Wilderness and Rescue Medicine 8th Edition

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Wilderness and Rescue Medicine

conditions. It can take two weeks or more to fully acclimatize to a hot environment. Heat response carries the anticipated prob- lems of heat exhaustion and heat stroke. It can be reversed by reducing heat exposure and pro- duction, and by fluid and electrolyte replacement as needed. Although urine output and color are often mentioned as the best field indicators of fluid status, thirst is probably more reliable. Thirst almost always precedes significant volume deple- tion and is a good reminder to drink before you Heat exhaustion is the term used for extreme fatigue from heat stress, and often dehydration. Symptoms can include nausea, weakness, and headache, making continued exertion nearly impossible. For field purposes, heat exhaustion is diminished performance due to heat stress. Heat exhaustion may also signal impending heat stroke. The heat exhausted patient is awake with normal mental status, but complains of nausea, headache, and weakness. The history may reveal inadequate time to acclimatize to a new environ- ment or increased work load. The patient may report low food and fluid intake and reduced urine output. Body core temperature is normal to slightly elevated. Fatigue is the primary problem and there may be some degree of dehydration. If addressed early this is not a serious problem, but it requires imme- diate treatment in the field. The progression of heat illness must be halted and reversed. Treatment of Heat Exhaustion The treatment of heat exhaustion is the same as it is for heat response, just more urgent. Move the patient into a cooler area and stop physical exertion to reduce heat production. Begin active cooling if not improving. If fuid replacement is needed, oral fluids are usually effective, but IV is faster. If the patient is vomiting, oral replacement is still possible by giv- ing fluid frequently in small amounts. Without IV fluids, it may take several hours to bring the have a fluid problem. Heat Exhaustion

Severe Hypothermia

Do Not Resuscitate : • Obvious lethal injury • The chest is frozen • The core temperature is below 10 ° C • Submerged underwater more than one hour • Airway packed with snow in avalanche burial > 35 minutes Wilderness Perspective

If an AED is available, we recommend one shock if prompted and one round of medications per protocol if the body core temperature is above 25°C. Rewarming efforts and CPR should be resumed, and a measurable increase in tempera- ture observed, before trying defibrillation and medications again. How long advanced level field resuscitation should continue is the subject of some debate. Real field experience is very limited, but one hour is probably a generous maximum. In any case, do not put yourself and your group at risk by continuing a resuscitation effort to the point of exhaustion. Heat-Related Illness Because vital organs work best at a temperature 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. Your primary mechanism for heat dissipation is skin vasodilatation and sweat. When sweat evaporates, it absorbs a tremendous amount of heat energy from the skin surface. This is a very effective cooling system if there is enough blood and sweat to keep it going. The body con- stantly sacrifices fluid to maintain normal tem- perature in hot environments. Like cold response, heat response is a normal process. If heat dissipation is not overwhelmed by heat production and retention, the body core temperature will remain within an acceptable range. Eventually, continued heat stress will result in diminished performance and less heat produc- tion, especially in people not acclimated to the