Behavior is the most effective response for thermoregulation. This includes dressing appropriately, modifying environmental temperature, assuming bodily positions that diminish or enhance heat loss, and increasing voluntary movement to generate heat production. Obviously, these considerations must be addressed before a patient is anesthetized and will be considered later in this review.
As temperature receptors transmit information to the hypothalamus, it is integrated and compared with threshold settings. Values above or below these thresholds determine the efferent response that is generated (Figure 1). Efferent outputs from the hypothalamus regulate body temperature by altering subcutaneous blood flow, sweating, skeletal muscle tone, and overall metabolic activity. Heat loss is promoted by vasodilation and sweating, while heat is conserved by inhibiting these processes. Production of heat (thermogenesis) is promoted by shivering and increases the overall metabolic rate. These influences are further explained and summarized in Table 1.
Figure 1
Hypothalamic thermoregulation. Temperature inputs to the hypothalamus are integrated and compared with threshold temperatures that trigger appropriate thermoregulatory responses. Normally these responses are initiated at as little as 0.1°C above ...
Table 1
Hypothalamic Responses to Temperature Receptor Input1–,3
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