Hypothermia

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1 General Information
2 Levels of Hypothermia
3 Hypothermia Symptoms
4 How the body loses heat
5 References

[edit] General Information

The human body functions only within a narrow temperature range. Warmth must be maintained to support the chemical and metabolic functions sustaining life. When the body cools below acceptable levels (hypothermia), there is a significant loss of strength, coordination, and alertness. Patients suffering from hypothermia may become unable to move effectively or to assist in their own rescue.

Canyoneers must often contend with water that is dangerously cold. The effects are felt with surprising speed. Just like the effects of windchill, those of moving water produce an enhanced cooling effect that multiplies the impact of cold water. But hypothermia does not always occur in cold weather. Unexpected wet conditions can drench an unprepared canyoneer, or the wind can steal heat from his body. An unprotected canyoneer who takes a long swim on a cool, overcast day may find it hard to rewarm. An injured victim may experience hypothermia as shock sets in.

Hypothermia is insidious. It comes on slowly and gradually. Aside from falls, hypothermia is probably the greatest danger to the canyoneer. Team members must be vigilant to observe signs of hypothermia in each other and willing to stop to rewarm before continuing down canyon.

The symptoms of hypothermia may be remembered by the simple mnemonic: He's got the umbles. Someone with hypothermia mumbles, grumbles, fumbles, stumbles, and tumbles. People feel crummy, groggy and uncoordinated. They lack judgment, making it difficult to recognize onset in oneself. The cold clouds the mind and the body, leading people with mild hypothermia to do incredibly stupid things contributing to their demise. Team members must rely on each other to appropriately intervene.

Treatment should focus on getting dry and out of the wind. Simple preparation for hypothermia might include a dry fleece jacket and hat in a garbage bag. Every party member should carry an emergency bag/blanket to survive a force bivy. Hard candy is a good source of quick energy to fuel the boiler. A magnesium strip will help get a driftwood fire going. And one might consider carrying a small stove, pot and bullion cube/ramen/tea bag. Honestly, a small can of Sterno and a Sierra cup won't even set you back half a pound, but a cup of warm tea will make you feel a lot better.

[edit] Levels of Hypothermia

The human body has three layers; an outer superficial layer, an intermediate layer; and the inner core. The superficial layer consists of the skin and subcutaneous tissue; the intermediate layer is made up of the extremities, skeletal and muscular tissues, and some lesser organs; the inner core contains the most critical organs; the heart, lungs, and brain. When hypothermia sets in, the body prioritizes heat distribution. It works to keep the vital core warm, hoarding the additional calories required to heat parts of the body that are not necessary for survival,

As the body begins to chill, the first signs of hypothermia come in the form of muscle tension and goose bumps. This non-shivering heat generation can double the metabolic rate. As the core temperature continues to drop, shivering begins. These uncontrolled contractions can increase the metabolism to five times the normal rate. Now the body is burning roughly 400 calories per hour. That's approximately the number of calories in two Snickers candy bars. Under the right conditions, the body can still rewarm itself.

At some point, the body starts to realize it is beginning to lose its battle to heat all its layers and decides it can survive without the superficial one. By shunting the blood flow away from the skin and outer tissues, it reduces the flow by about 1 to 2 percent. Strenuous activity could increase heat output, but the body has limited stores of fuel. Heating the entire body might burn what reserves are left and leave the victim to cool even more quickly. Progression to this step is exacerbated by dehydration. Without sufficient blood volume, it is difficult to maintain sufficient blood flow to warm the periphery and this space is more readily clamped off.

When core body temperature fails below 95F (35C), shivering diminishes. The patient may become confused; reasoning becomes clouded. With continued heat loss, the body decides to sacrifice parts of itself so that the brain can survive. By reducing the area being heated, life is prolonged. First, the body decides it doesn't need the extremities, and carbon dioxide and lactic acid build up in these areas. Then it begins to shut down blood flow to unnecessary organs. And finally, it will limit flow to the three organs that sustain life itself.

As the body continues to cool, the victim begins to lose touch with reality. In some cases. they experience atypical mood swings and may become argumentative or combative when assistance is offered. Once the core body temperature drops lo 90F, shivering is replaced by muscle rigidity, and mental facilities are severely impaired. The victim is semiconscious, progressing toward unconsciousness. As the core temperature continues to drop, the metabolic rate diminishes, oxygen consumption drops, and respiration slows. Cardiac output also slows and weakens, resulting in further reduction in blood flow.

As lung and cardiac function diminish, cardiac arrhythmias may develop. Death may occur from spontaneous ventricular fibrillation, a chaotic arrhythmia leading to incoordinate motion of the heart, circulatory failure, and death.

[edit] Hypothermia Symptoms

Temperature above 95F (35C). Conscious and alert. Vigorous uncontrollable shivering, pain or numbness in extremities, loss of manual dexterity, slurring of speech.
90F(32.2C) to 95F (35C). Conscious. Mildly impaired mental facilities. Diminished shivering is replaced by muscle rigidity.
86 (30C) to 90F (32.2C). Semi- or fully unconscious. Severely impaired mental abilities; may appear intoxicated. Rigid muscles, cardiac arrhythmias.
80 (26.7C) to 86F (30C). Unresponsive, unconscious. Rigid muscles, dilated pupils barely responsive to light, diminishing or nonexistent pulse and respiration, blue-gray skin color.
80F (26.7C) or lower. Ventricular fibrillation, cardiac arrest. Pupils fixed and dilated. Death or apparent death (where the person appears to be dead and may seem to dead on assesment). Death or braindeath cannot be confirmed until the person is normothermic.

[edit] How the body loses heat

Radiation: Heat is given off to a cooler environment directly. The amount lost to cold water is many times that of cold air.
Conduction: Heat passes out of the body directly into a cooler object, such as the ground an injured person is Iying on.
Convection: Heat rises away from the body into the air. Clothing helps prevent this.
Evaporation: Heat is removed from the body as water or perspiration evaporates and the skin dries. This is why wet clothing should be removed from hypothermia victims.
Respiration: Heat is continually lost as cold air is drawn into the lungs, warmed, and then exhaled.