Post operative changes of cerebral hemodynamics after unilateral internal carotid artery resection -Evaluation of cerebral blood flow by transcranial Doppler method-

应用经颅多普勒超声（TCD）研究单侧颈动脉切除术后患者脑血管的动态自动调节功能。观察大脑中动脉血流速度（FV_<MCA>）与脑灌注压（CPP）的相关性。CPP由调整到MCA水平的体循环动脉压（ABP_<MCA>）和临界关闭压（CCP）计算，临界关闭压由FV_和ABP_之间的收缩-舒张关系估计<MCA><MCA>。CCP显示动脉压低于MCA内血流停止。最初，我们研究了动态脑血管反应在8个健康人在重复逐步向上倾斜和向下倾斜。研究结果表明，<MCA>随着CPP的变化，FV_（1/2）也随之变化，而CPP的变化又与CCP的变化相一致。接下来，我们研究了4例单侧颈内动脉切除术后脑血流动力学的变化。颈内<MCA>动脉切除术后1-2天，FV_1恢复正常。术后<MCA>1-2天内，CPP升高，而CCP明显降低，但与ABP升高无关。颈内静脉阻断可使CCP升高，FV_2降低<MCA>，使单侧颈动脉切除患者脑血管的动态自动调节功能受到小范围的限制。从本研究的结果来看，<MCA>颈动脉切除术后，FV_的维持主要是通过降低CCP。对<MCA>脑血管自动调节功能不全的患者，采用动脉重建提高ABP_2，颈内静脉重建降低CCP，可改善脑血流。

We studied dynamic cerebrovascular autoregulation in the patients who had undergone unilateral carotid artery resection using ultrasonic transcranial Doppler method (TCD). The correlation between the flow velocity of the middle cerebral artery (FV_<MCA>) and the cerebral perfusion pressure (CPP) was investigated. CPP was calculated from the systemic arterial blood pressuure adjusted to the level of MCA (ABP_<MCA>) and the critical closing pressure (CCP), which was estimated from the systolic-diastolic relationship between FV_<MCA> and ABP_<MCA>. CCP demonstrates the arterial pressure below which blood flow stops within the MCA. Initially we studied dynamic cerebrovascular responses in eight healthy humans during repetitive stepwise upward tilt and downward tilt. The results of the study indicated that FV_<MCA> was changed in accordance with the changes of CPP, which was changed in accordance to the change of CCP. Next we studied post-operative changes of cerebral hemodynamics after unilateral internal carotid artery resection in four patients. FV_<MCA> recovered within 1-2 days after internal carotid artery resection. CPP was raised not because ABP_<MCA> elevated but CCP was markedly lowered in 1-2 days, after surgery. Interception of internal jugular/vein of these patients elevated CCP and lowerd FV_<MCA> resticting the dynamic cerebrovascular autoregulation of patients with unilateral carotid artery resection within a small range. From the results of this reserch, FV_<MCA> was maintained mainly by lowered CCP in patients with carotid artery resection. Reconstruction of artery which raise ABP_<MCA> and reconstruction of internal jugular vein which lowers CCP will improve the cerebral blood flow in those patients with insufficient dynamic cerebrovascular autoregulation.