Dobrydnjov I, Samarütel J
Department of Anaesthesiology and Intensive Care, Kohtla-Järve Hospital, Estonia.
Acta Anaesthesiol Scand. 1999 May;43(5):556-62. doi: 10.1034/j.1399-6576.1999.430512.x.
Enhancement of local anesthetic-produced regional blocks by clonidine seems well established. There are insufficient data about dose-effect relationship of combinations of clonidine with individual agents, efficiency of local versus systemic administration of clonidine, and comparative evaluation of clonidine with vasoconstrictors. Because of unavailability of long-acting local anaesthetics at the time of study, our aim was to evaluate augmentation of lidocaine spinal block with local or systemic clonidine and to compare the results with the efficacy of intrathecal phenylephrine.
Ninety pts of age 50-72 yrs with ASA 1-4 physical status, scheduled for open prostatectomies, hysterectomies or ostheosynthesis of fractured hip were randomized to one of 6 treatment groups, 15 pts in each. Patients received intrathecally (L3-L4) either 100 mg of plain lidocaine (group L100); or a mixture of lidocaine 40 and 80 mg with clonidine 100 micrograms (groups L40-C100 and L80-C100); or a combination of lidocaine 40 and 80 mg with clonidine 300 micrograms orally 60 min before spinal puncture (L40-C300 and L80-C300). Addition of intrathecal phenylephrine 5 mg to 80 mg of lidocaine was also investigated (L80-P5).
There were no significant intergroup differences concerning demographic data or type of surgery. All operations (duration up to 150 min) were completed without need for analgesic supplementation. The addition of clonidine resulted in a significant reduction of the onset time of spinal block and prolongation of the duration of sensory and motor blocks compared to plain lidocaine or lidocaine with phenylephrine. In spite of the well-known hypotensive action of alpha 2-agonists, haemodynamic depression only in group L80-C300 was significantly more pronounced than in L100 and L80-P5 groups. The least decrease of BP and minimal need of rescue ephedrine among all patients studied were recorded in the group receiving low dosage of lidocaine with intrathecal clonidine (L40-C100). Sedation occurred in most patients receiving clonidine.
Our results indicate that addition of clonidine to lidocaine, irrespective of the route of administration, prolongs the duration of spinal block and permits a reduction of the lidocaine dose needed for a given duration of block. Addition of phenylephrine results in a less pronounced statistically significant prolongation of anaesthesia. The regression of sensory block before restoration of motor function seems to be a specific (and unfortunate) effect of both clonidine and phenylephrine.
可乐定增强局部麻醉药产生的区域阻滞作用似乎已得到充分证实。关于可乐定与个别药物联合使用的剂量效应关系、可乐定局部给药与全身给药的效果以及可乐定与血管收缩剂的比较评估，目前的数据尚不充分。由于在研究时无法获得长效局部麻醉药，我们的目的是评估局部或全身应用可乐定对利多卡因脊髓阻滞的增强作用，并将结果与鞘内注射去氧肾上腺素的效果进行比较。
90例年龄在50 - 72岁、美国麻醉医师协会（ASA）身体状况分级为1 - 4级、计划行开放性前列腺切除术、子宫切除术或髋部骨折内固定术的患者被随机分为6个治疗组，每组15例。患者在L3 - L4水平鞘内注射以下药物：100mg单纯利多卡因（L100组）；40mg利多卡因与100μg可乐定的混合物以及80mg利多卡因与100μg可乐定的混合物（L40 - C100组和L80 - C100组）；在腰穿前60分钟口服300μg可乐定的同时鞘内注射40mg利多卡因以及80mg利多卡因（L40 - C300组和L80 - C300组）。还研究了在80mg利多卡因中添加5mg鞘内注射去氧肾上腺素的情况（L80 - P5组）。
在人口统计学数据或手术类型方面，组间无显著差异。所有手术（持续时间长达150分钟）均在无需补充镇痛药物的情况下完成。与单纯利多卡因或利多卡因加去氧肾上腺素相比，添加可乐定可显著缩短脊髓阻滞的起效时间，并延长感觉和运动阻滞的持续时间。尽管α2激动剂具有众所周知的降压作用，但仅L80 - C300组的血流动力学抑制明显比L100组和L80 - P5组更显著。在所有研究患者中，接受低剂量利多卡因联合鞘内可乐定（L40 - C100组）的患者血压下降最少，且抢救麻黄碱的需求最小。大多数接受可乐定的患者出现了镇静作用。
我们的结果表明，无论给药途径如何，在利多卡因中添加可乐定均可延长脊髓阻滞的持续时间，并允许在给定的阻滞持续时间内减少所需的利多卡因剂量。添加去氧肾上腺素导致麻醉时间延长的统计学意义较小。感觉阻滞在运动功能恢复之前消退似乎是可乐定和去氧肾上腺素两者的一种特殊（且不幸）的效应。
