Bosone Daniele, Ozturk Vesile, Roatta Silvestro, Cavallini Anna, Tosi Piera, Micieli Giuseppe
Neurovascular Unit, IRCCS C. Mondino Institute of Neurology, Pavia, Italy.
Funct Neurol. 2004 Jan-Mar;19(1):31-5.
The aim of this study was to evaluate, in a context of general inhibition of the sympathetic nervous system, the cerebral haemodynamic response to -30 degrees head-down tilt (HDT), a manoeuvre that produces an increase in intracranial arterial pressure. Nineteen healthy subjects were studied according to the following protocol: 10 min lying in supine position, 10 min HDT, 10 min recovery. Inhibition of the sympathetic system was confirmed by the decrease in heart rate (-3.6 bpm) and arterial blood pressure (-5.9 mmHg, p<0.05) in the late phase of the test. Blood velocity and blood pusatility index initially increased (+3.2 cm s(-1) and +9% respectively, p<0.01) then returned towards baseline before the end of HDT, while the cerebrovascular resistance index (=arterial blood pressure/blood velocity) dropped significantly and remained below control level (-7%, p<0.01) throughout the test. The changes in both these indices were opposite to those reported in several sympathetic activation tests, such as the handgrip and cold pressor tests. Conversely, arterial pressure at cranial level increased during HDT (as it also does during sympathetic activation tests), due to the development of a hydrostatic pressure gradient between heart and brain levels. Therefore, the effects observed on the pulsatility and resistance indices are not secondary to the increase in intracranial arterial pressure. It is suggested that the changes in these cerebrovascular indices are mediated by a reduction of sympathetic tone that presumably involves the cerebral as well as the peripheral vascular bed.
本研究的目的是在交感神经系统普遍受到抑制的情况下，评估大脑对 -30 度头低位倾斜（HDT）的血流动力学反应，这种操作会导致颅内动脉压升高。19 名健康受试者按照以下方案进行研究：仰卧位 10 分钟，头低位倾斜 10 分钟，恢复 10 分钟。在测试后期，心率下降（-3.6 次/分钟）和动脉血压下降（-5.9 mmHg，p<0.05）证实了交感神经系统受到抑制。血流速度和血流搏动指数最初升高（分别为 +3.2 cm s(-1) 和 +9%，p<0.01），然后在头低位倾斜结束前恢复到基线水平，而脑血管阻力指数（=动脉血压/血流速度）显著下降，并在整个测试过程中保持在对照水平以下（-7%，p<0.01）。这两个指数的变化与在一些交感神经激活测试（如握力测试和冷加压测试）中报告的变化相反。相反，在头低位倾斜期间，颅内水平的动脉压升高（交感神经激活测试期间也是如此），这是由于心脏和大脑水平之间形成了静水压力梯度。因此，观察到的对搏动性和阻力指数的影响并非颅内动脉压升高的继发结果。有人认为，这些脑血管指数的变化是由交感神经张力降低介导的，这可能涉及脑血管床以及外周血管床。
