脑血流自动调节范围内维持脑血流恒定的因素

摘要

目的：探讨脑血流自动调节范围内稳定脑血流速度的血流动力学因素。方法利用经颅多普勒检测SD大鼠大脑中动脉的血流速度（cerebral blood flow velocity, CBFV），并同步记录有创动脉血压，绘制自动调节曲线，判断脑血流自动调节上、下限。计算临界关闭压（critical closing pressure, CCP）和血管面积阻力指数（re⁃sistance area product, RAP）。分析CCP、RAP与平均动脉压（mean artery blood pressure, MABP）之间的关系。结果动脉血压升高或降低过程中，正常大鼠脑血流自动调节上、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（每10 mmHg MABP，升压：0.65±0.27 cm/s；降压：0.43±0.23 cm/s），而CCP和RAP则随动脉血压明显改变（每10 mmHg MABP，升压：4.60±1.06 mmHg、0.11±0.04mmHg；降压：6.74±0.59 mmHg、0.09±0.02 mmHg）。虽然CBFV、CCP、RAP的变化都与MABP相关，但控制CBFV的变动后， CCP和RAP随MABP改变相关性更加明显，其中CCP的变化幅度以及与MABP的相关性明显大于RAP（升压：Be⁃ta=0.561、0.418；降压：Beta=0.694、0.266，P均=0.000）。结论大鼠脑血流自动调节有效范围内，脑血流的稳定主要通过CCP和RAP改变对抗动脉血压的变动而实现，尤其是CCP相应升高或降低。%Objective To investigate the hemodynamic parameters to stabilize cerebral blood flow within limits of cerebral autoregualtion. Methods We assessed the flow velocity of middle cerebral artery using transcranial Doppler and recorded invasively the blood pressure simultaneously. We then analyzed the curves of cerebral blood flow autoregulation (CBFA) and calculated upper limit of autoregulation (ULA) and lower limit of autoregulation (LLA). The values of critical closing pressue (CCP) and resistance area product (RAP) were calculated according to previous theory. The relationship between CCP, RAP and MABP were analyzed. Results In the process of increasing or decreasing blood pressure, ULA and LLA of normal rats were 148.12 ± 7.49 mmHg or 62.96 ± 3.34 mmHg, respectively. When mean artery blood pressue (MABP) changed within limits of cerebral autoregulation, the cerebral blood flow velocity changed little (increasing:0.65± 0.27 cm/s/10mmHg MABP, decreasing:0.43±0.23cm/s/10 mmHg MABP), while CCP and RAP changed significantly (in⁃creasing: 4.60 ± 1.06 mmHg/10mmHg MABP and 0.11 ± 0.04/10 mmHg MABP, decreasing: 6.74 ± 0.59 mmHg/10 mmHg MABP and 0.09 ± 0.02/10mmHg MABP). After fixing change of blood flow velocity, CCP and RAP were correlated with MABP more remarkablely, although all blood flow velocity, CCP and RAP were significantly correlated with MABP. Conclusion Within limits of cerebral autoregulation, stable cerebral blood flow is mainly achieved by the change of CCP and RAP against blood pressure changing on normal rats, especially the increasing or de⁃creasing of CCP.