Heatstroke in Dogs

This article is written by Pet Circle veterinarian, Dr Brittany Ward BVSc

When we think of Summer with our dogs, we often think of beach trips, fun in the sun and Christmas celebrations. Have you thought about heatstroke though? Overdoing it with your dog in the hot weather can cause a potentially life threatening rise in their body temperature and land them with a hospital stay. Heatstroke is a medical emergency.

This article looks at Heatstroke, how it occurs, what the signs are and how you can prevent it from happening to keep your dog happy and healthy during the hot months ahead.

Contents:
Understanding Heatstroke
Signs and Symptoms of Heatstroke
Causes of Heatstroke
Diagnosis of Heatstroke
Treatment of Heatstroke
Recovery and Management Post-Heatstroke
Preventing Heatstroke
Heatstroke FAQs

Understanding Heat Stroke

Heatstroke is a common term used to describe hyperthermia, or a body temperature that has risen above the normal level. A dog's normal body temperature is 38.0-39.0 degrees celsius and temperatures higher than this are considered abnormal, warranting intervention. If your dog's body temperature exceeds 41.1 degrees, the body's organs start to fail and neurological symptoms can present.

Our dogs do not sweat the same way we do, they only have a limited number of sweat glands between their paws. Instead, their primary method of cooling is by panting. When panting is insufficient to cool them, their body temperature can quickly rise, leading to hyperthermia. Panting is most effective when the ambient temperature is 32 degrees Celsius and can actually increase body temperature during high humidity (greater than 80%). Panting is a form of evaporative cooling, meaning that water is also lost during the process and it can lead to dehydration if excessive.

Heatstroke can progress rapidly and can cause death in as little as 15 minutes, so it is important to monitor your dog for any signs and respond quickly. Every second counts and the longer your dog's temperature is raised the more severe effects can be. The longer the body temperature is elevated and the higher the temperatures, the higher the risk for long term health problems or death.

Hyperthermia is classified into three categories depending on its severity:

Signs and Symptoms of Heatstroke

It is important to recognise heatstroke quickly to ensure the best outcome as it can quickly progress to death. There are a number of signs and symptoms that you can look for in your dog.

Causes of Heatstroke

There are many possible reasons why your dog's temperature may become elevated and any dog may be affected by heatstroke at any time of year. We can group the causes into two main categories though.

Environmental Factors

Environmental factors are those around us that affect our body temperature; such as the summer heat and humidity. Factors such as ventilation, shade, access to water, excessive exercise and enclosed spaces can all increase your dog's risk of heatstroke. Your pet may also be more susceptible to the heat if they have not yet acclimatised to the area you live in; they can take up to 60 days to acclimatise.

One of the leading causes of heatstroke is leaving dogs in the car without adequate ventilation, which can allow their temperature to rise within minutes. Similarly, being enclosed in a house or garage without air conditioning can also cause heatstroke. Even leaving them in an enclosure or yard without adequate shade, ventilation or water access could put your dog at risk.

If your dog requires to be muzzled for any extended period of time and has an incorrectly fitting muzzle, they may not be able to pant correctly, leading to hyperthermia.

Predisposing Internal Factors

Internal factors are any factor related to your dog, particularly in relation to their breed and health status. These are physical features or illnesses that may predispose your dog to heatstroke.

For example, puppies and senior dogs are predisposed to heatstroke.

Some dog breeds are more likely to experience heatstroke, including large breed dogs and those with thick or long coats that can retain heat, such as Huskies and Pomeranians.

Brachycephalic (short-nose or flat-faced breeds) are overrepresented in heatstroke cases. This includes, French Bulldogs, Pugs and Boxers. These breeds have small, narrow nostrils, elongated soft palates and narrow airways that can make it difficult for them to self cool. They are 146% more likely to experience heatstroke compared to longer nosed breeds.

Overweight and obese dogs have a significantly increased risk of heatstroke because fat acts as an insulator and they generate excess heat during exercise, tiring more quickly. Overly active, working and hunting dogs like Labradors and Kelpies are also predisposed, particularly if they continue to be active and exercise for prolonged periods of time or during the heat of the day.

A number of health conditions can also increase the risk of heatstroke, such as heart disease and neurological disorders. Because canine cooling is heavily reliant on the respiratory system, respiratory disorders, like laryngeal paralysis or tracheal collpase are also predisposing factors. Infections causing fever (pyrexia) and seizures or tremors can also raise the body temperature, progressing to hyperthermia.

Diagnosis of Heatstroke

Your veterinarian will make a diagnosis of heatstroke following an examination based on their symptoms, a history of exposure and their body temperature. Information you provide to your vet about the events preceding your dog's symptoms can be critical for making an accurate diagnosis.

Remember that health conditions such as infection and seizures can also raise the body temperature and your vet will want to rule out these as an underlying cause for their hyperthermia.

Treatment of Heatstroke

Heatstroke can be fatal and is considered a medical emergency! Your dog requires immediate attention and the sooner they get to a vet, the better their prognosis. However, you will need to start the cooling process before transporting your dog.

