上胸段硬膜外交感神经阻滞对兔蛛网膜下腔出血诱发脑血管痉挛的影响

Effect of high thoracic epidural sympathetic block on cerebral vasospasm after subarachnoid hemorrhage in rabbits

目的 探讨上胸段硬膜外交感神经阻滞对兔蛛网膜下腔出血（SAH）诱发脑血管痉挛的影响。方法 日本大耳白兔24只，雌雄不拘，体重2．0～2．6kg，随机分为3组（n=8）。对照组（C组）枕大池注射生理盐水1ml／kg，硬膜外腔注射生理盐水0．5ml／2h；S组枕大池注射自体动脉血1ml／kg，硬膜外腔注射生理盐水0．5ml／2h；H组枕大池注射自体动脉血1ml／kg，硬膜外腔注射0．5％利多卡因0．5ml／2h。记录家兔实验第4、5、6天进食量和神经功能状态，经颅多普勒超声测定实验前（T0）和实验第7天（T1）颈总动脉血流速度[平均血流速度（Vm）、收缩期峰血流速度（Vs）、舒张末血流速度（Vd）]搏动指数（PI）、阻力指数（RI），连续监测心率（HR）、平均动脉压（MAP）、心电图。结果 与C组相比，S组进食量下降和神经功能障碍发生率增加（P〈0．05）；与S组相比，H组进食量下降和神经功能障碍发生率减少（P〈0．05）；与T0时相比，T1时S组Vs、Vm及Vd升高，PI及RI降低，H组HR及上述指标降低（P〈0．05）；与C组相比，L时S组Vs、Vm及Vd升高，H及RI降低，H组HR及上述指标降低（P〈0．05）；与S组相比，L时H组HR及上述指标降低（P〈0．05）。结论 0．5％利多卡因上胸段硬膜外交感神经阻滞可抑制交感神经兴奋，从而改善兔SAH后脑血管痉挛。

Objective To evaluate the effect of high thoracic epidural sympathetic block （HTESB） on cerebral vasospasm （CVS） after subarachnoid hemorrhage （SAH） in rabbits. Methods Twenty-four Japanese long-ear white rabbits of both sexes weighing 2.0-2.6 kg were randomly divided into 3 groups （ n = 8 each） ： group Ⅰ control; groupⅡ SAH and group Ⅲ SAH ＋ HTESB. The animals were anesthetized with iv 3 % pentobarbital 30 mg/kg. An catheter was inserted into epidural space at T3-4 interspace and advanced 1.5 cm cephalad with the tip directed at T2 vertebral body and fixed. Cerebral vasospasm （CVS） model was produced by injecting 1 ml/kg non-coagulated autologous arterial blood into cisterna magna twice at 48 h interval. In control group normal saline （NS） was injected into cistenla magna twice instead of non-coagulated autologous arterial blood, In group Ⅲ 0.5% lidocaine 0.5 ml was injected through the epidural catheter every 2 h and T1-5 sympathetic nerves were blocked. Blood flow velocity of common carotid artery was detected by transcranial Doppler （TCD） uhrasonography at 15 min after epidural lidocaine before （TG ） and at day 7 after operation （T1 ）. Mean velocity （Vm）, peak blood flow velocity at systole （Vs）, end-diastolic velocity （Vd） were measured and pulsation index （PI） and resistance index （RI） were calculated. ECG, MAP and HR were continuously monitored. Food intake and delayed ischemic neurological deficits （DIND） were evaluated evely day. Results The food intake was significantly decreased and DIND increased after SAH in group Ⅱ . High thoracic epidural block significantly attenuated the changes in food intake and DIND induced by SAH and there was no significant difference in food intake and DIND aher operation between control group and SAH ＋ HTESP group. Vm, Vs and Vd were significantly increased and PI and RI decreased after operation at T1 as compared with the baseline values at To in SAH group and control group. High thoracic epidural block significantly attenuated the changes in Vm, Vs, Vd and PI and RI induced by SAH. Conclusion High thoracic epidural sympathetic nerve block with 0.5% lidocaine can significantly improve food intake and attenuate DIND after SAH and decrease carotid artery blood flow velocity and HR, suggesting that overactivity of sympathetic nervous system may be involved in the pathogenesis of CVS induced by SAH.