الفهرس 
NORMAL THERMOREGULATIONOnly 14 pages are availabe for public view
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Abstract
Mammals are homeothermic, requiring a nearly constant internal body temperature. The thermoregulatory system usually maintains core body temperature within 0.2°C of “normal” which about 37°C in humans.
Thermoregulation is similar to many other physiologic control systems in that the brain uses negative and positive feedback to minimize disorders from preset “normal” values. When cold or warm thresholds are exceeded, physiological responses start to return temperature to its normal core of 37°C. When the cold threshold is exceeded, vasoconstriction and shivering occur. When the warm threshold is exceeded, active vasodilation and sweating occur.
Anesthesia and surgery commonly cause thermal disorders. Nearly all patients administered general anesthesia become hypothermic, typically by l-3°C, depending on the type, and dose of anesthesia, amount of surgical exposure, and ambient temperature. There is now convincing evidence that a typical degree of hypothermia (2°C below normal) predisposes to numerous complications such as post-anesthetic shivering, prolonged duration of action of several drugs, myocardial ischemia, coagulopathy and increased incidence of surgical wound infections, which alter patient outcome. Hypothermia may be induced to protect tissue ischemia, especially during cardiac, occasionally neurosurgery. Deliberate hypothermia is safe, only when anesthesiologists understand and treat the physiologic changes caused by core temperature lower than normal.
Core body temperature should be measured in most patients given general anesthesia for more than 30 minutes. Also, should be measured during regional anesthesia when changes in body temperature are expected. Unless hypothermia is specifically indicated, efforts should be made to maintain the intraoperative core temperature higher than 36°C. Core temperature measurements (e.g. tympanic membrane, pulmonary artery, distal oesophagus and nasopharynx) are used to monitor intraoperative hypothermia, to prevent overheating and facilitate detection of malignant hyperthermia. Both core and skin surface temperature measurements are required to determine the thermoregulatory effects of different anaesthetic drugs.