Zhang Rong, Crandall Craig G, Levine Benjamin D
Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, and University of Texas Southwestern Medical Center, Dallas, Tex 75231, USA.
Stroke. 2004 Apr;35(4):843-7. doi: 10.1161/01.STR.0000120309.84666.AE. Epub 2004 Feb 19.
The aim of this study was to differentiate the mechanical effects of the Valsalva maneuver (VM) from the effects of changes in autonomic neural activity on cerebral hemodynamics in humans.
Nine healthy subjects performed the VM before and after autonomic ganglionic blockade with trimethaphan. Blood pressure (BP) was measured in the radial artery with an indwelling catheter or at the finger by Finapres. Cerebral blood flow (CBF) velocity was measured in the middle cerebral artery with transcranial Doppler; end-tidal CO2 was measured by mass spectrometry.
Before blockade, during phase II of the VM, BP was reduced by 27% and CBF velocity was reduced by 33% (magnitude of changes during phase II divided by baseline measurements before the VM, P<0.05). Cerebrovascular conductance index (CVCI) increased by 21%. During phase IV, overshoot of CBF velocity was proportionately greater than that of BP (46% versus 30%). After blockade, during phase II, BP fell to a much greater degree by 50%, while CBF velocity decreased even more by 60% associated with an increase in CVCI by 33%. During phase IV, despite the absence of BP overshoot, CBF velocity still increased by 55% and CVCI by 33%. Both were significantly greater than before blockade.
After ganglionic blockade, cerebral autoregulation is unable to prevent the substantial fall in CBF induced by the marked reduction in BP during the VM. Enhanced phase IV increases in both CBF velocity and CVCI reflect the intrinsic characteristics of cerebral hyperemic responses, which are likely modified in part by the removal of vasoconstrictor effects of autonomic neural activity elicited during the VM.
本研究的目的是区分瓦尔萨尔瓦动作（VM）的机械效应与自主神经活动变化对人体脑血流动力学的影响。
9名健康受试者在使用三甲硫吩进行自主神经节阻断前后进行VM。通过留置导管在桡动脉或使用Finapres在手指处测量血压（BP）。使用经颅多普勒在大脑中动脉测量脑血流（CBF）速度；通过质谱法测量呼气末二氧化碳。
阻断前，在VM的II期，BP降低27%，CBF速度降低33%（II期变化幅度除以VM前的基线测量值，P<0.05）。脑血管传导指数（CVCI）增加21%。在IV期，CBF速度的过冲比BP的过冲更大（46%对30%）。阻断后，在II期，BP下降幅度更大，为50%，而CBF速度下降更多，为60%，同时CVCI增加33%。在IV期，尽管没有BP过冲，CBF速度仍增加55%，CVCI增加33%。两者均显著大于阻断前。
神经节阻断后，脑自动调节无法防止VM期间BP显著降低引起的CBF大幅下降。IV期CBF速度和CVCI增强的增加反映了脑充血反应的内在特征，这可能部分地因消除VM期间引发的自主神经活动的血管收缩作用而改变。
