Heatstroke in Dogs

Summary

Heatstroke is a type of heat related illness, and is always a life-threatening emergency. It is the direct result of thermal injury to the organs and systems within a dog’s body. Taking steps to avoid heatstroke is a priority for every pet parent. 

The normal body temperature range for dogs is 101.5°F(38.6°C) with variations of one degree higher or lower. Body temperatures from 105-110°F(40.5-43.3°C) are indicative of heat stroke. At these temperatures the body can not regulate itself and begins to shut down as organs are damaged and internal systems fail. Heat-related illnesses occur in sequence; signs of heat exhaustion occur prior to heatstroke, and the dog may progress from heat exhaustion to heatstroke quickly. Symptoms primarily result from shock and depend on how severe the heatstroke is and what systems have been damaged. Common symptoms are severe vomiting and diarrhea (often bloody), collapse, seizures, and loss of consciousness. There may also be a change in the color of the gums and other mucous membranes.

While heatstroke occurs most often in warmer environmental conditions, it is possible at other times. The probability of occurrence increases due to overexertion, sudden temperature shifts, certain medical conditions, surrounding environment, and other predisposing factors. 

Diagnosis depends on a physical exam, medical history, and the results of several tests to determine the extent and location of organ and internal system damage. The goal of treatment is to cool, hydrate, and treat accompanying shock, as well as any internal damage. This can include transfusions, antibiotics, and other medications. The likelihood of recovery depends on the response to treatment.

Risk Factors

Heatstroke occurs most commonly in warm environmental conditions, and can be prevented when pet parents are aware of the danger and respond to early warning signs. Heatstroke is life-threatening, and warrants immediate medical attention. 

Many factors contribute to heatstroke, but concern for it grows when:

• Ambient temperatures exceed 65°F (18°C) • Ambient relative humidity is high (above 65%)

• Access to shade and ventilation are limited • The dog is active/exercising

• The dog has predisposing conditions 

Certain underlying conditions put a dog at higher risk for heatstroke. Pets should be monitored more closely during exercise, especially in hot and humid conditions, if they have predisposing factors like: 

• Obesity • Being brachycephalic (breeds like pugs with short muzzles and flat faces) • Heart disease

• Other respiratory conditions • Neurologic disorders like epilepsy • Prior history of heatstroke

Dogs who are unacclimated to the heat are also at increased risk, as are dogs who engage in physical activity beyond their fitness level. Golden retrievers and Labrador retrievers have been shown to be predisposed to heatstroke, although the cause is unknown.

Possible Causes

Heatstroke is caused anytime a dog’s ability to get rid of body heat is outpaced by the environmental conditions. This can occur passively in hot environments, especially when the humidity is high (non-exertional heatstroke), or actively when the dog exercises (exertional heatstroke). Exertional heatstroke is more common during the summer, but can occur in cooler temperatures. Many occurrences of heatstroke result when dogs are left without adequate ventilation in hot vehicles.

Main Symptoms

The primary symptoms of heatstroke in dogs are:

• Elevated body temperature of 105°F (38.6°C) • Severe vomiting and diarrhea (often bloody)

• Collapse• Spontaneous bleeding, especially from the gums • Seizures • Loss of consciousness

• Pale, muddy, or dark red gum color

Detailed Characterization

In cases where organ failure has occurred, symptoms differ depending on what system has been damaged and can include:

• Hypovolemia (low blood pressure) • Hypoxia (low oxygen levels) • Arrhythmia (abnormal heart rate) 

• Hypoglycemia (low blood sugar) • Tremors • Abnormally high or low urination

If a pet is left in heatstroke-inducing conditions for too long, they will fall into a coma, or die.

Testing and Diagnosis

Diagnosis begins with determining medical history and performing a physical examination, which includes a measurement of body temperature. Possible tests include, but are not limited to: 

• Hemogram or complete blood count(CBC) • Blood serum chemistry profile • Coagulation testing

• Chest X-rays • Electrocardiogram

Steps to Recovery

Treatment is determined case by case based on the symptoms displayed. General treatment begins with first aid efforts by pet parents to wet down and cool the pet on the way to veterinary care. These are short term actions a pet owner should take while on the way to professional care:

• Remove pet from hot environment • Make water available to drink, but don't force them

• Wet down the pet, targeting heat exchange areas; groin, armpits, back of neck, ear flaps, and paws.

• Speed up cooling with a fan, open car windows, or turn on air conditioning

Depending on the results of the diagnostic tests, other treatments may be added to the cooling efforts including:

• IV fluids • Oxygen therapy • Ventilatory support • Antibiotics • Plasma transfusions

• Gastroprotectants (medication to protect the stomach and intestinal lining) • Blood pressure medications

Severe symptoms that don’t improve with cooling efforts and treatment for shock indicate a very poor prognosis.  Recovery is based on the severity of heat stroke, how the patient responds to treatment, and if there are secondary conditions or complications.

Prevention

Heat stroke is not contagious. It is prevented by monitoring a pet for signs of heat exhaustion and taking corrective action before symptoms develop into a life threatening condition. Ensuring that dogs are always in well ventilated areas with access to shade and water can help prevent heat stroke.

Is Heatstroke Common in Dogs?

Heat stroke is frequently reported in cases where dogs have been left in enclosed conditions, such as a car. It can be prevented if pet owners are aware of how dangerous it is and what steps can be taken to stop it from progressing.

Typical Treatment

Treatment will depend on the severity of the symptoms at the time of diagnosis. Most cases of heatstroke treatment will include cooling, IV fluids, oxygen therapy, and gastroprotectants.

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