How is heat acquired in the pathophysiology of heat stroke?

Updated: Nov 06, 2018
  • Author: Robert S Helman, MD; Chief Editor: Joe Alcock, MD, MS  more...
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Answer

Heat may be acquired by a number of different mechanisms. At rest, basal metabolic processes produce approximately 100 kcal of heat per hour or 1 kcal/kg/h. These reactions can raise the body temperature by 1.1°C/h if the heat-dissipating mechanisms are nonfunctional. Strenuous physical activity can increase heat production more than 10-fold, to levels exceeding 1000 kcal/h. Similarly, fever, shivering, tremors, convulsions, thyrotoxicosis, sepsis, sympathomimetic drugs, and many other conditions can increase heat production, thereby increasing body temperature.

The body also can acquire heat from the environment through some of the same mechanisms involved in heat dissipation, including conduction, convection, and radiation. These mechanisms occur at the level of the skin and require a properly functioning skin surface, sweat glands, and autonomic nervous system, but they also may be manipulated by behavioral responses.

Conduction refers to the transfer of heat between 2 surfaces with differing temperatures that are in direct contact. Convection refers to the transfer of heat between the body's surface and a gas or fluid with a differing temperature. Radiation refers to the transfer of heat in the form of electromagnetic waves between the body and its surroundings. The efficacy of radiation as a means of heat transfer depends on the position of the sun, the season, clouds, and other factors. For example, during summer, lying down in the sun can result in a heat gain of up to 150 kcal/h.


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