ABSTRACT
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.