Wilderness and Rescue Medicine 7th Edition Jeffrey Isaac, PA-C and David E. Johnson, MD

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Wilderness and Rescue Medicine

Treatment of Mild Hypothermia Mild hypothermia is an urgent problem requiring immediate and aggressive treatment in the field. The anticipated problem, severe hypothermia, will be much more difficult to handle. The treatment is essentially the same as that for cold response: pro- tect from heat loss and restore calories and fluid. Vigorous shivering is the most efficient form of field rewarming for the mildly hypother- mic patient. Shivering needs just fluid and fuel. Adding external heat with hot water bottles or body heaters is generally safe and certainly more comfortable, but no attempt to mobilize and exercise the patient should be made until obvious improvement in mental status is noted, especially in cases of subacute hypothermia. All hypothermic patients experience some degree of afterdrop, where the body core tempera- ture continues to decrease even after rewarming has begun. This is due to the physics of heat trans- fer through any medium, but it is exacerbated by vasodilatation of the body shell and circulation of blood through the cooler extremities as the patient rewarms. As a result, your patient may get a little worse before getting better, especially if you exercise him or her too soon, which seems to cause a greater degree of afterdrop. It may require over 40 minutes of shivering, sugar, fluids, and aggressive external rewarming before an improve- ment in symptoms indicates that it is safe to allow the patient to exercise. In many cases field treatment for mild hypo- thermia will be definitive and evacuation will not be necessary. Remember, however, that mild hypothermia that cannot be fixed will eventually become severe hypothermia. Inadequate response to field treatment warrants evacuation.

General Principles

Mild Hypothermia

Treatment: • Immediate field rewarming • Food and fluids • Trap heat generated by shivering

• Insulate from convection, conduction, radiation • Dry skin and clothing to reduce evaporation • Exercise only when improvement is noted • Package and evacuate if not improving

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Severe Hypothermia For hospital treatment, several distinct stages of hypothermia are defined to guide the resuscita- tion effort. Most commonly these are referred to as mild, moderate, severe, and profound. For field treatment, however, the distinction is mostly prac- tical: can the patient cooperate with your treat- ment or not? A very cold patient who is not awake and/or is not shivering and cannot cooperate with treatment is treated as severely hypothermic. An accurate measurement of core temperature is not required. As the core temperature falls below 32°C, mental status changes are followed by a drop to V, P, or U on the AVPU scale. This is quite different from the subdued but awake mild hypothermic. Shivering stops as muscles are deactivated by shell cooling and lack of calories to burn.

General Principles

Severe Hypothermia

Signs and Symptoms: • Brain failure (V, P, or U on AVPU) • Shell/core effect, no shivering • Core temperature < 32°C • VS may be undetectable • Cardiac irritability • Dehydration, metabolic derangement

Low Risk

High Risk

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