中文摘要：

目的 通过比较上午、下午静脉输注右美托咪定的镇静效果,探讨近日节律对右美托咪定镇静效果的影响。方法 选择施行大隐静脉曲张手术患者60例,ASAⅠ~Ⅱ级。随机数字表法分为上午8：00~9：00组（A组）和下午13：00~14：00组（B组）,每组30例。麻醉均选择腰硬联合麻醉,麻醉平面控制在胸10左右。麻醉平面固定后微泵静注右美托咪定负荷剂量0.4μg/kg,10 min注完,然后以0.4μg/（kg·h）维持静脉泵注30 min。观察记录2组用药前（T0,基础值）,微泵输注负荷剂量后（T1）,维持静脉泵注10 min、20 min、30 min（T2~4）5个时间点的脑电双频谱指数（BIS）、听觉诱发电位指数（AAI）、OAA/S分值。采用SPSS 13.0统计学软件进行统计学处理,P〈0.05视为差异有统计学意义。结果 2组患者负荷剂量输注完毕（T1）及维持期间（T2~4）BIS、AAI、OAA/S分值较T0均明显降低（P〈0.01）。组间比较,B组在T1~4BIS、AAI、OAA/S分值较A组均降低（P〈0.05）。结论 近日节律可影响右美托咪定的镇静效应,表现为下午13：00~14：00时的镇静效果明显强于上午8：00~9：00时。

英文摘要：

Objective To explore the effects of circadian rhythm on sedative effect ofdexmedetomidine by comparing the sedative effect of dexmedetomidine which were infusion given in the morning and afternoon. Methods All 60（ASA I - II ） patients who undergoing great saphenous vein surgery were randomly divided into two groups （ Group A, B ） with 30 cases in each group： morning group（8：00 to 9：00,group A ） and afternoon group（13：00 to 14：00,group B）. All pa- tients received the combined spinal and epidural anesthesia, anesthesia controlled in the T 10. After the anesthesia fixed, micropump injection dexmedetomidine loading dose 0.4 p,g/kg（ within 10 min）, then maintain intravenous infusion 0.4 p,g/（kg·h） （infusion within 30 min）. The BIS value,AAI value, OAA/S scores were observed and recorded at time points of before treatment （To, baseline） ;after a loading dose infusion by micropump （T1 ）, the intravenous infusion of 10 min,20 min,30 min （T2.4 ） were maintained. SPSS statistical software was used for the statistical analysis, P 〈 0.05 denoted statistical significance. Results The BIS, AAI, OAA/S scores of T1-5 were significantly lower than that of the TO （P 〈 0.01 ）. Between the two groups, BIS, AAI, OAA/S scores of the group B in T1-4 were lower than those of the group A （P 〈 0. 05 ）. Conclusion The circadian rhythm can affect the sedative effect ofdexmedetomidine, the performance of PM 13：00 to 14：00 sedative effect is significantly stronger than the AM 8：00 to 9：00.