Low Body Temperature in Dogs

Hypothermia can be a progressive condition. As low body temperature continues, the body's ability to bring itself back to normal temperatures can decrease.  Depression of the circulatory, central nervous, respiratory and the immune systems are seen with hypothermia. Untreated, low body temperature can lead to difficulty breathing, an irregular heartbeat, and unconsciousness. Hypothermia is the term for an abnormally low body temperature. At below normal temperature levels, the body’s physiologic and metabolic functions are depressed. An irregular heartbeat, trouble breathing, and impaired consciousness to the point of coma may result.

Initial signs, seen in cases of mild hypothermia include:

• Heat-seeking/burrowing in blankets
• Shivering
• Weakness
• Mental depression

As hypothermia progresses to a moderate level, signs include:

• Shallow breathing
• Stiff movement
• Hypotension (low blood pressure)
• Lethargy

Severe hypothermia is exhibited by the following signss:

• Labored breathing
• Slow, weak heartbeat
• Fixed and dilated pupils
• Unconsciousness or coma
• Death

Types

• Primary hypothermia: The body exhibits normal heat production. Low body temperature results from exposure to low environmental temperatures.
• Secondary hypothermia: The body exhibits abnormal heat production as a result of injury, illness, or drugs.

Hypothermia severity may be classified by body temperature:

• Mild: Body temperature of 90 - 99°F (32 - 35°C)
• Moderate: Body temperature of 82 - 90°F (28 - 32°C)
• Severe: Body temperature less than 82°F (28°C)

• Exposure to external cold, wet and/or extreme drafts can result in heat loss.
• Smaller animals have high surface-area-to-body-mass ratios and are more susceptible.
• Injury can prevent seeking heat and/or thermoregulation
• Certain drugs such as those used for anesthesia in surgery can inhibit the body’s ability to regulate temperature.
• Newborn pups are more susceptible to hypothermia even at normal room temperatures.
• Geriatric pets can be more susceptible to hypothermia.
• Hypothalamic disease affects the brain’s regulation of body temperature and can contribute to heat loss.
• Hypothyroidism, low thyroid hormone production, can contribute to heat loss.

The best chance of recovery from hypothermia comes with early diagnosis and treatment. If your pet is exhibiting symptoms of hypothermia such as heat-seeking, weakness, lethargy, or others mentioned above, carefully and gently wrap the pet in blankets and transport them to the veterinarian.

At the veterinarian, a thermometer will be used to measure the pet’s body temperature. A thorough history will often be obtained to aid in determining the possible causes of the observed symptoms. A physical examination for heartbeat irregularities or abnormal breathing can establish whether the hypothermia is mild, moderate or severe.

Blood tests may be performed to determine possible alternative contributors to the hypothermia such as the presence of drugs, hypoglycemia, hypothyroidism, or other physical disorders. Analysis of the urine can also reveal possible reasons for abnormal thermoregulation. The veterinarian may choose to monitor the pet’s heart rhythms with an electrocardiogram (EKG).

Therapeutic goals are directed toward rewarming the patient and preventing additional body heat loss. The body can be safely rewarmed at 0.5-1.5 degrees Celsius per hour. Three rewarming techniques are available and used according to the degree of hypothermia severity.

• Passive External Rewarming
• In mild hypothermia, the animal’s own metabolism continues to produce heat. Blankets or other insulating covers will aid in preventing further heat loss. Natural body functions such as shivering will also contribute to rewarming.
• Active External Rewarming
• Moderate cases of hypothermia require the use of external heat sources such as hot water bottles, heating pads and radiant heaters.
• Active Internal Rewarming
• Severe cases of hypothermia require the use of invasive warming. Administration of warm intravenous (IV) fluids can aid in bringing body temperatures back to normal levels. Oxygen administration may also be used to promote recovery.

• Treatment risks:
• Rewarming must be conducted carefully and body temperature monitored constantly to avoid complications.
• After drop is a phenomenon seen as the body temperature continues to decrease during rewarming. Rewarmed blood moves to the extremities, pushing cold blood from the extremities inward to core organs.
• Rewarming shock can result from rapid rewarming causing a sudden drop in blood pressure. Combined with low cardiac output, this can potentially further compromise the circulatory system.

Treatment duration:
Rewarming therapy should continue until normal body temperature is reached (usually 2-10 hours, depending on severity). The patient may then continue to be monitored for 24-72 hours, depending on severity.

Recovery from hypothermia can be complete if the condition is diagnosed early and treated. Follow up appointments at and/or two weeks following treatment may be suggested to monitor the patient for any long-term complications.

In moderate to severe cases, long-term damage can occur to organs that were not supplied with sufficient circulation while at low body temperature. The extent of long-term damage may not be detectable for days or weeks post-treatment. The veterinarian may suggest various follow up appointments to monitor physiologic processes post-treatment for hypothermia.

Patients who are at high risk for hypothermia may require long-term care, such as incubation, to keep the body temperature stable.

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