Environmental Emergencies

Chapter 31 Environmental Emergencies



S. Kay Sedlak


This chapter discusses specific emergencies that occur because of the body’s exposure to changes in or extremes of environmental conditions. The most common environmental emergencies involve the body’s inability to thermoregulate due to exposure to cold or heat.


Thermoregulation, or the maintenance of a fairly constant body temperature, is important because the human body functions optimally within a specific temperature range. The body attempts to maintain a temperature of 37°C (98.6°F) and the hypothalamus reacts to changes in blood temperature of as little as 0.5°C (roughly 1°F). There can be negative consequences to both too little heat and too much heat.



Cold-Induced Injuries


Cold-induced injuries include both tissue injuries (chilblains, immersion foot, and frostbite) and a decrease in core body temperature. Table 31-1 lists factors that increase susceptibility to cold.



TABLE 31-1 FACTORS THAT INCREASE SUSCEPTIBILITY TO COLD

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Chilblains1


Chilblains, also known as pernio, are localized areas of itching, painful redness, and recurrent edema on exposed areas such as the earlobes, fingers, and toes. Chilblains are a mild form of frostbite that develop in cool, damp climates when temperatures are above freezing. Symptoms (usually numbness and tingling) are generally self-limiting and resolve with symptomatic treatment.



Immersion Foot


Immersion foot, or “trench foot,” occurs when the feet are wet and subjected to cold temperatures for prolonged periods inside a nonbreathing boot or shoe. This condition is typically seen in foot soldiers, hunters, and the homeless. Initially the foot appears pale and wrinkled. Tissue sloughing can develop if the condition is allowed to persist. Dry shoes and socks are necessary to prevent this condition.



Frostbite2–6


Frostbite is a traumatic condition that results when ice crystals form in the cells and extracellular spaces, causing direct cellular damage. In addition, there is indirect damage secondary to vasospasm and arterial thromboses. Once the cells are frozen, damage is irreversible. Further exposure or trauma worsens the injury. Protecting the tissues surrounding frostbitten areas helps prevent additional tissue loss. The full extent of injury will not be apparent for several days. Frostbite can be accompanied by hypothermia. Depending on the extent of hypothermia, treatment of this condition may take precedence over frostbite interventions.



Superficial Frostbite


Superficial frostbite usually involves the fingertips, ears, nose, cheeks, or toes. The skin will retain some resistance when pressed down upon.



Signs and Symptoms




• Local burning, numbness, tingling


• Whitish, waxy skin color


• Stinging, hot feeling after the skin thaws


• Large blisters, depending on length of exposure



Deep Frostbite


Deep frostbite produces local vascular and tissue changes resulting in cellular injury and death. Deep frostbite can involve muscle, fat, bones, and tendons as well as skin. Factors that influence the probability of sustaining frostbite include the following:



• Ambient temperature


• Windchill factor


• Duration of exposure


• Contact with moisture or metal objects


• Type and number of layers of clothing



Signs and Symptoms




• Slight burning pain followed by a feeling of warmth and then numbness as the area freezes


• Whitish or yellow-white discoloration of the skin followed by a waxy appearance


• Swelling and intense burning accompanying thawing


• Blisters (usually appear in 1 to 7 days)


• Edema of the entire extremity that may persist for months


• Severe discoloration and gangrene are late findings



Therapeutic Interventions


Escharotomy is indicated for treatment of severe vascular compromise in deep frostbite.


Amputation of body parts affected by frostbite is not an emergency procedure. As edema resolves, early necrosis becomes apparent. Final demarcation often is delayed for more than 60 to 90 days. Hence the aphorism “frostbite in January, amputate in July.”


image

Fig. 31-1 Spiderlike cutaneous burns from path of lightning over surface of body.


(Courtesy Mary Ann Cooper, MD. From Marx, J. A., Hockberger, R. S., & Walls, R. M. [2009]. Rosen’s emergency medicine [7th ed.]. Philadelphia, PA: Mosby.)


General guidelines for the management of cold-related tissue injury are listed in Table 31-2.


TABLE 31-2 GENERAL MANAGEMENT PRINCIPLES FOR COLD-RELATED TISSUE INJURY







• Do not thaw areas if they are likely to be refrozen before definitive care. Repeated freeze-thaw cycles cause additional tissue necrosis.


• Protect the injured part from further damage.


• Do not use ice or snow and friction to massage the frozen extremity. This outmoded intervention promotes further tissue damage.


• Immerse the injured part in circulating water that is temperature controlled at 37°C–40°C (98.6–104°F).


• Encourage gentle motion of the injured part in water, but do not rub injured tissues.


• Once thawed, protect and immobilize the extremity with splints and bulky sterile dressings (avoid pressure).


• Administer nonsteroidal anti-inflammatory medication and additional analgesics if necessary.


• Provide topical care for areas of open wounds.


• Ensure tetanus prophylaxis.


• Rehydrate patient and address other medical and surgical conditions.



Prevention




• Dress properly for the climate; wear layers of loose-fitting clothing.


• When outdoors in cold areas, eat a diet high in carbohydrates and fats.


• Do not smoke or drink alcoholic or caffeinated beverages in extreme weather.


• Prevent bare skin contact with metal objects.


• Keep skin and clothing dry.


• Avoid exhaustion.


• Protect previously frostbitten parts from re-exposure.



Hypothermia


Hypothermia is defined as a core body temperature of less than 35°C (95°F). Severe hypothermia occurs at a core body temperature of 32.2°C (90°F). Below this temperature, profound physiologic derangements take place. Death usually results when core body temperature falls below 25.6°C (78°F). The following populations are especially prone to hypothermia:



• Neonates, because of limited body fat and an inability to shiver or seek warmth


• Elderly persons, because of medications, loss of body fat, and cardiovascular changes associated with aging


• Alcoholics and the homeless, because of poor nutrition and environmental exposure



Pathophysiology


Body heat loss occurs by four different means, which alone or in combination can result in losses that overwhelm the body’s ability to compensate: convection, conduction, radiation, and evaporation (Table 31-3).



TABLE 31-3 MECHANISMS OF HEAT LOSS

image


Normal body heat lost by conduction is only 2% but it may increase 5 times with wet clothes or 25 times with cold water immersion.7


Most of the metabolic and enzymatic processes of the body are temperature dependent and changes evolve with decreasing temperatures. At core body temperatures less than 32°C (90°F), defined as profound or severe hypothermia, pathologic changes are noted as the cold directly affects various body functions. Table 31-4 summarizes potential changes in various body systems.


TABLE 31-4 POTENTIAL PATHOLOGICAL CHANGES IN VARIOUS BODY SYSTEMS












BODY SYSTEM POTENTIAL PATHOLOGICAL CHANGE
Central nervous system

Progressive decline in level of consciousness as temperature decreases


Sluggish pupillary response


Decrease in cerebral metabolism, causing impaired judgment and disorientation


Consciousness may be lost between 32°C (89.6°F) and 30°C (86°F)

Cardiovascular system

Initially, increased blood pressure, heart rate, and cardiac output; later, bradycardia


Atrial fibrillation commonly occurs and spontaneously resolves with rewarming


Prolonged QT interval


Asystole almost universal at temperatures ≤18°C (64.4°F)


Death most commonly from asystole


Dysrhythmias refractory to defibrillation, medications, and artificial pacing until heart rewarmed to >28°C (82.4°F)


Osborn or J wave (extra deflection at QRS-ST junction) may be seen

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Aug 9, 2016 | Posted by in EMERGENCY MEDICINE | Comments Off on Environmental Emergencies

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