**5.1 Thermoregulation**

The human body maintains a temperature of 37 C, through convection, conduction, radiation, and vaporization, which are controlled by the hypothalamus. In cases of an increase in body temperature, the sympathetic system is activated, causing cutaneous vasodilation and thermal sweating. These also cause a loss of intravascular volume and salt, leading to dehydration. Increased severity causes further loss of water with salt, leading to impaired thermoregulation and reduction of visceral blood volume with shunting to the skin and muscles, resulting in organ dysfunction (above). In response to stress, body cells generate heat stroke proteins (HSP). An increase in HSP is essential for heat tolerance, and overexpression of HSP protects against organ impairment.

The increase in body temperature causes intestinal mucosal injury, and the release of endotoxins and proinflammatory mediators interleukins 1 and 6 from muscles to the systemic circulation, these chemicals leucocytes and endothelial cells, and the release of various cytokines and HMGB (high mobility group box 1 protein), all in combination stimulate SIRS (systemic inflammatory response syndrome) (**Figure 1**) [5].

The heat stroke thus generates inflammatory and coagulopathy responses; the direct effect of heat also causes endothelial injury and generates microthromboses, leading to a disseminated intravascular coagulation (DIC) response.

#### **Figure 1.**

*A simplified human thermoregulation –the hypothalamus checks the body's core temperature and starts necessary thermogenesis or heat dissipating processes to maintain the body's core temperature. Modified from Nkurikiyeyezu K. An efficient thermal comfort delivery in workplaces. 978-1-5386-9151-9/19.*


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Table 1.
Prognostic factors.
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