A study on conscious sedation with alpha_2 -agonist and alpha_2-antagonist

可乐定是α ^2激动剂的原型，最初是作为抗高血压药物引入临床实践的。本研究的目的是评价可乐定在静脉清醒镇静中的辅助作用。我们评估了伤害性刺激对血流动力学和肾上腺素能反应的影响，镇静和镇痛作用。20名志愿者静脉注射可乐定2 μ g/kg。将恒流、方波电刺激（持续时间20 msec，间隔100 msec，训练10、5 mA）作为伤害性刺激传递给正中神经。每5 min测定一次血压、心率（HR），注射可乐定前及注射后15、30、45、60、90 min测定血浆肾上腺素、去甲肾上腺素、皮质醇水平，注射前及用药后15、30、45、60、90 min用目视模拟量表测定镇静镇痛效果。注射可乐定后0、20、30、50、60分钟HR显著降低。HR最大降幅在10%以内（8.4%）。收缩压（SP）在20分钟后明显下降。在舒张压（DP）的任何一点上与对照组没有显著差异。SP下降幅度在10%以内，在整个研究过程中，静脉注射2mug/kg可乐定未引起任何受试者的严重低血压。可乐定在静脉注射15分钟和60分钟后肾上腺素水平显著降低。注射后15、60、90分钟去甲肾上腺素浓度显著降低。在给药15、30、60和90分钟后，血浆皮质醇水平与对照组有显著差异。口干和疲劳或疲倦是最常见的感知副作用。静脉注射2 μ g/kg可乐定未引起严重心动过缓、低血压等严重副作用。它能减弱对伤害性刺激的肾上腺素能反应，并具有良好的镇静作用。

Clonidine is a prototype of alpha^2-agonist and was originally introduced to clinical practice as an antihypertensive drug. The objective of this study is to evaluate the effects of clonidine as anadjunct in intravenous conscious sedation. We assessed the effects on haemodynamic and adrenergic responses to nociceptive stimuli, sedation and analgesic effects. 20 volunteers received 2 mu g/kg of clonidine intravenously. Constant current, square-wave electric stimuli (duration 20 msec, interval 100 msec, train 10, 5 mA) were delivered as nociceptive stimuli to the median nerve. We measured blood pressure, heart rate(HR) every 5 min, and plasma levels of adrenaline, noradrenaline and cortisol before and 15, 30, 45, 60 and 90 min after clonidine injection, sedative and analgesic effects were measured by visual analogue scale before and 15, 30, 45, 60 and 90 min after drug. HR decreased significantly 0, 20, 30, 50 and 60 minutes after clonidine injection. The maximum decrease in HR was within 10% (8.4%). Systoli pressure(SP) decreased singnificantly 20 minutes later. There was no significant difference from the control at any point in diastolic pressure(DP). The decrease in SP was within 10%, and 2mug/kg of intravenous clonidine did not induce severe hypotension throughout the study in any subject. Clonidine produced significant decrease in adrenaline levels 15 and 60 minutes after intravenous injection. Noradrenaline concentrations significantly decreased 15, 60 and 90 minutes after the injection. Plasma cortisol levels showed significant differences from the control 15, 30, 60 and 90 minutes after clonidine administration. Dry mouth and fatigue or weariness were the most frequent perceptive side effects. 2 mu g/kg of intravenous clonidine did not induce severe bradycardia, hypotension or other serious side effects. it attenuated the adrenergic responses to nociceptive stimuli, and exerted good sedative effect.