Heat stroke or hyperthermia to use it’s correct name, is a body temperature that is so far above normal that physiological processes are subject to damage and dysfunction.
The damaging effects of hyperthermia can be transient or permanent and may cause sudden death.

The effects on dogs, cats man and any other life form depends very much upon time and temperature. The higher the temperature and the longer the hyperthermia persists, the more damage it causes.

HEAT STROKE. It might only be ten minutes and your dog (or cat) will be near death. Even if heroic treatment measures are taken the animal may die from massive intra vascular clotting, haemorrhaging, cerebral oedema and kidney failure.
It is not a pleasant thought but, every day, dogs suffer heat stroke as a result of inattention by their owners. Most cases see the pet left for “only a moment” …. but for various reasons the pets owner is distracted or delayed beyond what they expected. They return to their car and find their pet in a collapsed state, salivating, panting uncontrollably and losing consciousness. DO NOT LEAVE YOUR PET IN A LOCKED, UNVENTILATED CAR.

It takes minutes for the internal heat in a car to increase forty degrees above the outside temperature, especially in direct sunlight. Even a dogs body heat (expired air in the dogs breath is 102 degrees and has 100% humidity) can act like a heater inside an enclosed space.

Pets left in unventilated cars are severely disadvantaged at being able to dissipate heat from their bodies.
Even in the shade, and especially in humid conditions, dogs need to inhale air cooler than their normal body temperature of 102 degrees (100.9 - 101.7f).
Heat stroke is a 100% emergency and one from which many pets do not recover. You would be shocked to discover just how quickly it’s onset can occur!!!!!
IF YOU EVER FIND YOUR PET DISTRESSED FROM OVERHEATING AS A RESULT OF BEING LEFT IN A CAR SEEK VETERINARY HELP IMMEDIATELY.


WHAT IS HEATSTROKE All living cells have temperature tolerance limits. Beyond those limit’s, the cell begins to break down thus losing functional capacity. Chemicals are released within the cell which create more adverse reactions until, eventually, the cell ceases to function and dies.

Tolerance to high temperatures for mammals breaks down at around 107 degrees and the death of the cell, (that state where the traumatised cell cannot recover from the heat injury), occurs when time and temperature factors combine to terminate the cells integrity. Above 107 degrees the less chance there is for the cell to recover and the higher the temperature becomes over that level the faster cell death occurs.
In pets confined to a space where the surrounding temperature and humidity are above tolerable levels the animals body will begin to acquire heat from the environment faster than it can dissipate that heat.

When we as humans overheat, we begin to sweat ( or, in the case of you ladies out there, perspire) which in turn evaporates ( unless the humidity is 100% ) thus cooling the skins surface and assists in dissipating that heat.
Dogs and cats have very few sweat glands and so the only means of dissipating body heat is by panting.

This is an inefficient means of dissipating body heat and actually generates more heat due to the muscle activity involved. Bear in mind that, as an animal is confined to a closed space, the expired air, which is at 100% humidity and 102 degrees, will eventually increase the surrounding humidity and temperature of that space. In effect the more panting the dog does to cool down, the hotter he will become. Larger animals will obviously increase the surrounding temperature in the vehicle quicker.
Time, temperature and humidity are critical factors in the development of heat stroke in pets and, once the animals cells reach 107 degrees, it is vital for any chance of recovery to lower that temperature as fast as possible. If not then death will occur no matter what you do.

SIGNS OF HEAT STROKE Are intense, rapid panting, wide eyes, salivating, staggering and weakness. Advanced heat stroke victims will collapse and become unconscious and the gums will appear pale and dry.
If you suspect heat stroke and can take the animals temperature rectally, any temperature above 106 degrees is dangerous. The longer the temperature remains at or above 106 degrees the more serious the situation.
If, on returning to your car or the area in which your pet was confined, you find your pet agitated, wide eyed and panting uncontrollably, suspect heat stroke and get to the nearest veterinary surgery straight away with your air conditioning on full blast. If that is not possible then get the animal to a cool place and begin the treatment for heat stroke.

