Hypothermia in Dogs

Your dog may love romping through the snow or taking a mountain hike with you, but dogs who are exposed to prolonged cold temperatures or icy water can develop hypothermia. Hypothermia occurs when your dog’s body loses heat faster than it can be produced. If this goes on for a prolonged period of time, your dog’s body starts using up stored energy, which eventually leads to an inability to maintain a safe core body temperature. Cold weather isn’t the only reason dogs develop hypothermia—underlying endocrine, metabolic, and cardiac diseases can lead to the inability to regulate body temperature. Shock, low blood pressure, and loss of body heat under anesthesia also can cause hypothermia.

What is Hypothermia in Dogs?

Hypothermia is a life-threatening condition that occurs either due to prolonged exposure to cold conditions, as a result of underlying illness or injury, or from anesthetic procedures and certain drugs that affect a dog’s ability to maintain core body temperature. When hypothermia occurs from a cold environment, it is called primary hypothermia. Secondary hypothermia results from underlying conditions and can happen even in warm environments.

A dog’s normal body temperature ranges from 101.0 to 102.5 degrees Fahrenheit, and hypothermia occurs when body temperature falls below this range. If your dog’s temperature drops to 98 degrees Fahrenheit and they are unable to bring it up, you should seek veterinary help immediately. If your dog’s temperature drops below 94 degrees Fahrenheit, their ability to effectively raise their body temperature back to normal (called thermoregulation) is severely impaired. At 88 degrees Fahrenheit, your dog loses the ability to thermoregulate and may suffer cardiac and respiratory failure, coma, and death.

Symptoms of Hypothermia in Dogs

Symptoms of hypothermia depend on the cause and severity and may progress from behaviors like shivering and heat-seeking to mental confusion, unconsciousness, and decreased respiration and heart rate as thermoregulation ceases.

Shivering

Shivering is an involuntary muscle movement that can generate a large amount of heat quickly to raise core body temperature. It is a sign that your dog’s body temperature is dropping. Shivering stops as hypothermia progresses, so if your dog stops shivering but they are still cold, don’t assume they are okay. 

Heat-Seeking Behavior

Heat-seeking behaviors include curling up, seeking warmth from other dogs or people, and looking for other heat sources like blankets, radiators, and fireplaces. Your dog may lie down close to these heat sources in an attempt to get warm. As hypothermia progresses, these behaviors cease. 

Incoordination

Incoordination is an early sign of hypothermia. If your dog is stumbling or having difficulty moving, get immediate veterinary care. 

Cold Extremities

Cold extremities occur because your dog’s blood vessels are constricting to prevent further external heat loss and shunting blood to vital internal organs. As a result, feet, tails, and ears will feel cold. 

Pale, Cold Gums

Your dog’s gums will appear pale and feel cold, also due to vasoconstriction as the body tries to raise its internal temperature.

Muscle Stiffness

Muscle stiffness occurs as shivering ceases and is a sign that the hypothermia is worsening.  

Lethargy and Confusion

Lethargy and confusion are the result of negative effects on the brain’s function as hypothermia progresses. Dogs will stop trying to get warm and may move away from heat sources or not seek them out. Your dog may be difficult to rouse or appear to not understand or recognize you. 

Respiratory and Heart Rates

Respiratory and heart rates are initially high as your dog’s body tries to correct the temperature deficit but will slow as the hypothermia progresses. Fast breathing, especially if your dog was just in a cold environment, is a warning sign to immediately assess for hypothermia before it reaches a more serious stage. 

Delayed Reflexes

Delayed to absent reflexes will occur in severe hypothermia, generally accompanied with collapse. Unconsciousness may follow shortly after and indicates profound hypothermia. At this stage, the dog will die without immediate and aggressive veterinary treatment.

Causes of Hypothermia

Your dog’s core body temperature is maintained by balancing heat loss to the environment with internal metabolic processes that make up for that heat loss. As a result, external body temperature may fluctuate considerably throughout the day, but core body temperature (the temperature that’s taken with a thermometer in your dog’s ear or rectum) should remain stable. This ensures that the physiological processes necessary for life can continue to function within your dog. When the core body temperature drops, it interferes with normal physiology and metabolism, causing what could be deadly effects. 

