By Jonathan Schnier, DVM, DACVIM

Anatomy

Heat Stroke is an elevation of the core body temperature resulting from excessive external heat exposure.

Risk Factors

Both dogs and cats are at risk for heat stroke; pediatric and geriatric patients are at an even higher risk.

Dogs with compressed short, noses/flattened faces (brachycephalic breeds) such as English Bulldogs, Pugs, etc. are at an increased risk along with animals affected with pre-existing upper airway disease such as laryngeal paralysis. Obese animals and dark-colored or longhaired breeds may also demonstrate an increased risk for heat stroke.

Heat stroke may result from exposure to excessive external heat sources and/or inadequate heat dissipation.

Cause of Heat Stroke

Exposure to high ambient temperatures, including enclosure in small spaces such as clothes dryers or cars is a common cause for heat stroke.

Vigorous exercise can also result in heat stroke, especially when exercise is combined with excessive external heat and/or pre-existing respiratory disease, heart disease, or obesity.

Diagnostics

In Arizona, heat stroke may occur at any time of the year; however, it is most common in early summer before heat acclimatization occurs.

Dogs and cats affected with heat stroke generally demonstrate an elevated rectal temperature (>105.5 degrees F). Aside from an elevated temperature, affected patients may also demonstrate altered mental status, brick red mucous membranes, increased effort associated with breathing, loud breathing sounds, and/or pin-point bruises (best visualized over the gums, inner ears, and non-haired skin).

Cardiovascular disturbances, respiratory problems, gastrointestinal signs, abnormal blood clotting (disseminated intravascular coagulation), liver failure, renal failure, and neurological abnormalities are relatively common with severe heat stroke.

Diagnosis of hyperthermia/heat stroke is generally straightforward (based on a markedly elevated body temperature with a consistent history). Diagnostic efforts are focused at identifying and monitoring secondary complications that may occur in severe cases.

Treatment

Recommended treatment for heat stroke victims may vary depending on presenting signs in both dogs and cats. Hospitalization and supportive treatment is often recommended. Patients that are obtunded or comatose may require immediate placement of a breathing tube (intubation) to secure the airway and to allow for oxygen supplementation. Active cooling may be implemented through placement of an intravenous catheter with administration of intravenous fluids. Cool water baths may also be helpful. Additional cooling techniques can include infusing the urinary bladder with sterile, lukewarm solutions. Active external cooling must be discontinued once the rectal temperature reaches 103-103.5 degrees F as continued cooling can result in hypothermia.

Treatment with broad-spectrum antibiotics is often warranted and specific treatment for cardiac arrhythmias, low blood sugar, and abnormal blood clotting may be required.

The prognosis associated with heatstroke will vary widely depending on clinical severity at the time of presentation. Patients recovering from heat stroke typically do not suffer any long-term adverse effects; however, these patients may demonstrate an increased risk for heatstroke in the future.

It is interesting to note that the initial core body temperature has NOT been correlated with outcome. Patients with extremely high temperatures may demonstrate good outcomes while it is possible for patients with less severe hyperthermia to die. Delayed admission to hospital has been associated with a poor prognosis. If heat stroke is suspected, aggressive early cooling is warranted and can be helpful.

Contact a veterinarian ASAP for specific recommendations. Your veterinarian may recommend initial cooling procedures at home or immediate transport to a veterinary hospital/emergency facility. Overcorrection of hyperthermia resulting in hypothermia must be avoided. Multiple organ failure can occur in severe cases or in pets for which treatment is delayed. Certain practices may be instituted at home to help prevent heat stroke. Avoid exposing pets to high ambient temperatures or prolonged physical exercise. Also, remember that dogs may be at increased risk for heat stroke with pre-existing respiratory disease, cardiac disease, and obesity. Signs of weakness and panting in hot weather may represent an emergency.

Dr. Jonathan SchnierAbout Dr. Schnier

Dr. Jonathan Schnier received his Doctorate of Veterinary Medicine from the Ontario Veterinary College in 2004. He then completed an internship in Tucson. Dr. Schnier returned to Canada following his internship in order to pursue a small animal internal medicine residency at the Atlantic Veterinary College in Prince Edward Island. He became a Diplomate of the American College of Internal Medicine in 2008, and spent several years practicing internal medicine in Cape Cod, Massachusetts, before returning to AZ in 2010. Dr. Schnier enjoys practicing all areas of internal medicine and has special interests in immune mediated, endocrine, and gastrointestinal disease. He has extensive experience and training in endoscopy and ultrasound, and has also received training in medical oncology and chemotherapy. Dr. Schnier has presented lectures for the AZ Veterinary Medical Association regarding canine hyperadrenocorticism and immune-mediated hemolytic anemia. Outside of work, Dr. Schnier enjoys spending time with his wife, Lisa (also a veterinarian), and their many pets. Dr. Schnier is an avid alpine skier and enjoys SCUBA , hiking, running, and cycling.