兔全脑缺血-再灌流脑血流及二氧化碳舒缩反应性实验研究

目的：观察全脑缺血－再灌流兔脑血流及脑血管CO2收缩反应性变化，探讨复苏后过度通气降颅压的临床应用价值。方法：四血管阻断法制作兔全脑缺血－再灌流模型，随机分对照组和脑缺血组。经颅多普勒超声（TCD）探测大脑中动脉平均血流速度（Vm)，过度通气法测定CO2诱发的脑血管收缩反应。结果：缺血组於再灌流2、6、24h所测Vm、脑血管CO2收缩反应性均明显低于缺血前及同时间点对照组（P＜0．001），CO2收缩反应性以再灌流2h再低，24h有所回升。对照组脑缺血前后Vm及CO2收缩反应性无显著变化（P＞0．05）。结论：兔全脑缺血－再灌流2－24h内前脑循环呈低灌注状态，脑血管CO2收缩反应性降低。该结果提示在脑血流监测的条件下，心肺复苏早期常规使用过度通气降颅压有可能加重脑缺血。

Cerebral blood flow,carbon dioxide reactivity in global cerebral ischemic/reperfusion in rabbits

Objective To observe the changes of cerebral blood flow,carbon dioxide(CO 2)reactivity of cerebral vessels in rabbits with global ischemic/reperfusion and explore the values of hyperventilation early after brain ischemia in cerebral resuscitation.Methods Sixteen healthy New Zealand white rabbits were randomly divided into control group and ischemia group( n =8 for each group).The models of global cerebral ischemic/reperfusion in rabbits were produced by clamping both carotid arteries and vertebral arteries for 30 minutes and then removing the clamps .The mean flow velocity( V m)of middle cerebral artery(MCA)was monitored by transcranial Doppler(TCD).CO 2 reactivity of cerebral vessels was induced by hyperventilation.Results The Vm of right MCA and CO 2 reactivity in ischemic group was significantly reduced at the time of reperfusion 2,6,24 hours compared with that of pre ischemia and the control group at the same time (p<0 001).No significant difference of Vm and CO 2 reactivity were found before and after operation in control group.Conclusion The results suggested that from 2 hour to 24 hour after cerebral ischemia,the rabbits with cerebral ischemic/reperfusion were at a state of postischemic hypoperfusion and decreased CO 2 reactivity.The use of hyperventilation early after brain ischemia has the potential to further reduce cerebral blood flow and worsen outcome.