Core body temperature is determined by the hypothalamus, an area deep in the brain that controls aspects like temperature, hunger, and thirst. Cold and heat receptors in your dog’s skin throughout the body sense temperature changes as they occur. These sensors communicate via the nervous system to the hypothalamus. The hypothalamus responds by activating metabolic processes to correct the temperature change and ensure the core temperature remains stable.

Shivering is one example of how your dog’s body may attempt to restore heat lost to the environment. This process of communication between cold receptors, the nervous system, and the hypothalamus is called thermoregulation. A dog’s ability to thermoregulate is also affected by fur thickness and length and the amount of body fat present.

When your dog’s ability to thermoregulate is lost, this becomes a life-threatening situation because the cells within your dog’s body cannot continue to function normally. There are several conditions that can disrupt the ability to thermoregulate and cause hypothermia.

Causes of Primary Hypothermia

• Exposure to a cold environment 
• Immersion in freezing water (e.g., falling into a frozen lake) 

Causes of Secondary Hypothermia

• Hypothyroidism 
• Hypoadrenocorticism
• Kidney disease
• Cardiac disease 
• Shock
• Trauma
• Infection
• Dangerously low blood pressure (hypotension) 
• Anesthesia and certain drugs

Diagnosing Hypothermia in Dogs

Hypothermia is diagnosed by body temperature, symptoms, and history, including recent exposure to a cold environment, suffering from an illness, injury, or shock, or undergoing an anesthetic procedure. Your veterinarian will conduct an examination of your dog, including assessing body temperature, heart rate, respiratory rate, and other indicators. Sometimes specialized thermometers must be used if your dog’s body temperature is very low.

Treatment

Dogs with suspected hypothermia should be taken immediately for emergency veterinary treatment. Hypothermia is treated by rewarming the patient and supportive care, like maintaining electrolyte balances and monitoring metabolic functions.

Rewarming may be accomplished using three different methods depending on the severity of hypothermia: core rewarming, which may include treatments like warmed IV fluids and warm enemas, active surface rewarming using a forced air warming system (such as the 3M Bair hugger) and circulating heated water blankets, and passive surface rewarming using blankets. Your dog will need to be hospitalized for treatment.

As you seek veterinary treatment, you can help your dog by taking the following steps:

• Move your dog to a warm environment
• Bundle your dog in blankets warmed in a clothes dryer
• Wrap a hot water bottle in the blankets

Do not: 

• Use blankets or water bottles that are too hot as this can cause serious burns 
• Expose your dog to high heat, which can lead to shock
•  Place your dog directly on a heating pad, which can cause excessive heat and burns or a hot water bottle. Be sure to layer towels between heating pads or hot water bottles and set temperatures to low to make sure warming is gradual and not too rapid, which can worsen shock. 

Rewarming of a hypothermic dog must be conducted carefully and under veterinary supervision. If a dog’s body temperature is raised too quickly, this can cause rewarming shock.

Prognosis for Dogs with Hypothermia

If dogs with mild hypothermia are treated immediately, they have a good chance of recovery. More severe hypothermia is more likely to result in complications and death, so preventing hypothermia in the first place and recognizing the early symptoms is crucial to your dog’s survival. In cases of secondary hypothermia, recovery depends on the severity of the underlying condition. 

How to Prevent Hypothermia

To prevent primary hypothermia, make sure your dog stays warm in cold environments. Keep your dog indoors when temperatures outside plummet, and if their fur gets wet, dry them right away. Keep their bedding and blankets dry as well, and always make sure they have access to warm, dry shelter if you’re out doing winter activities.

While all dogs can experience hypothermia, some dogs are at greater risk, including:

• Very old or very young dogs
• Dogs with impaired mobility 
• Dogs with low body fat 
• Dogs with short or thin coats
• Dogs who are not acclimated to a cold climate
• Toy breeds

Winter jackets and booties can help keep dogs warm and stave off hypothermia as well. And keep in mind, if a dog isn’t used to the cold, they are going to have a harder time thermoregulating. 

If your dog has an underlying illness that can cause hypothermia, be sure to follow all directions given by your veterinarian for treatment of the condition. Schedule regular follow-up appointments to monitor your dog’s health.