Thermoregulation, mild perioperative hypothermia and post-anaesthetic shivering

The maintenance of normothermia is an important function Physiology of the autonomic nervous system in homeothermic mammals Thermoregulation is achieved by a physiological control such as man, as cellular and tissue dysfunction become system consisting of peripheral and central thermoreceptors, evident at even minor deviations from normal core body an integrating control centre and efferent response systems temperature. 48 53 113 In man, core temperature is normally which take compensatory action. 113 Afferent thermal input maintained within narrow limits of 36.5–37.5°C, 48 even in comes from anatomically distinct cold and warmth recepthe presence of an adverse environmental temperature, by tors, which may be peripheral or central. 53 The central a combination of behavioural and physiological responses. control mechanism, situated in the hypothalamus, deterAnaesthesia abolishes behavioural mechanisms and has mines mean body temperature by integrating thermal signals the potential to disrupt the physiological mechanisms of from peripheral and core structures, and comparing mean thermoregulation. Adverse postoperative outcomes, includ- body temperature with a pre-determined ‘set-point’ ing wound infection, increased surgical bleeding and morbid temperature. 48 In man, the efferent response to effect change in body heat content as required is by behavioural and cardiac events are being associated with mild perioperative autonomic means. The latter involves control of cutaneous hypothermia (33.0–36.4°C). 21 22 26 42–44 52 74 80 84 85 90 109