Hutschala D, Mascher H, Schmetterer L, Klimscha W, Fleck T, Eichler H G, Tschernko E M
University of Vienna, Department of Cardiothoracic Anesthesia, Austria.
Eur J Anaesthesiol. 2004 Mar;21(3):198-204. doi: 10.1017/s0265021504003060.
The addition of clonidine to local anaesthetics enhances pain relief after peripheral nerve block, but the site of action is unproven.
Seven healthy volunteers underwent three brachial block procedures using bupivacaine 0.25% 1 mg kg(-1) + epinephrine 1:200,000 (=local analgesic) in a randomized, double-blind cross-over fashion: (a) control treatment: local analgesic with 0.9% sodium chloride solution for the block and an intramuscular injection of saline; (b) intramuscular treatment: local analgesic with 0.9% NaCl for block and an intramuscular injection of clonidine 2 microg kg(-1) and (c) block treatment: local analgesic with clonidine 2 microg kg(-1) for block and an intramuscular injection of saline.
The onset and duration of complete blockade (sensory/motor/temperature) was evaluated in the four nerve regions of the hand and forearm. Additionally, sedation score, blood pressure, heart rate and plasma clonidine concentrations were determined. The median duration of complete sensory blockade was 270 min (range 0-600) for block treatment compared to 0 min (range 0-480) for intramuscular treatment (P < 0.05) and 0 min (range 0-180) for control treatment (P < 0.05). Motor and temperature blockade exhibited similar results. Administration of clonidine was associated with sedation and a decrease in heart rate and blood pressure independent of the route of administration. Plasma clonidine concentrations were lower for block compared to the intramuscular treatment.
The admixture of clonidine to bupivacaine plus epinephrine prolongs and enhances brachial plexus blockade. Lower clonidine plasma concentrations for block treatment strongly suggest a local effect.
在局部麻醉药中添加可乐定可增强外周神经阻滞后的镇痛效果，但其作用部位尚未得到证实。
7名健康志愿者以随机、双盲交叉方式接受了3次臂丛神经阻滞操作，使用0.25%布比卡因1mg/kg（-1）+肾上腺素1:200,000（=局部镇痛药）：（a）对照治疗：用0.9%氯化钠溶液进行局部阻滞并肌肉注射生理盐水；（b）肌肉注射治疗：用0.9%氯化钠溶液进行局部阻滞并肌肉注射2μg/kg（-1）可乐定；（c）阻滞治疗：用2μg/kg（-1）可乐定进行局部阻滞并肌肉注射生理盐水。
对手和前臂的四个神经区域的完全阻滞（感觉/运动/温度）的起效时间和持续时间进行了评估。此外，还测定了镇静评分、血压、心率和血浆可乐定浓度。阻滞治疗的完全感觉阻滞中位持续时间为270分钟（范围0-600），肌肉注射治疗为0分钟（范围0-480）（P<0.05），对照治疗为0分钟（范围0-180）（P<0.05）。运动和温度阻滞呈现相似结果。无论给药途径如何，可乐定的给药都与镇静以及心率和血压降低有关。与肌肉注射治疗相比，阻滞时的血浆可乐定浓度较低。
可乐定与布比卡因加肾上腺素混合可延长并增强臂丛神经阻滞。阻滞治疗时较低的可乐定血浆浓度强烈提示有局部作用。
