What is hypothermia?

Hypothermia is a condition that occurs when the body’s temperature drops below 95° F (35° C). Normal body temperature is 98.6° F (37° C). Hypothermia is a medical emergency.

When a person’s body temperature is dangerously low, the brain and body cannot function properly. Left untreated, hypothermia can lead to cardiac arrest (heart stops beating) and death.

How common is hypothermia?

Mild, treatable cases of hypothermia are more common, especially among groups of people who are at risk. In the United States, more than 1,300 people die every year from hypothermia.

Who is at risk for developing hypothermia?

Although anyone can get hypothermia, certain people, conditions and situations increase the risk of developing hypothermia. These include:

  • Older people. The ability to control body temperature lessens with age. Elderly also tend to expend less energy (which generates heat to keep the body warm) because they are less active than younger people. They may live in a house or other environment that is too cold.
  • Young children. Children use more calories (energy) than adults and may use up their reserve while playing and not even realize they are cold.
  • Babies. Infants lose body heat more easily than adults, don’t have the energy reserve to shiver to increase their body heat and can even become hypothermic if they sleep in a cold room. Signs of hypothermia in an infant include cold skin, bright red skin, inactivity/lack of energy, and body temperature under 95° F (35° C).
  • Inexperienced outdoor adventure seekers such as hikers, hunters, fishers who do not have appropriate gear for the cold and wet conditions they may encounter.
  • People who abuse alcohol or recreational drugs. Alcohol expands blood vessels, allowing heat to leave the skin surface more rapidly. Alcohol as well as drug use can impair a person’s ability to feel cold and/or not have good judgment about wearing appropriate clothing to match the weather conditions or coming inside when cold.
  • Homeless people. Homeless people may not have or not choose indoor shelter options with heat. They also may not have clothing appropriate for the weather conditions.
  • People with mental health problems. People who have dementia or other intellectual impairment may lack the ability to judge weather conditions, may wander away from home and get lost, and may not wear appropriate clothing to stay warm for an extended time in cold weather.
  • People with certain medical conditions may be more susceptible to cold temperature. These conditions include hypothyroidism, hypoglycemia, hypopituitarism, shock, sepsis, anorexia nervosa, stroke, Parkinson’s disease, peripheral neuropathy, spinal cord injury.
  • Medications that can impair a person’s response to cold include sedatives, anesthetics, opioids, phenothiazine antipsychotics and clonidine

How do people get hypothermia?

Hypothermia occurs after exposure to cold, wet or windy conditions. When you are exposed to cold, your body expends energy to keep you warm. Eventually, with continued exposure to cold temperature, your body uses up its stored energy and your body temperature begins to fall.

It should be noted that hypothermia can occur in temperatures over 40° F. Hypothermia occurs under environmental conditions (wet, cool/cold, or windy) that cause a person’s body to lose more heat than it generates.

What are the symptoms of hypothermia?

Signs of mild hypothermia (95° F to 89.6° F // 35° C to 32° C) include:

  • Shivering and chattering teeth
  • Exhaustion
  • Clumsiness, slow movements and reactions; prone to falling
  • Sleepiness
  • Weak pulse
  • Fast heart rate (tachycardia)
  • Rapid breathing (tachypnea)
  • Pale skin color
  • Confusion and poor judgment/loss of awareness
  • Excessive urination

Signs of moderate hypothermia (89.6° F to 82.4° F // 32° C to 28° C) include:

  • Slowdown in breathing and heart rate
  • Slurred speech
  • Decline in mental function
  • Loss of shivering
  • Bluish color to skin
  • Muscle stiffness
  • Dilated pupils
  • Abnormal heart rhythm
  • Decreased blood pressure
  • Weakened reflexes
  • Loss of consciousness

Signs of severe hypothermia (< 82.4° F // 28° C) include:

  • Low blood pressure
  • Fluid in lungs
  • Absence of reflexes
  • Low urine output
  • Heart stops beating (cardiac arrest)
  • Coma that may mimic death
  • Death

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