右美托咪啶用于臂丛神经阻滞的半数镇静有效剂量

The 50% effective dose of dexmedetomidine for sedation in the brachial plexus block

目的探讨静脉注射右美托咪啶用于臂丛神经阻滞镇静的半数有效剂量（ED50），以便为临床提供参考。方法23例患者行超声引导下臂丛神经阻滞，待阻滞后30min效果确切后，静脉持续泵入右美托咪啶，采用警觉／镇静评分（OAA／S）评估镇静水平，同时使用听觉诱发电位指数（AEPI）监测镇静深度。根据上下序贯法，设定第1例患者负荷量为1μg／kg，以0．1μg／kg为试验间隔，OAA／S≤3分为镇静有效，直到序贯反应曲线出现7个折点为止。结果臂丛神经阻滞时静脉注射右美托咪啶镇静的ED50为0.78μg／kg（95％CI：0．66～0．86μg／kg）。听觉诱发电位指数（X）与OAA／S（Y）呈直线正相关（R^2=0．919，P=0．000），直线回归方程：Y=-1．43＋0．109X。结论臂丛神经阻滞时静脉注射右美托咪啶镇静的ED50为0．78μg／kg（95％CI：0．66～0．86μg／kg）。

Objective To determine the 50% effective dose （ED50） of dexmedetomidine for sedation in the braehial plexus block, so as to provide reference for clinical. Methods Twenty-three patients underwent the brachial plexus block using an ultrasound guided technique. After blocked for 30 min, the dexmedetomidine was infused by a intravenous continuous pump,and an observer＇ s assessment of alertness/sedation score （OAA/S） and auditory evoked potential index （AEPI） were used for monitoring the depth of sedation. The dexmedetomidine was adjusted according to the response of the previous patient using a up-and-down sequential method until the sequential response curve appeared seven fold points. The initial dexmedetomidine of the first patient was 1 μg/kg. Each time the dosage increased / decreased by 0.1 μg/kg. The OAA/S score of no more than 3 was defined an effective sedation. Results The ED50 of dexmedetomidine for sedation was 0.78 μg/kg （95% CI 0.66 - 0.86 μg/kg）. The AAI was positively correlated to the OAA/S score, and linear regression equation was Y=1.43 ＋ 0.109 X, R^2 = 0.919. Conclusion The ED50 of dexmedetomidine for sedation in the brachial plexus block is 0.78 μg/kg （95% CI 0.66 - 0.86μg/kg）.