Rex S, Meyer P T, Baumert J-H, Rossaint R, Fries M, Büll U, Schaefer W M
Department of Anaesthesiology, University Hospital, Technical University Aachen, Aachen, Germany.
Br J Anaesth. 2008 May;100(5):667-75. doi: 10.1093/bja/aen036. Epub 2008 Mar 15.
The effects of xenon on regional cerebral blood flow (rCBF) are controversial. Moreover, the precise sites of action at which xenon exerts its effects in the human brain remain to be established.
rCBF was sequentially assessed by H(2)(15)O positron emission tomography in six volunteers. rCBF was determined at baseline and during general anaesthesia induced with propofol and maintained with one minimum alveolar concentration xenon. rCBF measurements were started after the calculated plasma concentration of propofol had decreased to subanaesthetic levels (<1.0 microg ml(-1)). Changes in rCBF were calculated for 13 cerebral volumes of interest by measurement of a semi-quantitative perfusion index (PI). In addition, voxel-wise changes in rCBF were analysed using statistical parametric mapping.
Xenon had only minor effects on PI in grey matter volumes of interest. In contrast, PI was increased in white matter [from 1.01 (0.11) to 1.24 (0.15) kcnt ml(-1) MBq(-1), P=0.05, mean (SD)]. Voxel-based analysis showed an increase of rCBF in white matter and a relative decrease of rCBF during xenon anaesthesia in distinct grey matter regions, particularly the orbito- and mesiofrontal cortex, cingulate gyrus, thalamus, hippocampus and bilateral cerebellum (P<0.05 corrected). When correlating PI with cerebral metabolic rate of glucose (previously obtained in another group of six volunteers using (18)F-fluorodeoxyglucose as tracer), the flow-metabolism coupling was preserved during xenon anaesthesia.
Xenon exerted distinct regional effects on CBF: relative decreases in several cortical, subcortical, and cerebellar areas were accompanied by an increase in white matter. Flow-metabolism coupling was not impaired during xenon anaesthesia.
氙气对局部脑血流量（rCBF）的影响存在争议。此外，氙气在人脑中发挥作用的确切作用部位仍有待确定。
通过H(2)(15)O正电子发射断层扫描对6名志愿者的rCBF进行连续评估。在基线时以及在丙泊酚诱导并维持在一个最低肺泡浓度的氙气麻醉期间测定rCBF。在计算出的丙泊酚血浆浓度降至亚麻醉水平（<1.0微克/毫升(-1)）后开始进行rCBF测量。通过测量半定量灌注指数（PI）计算13个感兴趣脑区的rCBF变化。此外，使用统计参数映射分析rCBF的体素水平变化。
氙气对感兴趣灰质区域的PI影响较小。相比之下，白质中的PI升高[从1.01（0.11）升至1.24（0.15）千计数/毫升(-1)兆贝克(-1)，P = 0.05，均值（标准差）]。基于体素的分析显示，在氙气麻醉期间白质中rCBF增加，而在不同的灰质区域特别是眶额和内侧额叶皮质、扣带回、丘脑、海马体和双侧小脑rCBF相对降低（校正后P<0.05）。当将PI与葡萄糖脑代谢率相关联时（先前在另一组6名志愿者中使用(18)F-氟脱氧葡萄糖作为示踪剂获得），在氙气麻醉期间血流-代谢耦合得以保留。
氙气对CBF产生不同的区域影响：几个皮质、皮质下和小脑区域的相对减少伴随着白质增加。在氙气麻醉期间血流-代谢耦合未受损。
