Abstract: AIM: To evaluate the efficacy of different doses of dexmedetomidine(dex) in preventing shivering in patients with combined spinal epidural anesthesia.METHODS: One hundred and twenty patients, ASA physical statusⅠ-Ⅱ, aged 33-65yr, weighing 45-76 kg, undergoing elective gynecological operations with combined spinal epidural anesthesia, were randomly divided into 4 group (n=30 each). Ⅰ-Ⅲ groups received i.v. infusion of dex of 0.2 μg/kg , 0.4 μg/kg, 0.6 μg/kg at a rate of 0.05 μg/kg respectively after combined spinal epidural anesthesia .Group C received normal saline in ten minutes. Mean arterial pressure ,heart rate, BIS value and tympanic temperature were recorded before administration (T₀), 5min (T₁), 15min (T₂) and 30min (T₃) after dex and the end of surgery (T₄) .The adverse event including nausea, vomiting, hypotension and usage of atropine were recorded. Level of sedation were assessed by BIS monitor and tympanic temperature were recorded in each point.RESULTS: The incidence of shivering were 43.3% , 16.6% , 6.7% and 40%. The incidence of hypotension were 5%, 7%, 8%, 8%, the usage incidence of atropine were 2%, 10%, 20% and 2%, BIS value were significantly decreased in dex groups at T₁-T₄ when compared with those in group C(P<0.05). Incidence of nausea or vomiting had no significantly difference in all groups. Tympanic temperature of patients in all groups was significantly lower than the baseline level(P<0.05).CONCLUSION: Dexmedetomidine can significantly reduce the incidence of shivering in patients with combined spinal epidural anesthesia. The mechanism is concerned with lower core temperature triggering shivering threshold. The optimal maintain dose of dex is 0.4 μg/kg.

Key words: dexmedetomidine, combined spinal-epidural anesthesia, shivering, tympanic temperature