Wilderness and Rescue Medicine 8th Edition

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Section V: Environmental Medicine

Chapter 17 Review: Thermoregulation

• Heat energy is transferred by conduction, convection, radiation, and evaporation. All are important to consider when assisting a patient with thermoregulation. • The key signs and symptoms of mild hypothermia include cold and pale skin, uncontrollable shiver- ing, and altered mental status. • Acute hypothermia is rapid onset with less dehydration and calorie depletion. Spontaneous rewarm- ing is possible. Subacute hypothermia develops over hours or days and is accompanied by dehydra- tion and calorie depletion. Insulation, rehydration, and restoration of energy stores are necessary for rewarming. • The key signs and symptoms of severe hypothermia are a cold person who is V, P, or U on the AVPU scale or shivering has stopped. The pulse may be slow or undetectable. Body core temperature is below 32°C. • Severe hypothermia should be considered an emergency. The ideal treatment is controlled rewarming in a hospital. Evacuation should be gentle but expeditious with rewarming around the thorax en route. • If evacuation is impossible, severe hypothermia can be rewarmed in the field by applying heat around the thorax. Sugar can be given under the tongue as a paste or gel when the patient is positioned to protect the airway. Warmed IVs and dextrose may be given. Urgent but gentle evacuation should be accomplished when it becomes possible. • CPR may cause cardiac arrest in a severely hypothermic patient. CPR should be initiated only when a palpable pulse or monitored rhythm is lost and/or it will not interfere with efficient evacuation to definitive care. • Because vital organs work best at a temperature of around 37°C, the body conserves only as much heat as it needs to keep it at that temperature and gets rid of the rest, primarily through skin vaso- dilatation and sweat. • Heat exhaustion is extreme fatigue from heat stress. It may be associated with dehydration. • The field treatment for heat exhaustion is shade, rest, and adequate hydration. • Heat stroke is a major critical system problem requiring immediate and aggressive cooling. The primary problem is dangerously elevated body core temperature, which is capable of significant damage to the central nervous system and other vital organs. • It is ideal to evacuate any heat stroke patient to hospital care once temperature is controlled. Patients who recover quickly in the field to normal mental status and have normal urine output may be considered less urgent for evacuation.