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HYPOTHERMIA (COLD INJURY)
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Cold injuries are classified as systemic or localized and as freezing (eg, frostbite) or nonfreezing (eg, immersion foot). Factors influencing the risk for these injuries include the atmospheric or water temperature, humidity, wind velocity, duration of exposure, type of protective equipment or clothing, type of work being performed and associated energy expenditure, and age and health status of the worker. Wet conditions, especially immersion, substantially increase the risk of hypothermia.
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Workers at risk include both indoor and outdoor workers exposed to cold, such as meat packers and others who work inside freezers, construction workers, cold-room personnel, fishermen, woodsmen, divers, mail carriers, firefighters, utility repair workers, search and rescue staff, and road maintenance workers. The risk of hypothermia increases with age and also is increased if the individual is intoxicated with drugs or alcohol; is receiving medications such as barbiturates, antipsychotics; smokes; or has adrenal insufficiency, diabetes, myxedema, neurologic disease (affecting hypothalamic or pituitary function or causing peripheral sensory impairment), peripheral vascular disease, or cardiovascular disease (CVD) (causing diminished cardiac output).
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1. Systemic Hypothermia
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Systemic hypothermia is reduction in the body’s core temperature below 35°C (95°F). When the body is exposed to cold environments, it has two types of normal physiologic reactions: (1) constriction of superficial blood vessels in the skin and subcutaneous tissue, resulting in heat conservation, and (2) increase in metabolic heat production through voluntary movement and by shivering. In cases of systemic hypothermia, cellular and physiologic functions are diminished. Oxygen consumption is decreased by approximately 7%/°C, myocardial repolarization is slowed, and ventricular fibrillation is a major hazard.
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The medical history should address the circumstances under which the patient was found, the probable duration of exposure, associated injuries or frostbite, preexisting medical conditions, alcohol or drug use, and recent changes in the level of consciousness. Because body heat is lost more quickly when a person is wet, immersed in water, or exhausted, these factors should be considered.
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The onset of hypothermia often is insidious, without any specific characteristics. With profound hypothermia, there is often diminished memory, a decrease in or absence of shivering, and combativeness. Initial findings may include drowsiness, slurred speech, irritability, impaired coordination, general weakness and lethargy, recent diuresis, and puffy and cool skin and face.
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Physical examination often reveals diminished neurologic reflexes, slow mental and muscular reactions, weak or nonpalpable pulse, arrhythmia, low blood pressure, and increased blood viscosity. Shivering and peripheral vasoconstriction are present with the core temperature at 35°C (95°F). Heart rate, respiratory rate, and blood pressure decrease with reduced temperature. With mild hypothermia (33–35°C [91.4–95°F]), there is extensive shivering, which decreases as temperature drops below 33°C (91.4°F), wherein joint and muscle stiffness becomes more predominant.
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Core temperature should be taken with a thermometer or thermocouple capable ...