Overview of Heat Stroke in Dogs
Heat stroke is a condition arising from extremely high body temperature (rectal temperature of 105 to 110 degrees Fahrenheit), which leads to nervous system abnormalities that may include lethargy, weakness, collapse or coma. Abnormally high body temperature (also called hyperthermia) develops in dogs after increased muscular activity with impaired ability to give off heat due to high heat and humidity or respiratory obstruction. Allowing a dog to remain in a car with closed windows on a hot summer day is probably the most common cause of heat stroke.
Below is an overview of heatstroke in dogs followed by in-depth information about the diagnosis, treatment and prognosis associated with canine heatstroke.
Normal dogs dissipate heat from their skin. In addition, panting allows evaporation of water from the respiratory tract and is an effective method of heat dissipation. When these mechanisms are overwhelmed, hyperthermia and heat stroke usually develop. The elevation in body temperature stimulates the body to release substances that activate inflammation. At temperatures greater than 109 Fahrenheit, failure of vital organs, and consequently death, can occur.
Heat-related illnesses, including heat stroke, heat exhaustion and heat cramps can occur after exposure to extremely high environmental temperatures. These illnesses occur in all mammals and can be prevented by taking proper precautions.
Animals at greatest risk for heat-related illness include:
- Puppies up to 6 months of age
- Overweight dogs
- Dogs overexerted during exercise
- Dogs that are ill or receiving certain medications
- Brachycephalic breeds (dogs with short, wide heads like pugs, English bulldogs, Boston terriers)
- Dogs with obstructive airway diseases
- Dogs with pre-existing fever
- Dogs that are dehydrated
- Dogs with heart disease
- Dogs with poor circulation due to cardiovascular or other underlying disease
- Older pets (large breed dogs over 7 years of age, small breed dogs over 14 years of age)
- Pets with a history of seizures
What to Watch For
- Noisy breathing that may indicate upper airway obstruction
- Excessive panting
- Bright red mucous membranes (gums, conjunctiva of the eyes)
- Altered mentation
- Petechiae (pinpoint hemorrhages on the gums and/or skin)
Diagnosis of Heatstroke in Dogs
Diagnostic tests are needed to diagnose heat stroke and assess the extent of vital organ dysfunction, including:
- A complete medical history and thorough physical examination, including rectal temperature.
- A complete blood count (CBC or hemogram) to assess the severity of dehydration and cardiovascular stress.
- Tests of coagulation including: activated coagulation time (ACT); prothrombin time (OSPT); partial thromboplastin time (APTT); serum fibrinogen concentration; platelet count; and fibrin degradation products (FDPs) to identify the presence of disseminated intravascular coagulation (DIC) a life-threatening body-wide failure of blood clotting that is often a complication of heat stroke. The presence of breakdown products of fibrin (called fibrin degradation products) can serve as an important clue to the presence of DIC.
- Serum biochemistry tests to check blood glucose concentration, assess the extent of damage to vital organs, such as muscles, kidneys and liver, and to evaluate the electrolyte and acid base status.
Treatment of Heatstroke in Dogs
Intensity of treatment depends upon the cause and severity of the heat illness.
- Mildly increased temperature (less than 105 F) may only require rest, a fan to increase air circulation, fresh water to drink and careful observation.
- Temperatures of 105 to 107 F should be hospitalized on intravenous fluids and other medications.
- Markedly increased temperature (greater than 107 F) must be treated more aggressively. Cooling can be promoted externally by immersion in cool water, or internally by administering a cool water enema.
- Underlying aggravating conditions, such as upper airway obstructive diseases, heart disease, pulmonary disease and dehydration may be treated with appropriate medications, supplemental oxygen or fluid therapy.
- Treatment with cortisone-like drugs such as short-acting forms of dexamethasone or prednisone may be recommended.
The need for additional treatments depends on the severity of heat stroke and secondary complications that may arise. Complications of heat stroke may include:
- Disseminated intravascular coagulation (DIC)
- Liver failure
- Acute kidney failure
- Muscle breakdown
- Low blood pressure (hypotension)
- Low blood sugar (hypoglycemia)
- Convulsions (seizures)
- Secondary infections (including pneumonia)
- Gastrointestinal problems including bleeding and absorption of bacteria or toxins from the intestine with development of systemic infection (sepsis)
Home Care and Prevention
Heat stroke is a life-threatening emergency. Check your dog’s temperature rectally if you suspect heatstroke. Normal body temperature in dogs is higher than in humans (99.5 to 102.5 F as compared to 98.6 F). If your dog’s temperature is over 105 F, call your veterinarian and remove your dog from the heat source immediately.