Giller C A, Purdy P, Lindstrom W W
Department of Neurological Surgery, University of Texas Southwestern Medical Center, Dallas 75235-8855.
AJNR Am J Neuroradiol. 1990 Jan-Feb;11(1):177-82.
The effects of inhaled stable xenon gas on cerebral blood flow were studied with 23 transcranial Doppler examinations performed in 13 normal volunteers while breathing, 25, 30, or 35% xenon for 5 min. Doppler velocities from the middle cerebral artery rose significantly during inhalation in 85% of subjects and 78% of studies and decreased significantly in 15% of subjects and 17% of studies. These different velocity responses may represent different responses of pial vasculature to xenon. The mean velocity rise among those studies showing a significant increase was 38 +/- 3.6% (SEM). The velocity rise began 2 min after the start of xenon inhalation and increased rapidly, so that the velocities measured at the four times at which scans were obtained in our xenon CT protocol (0, 1.5, 3, and 5 min after the start of xenon inhalation) were significantly different. A consistent fall in the pulsatility of the Doppler waveform as the velocity increased provided evidence for xenon-induced vasodilation of the small-resistance vessels as the cause of the increase in flow velocity. Most subjects became mildly hyperventilated, so that the observed changes could not be attributed to hypercapnia. Inhalation of 25, 30, or 35% xenon for 5 min induces a delayed but significant rise in cerebral blood velocity. This suggests that cerebral blood flow itself may be rapidly changing during the process of xenon CT scanning. These changes may compromise the ability of the xenon CT technique to provide reliable quantitative measurements of cerebral blood flow.
对13名正常志愿者进行了23次经颅多普勒检查，研究吸入稳定氙气对脑血流量的影响。志愿者在呼吸25%、30%或35%氙气的情况下持续5分钟。在85%的受试者和78%的检查中，吸入过程中大脑中动脉的多普勒速度显著升高；在15%的受试者和17%的检查中，速度显著降低。这些不同的速度反应可能代表软脑膜血管对氙气的不同反应。在那些显示出显著增加的检查中，平均速度升高为38±3.6%（标准误）。速度升高在氙气吸入开始2分钟后开始，并迅速增加，因此在我们的氙CT方案中获取扫描的四个时间点（氙气吸入开始后0、1.5、3和5分钟）测量的速度有显著差异。随着速度增加，多普勒波形的搏动性持续下降，这为氙气引起小阻力血管舒张导致流速增加提供了证据。大多数受试者出现轻度通气过度，因此观察到的变化不能归因于高碳酸血症。吸入25%、30%或35%氙气5分钟会导致脑血流速度延迟但显著升高。这表明在氙CT扫描过程中脑血流量本身可能在迅速变化。这些变化可能会损害氙CT技术提供可靠的脑血流量定量测量的能力。
