• Avoid hot sand, concrete, asphalt areas or any other areas where heat is reflected
• Be aware of symptoms and look out for the signs in your dog

Hyperthermia is a very serious, life-threatening condition. It can cause damage to your dog’s internal organs, sometimes to the point where they stop functioning. This requires urgent treatment before it becomes fatal. 

Author Bio: Luke Fitzpatrick has been published in Forbes, Yahoo! News, and Influencive. He is also a guest lecturer at the University of Sydney, lecturing in Cross-Cultural Management, the Pre-MBA Program and is proud to be a dog owner. You can connect with him on LinkedIn.