上胸段硬膜外阻滞对兔蛛网膜下腔出血后脑血管痉挛的预防作用

Preventive effects of high thoracic epidural block on cerebral vasospasm following subarachnoid hemorrhage in rabbits

目的：建立兔上胸段硬膜外阻滞（HTEB）模型和蛛网膜下腔出血（SAH）模型，探讨HTEB对SAH后脑血管痉挛（CVS）的预防作用。方法：切开置管法制备新西兰兔HTEB模型30只，随机分为3组（n=10）：正常组（N组）、单纯SAH组（S组）和HTEB＋SAH组（TS组）。硬膜外1g／L罗哌卡因1mL／h持续给药至实验完毕，用枕大池穿刺一次注血法（0．5mL／kg）制成兔SAH模型。饲养7d，观测兔日食量；用经颅多普勒（TCD）观察第七日兔基底动脉（BA）痉挛情况；HE染色后光镜观察BA痉挛及病变情况．结果：①食量：N组枕大池注入生理盐水后1d明显减退（P〈0．05），2d后恢复正常；S组枕大池注血后1～3d和4～7d均明显减少（P〈0．01，P〈0．05）；TS组1～2d明显减少（P〈0．01），4d后恢复，与N组相比，S组1～2d和3～7d均明显减少（P〈0．01，P〈0．05）；TS组1～3d减少（P〈0．05），4d后无显著差异（P〉0．05）。②实验第七日TCD测定：S组的收缩期峰值（Vs）、平均血流速度（Vm）较N组明显升高（P〈0．05），搏动指数（PI）、阻力指数（RI）明显降低（P〈0．05）；TS组Vs，Vm，PI，RI与N组间差异无统计学意义。③BA光镜观察：N组未见异常，S组管壁收缩、管腔狭窄，TS组变化程度均轻于S组。结论：预先HTEB可减轻兔SAH后CVS。

AIM： To establish the rabbit model of high thoracic epidural block （ HTEB ） and subarachnoid hemorrhage （ SAH ） , and to investigate the preventive effects of HTEB on cerebral vasospasm（CVS） following SAH in rabbits. METHODS： Thirty rabbit models of HTEB were randomly assigned into 3 groups（ with 10 in each group） ： the normal group（N） , SAH group（S） , HTEB plus SAH group（TS）. T6-7 epidural space was explored, and an epidural pipe was introduced. The 1 g/L ropivacaine was injected continually through the pipe at 1 mL/h to block T1-5 sympathetic nerves. CVS was developed by injecting non-anticoagulant autologous arterial blood 0.5 mL/kg into the cisterna magna. In-taking food was evaluated every day for 7 days. Transcranial Doppler （TCD） uhrasonography was used to detect the basilar artery blood flow velocity changes on the 7 th day after SAH. The lesion and spasm of the basilar artery were observed under microscope. RESULTS： In-taking food was not significantly decreased in group N except the first day after injecting Sodium Chloride into the cisterna magna. In group S, it was decreased significantly throughout the 7 days. It was decreased in the first two days, and returned to normal from the fourth day in group TS. The peak value in systolic period（Vs） and mean blood flow velocity（Vm） in group S were higher than those in group N（ P 〈 0.05 ） on the 7 th day after SAH, whereas, pulsation index （ PI ） and resistance index（RI） in group S were lower than those in group N（P 〈 0.05 ）. However, there were no significant differences in TCD parameters （ Vs, Vm, PI, RI） between group TS and N on the 7 th day after SAH. The structure of the basilar artery in group N was normal. The vessel wall was shrunk and the lumina became narrow in group S. The pathologic changes in group TS were slighter than those in group S. CONCLUSION： HTEB has the preventive effects on CVS induced by SAH in rabbits.