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Hypothermia in Dogs

Hypothermia is a medical condition that is characterized by an abnormally low body temperature. It has three phases: mild, moderate, and severe. Mild hypothermia is classified as a body temperature of 90 - 99°F (or 32 - 35°C), moderate hypothermia at 82 - 90°F (28 - 32°C), and severe hypothermia is any temperature less than 82°F (28°C). Hypothermia occurs when an animal’s body is no longer able to maintain normal temperature, causing a depression of the central nervous system (CNS). It may also affect heart and blood flow (cardiovascular), breathing (respiratory), and the immune system. An irregular heartbeat, trouble breathing, and impaired consciousness to the point of coma may result.

Symptoms and Types

Hypothermia symptoms vary with the level of severity. Mild hypothermia is evident through weakness, shivering, and lack of mental alertness. Moderate hypothermia reveals characteristics such as muscle stiffness, low blood pressure, a stupor-like state, and shallow, slow breathing. Characteristics of severe hypothermia are fixed and dilated pupils, inaudible heartbeat, difficulty breathing, and coma.

Causes

Hypothermia usually occurs in cold temperatures, although newborns may suffer hypothermia in normal environmental temperatures. Smaller breeds and very young animals, more prone to rapid surface loss of body heat, are at higher risk, as are old (geriatric) pets. Animals under anesthesia are also at higher risk.

Other factors that may increase risk are disease of the hypothalamus, the part of the brain that regulates appetite and body temperature, and hypothyroidism, a condition characterized by low levels of thyroid hormone in the body.

Diagnosis

If hypothermia is suspected, your dog's body temperature will be measured with a thermometer or, in severe cases, with a rectal or esophageal probe. Irregularities in breathing and heartbeat will also be checked. An electrocardiogram (ECG), which records the electrical activity of the heart, can determine your dog's cardiovascular status.

A urinalysis and blood tests are commonly used to diagnose alternative causes for below normal body temperature and unresponsiveness. These tests may reveal low blood sugar (hypoglycemia), metabolic disorders, primary heart (cardiac) disease, or anesthetics or sedatives in your dog's system.