Summer Safety Tips for Pets: Heatstroke

posted: by: Christina Miller RVT, BSc Tags: "Clinic Specials" "News" 

Summer in Nova Scotia is wonderful, but our pets are exposed to some unique hazards that aren't around the rest of the year. Here's a refresher on some summer hazards to watch out for to keep your companion animals safe and healthy.

Summer Heat and Heatstroke

Our pets can suffer from heatstroke just like we do, and many pets will heat up faster because of their furry coats acting as insulation. Brachycephalic breeds that have a shortened facial conformation (dogs such as Pugs, Cavalier King Charles Spaniels, Shih Tzus, Lhasa Apsos, and others, and cat breeds such as Himalayans and Persians) are at a greater risk of developing heat stroke because their upper respiratory tract anatomy does not allow for efficient cooling compared to other breeds. Dogs and cats that are too warm will move away from the heat and may drink more. Dogs will pant to disperse heat, and have some ability to "sweat" through the paw pads. Cats also sweat through their paw pads, but they are less efficient than dogs because of the relatively smaller paw pad area. Cats may also pant, but this should always be taken as a sign of distress! A panting cat typically needs emergency care, as it suggests that they are reaching a dangerously high body temperature (unlike in dogs who typically pant to "prevent" themselves from becoming too warm), and can even occur in cats who have been hiding underlying heart or lung disease.

Heatstroke, or non-malignant, non-fever hyperthermia, occurs when the pet's normal behaviours for reducing body temperature cannot compensate for the extra heat. Normal body temperature ranges vary a little bit depending on your reference, but commonly quoted normal ranges are 37.5-39.0 C in dogs and 38.0-39.5 C in cats (Veterinary Information Network 2013). While pets are typically going to start trying to cool down when they're in the high end of that range, heatstroke is generally accepted to occur when the body reaches 41 C (PetMD 2017).

Heatstroke is a serious condition that needs emergency medical attention. Our bodies run a very tight ship when it comes to body temperature, and many systems fail when that temperature drops too low or is raised too high. Some of the physiological changes seen with heatstroke include (Veterinary Information Network 2007):
  • The heart has to start working harder to pump blood, because heat causes peripheral blood vessels to dilate. Blood leaves the general circulation and begins pooling in the pet's internal organs, resulting in a decrease in blood pressure (hypotension). This decrease in blood pressure contributes to quicker heating of the pet, as cooling mechanisms like sweating and panting become less efficient.
  • Excessive panting leads to a condition called respiratory alkalosis. The blood buffer system is complex, but basically, excessively fast breathing (tachypnea) contributes to a change in blood composition that results in compensatory mechanisms, eventually causing a metabolic acidosis. This imbalance creates further physiological changes.
  • An increased core body temperature leads to cell death because the proteins that make up the body's tissue start to denature (they begin to "cook"). This includes cells of important internal organs: Kidney failure and damage to the lining of the intestines occur, among other damage.
  • Clotting disorders (coagulopathies) occur because the clotting proteins become denatured, and liver damage prevents more from being manufactured by the body.
  • Cerebral edema (swelling of the brain due to fluid accumulation) occurs because of cellular damage. This results in coma and brain death.
This is all very serious, so recognizing the signs of heatstroke early is critical (Veterinary Information Network 2007, PetMD 2017):
  • Panting and excessive drooling (ptyalism).
  • Sudden bright red colouration of the oral mucosa (gum tissue) and other moist tissues, like the conjunctiva (pink, moist tissue around the eyes and under the eyelids).
  • Rapid and/or irregular heartbeat: Normal heart rate varies depending on the species, breed, and age of the pet (Veterinary Information Network 2013).
        Cats (young): 130-140 bpm (beats per minute)
        Cats (adult): 100-120 bpm
        Dogs (young): 110-120 bpm
        Dogs (small breed, adult): 80-120 bpm
        Dogs (large breed, adult): 60-80 bpm
    Taking a heart rate can be done by feeling the heart over the rib cage. A nice anatomical marker is to feel where the elbow naturally sits over the side of the chest wall. Count the number of heart beats felt over 15 seconds, and multiply this by 4 to give you beats per minute.
  • Changes in mental status, like sleepiness, drowsiness, or lethargy.
  • Poor coordination or lack of coordination (ataxia), "drunken" or "wobbly" gait.
If you suspect that your pet is suffering from heatstroke, prompt emergency treatment is critical. Call our hospital at (902) 434-3111 for further instructions. Outside of our regular office hours, contact Metro Animal Emergency Clinic at (902) 468-0674. Remove your pet from the heat immediately. You may start cooling your pet down by gently spraying him or her with cool water, and/or wrapping his or her body in cool, water-soaked towels. Do not use cold water or ice water, as this causes peripheral vasoconstriction (blood vessels in the skin become smaller), making your cooling efforts less efficient. Cooling efforts need to slow down or stop when your pet's rectal temperature reaches 39.0-39.4 C, which may be difficult to take in pets at home.

Getting your pet to the veterinary hospital quickly is critical: Our team may need to administer further emergency care such as intravenous fluids and cool water enemas to reduce your pet's core body temperature. Intravenous fluid therapy may also be necessary to help support the body's tissues because of the severe physiological changes from heatstroke. Depending on the severity of heatstroke, some pets may need to remain hospitalized for several days.

Unfortunately, we sometimes only see the real damage from heatstroke 24-72 hours after the incident. Your pet's doctor will advise you depending on your pet's situation.

Prevention is always the best "cure." Keep these tips in mind with your pets during hot summer days:
  • Keep pets indoors during the warmest parts of the day, typically from 11:00 AM to 3:00 or 4:00 PM. Short trips outside to "do their business" are fine, but exercise including walking and running should be avoided. Try to walk dogs during dawn and dusk hours when the temperature is cooler outdoors.
  • Always ensure that your pet has access to fresh water in a dish that is accessible. Tall dogs or dogs with arthritis often benefit from raised water dishes, and cats often prefer water fountains to dishes (but every cat has their preference!). Some pets will enjoy ice cubes in their water dish to keep it cool. You can also try freezing a small amount of water in the bottom of the dish, then adding cool water on top can keep the water chilly for several hours.
  • Never leave pets unattended in the car on a hot day. Even with the windows "cracked," even with the car parked in the shade, cars heat up very rapidly and heatstroke can occur within minutes. Every year, veterinary practices and humane societies have public awareness campaigns to prevent more of these deaths from occurring, yet every year it keeps on happening.

    Estimates for how long it takes your car to become dangerously hot vary, but they are always very worrisome:
    -If it's 21 C outside, after 10 minutes your car will be 32 C inside, and after 30 minutes it will be 40 C inside.
    -If it's 24 C outside, after 10 minutes your car will be 34 C inside, after 30 minutes it will be 40 C inside.
    -If it's 27 C outside, after 10 minutes your car will be 37 C inside, after 20 minutes it will be 46 C inside.
  • Remember that brachycephalic ("short-faced") breeds, senior pets, pets with heart and/or lung disease, and overweight/obese pets are at a greater risk of developing heatstroke. Be extra careful with these animals.
Please do not hesitate to talk to your pet's veterinary team if you have any further questions or concerns.