Grüne Frank, Kazmaier Stephan, Stolker Robert J, Visser Gerhard H, Weyland Andreas
Department of Anesthesiology, Erasmus MC, Rotterdam, The Netherlands.
Center of Anesthesiology, Critical Care, Emergency Medicine and Pain Therapy, University-Hospital of Göttingen, Göttingen, Germany.
J Cereb Blood Flow Metab. 2015 Sep;35(9):1470-7. doi: 10.1038/jcbfm.2015.63. Epub 2015 Apr 15.
In addition to cerebrovascular resistance (CVR) zero flow pressure (ZFP), effective cerebral perfusion pressure (CPPe) and the resistance area product (RAP) are supplemental determinants of cerebral blood flow (CBF). Until now, the interrelationship of PaCO2-induced changes in CBF, CVR, CPPe, ZFP, and RAP is not fully understood. In a controlled crossover trial, we investigated 10 anesthetized patients aiming at PaCO2 levels of 30, 37, 43, and 50 mm Hg. Cerebral blood flow was measured with a modified Kety-Schmidt-technique. Zero flow pressure and RAP was estimated by linear regression analysis of pressure-flow velocity relationships of the middle cerebral artery. Effective cerebral perfusion pressure was calculated as the difference between mean arterial pressure and ZFP, CVR as the ratio CPPe/CBF. Statistical analysis was performed by one-way RM-ANOVA. When comparing hypocapnia with hypercapnia, CBF showed a significant exponential reduction by 55% and mean VMCA by 41%. Effective cerebral perfusion pressure linearly decreased by 17% while ZFP increased from 14 to 29 mm Hg. Cerebrovascular resistance increased by 96% and RAP by 39%; despite these concordant changes in mean CVR and Doppler-derived RAP correlation between these variables was weak (r=0.43). In conclusion, under general anesthesia hypocapnia-induced reduction in CBF is caused by both an increase in CVR and a decrease in CPPe, as a consequence of an increase in ZFP.
除脑血管阻力（CVR）、零流量压力（ZFP）外，有效脑灌注压（CPPe）和阻力面积乘积（RAP）是脑血流量（CBF）的补充决定因素。到目前为止，PaCO2诱导的CBF、CVR、CPPe、ZFP和RAP变化之间的相互关系尚未完全明确。在一项对照交叉试验中，我们以30、37、43和50 mmHg的PaCO2水平为目标，对10例麻醉患者进行了研究。采用改良的Kety-Schmidt技术测量脑血流量。通过对大脑中动脉压力-血流速度关系进行线性回归分析来估计零流量压力和RAP。有效脑灌注压计算为平均动脉压与ZFP之差，CVR计算为CPPe/CBF之比。采用单向重复测量方差分析进行统计分析。与高碳酸血症相比，低碳酸血症时CBF显著呈指数下降55%，平均大脑中动脉血流速度（VMCA）下降41%。有效脑灌注压线性下降17%，而ZFP从14 mmHg增加到29 mmHg。脑血管阻力增加96%，RAP增加39%；尽管平均CVR和多普勒衍生的RAP有这些一致的变化，但这些变量之间的相关性较弱（r = 0.43）。总之，在全身麻醉下，低碳酸血症诱导的CBF降低是由CVR增加和CPPe降低共同引起的，这是ZFP增加的结果。
