Disease: Hypothermia

    What is hypothermia?

    Hypothermia is defined as a body temperature (core, or internal body temperature) of less than about 95 F (35 C). Usually, hypothermia occurs when the body's temperature regulation is overwhelmed by a cold environment. However, in the medical and lay literature there are essentially two major classifications, accidental hypothermia and intentional hypothermia.

    Accidental hypothermia usually occurs from an exposure to cold that results in lowering the body temperature.

    Intentional hypothermia is body temperature lowering induced usually for a medical procedure.

    This article will focus on accidental hypothermia. Hypothermia is a medical emergency that, when quickly and appropriately treated, people can recover with little or no consequences.

    Body temperature, when discussing hypothermia, is usually termed "core" temperature. This temperature is the temperature measured inside the body. It's a measurement that is most accurately done by a rectal thermometer, a rectal probe thermometer that has a constant temperature readout or by a bladder or esophageal temperature device. Temperatures taken by other methods may not adequately measure core temperature.

    What are the risk factors for hypothermia?

    The highest risk factor for hypothermia is losing body heat due to exposure to cold weather or partial or complete immersion in cold water. Examples of include:

    • Not dressing appropriately for cold weather
    • Walking on a partially frozen body of water (rivers, lakes, ponds, etc.)

    Other risk factors for hypothermia include:

    • The young and elderly because their bodies do not have the ability to regulate body temperature efficiently
    • People with mental illness
    • People with alcohol or drug problems
    • Some medications

    Some medical diseases or conditions may decrease the body's ability to regulate its internal temperature, for example:

    • Diabetes
    • Stroke
    • Burns
    • Hypothyroidism
    • What body parts are more susceptible to hypothermia?

      The body parts most susceptible to injury in patients with hypothermia are those that may suffer from poor circulation or often have the least protection from the cold environment (feet, hands, nose and ears). These extremities usually cool faster than the body's core. The internal organ most susceptible to hypothermia is the heart (dysrhythmias).

      What causes hypothermia?

      The cause of hypothermia is the inability of the body's temperature regulation system to keep the body's core temperature between 35.6 C and 37.5 C (96.08 F and 99.5 F), so any body temperature below about 35.6 C (96.08 F) is considered hypothermic by many doctors.

      The body regulates the core temperature by either:

      • generating heat
      • cooling, or
      • heat conservation. Heat conservation can be accomplished by peripheral vasoconstriction and by behavior; heat production is done by shivering and by increasing levels of thyroxine and epinephrine.

      What are the signs and symptoms of hypothermia?

      The signs and symptoms of hypothermia vary depending upon how severe the hypothermia becomes. In general, there is a sequence of symptoms that can be roughly graded as mild, moderate or severe (not all doctors agree with grading or fixed temperatures). However, the following is a list of symptoms that may occur as hypothermia progresses from mild to severe (temperatures are approximate and some symptoms may overlap).

      Mild hypothermia symptoms (core temperature 32 C to 35 C (90 F to 95 F) are:

      • Shivering
      • Fatigue
      • Increased respiratory rate
      • Hunger
      • Nausea
      • Mild confusion
      • Some difficulty with speech and coordination

      Moderate hypothermia (core temperature 28 C to 32 C (82 F to 90 F) are:

      • Increasing difficulty with all the moderate symptoms (for example, inability to do simple tasks, slurred speech)


      Severe hypothermia (core temperature below 28 C (82 F) are:

      • Shivering stops
      • Extreme confusion (for example, removing clothing or extreme risk-taking behavior)
      • A decline in consciousness
      • A weak and/or irregular pulse
      • Slow and shallow breathing
      • Coma that can result in death

      Picture of the Stages of Frostbite

      What are the symptoms of hypothermia in infants and children?

      Newborns, infants, and young children are more likely to develop hypothermia because they have a larger surface area compared to body weight so they can lose body heat faster than older children and adults. WHO suggests slightly different temperature values for hypothermia levels in infants:
      • Cold stress or mild hypothermia: 36.0 C to 36.4 C (96.8 F - 97.5 F)
      • Moderate hypothermia: 32.0 C to 35.9 C (89.6 F to 96.6 F)
      • Severe hypothermia: <32 C (89.6 F)

      There may be some variation in these temperature values by some researchers, but these temperature levels can serve as guidelines in assessing hypothermia levels in infants and young children.

      Since infants and young children either cannot or will not communicate with adults about hypothermia, parents, caregivers, and medical personnel rely on other clues or symptoms of hypothermia, which include:

      • An accurate axillary (armpit) or rectal temperature below 36.4 C (97.5 F)
      • A weak cry
      • Low energy level
      • Lethargic
      • Reddish and cold skin
      • Cool feeling of extremities and abdomen
      • Poor feeding
      • Heart arrhythmias

      Some infants and children may experience chronic hypothermia and show symptoms of:

      • weight loss,
      • no weight gains, or
      • failure to thrive.

      Children and teens that can communicate have symptoms like those described for adults, but may occasionally have a combination of symptoms of those of a child or adult.

      Can a person experience hypothermia indoors?

