OBJECTIVE:To explore the minimum effective dose of dexmedetomidine for prevention of chills in patients under-going combined spinal-epidural anesthesia (CSEA). METHODS:A total of 136 patients undergoing surgery of lower abdomen or lower limb following CSEA were randomly assigned to receive dexmedetomidine[0.2 μg/kg(group A),0.4 μg/kg(group B),0.6μg/kg(group C)]or physiological saline(control group)by venous pump infusion. Patients’body temperature,incidence of chills reaction,Ramsay sedation score and incidence of adverse drug reactions before anesthesia,15 min,30 min and 60 min after pump-ing infusion of drugs and after completion of surgery were recorded. RESULTS:The body temperature in group A,B and C at all time points following infusion of dexmedetomidine were all lower than before anesthesia,indicating hypothermia;however,no sig-nificant differences were noted between the three test groups and the control group(P>0.05). The chills were mild in group B and C,and the incidence rates of chills in group B and group C were significantly lower than in the control group(P0.05). Ramsay sedation scores in group A at different time points after pumping infusion of dexmedetomidine were significantly higher than before pumping infusion;however, the Ramsay sedation scores in other groups showed no significant differences as compared before pumping infusion(P>0.05);the differences between group B or group C at different time points and the control group were significant(P<0.05). 3 cases presented with dry mouth and 3 showed decrease of heart rate in group C after dexmedetomidine infusion,but no adverse reaction was noted in other groups. CONCLUSIONS:The minimum effective dose of dexmedetomidine is 0.4 μg/kg for prevention of chills in patients undergoing combined spinal-epidural anesthesia,and it can effectively attenuate the degree of chills and reduce the incidence of chills yet without causing excessive sedation or significant adverse reactions.%目的：探讨右美托咪定防治腰硬联合麻醉后寒战反应的最小有效剂量。方法：选择经腰硬联合麻醉行下腹部及下肢手术的患者136例，随机分为对照组与3个剂量试验组，各试验组麻醉后分别泵注不同剂量的右美托咪定[0.2μg/kg（A组）、0.4μg/kg（B组）、0.6μg/kg（C组）]，对照组静脉泵注生理盐水。观察各组患者麻醉前、右美托咪定（或生理盐水）泵注后15 min、30 min、60 min、术毕各时间点的体温、寒战反应发生率、Ramsay镇静评分及药物不良反应发生情况。结果：A、B、C组患者泵注右美托咪定后各时间点体温均低于麻醉前，即均处于低体温状态，与对照组比较差异无统计学意义（P＞0.05）。B、C组寒战程度较轻，寒战发生率显著低于对照组（P＜0.05）；A组寒战程度及寒战发生率与对照组比较差异无统计学意义（P＞0.05）。泵注右美托咪定后各时间点A组镇静Ramsay评分均显著高于泵注前，其余各组Ramsay评分与泵注前比较差异无统计学意义（P＞0.05）；B、C组泵注右美托咪定后不同时间点Ramsay评分与对照组比较差异有统计学意义（P＜0.05）。C组泵注右美托咪定后有3例出现口干、5例出现心率下降，其余各组均未见明显不良反应。结论：右美托咪定防治腰硬联合麻醉后寒战的最小有效剂量是0.4μg/kg，既可有效减轻寒战程度，降低寒战反应发生率，又不使患者过度镇静，无明显不良反应。
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