By definition, hypothermia is the lowering of the bodies core temperature. Hypothermia is the number 1 killer of people in the outdoors. People often die of hypothermia or make poor decisions due to thier altered mental status that accompanies moderate hypothermia gets them killed.

1. Causes of Hypothermia

a. Heat loss

Conduction: Direct contact with surfaces such as wet clothing or cold sleeping surface.

Convection: Heat transfer by motion such as wind blowing layers of warm air off skin.

Radiation: Temperature gradient between body and air.

Wind chill: Effective temperature on wet skin.

Wet chill: Heat loss to wet skin.

Air layer: The thin layers of air that covers your body that helps protect you from the elements.

b. Typical hypothermia patients have the following things in common:

    -Its a little windy

    -Moderate to cold temperatures

    -They are wet due to weather or perspiring

    -Poor clothing choices such as cotton, no hat

    -They are a little dehydrated

    -They have not had much to eat

    -They're a little tired, overextended

    -They're not near obvious shelters

Look at the above list, how many times have you met much of the above criteria? The above circumstances have lead to many, many deaths. Not all of the above factors must be present for a severe case of hypothermia.

2. Stages of Hypothermia

    99 Degrees normal oral temperature.

    97 Shivering starts.

    95 Heat production 6 X basil (this means your body is generating 6 times the body heat it usually needs to in order to keep up).

    93 Weakness starts, poor coordination.

    91 Shivering decreases, altered mental status sets in.

    90 Metabolism declines-body systems slow down.

    86 Heat control lost, shivering stops and death is quickly approaching.

    84 Atrial Fibrillation.

3. Signs and symptoms

a. Early

    -Shivering

    -Fatigue

    -Patient will feel cold, clothing often is wet or skin exposed

b. Moderate

    -Patient stops talking, seems quiet

    -Irritability

    -Loses will power to continue with task

    -Looses coordination, such as unable to zip up pants

    -Begins to have an altered mental status.  This is the stage when people make poor decisions that often get them into more trouble. To diagnose hypothermia test them on simple commands or do DUI type tests.

c. Late

    -Patient will have severely altered mental status.

    -Stops shivering.

    -Extremities very cold to touch.

    -Low blood pressure/pulse.

    -Unconsciousness-Atrial Fibrillation.

    -Death.

4. Treatment

a. Early to moderate stages (97 to 90 degrees) conscious patient still talking.

    -Remove wet clothing, provide warm environment and dry clothing.

    -Hot drinks and easy to digest snacks.

    -Heat packs under arm pits and groin.

    -02-6 lpm by cannula.

    -Assess vital signs.

    -Prepare for transport.

b. Severe stages (90 to 74 degrees) patient unable to speak or unconscious.

    -Do not attempt field re-warming; re-warming shock will often cause death if not closely        monitored. The re-warming should be done in the hospital environment at there are often severe complications.

    -Prepare patients for immediate transport, true emergency!

    -Gentle handling of severe hypothermia patient very important to prevent arrhythmia's.

    -High flow 02 via mask.

    -Monitor vital signs.

5. Important Notes

a. Early detection of Hypothermia and rapid treatment are critical in treating hypothermia patients. As you can see, treatment in the early and moderate stages of hypothermia can be relatively simple and effective. In later stages treatment in the field is difficult at best. When early stages of hypothermia are detected, set up camp, get the patient into a sleeping bag, set up the tent and get the stove going. Abandon the task at hand and focus on treatment of patient. All to often people underestimate the problem and the patient ends up dead from "too little, too late".

b. Trauma patients in the outdoor setting have an increased mortality rate of 50% due to hypothermia. Patients with Trauma or other illnesses are much more prone to getting hypothermia in the field. Monitor and treat all patients for Hypothermia, even when not initially obvious. Maintaining body temperature with sleeping bags or other means is key.

c. Most hypothermia patients die 30 minutes to 1 hour after rescue. This is due to hypothermia shock, an unstable period when re-warming of severe hypothermia patients occurs. Patients generally survive this only when they are in a fully equipped E.R. monitored by a physician.

6. Prevention

a. Good food and water intake more important than equipment. Your body needs food and water to generate heat and handle exertion. Eating well and staying hydrated is the best way to prevent hypothermia.

b. COTTON KILLS Never wear cotton or like clothing in cold and/or wet environments. Cotton absorbs water/perspiration and keeps it close to your body. The wet clothing sucks warmth out of your body faster than your metabolism can generate heat.

c. SAR field clothing should consist of synthetic clothing, Gortex or like shells and layering systems (see clothing section).

d. Avoid over extending yourself in poor weather environments, breaks are good for prevention and give you the opportunity to evaluate others in your group

e. Watch others for signs of hypothermia. Often people will not be aware they are in beginning stages of hypothermia or will be in denial of a problem.

f. Finally, wear a hat. 90% of your heat loss is from your head.

Prepared by Michael St. John