Hypothermia in Horses

The average body temperature for a mature horse is between 37.5 and 38 degrees Celsius (99.5 and 100.4º F). Any temperature below that is considered hypothermia.

Hypothermia is rare in horses, and typically only happens when horses accidentally fall into frozen bodies of water or get stuck in muddy, cold conditions.

Hypothermia is a potentially fatal condition and must be considered an emergency that requires immediate veterinary intervention.

Depending on the temperature the body reaches, hypothermia can be divided into three categories.

Mild: 32 to 37 degrees Celsius (89.6 to 98.6ºF). It is generally characterized by shivering and tachycardia.

Moderate: 28 to 32 degrees Celsius (82.4 to 89.6ºF). The shivering becomes more severe, and cyanosis (blue gums) starts to appear.

Severe: below 28 degrees Celsius (82.4ºF). At this temperature, cellular metabolism starts to shut down, and horses develop cardiac abnormalities that can result in sudden death.

As hypothermia progresses, internal organs start to fail, and permanent tissue damage is a real risk.

Aside from environmental conditions, predisposing factors might interfere with the standard response to maintain a natural body temperature. These factors include:

• Old or very young age
• Malnutrition
• Endocrine disorder

Most cases of hypothermia are associated with horses falling into frozen bodies of water, or becoming stuck in cold, muddy conditions. Wet fur is unable to properly insulate against cold temperatures, making wet or damp horses highly susceptible to hypothermia.

When a veterinarian suspects hypothermia, they perform a complete physical examination and measure the core body temperature. If the core body temperature drops below 37.5ºC (99.5ºF), the horse is diagnosed as hypothermic.

The goal of treatment is to raise core body temperature back to normal range. The method of rewarming depends on the severity of the case. Strategies include:

Passive external rewarming works for mild cases, where the horse still produces heat by shivering. It involves wrapping the horse in a blanket and sheltering its body with a tarp to prevent further heat loss.

Active external rewarming is often used alongside another rewarming option. It consists of warming using warm-water baths, forcing warm air, or through other heating sources. If not performed correctly, this method might be counterproductive and end up burning the horse.

Active internal rewarming consists of injecting the patient with warmed intravenous fluids. It is usually performed in combination with an external rewarming method.

Every attempt at rewarming must be performed by a professional as sudden changes in body temperature can lead to shock. In extreme cases, shock can lead to organ failure and even death.

Horses often benefit from additional treatments such as supplemental oxygen, anti-inflammatory medications, and antibiotics to prevent respiratory infections while recovering from hypothermia.

Prognosis depends on the severity of the hypothermic condition. In mild cases, a complete recovery is very likely. More severe cases have less chance of full recovery as the organs might have already started failing. If the horse survives the hypothermic shock there is still a risk of post-rescue collapse or rewarming shock.

Prevention proves to be a difficult task due to the accidental onset of the condition. Whenever possible, access to frozen ponds, deep mud, or other difficult-to-maneuver surfaces should be limited, especially during extreme weather conditions. Some precautions can help minimize the severity of hypothermia. Poor hydration, poor body condition, and malnutrition can be important factors that affect the onset of hypothermia and its severity.

Hypothermia is rare in horses and typically only occurs due to environmental risk factors.

• Gradual rewarming
• Symptomatic treatment
• Supportive care