Fu E S, Naidu K A, Prockop L D
Department of Anesthesiology, University of South Florida College of Medicine, Tampa 33612-4799, USA.
Anesth Analg. 1997 Aug;85(2):324-7. doi: 10.1097/00000539-199708000-00015.
Epinephrine is often given with epidurally administered drugs to prolong and enhance analgesia, which is partly attributed to alpha-adrenergic processes. This investigation evaluates the effect of epinephrine on the distribution of epidurally administered [3H]-clonidine hydrochloride (clonidine HCl) in serum and in the central nervous system. After placing a lumbar epidural catheter via a laminectomy, rabbits were randomly assigned to receive 20 microCi of clonidine HCl with epinephrine (1:200,000) (n = 5) or without (control; n = 5) for 90 min. During the administration, which included bolus and slow infusion, blood samples were collected at 15-min intervals. At the end of the administration, rabbits were perfused with normal saline, leading to exsanguination. Brain and spinal cord tissues were excised for radiometric analysis. In both groups, the concentration of clonidine HCl was greatest in the lumbar cord. Epinephrine further enhanced accumulation of clonidine HCl into the lumbar cord but did not alter the concentration of clonidine HCl in serum, brain, cervical cord, and thoracic cord. We conclude that lumbar administration of epidural clonidine HCl leads to increased concentrations in the lumbar cord, which is further enhanced by epinephrine. The increased spinal cord accumulation of clonidine may be another mechanism by which epinephrine improves epidural analgesia.
肾上腺素常与硬膜外给药的药物联合使用，以延长和增强镇痛效果，这部分归因于α-肾上腺素能作用过程。本研究评估肾上腺素对硬膜外给予的[3H]-盐酸可乐定（可乐定盐酸盐）在血清和中枢神经系统中分布的影响。通过椎板切除术放置腰段硬膜外导管后，将兔子随机分为两组，一组接受20微居里的可乐定盐酸盐与肾上腺素（1:200,000）（n = 5），另一组不接受肾上腺素（对照组；n = 5），给药90分钟。在给药过程中（包括推注和缓慢输注），每隔15分钟采集血样。给药结束时，用生理盐水灌注兔子，使其放血。切除脑和脊髓组织进行放射性分析。在两组中，可乐定盐酸盐的浓度在腰段脊髓中最高。肾上腺素进一步增强了可乐定盐酸盐在腰段脊髓中的蓄积，但未改变其在血清、脑、颈段脊髓和胸段脊髓中的浓度。我们得出结论，腰段硬膜外给予可乐定盐酸盐会导致腰段脊髓中浓度升高，而肾上腺素会进一步增强这种升高。可乐定在脊髓中蓄积增加可能是肾上腺素改善硬膜外镇痛的另一种机制。
