During G.A. shivering is abolished by suppression of
A i.e. Hypothalmus Temperature regulation during G.A. OWI Normally hypothalmus maintain core body temperatureQ (central blood temperature) within very narrow range (intehreshold range). Temperature of patient undergoing G.A. should be monitored (except for < 15 minutes procedure) by thermistor or thermocouple with a probe placed over tympanic membrane, rectum, nasopharynx, esophagus, bladder & skin. Hypothermia (ie body temperatureprotective during times of cerebral or cardiac ischemiaQ Raising body temperature induces vasodialation & sweating while hypothermia triggers vasoconstriction & shivering as compensatory mechanism. During G.A. body cannot compensate for hypothermia because anesthetics inhibit central thermoregulation by interfering with hypothalamic function.Q Spinal & epidural anesthesia also lead to hypothermia by vasodialation & internal redistribution of heat. The accompanying thermoregulatory impairment from regional anesthesia is due to an altered perception of temperature in bloacked dermatomes by hypothalmus as opposed to central effect of G.A. Postanesthetic shivering or shaking that is not related to hypehermia can be abolished by ceain opioids e.g. meperidine, butrophanol & tramadol (but not morphine).
Hypothalmus
Thalmus
Cerebral Coex
Medulla