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Hypothermia

Low body temperature; Cold exposure; Exposure

Hypothermia is dangerously low body temperature, below 95°F (35°C).

Considerations

Other types of cold injuries that affect the limbs are called peripheral cold injuries. Of these, frostbite is the most common freezing injury. Nonfreezing injuries that occur from exposure to cold wet conditions include trench foot and immersion foot conditions. Chilblains (also known as pernio) are small, itchy or painful lumps on the skin that often occur on the fingers, ears, or toes. They are a type of nonfreezing injury that develops in cold, dry conditions.

You are more likely to develop hypothermia if you are:

  • Very old or very young
  • Chronically ill, especially people who have heart or blood flow problems
  • Malnourished
  • Overly tired
  • Taking certain prescription medicines
  • Under the influence of alcohol or drugs

Causes

Hypothermia occurs when more heat is lost than the body can make. In most cases, it occurs after long periods in the cold.

Common causes include:

  • Being outside without enough protective clothing in winter
  • Falling into cold water of a lake, river, or other body of water
  • Wearing wet clothing in windy or cold weather
  • Heavy exertion, not drinking enough fluids, or not eating enough in cold weather

Symptoms

As a person develops hypothermia, they slowly lose the ability to think and move. In fact, they may even be unaware that they need emergency treatment. Someone with hypothermia also is likely to have frostbite.

The symptoms include:

  • Drowsiness
  • Weakness and loss of coordination
  • Pale and cold skin
  • Confusion
  • Uncontrollable shivering (although at extremely low body temperatures, shivering may stop)
  • Slowed breathing or heart rate

Lethargy, cardiac arrest, shock, and coma can set in without prompt treatment. Hypothermia can be fatal.

First Aid

Take the following steps if you think someone has hypothermia:

  1. If the person has any symptoms of hypothermia that are present, especially confusion or problems thinking, call 911 right away.
  2. If the person is unconscious, check airway, breathing, and circulation. If necessary, begin rescue breathing or CPR. If the victim is breathing fewer than 6 breaths per minute, begin rescue breathing.
  3. Take the person inside to room temperature and cover with warm blankets. If going indoors is not possible, get the person out of the wind and use a blanket to provide insulation from the cold ground. Cover the person's head and neck to help retain body heat.
  4. Victims of severe hypothermia should be removed from the cold environment with as little exertion as possible. This helps to avoid warmth from being shunted from the person's core to the muscles. In a very mildly hypothermic person, muscular exercise is thought to be safe, however.
  5. Once inside, remove any wet or tight clothes and replace them with dry clothing.
  6. Warm the person. If necessary, use your own body heat to aid the warming. Apply warm compresses to the neck, chest wall, and groin. If the person is alert and can easily swallow, give warm, sweetened, nonalcoholic fluids to aid the warming.
  7. Stay with the person until medical help arrives.

Do Not

Follow these precautions:

  • DO NOT assume that someone found lying motionless in the cold is already dead.
  • DO NOT use direct heat (such as hot water, a heating pad, or a heat lamp) to warm the person.
  • DO NOT give the person alcohol.

When to Contact a Medical Professional

Call 911 anytime you suspect someone has hypothermia. Give first aid while waiting for emergency help.

Prevention

Before you spend time outside in the cold, DO NOT drink alcohol or smoke. Drink plenty of fluids and get enough food and rest.

Wear proper clothing in cold temperatures to protect your body. These include:

  • Mittens (not gloves)
  • Wind-proof, water-resistant, many-layered clothing
  • Two pairs of socks (avoid cotton)
  • Scarf and hat that cover the ears (to avoid major heat loss through the top of your head)

Avoid:

  • Extremely cold temperatures, especially with high winds
  • Wet clothes
  • Poor circulation, which is more likely from age, tight clothing or boots, cramped positions, fatigue, certain medicines, smoking, and alcohol

References

Giesbrecht GG. Cold stress, near drowning and accidental hypothermia: a review. Aviat Space Environ Med. 2000;71(7):733-752. PMID: 10902937 www.ncbi.nlm.nih.gov/pubmed/10902937.

Sawka MN, O'Connor FG. Disorders due to heat and cold. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 109.

Zafren K, Danzl DF. Frostbite and nonfreezing cold injuries. In: Walls RM, Hockberger RS, Gausche-Hill M, eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 9th ed. Philadelphia, PA: Elsevier; 2018:chap 131.

Zafren K, Danzl DF. Accidental hypothermia. In: Walls RM, Hockberger RS, Gausche-Hill M, eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 9th ed. Philadelphia, PA: Elsevier; 2018:chap 132.

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  • Exercise - dress appropriately - illustration

    Dressing appropriately is important when exercising in cold weather. Wear several layers, including gloves and a hat. Remove layers when you warm up, and replace them during the slower portions of your workout. If it is snowing or icy, be extra careful to not fall. Remember, you can still become dehydrated in cold weather, you still need plenty of fluid before, during, and after exercise.

    Exercise - dress appropriately

    illustration

  • Skin layers - illustration

    The skin is the largest organ of the body. The skin and its derivatives (hair, nails, sweat and oil glands) make up the integumentary system. One of the main functions of the skin is protection. It protects the body from external factors such as bacteria, chemicals, and temperature. The skin contains secretions that can kill bacteria and the pigment melanin provides a chemical pigment defense against ultraviolet light that can damage skin cells. Another important function of the skin is body temperature regulation. When the skin is exposed to a cold temperature, the blood vessels in the dermis constrict. This allows the blood which is warm, to bypass the skin. The skin then becomes the temperature of the cold it is exposed to. Body heat is conserved since the blood vessels are not diverting heat to the skin anymore. Among its many functions the skin is an incredible organ always protecting the body from external agents.

    Skin layers

    illustration

  • Exercise - dress appropriately - illustration

    Dressing appropriately is important when exercising in cold weather. Wear several layers, including gloves and a hat. Remove layers when you warm up, and replace them during the slower portions of your workout. If it is snowing or icy, be extra careful to not fall. Remember, you can still become dehydrated in cold weather, you still need plenty of fluid before, during, and after exercise.

    Exercise - dress appropriately

    illustration

  • Skin layers - illustration

    The skin is the largest organ of the body. The skin and its derivatives (hair, nails, sweat and oil glands) make up the integumentary system. One of the main functions of the skin is protection. It protects the body from external factors such as bacteria, chemicals, and temperature. The skin contains secretions that can kill bacteria and the pigment melanin provides a chemical pigment defense against ultraviolet light that can damage skin cells. Another important function of the skin is body temperature regulation. When the skin is exposed to a cold temperature, the blood vessels in the dermis constrict. This allows the blood which is warm, to bypass the skin. The skin then becomes the temperature of the cold it is exposed to. Body heat is conserved since the blood vessels are not diverting heat to the skin anymore. Among its many functions the skin is an incredible organ always protecting the body from external agents.

    Skin layers

    illustration

Self Care

 
 

Review Date: 10/16/2017

Reviewed By: Jesse Borke, MD, FACEP, FAAEM, Attending Physician at FDR Medical Services/Millard Fillmore Suburban Hospital, Buffalo, NY. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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