临界关闭压对于正常大鼠脑血流自动调节的作用

Role of Critical Closing Pressure to Cerebral Blood Flow Autoregulation on Normal Rats

目的探讨正常大鼠脑血流自动调节范围内和超出自动调节范围后,临界关闭压（critical closing pressure,CCP）对脑血流的调控作用。方法健康雄性SD大鼠随机分为升压组和降压组各70只,除去手术失败的动物,完整采集数据升压组69只,降压组54只。分别以10-15 mm Hg为一级逐步升高、降低血压,同步记录大鼠大脑中动脉血流速度（cerebral blood flow velocity,CBFV）和有创血压,绘制自动调节曲线,并按照CCP理论计算CCP和血管面积阻力指数（resistance area product,RAP）,分析血流动力参数之间,以及血流动力学参数与血压变化间的关系。结果动脉血压升高或降低过程中,正常大鼠的脑血流自动调节上、下限分别为（148.12±7.49）mm Hg、（62.96±3.34）mm Hg。脑血流自动调节范围内,CBFV随动脉血压改变轻微,超出自动调节范围后,CBFV随动脉血压升高明显增加（r=0.896,P=0.000）,或随动脉血压降低明显减小（r=0.945,P〈0.001）。CCP变化恰好与CBFV相反,自动调节范围内随动脉血压改变明显,与平均动脉压呈明显正相关（升压r=0.967、降压r=0.969,P均〈0.001）,超出自动调节范围后改变量明显减小。RAP也有CCP的类似趋势,但数值变化量不是很明显,只有降压过程自动调节范围内的改变量明显大于超出自动调节范围后。结论大鼠脑血流调控过程中,自动调节有效范围内,脑血流的稳定与CCP和RAP密切相关,尤其是CCP。微动脉血管紧张度和微动脉直径变化共同参与了脑血流的调控。

Objective To validate the role of the model of critical closing pressure（CCP） of normal rats on cerebral blood regulation in and out the range of cerebral blood fl ow autoregulation（CBFA）.Methods Total 123 rats were randomly divided into rising blood pressure group（69） and lowering blood pressure group（54）, after excluding unsuccessful operating animals. Higher and lower blood pressure were induced by gradually increasing or decreasing mean arterial blood pressure（MABP） per 10-15 mm Hg. The cerebral blood fl ow velocity（CBFV） and artery pressure were monitored simultaneously and the curves of CBFA were analyzed. The values of CCP and resistance area product（RAP） were worked out according to CCP theory. The relationship between hemodynamics parameters and the association between hemodynamics and the changes of blood pressure were evaluated.Results The upper limit of autoregulation（ULA） and the lower limit of autoregulation（LLA） of normal rats were（148.12±7.49） mm Hg and（62.96±3.34） mm Hg, respectively. The rising and lowering blood pressure group, when MABP changed in the range of CBFA, the CBFV changed little. Beyond the limits of CBFA, CBFV increased（r =0.869, P〈0.001） following MABP rising, and CBFV decreased（r =0.945, P〈0.001） when MABP declining. CCP correlated with MABP positively（r =0.967, 0.969, P =0.000）. RAP had a similar tendency of CCP. But only in the hypotensive process,the variable quantity of RAP in the range of CBFA was greater than out the range.Conclusion In the range of CBFA, cerebral blood flow is closely related to CCP and RAP, especially CCP. Cerebrovascular tone and the changes of arterioles＇ diameter contribute to the process of cerebral autoregulation.