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INTRODUCTION

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EMS providers often encounter patients who have become victims of environmental emergencies. Even in urban areas, patients may suffer from heat- or cold-related illnesses. In more remote areas, altitude illness, undersea illness, and decompression sickness may be encountered. Electrical injuries from both lightning and electrical sources may be seen. EMS workers need to understand how to stabilize these illnesses and injuries, while remaining safe.

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OBJECTIVES

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  • Understand the pathophysiology, diagnosis, and management of hypothermia, frostbite, nonfreezing cold injury, and other cold-related injuries.

  • Understand the pathophysiology, diagnosis, and management of heat stroke, heat exhaustion, and other heat-related injuries.

  • Understand altitude-related illness, including AMS, HACE, HAPE.

  • Understand the pathophysiology and treatment of undersea-related illnesses. Understand the diagnosis and management of electrical injuries.

  • Understand the pathophysiology of electrical injuries.

  • Understand that standard triage decisions may be reversed in the case of electrical injuries.

  • Appreciate possible risks to the rescuer in electrical injuries.

  • Understand the pathophysiology of decompression sickness.

  • Understand barotrauma injuries

  • Be familiar with treatment of diving and undersea injuries.

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COLD-RELATED ILLNESS

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MECHANISMS OF HEAT LOSS AND COMPENSATORY MECHANISMS

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Heat transfer occurs through radiation, conduction, convection, and evaporation. Each of these mechanisms serves to transfer heat to and from the body. In homeostasis, these mechanisms of energy diffuse heat generated through the body's metabolic processes. Conduction is the transfer of heat between objects in direct contact. The amount of energy lost by a body in contact with another object depends on several factors, including the amount of the body in contact with the object, the conductivity of the objects, and the difference in temperature between the two objects. Conduction is a major cause of profound heat loss among victims who have fallen into cold water, for example. Convection is the transfer of heat caused by the movement of molecules of gas of liquid near the body. Convection explains why wind can exacerbate cold temperatures (the wind chill index). Radiation refers to the transfer of electromagnetic radiation between objects, in this case between humans and the environment. Evaporative heat loss takes place when water changes state, from liquid to gas. Heat loss increases with sweating.1

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RISK/CONTRIBUTING FACTORS

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Certain populations are more at risk for accidental hypothermia than others. Patients at either end of the human age spectrum are particularly at risk for hypothermia.

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In the elderly, both metabolic and behavioral factors contribute to a propensity for rapid development of hypothermia in cold conditions.2 In infants, increased surface area and absence of behavioral adaptations to cold exposure contribute to a high risk of hypothermia, even in ambient conditions.

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Next, ingestion of certain medications places patients at risk for hypothermic illness. Medications can either interfere with thermogenesis or promote heat loss through various processes, including vasodilatation. Sedatives and psychotropic medications, including barbiturates, benzodiazepines, phenothiazines, lithium, and ...

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