Cessation of Diastolic Cerebral Blood Flow Velocity: The Role of Critical Closing Pressure

Background Reducing cerebral perfusion pressure (CPP) below the lower limit of autoregulation (LLA) causes cerebral blood flow (CBF) to become pressure passive. Further reductions in CPP can cause cessation of CBF during diastole. We hypothesized that zero diastolic flow velocity (FV) occurs when diastolic blood pressure becomes less than the critical closing pressure (CrCP). Methods We retrospectively analyzed studies of 34 rabbits with CPP below the LLA, induced with pharmacologic sympathectomy ( N = 23) or cerebrospinal fluid infusion ( N = 11). Basilar artery blood FV and cortical Laser Doppler Flow (LDF) were monitored. CrCP was trended using a model of cerebrovascular impedance. The diastolic closing margin (DCM) was monitored as the difference between diastolic blood pressure and CrCP. LDF was recorded for DCM values greater than and less than zero. Results Arterial hypotension caused a reduction of CrCP ( p