右美托咪定引起外显记忆消失时的半数有效浓度

Medium effective concentration of dexmedetomidine which cause explicit memory disappeared

目的测定右美托咪定引起患者外显记忆消失的半数有效浓度（EC50）。方法拟行下肢手术的患者40例,ASAⅠ~Ⅱ级。均行腰麻-硬膜外联合麻醉,待麻醉平面稳定、患者血流动力学平稳（T0时）后靶控输注右美托咪定,达设定血药浓度时（T1时）进行麻醉学习。第1例患者血药浓度定为4 ng·m L-1,根据外显记忆是否消失决定下一例浓度,相邻浓度比值为1.2。采用加工分离程序结合词干补笔法计算患者外显记忆成绩,通过SANDIN的方法评判外显记忆是否消失,并应用Dixon法计算患者外显记忆消失时右美托咪定的EC50及其95%可信区间（CI）。观察患者的平均动脉压（MAP）、心率（HR）及脉搏血氧饱和度（Sp O2）变化。结果右美托咪定引起患者外显记忆消失的ED50为5.23 ng·m L-1（95%CI：4.07~6.39 ng·m L-1）。试验期间患者Sp O2无明显变化。T1时、麻醉学习开始后5 min（T2）、麻醉学习结束（T3）及麻醉学习结束后5 min（T4）时患者MAP和HR均低于T0时（P〈0.05）,T2~T4时MAP和HR均高于T1时（P〈0.05）,T2、T3、T4三个时刻的MAP和HR无显著差异（P〉0.05）。试验期间MAP和HR下降均未超过基础值的20%。结论右美托咪定引起外显记忆消失的ED50为5.23 ng·m L-1,在该镇静深度下,患者MAP和HR明显下降,但在可接受范围内,呼吸则未受明显影响。

AIM To determine the medium effective concentration（ EC50） of dexmedetomidine（ Dex）which cause explicit memory disappeared. METHODS Forty patients, ASA Ⅰ-Ⅱ, undergoing elective lower extremity surgery were enrolled and received combined spinal epidural anesthesia（CSEA）. When the anesthesia plane and hemodynamics of patients became stable（T0）, the Dex was given by target controlled infusion until reached the set concentration（T1）. Then patients started learning in anesthesia, and Dex target concentration of the first patient was set to 4 ng·m L-1, and adjusted according to explicit memory disappeared or not,concentration of two adjacent patients with ratio of 1.2. The explicit memory performance of each patient was calculated by separation processing program combining stem fill brushwork. Whether explicit memory disappeared was judged by the method of SANDIN. The EC50 and its 95% confidence interval（CI） of Dex were determined by the method of Dixon. The change of mean arterial pressure（ MAP）, heart rate（ HR） and pulse oxygen saturation（Sp O2） were observed. RESULTS The ED50 of Dex which caused explicit memory disappeared was5.23 ng·m L-1（95%CI： 4.07- 6.39 ng·m L-1）. The Sp O2 showed no obvious change during the trial. The MAP and HR at T1, 5 min after anesthesia learning start（ T2）, end of anesthesia learning（ T3）, 5 min after anesthesia learning end（T4） were lower than that of based state（T0, P〈0.05）. The MAP and HR at T2- T4 were higher than that of T1（P〈0.05）. There showed no significant difference amount T2, T3, T4. The MAP and HR declined proportion of each patient was no more than 20 percent. CONCLUSION The ED50 of Dex which caused explicit memory disappeared was 5.23 ng·m L-1. Under this depth of sedation, MAP and HR significantly decreased, but it was still in the acceptable range, and breathing was unaffected obviously.