ACCIDENTAL HYPOTHERMIA - 08/09/11
Résumé |
The normal range of human core body temperature is 36.4°C to 37.5°C (97.5°F to 99.5°F). Body temperature is closely regulated through a balance between heat production and heat dissipation.45 The majority of endogenous heat production results from metabolic activity in the heart and liver. The skin accounts for 90% of heat loss, and the lungs contribute the rest. Loss of heat by radiation is the primary method of thermal-load dissipation. The preoptic nucleus of the anterior hypothalamus is the thermal control center, maintaining body temperature at a given set value. In a conscious individual, the appreciation of cold induces the individual to exercise, wear more clothes, or move to a warmer environment. In response to a drop in core body temperature, the hypothalamus conserves heat by producing cutaneous vasoconstriction and stimulating muscular activity in the form of shivering.2, 45 Inhibition of shivering with medications such as meperidine may attenuate rewarming and worsen core temperature afterdrop in hypothermic individuals.16 Heat production increases twofold to fourfold with shivering and exercise.
Hypothermia is defined as an unintentional decline in the core temperature below 35°C (95°F). At this temperature, the coordinated systems responsible for thermoregulation begin to fail because the compensatory physiologic responses to minimize heat loss are very limited.9 Primary hypothermia (accidental hypothermia) refers to a spontaneous reduction of core body temperature, usually as a result of exposure to cold environments without adequate protection. Environmental hypothermia results from a combination of heat loss by convection (degree of wind exposure), conduction, and radiation to the surrounding ambient air. Secondary hypothermia represents a complication of an underlying disorder. Some of the disorders and conditions that may predispose an individual to hypothermia by decreasing heat production, increasing heat loss, or interfering with the central or peripheral control of thermoregulation are listed in Table 1.2, 8, 27, 34, 35, 37, 45.
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| Address reprint requests to Nicola A. Hanania, MD, Ben Taub General Hospital, 1504 Taub Loop, Houston, TX 77030, e-mail: Hanania@bcm.tmc.edu |
Vol 15 - N° 2
P. 235-249 - avril 1999 Retour au numéro
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- PREFACE
- KALPALATHA K. GUNTUPALLI, NICOLA A. HANANIA
- HEAT-RELATED ILLNESSES
- Rahul Khosla, Kalpalatha K. Guntupalli
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