First Aid

If your dog is showing any of the above signs of hyperthermia, follow the below steps to help your dog start cooling down on the way to the vet clinic.

Veterinary Treatment

Once you arrive at the clinic, your vet will examine your dog and start or continue emergency cooling. They will start intravenous fluids to manage dehydration, shock and cool the body internally. Oxygen therapy will also be started.

For patients with respiratory difficulties or that are unconscious, anaesthesia and intubation may be used to ensure sufficient oxygen intake. Gastroprotectants or anti-nausea medications may be started for patients with vomiting and/or diarrhoea. Antibiotics may also be given to prevent a secondary infection. If required, your vet may also use cardiac medications.

Once cooling is in effect, your vet may recommend blood tests to assess the level of dehydration, look for clotting issues, assess organ function and determine the success of treatment. Prolonged hyperthermia can lead to clotting disorders and internal bleeding, so it is important to assess for these. If your dog has developed clotting problems, a blood or plasma transfusion may be required.

Heatstroke DONT'S

If your dog has heatstroke, NEVER use ice or ice water to cool them down. Ice and cold water will cause the blood vessels to constrict, retaining heat. Room temperature or cool water is best. If you are using air conditioning, this should also be kept at a comfortable, ambient temperature, such as 24-26 degrees Celsius to avoid cooling too quickly. Cooling too quickly can cause Hypothermia.

NEVER place a wet towel or cloth over your dog. These will absorb the heat from their body and create humidity, further raising your dog's temperature.

Recovery and Management Post Heatstroke

Once your dog has been cooled down, they will be hospitalised and closely monitored. Depending on the severity of the heatstroke, they may remain in Intensive Care until they have fully recovered. Early diagnosis and prompt, aggressive treatment are essential factors in determining prognosis. Heatstroke is generally considered to have a poor prognosis and because of the severe effects on the body, may be fatal or cause permanent damage even despite treatment.

Temperatures higher than 41 degrees Celsius or prolonged high temperatures can denature (breakdown) the proteins in cells and cause cellular damage. Proteins are essential for cell structure and many of our body functions, so their breakdown can lead to multiple organ failure and systemic shock. The more organs affected, the poorer the prognosis for the patient.

The higher the temperature your pet's body elevates to and the longer they are exposed impacts the likelihood and severity of the above systemic effects. The first 24 hours are the most critical, and pets surviving this period are likely to recover. Most surviving cases do recover without long term complications. Your dog will likely remain in hospital for 2-3 days, up to a week in more severe cases.

Once your dog is discharged, they will need lots of rest, to be kept at a comfortable temperature and plenty of TLC, for at least the first two weeks. Your vet may also request to do repeat blood tests 1-2 weeks post treatment to assess if any permanent damage has occurred and if any ongoing care is required.

Pets that have experienced heatstroke are susceptible to repeat episodes. Increased body temperatures can damage the natural temperature control system in your dog's body. This means they can no longer regulate their body temperature as well as before and the body temperature could easily elevate if they are in a hot environment. Ongoing prevention is even more important for past heatstroke patients.

Preventing Heatstroke

Preventing heatstroke is all about keeping your pet cool! Prevention is important for all dogs, but especially if you have a high risk breed. Here are some simple tips for preventing heatstroke in your dog.

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Providing Enrichment and Exercise

Even though it is hot out, your dog still needs plenty of mental and physical stimulation to prevent them resorting to destructive behaviours for entertainment. So what activities can you do without risking heatstroke?

Scent Games

Scent games are a great indoor activity that is mentally challenging for your dog and a lot of great fun to play! Dogs love to engage in this kind of training as it simulates their natural hunting instincts and it's a great way to strengthen your bond with your dog. There are lots of scent game options, such as Seek, Find The Food and Identify the Smell, you just have to start searching and training. Who knows, your dog may even be able to find your house keys next time you lose them!

Swimming

Why not try swimming? Swimming is an excellent summer activity. Avoid going in the hottest part of the day or use a pool that has been kept in the shade to help your dog cool down. Swimming is also great for assisting weight loss and providing low impact exercise for arthritis.

Keep in mind if you have a Brachycephalic, or pushed in face, breed, Swimming may not be a safe activity for them. Dogs will need to hold their head above water to continue to breathe while swimming, but for Brachycephalic breeds this may reduce their airflow. Water play with a sprinkler or a shallow body of water would be a great, safer alternative.

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Interactive Toys and Puzzles

Puzzles and interactive toys are the perfect way to keep your dog occupied while they are cooped up on a hot day. These activities provide mental stimulation, which is more tiring than physical activity, as well as gentle exercise. They can keep your dog distracted for an extended period of time, within the comfort of your own home or in a shaded area of the yard.

For more information about the range of puzzle toys available, how to use them and their benefits, check out our articles Boredome Busters for Dogs and The Benefits of Puzzle Feeders.

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