TREATMENT FOR HEAT STROKE Take the pets temperature rectally if possible. A body temperature of 105 degrees or more is probable evidence of heat stroke. Place your pet in a tub of cool running water or spray with a hose pipe making sure the water contacts the skin and not simply run off the coat. Thoroughly wet the belly and inside the legs and run the cool water over the tongue and mouth. If possible take another rectal temperature so you know when to stop cooling. Stop cooling when the temperature reaches about 103 - 104 degrees as the cooling effects will continue to bring the temperature down. A small dog will cool down faster than a large dog.
SEEK VETERINARY ATTENTION AS SOON AS POSSIBLE.

Should you be near a veterinary surgery then go there straight away. The vet may administer oxygen, cortisone and dextrose to help protect the traumatised cells. Proper cooling methods will be administered and the animals temperature and heart rate can be properly monitored. Intravenous fluids and anticoagulants may be used as well.

WHAT DOES HEAT STROKE DO ? In very severe cases the elevated body temperature triggers chemical reactions in the cells of the body. Highly active cells such as brain, intestinal and liver cells are at the greatest risk for heat trauma. The metabolic disturbances brought on by excessive heat instigate the release of chemicals within the cells that cause the ultimate destruction and death of the cell.
Heat stroke victims are dehydrated and their blood thickens to the point that severe stress is placed upon the heart as it attempts to pump the abnormally viscous blood through the blood vessels.

The result is stagnating blood, blood clotting and eventual death of tissue due to what is termed Ischemic Necrosis. When a clot forms, the tissues nourished by that clogged vessel die from metabolic starvation. Those dying cells in turn give off chemicals that further damage surrounding tissues until a point is reached beyond which no recovery is possible.

Unfortunately, in situations where the heat stroke victim has experienced a dangerously high body temperature for a long time, too many brain and other body cells may have been damaged to the extent that, no matter what life saving measures are employed, and bio protective medicines are administered, death will result.

HOW TO AVOID HEAT STROKE Never leave your pet in a vehicle or tied out in direct sunlight during warm, sunny days. Remember even a few minutes can prove critical. Do you really need to take your pet around markets or other outdoor activities on a hot summer day?

Factors that increase an animals risk of developing heat stroke include -

Water deprivation
Enclosed space
Excessive humidity
Obesity
Exercise
Age
Cardiovascular disease
Lack of acclimatization

Short faced (Brachycephalic) breeds such as Boxers, Pekingese, Pugs and those breeds with heavy coats are at greater risk of heat stroke.

Age, heart problems and physical conditions such as being overweight can all contribute to a lesser efficiency in dissipating built up body heat.
Any animal, or human, when faced with the conditions of high temperature and high humidity and time to build up heat within the body faster than it can be dissipated, may face the tragedy of being a victim of heat stroke.
Older pets have less resistance to stresses such as travelling, heat, noise and unusual activities. Excitement or discomfort brings on panting and a raised metabolic rate which then raises the animals temperature.

If the animal cannot remove that heat build up within its body then it may be just a few minutes before that animal is into some serious medical difficulty.
ALL IT TAKES TO AVOID THIS SERIOUS PROBLEM IS COMMON SENSE.

This condition is different from what is commonly called heat stroke.
Malignant hyperthermia is a well documented metabolic disorder of skeletal muscle that can occur with the inhalation of anaesthetic agents or sometimes stress. There may be an inherited predisposition to develop malignant hyperthermia in dogs, man and other animals.
The condition is most commonly seen in heavily muscled dogs.
Merck Veterinary Manual says it is abnormal “calcium regulation, glycogenolysis and contractile protein activity resulting in production of heat, CO2 and lactic acid. Clinical signs include tachycardia (rapid heart rate), tachypnea (rapid breathing), pyrexia (fever), muscle rigidity and cardiopulmonary failure. Signs develop 5 - 30 minutes after exposure to the anaesthetic agent.
Treatment consists of immediate withdrawal of anaesthesia followed by hyperventilation with oxygen. IV fluid therapy, corticosteroids and ice packs are also used. A muscle relaxant may be given but prognosis is poor in severe cases. Serum potassium levels urinary output and cardiac function should all be monitored