      Yes, a person can become hypothermic indoors; however, the symptoms may develop slowly or not seem as obvious to family, friends, or even health care individuals unless a core body temperature is measured.

      Individuals at risk for hypothermia indoors are the elderly or young living in an unheated homes in cold temperatures, or living in an over-air-conditioned home.

      When should I call my doctor for hypothermia?

      Any person that is at risk for hypothermia (see previous section on risk factors) and has had exposure to cold weather or cold water immersion, and exhibits any symptoms of hypothermia should be seen in the emergency department. Individuals exhibiting intense shivering, numbness, clumsiness, confusion and/or amnesia after exposure to cold should be seen immediately.

      How is hypothermia diagnosed?

      For many people, hypothermia is diagnosed by the patient's history and physical exam; especially pertinent is the patient's core temperature. As previously stated any core temperature below 95 F or 35 C for an adult is considered to be hypothermic (for an infant, consider 36.4 C or 97.5 F) .

      Most individuals with hypothermia are considered to have a medical emergency so that diagnosis and treatment begins simultaneously. Some patients can develop bradycardia and show electrocardiogram (EKG, ECG) abnormalities.

      What are the signs and symptoms of hypothermia?

      The signs and symptoms of hypothermia vary depending upon how severe the hypothermia becomes. In general, there is a sequence of symptoms that can be roughly graded as mild, moderate or severe (not all doctors agree with grading or fixed temperatures). However, the following is a list of symptoms that may occur as hypothermia progresses from mild to severe (temperatures are approximate and some symptoms may overlap).

      Mild hypothermia symptoms (core temperature 32 C to 35 C (90 F to 95 F) are:

      • Shivering
      • Fatigue
      • Increased respiratory rate
      • Hunger
      • Nausea
      • Mild confusion
      • Some difficulty with speech and coordination

      Moderate hypothermia (core temperature 28 C to 32 C (82 F to 90 F) are:

      • Increasing difficulty with all the moderate symptoms (for example, inability to do simple tasks, slurred speech)


      Severe hypothermia (core temperature below 28 C (82 F) are:

      • Shivering stops
      • Extreme confusion (for example, removing clothing or extreme risk-taking behavior)
      • A decline in consciousness
      • A weak and/or irregular pulse
      • Slow and shallow breathing
      • Coma that can result in death

      Picture of the Stages of Frostbite

      What are the symptoms of hypothermia in infants and children?

      Newborns, infants, and young children are more likely to develop hypothermia because they have a larger surface area compared to body weight so they can lose body heat faster than older children and adults. WHO suggests slightly different temperature values for hypothermia levels in infants:
      • Cold stress or mild hypothermia: 36.0 C to 36.4 C (96.8 F - 97.5 F)
      • Moderate hypothermia: 32.0 C to 35.9 C (89.6 F to 96.6 F)
      • Severe hypothermia: <32 C (89.6 F)

      There may be some variation in these temperature values by some researchers, but these temperature levels can serve as guidelines in assessing hypothermia levels in infants and young children.

      Since infants and young children either cannot or will not communicate with adults about hypothermia, parents, caregivers, and medical personnel rely on other clues or symptoms of hypothermia, which include:

      • An accurate axillary (armpit) or rectal temperature below 36.4 C (97.5 F)
      • A weak cry
      • Low energy level
      • Lethargic
      • Reddish and cold skin
      • Cool feeling of extremities and abdomen
      • Poor feeding
      • Heart arrhythmias

      Some infants and children may experience chronic hypothermia and show symptoms of:

      • weight loss,
      • no weight gains, or
      • failure to thrive.

      Children and teens that can communicate have symptoms like those described for adults, but may occasionally have a combination of symptoms of those of a child or adult.

      Can a person experience hypothermia indoors?

      Yes, a person can become hypothermic indoors; however, the symptoms may develop slowly or not seem as obvious to family, friends, or even health care individuals unless a core body temperature is measured.

      Individuals at risk for hypothermia indoors are the elderly or young living in an unheated homes in cold temperatures, or living in an over-air-conditioned home.

      When should I call my doctor for hypothermia?

      Any person that is at risk for hypothermia (see previous section on risk factors) and has had exposure to cold weather or cold water immersion, and exhibits any symptoms of hypothermia should be seen in the emergency department. Individuals exhibiting intense shivering, numbness, clumsiness, confusion and/or amnesia after exposure to cold should be seen immediately.

      How is hypothermia diagnosed?

      For many people, hypothermia is diagnosed by the patient's history and physical exam; especially pertinent is the patient's core temperature. As previously stated any core temperature below 95 F or 35 C for an adult is considered to be hypothermic (for an infant, consider 36.4 C or 97.5 F) .

      Most individuals with hypothermia are considered to have a medical emergency so that diagnosis and treatment begins simultaneously. Some patients can develop bradycardia and show electrocardiogram (EKG, ECG) abnormalities.

      Source: http://www.rxlist.com

    The body parts most susceptible to injury in patients with hypothermia are those that may suffer from poor circulation or often have the least protection from the cold environment (feet, hands, nose and ears). These extremities usually cool faster than the body's core. The internal organ most susceptible to hypothermia is the heart (dysrhythmias).

    Source: http://www.rxlist.com

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