Objective: We studied the conscious-sedation effects of a single loading dose (1 μg/kg) of dexmedetomidine in the procedure of employing subarachnoid block in spinal anesthesia to accomplish analgesia and compared it with that of midazolam in the dosage recommended by clinical trials. We evaluated the sedative effects of these two medications by analyzing the collected bispectral index (BIS) data. Methods: Forty patients in American Society of Anesthesiologists (ASA) grade I and II, age 20-60 and body mass index (BMI) 19-26 kg/m2, scheduled to undergo lower extremity surgery with subarachnoid block in spinal anesthesia. They were randomly assigned to one of two groups (n - 20 each group). Level of anesthesia was controlled beneath T10. Group D patients received intravenous infusion of 1 fig/kg of dexmedetomidine within a 10-minute period. Group M patients were administrated 50 μg/kg of midazolam during 10 minutes as well. We collected BIS, systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR) and SPO2 figures of both groups at pre-anesthesia time (TO), when level of anesthesia stabilized (T1), 1 minute (T2), 5 minutes (T3), 10 minutes (T4), 20 minutes (T5) and 30 minutes (T6) subsequent to dosing, respectively. Results: At T4,T5 and T6, BISs of Group D patients were significanT1y lower than those of Group M (P<0. 05); At the corresponding instances (T4, T5 and T6), SBP and DBP of group D patients were lower than those of Group M patients (P<0. 05); HR of group D patients were lower than those of Group M patients (P<0. 05). Compared with same group at T1, SBP, DBP, and HR of Group D patients went down considerably (P<0. 05) at T4, T5 and T6. There were 4 and 13 patients got SPO2<95% in Group D and M, respectively. The incidence of minor respiratory depression of Group M patients was noticeably higher than that of Group D patients (P<0. 05). Conclusions: As an adjuvant medication in the procedure of employing subarachnoid block in spinal anesthesia, the sconscious-sedation sedative effect of 1 μg/kg of dexmedetomidine is stronger than that of 50 μg/kg of midazolam, the dosage recommended by clinical trials. Compared with midazolam, patients receiving dexmedetomidine stand a better chance to wake up and have lower incidence of respiratory depression. Although the decreases of blood pressure and heart beat rate are substantial, they are yet in the controllable range.%目的:在蛛网膜下隙阻滞完善镇痛时比较单次负荷剂量1 μg/kg右旋关托咪定和临床推荐剂量的咪达唑仑的清醒镇静效应,并以脑电双频指数( BIS)来评估两药的镇静深度变化.方法:选择40例美国麻醉医师协会(ASA)分级为Ⅰ～Ⅱ级,年龄22～60岁,体质量指数(BMI) 19～26 kg/m2,拟在蛛网膜下隙阻滞下行下肢手术的择期手术患者.阻滞平面均控制在T10以下,随机分2组,D组(n =20):右旋美托咪定1 μg/kg 10 min静脉泵入；M组(n=20):咪达唑仑50 μg/kg静脉注射.所有患者均在麻醉前(T0)、脊麻平面固定后(T1)、给药后1 min(T2)、5 min(T3)、10 min(T4)、20 min(T5)、30 min(T6)各时间点记录BIS值、收缩压(SBP)、舒张压(DBP)、心率(HR)和脉搏血氧饱和度(SpO2).结果:D组在T4、T5和T6时间点的BIS值均显著低于M组(P＜0.05)；在T4、T5和T6时间点:D组SBP、DBP显著低于M组(P＜0.05)；D组HR显著低于M组(P＜0.05).D组T4、T5和T6时间点的SBP、DBP、HR分别显著低于同组T1时间点(P＜0.05).D组中有4例患者发生SpO2＜95％,M组中有13例患者发生SpO2＜95％,呼吸抑制的发生率D组显著低于M组(P＜0.05).结论:作为蛛网膜下隙阻滞的辅助用药,1 μg/kg的右旋美托咪定具有强于临床推荐剂量50 μg/kg的咪达唑仑的清醒镇静效应,与咪达唑仑相比,睡眠中更容易唤醒,且呼吸抑制的发生率低.虽然其血压与心率的下降比较明显,但是仍然在可控范围内.
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