氙气麻醉对健康受试者大脑糖代谢与脑血流耦联关系的影响：采用正电子计算机断层显像技术的研究

背景全身麻醉药能够改变脑局部糖代谢（regionalcerebralglucosemetabolism，rCMRgk）和脑血流（cerebralbloodflow，CBF）之间的相互关系。本研究应用正电子计算机断层显像（positronemissiontomography，PET）研究技术评价氙气麻醉对健康受试者rCMRgk及rCBF的影响。方法采用纯氙气对5例男性健康受试者进行麻醉，分别用埔F标记的氟脱氧葡萄糖和^15O标记的水分子测量基础值（清醒时）及1个肺泡最低有效浓度（minimumalveolarconcentration，MAC）下的rCMRgk及rCBF值。采用兴趣区（region-of-interest，ROI）分析及体素定量分析测量rCMRgk及rCBF的变化。结果麻醉期间氙气平均浓度为67．2％±0．8％（均数±标准差）。氙气麻醉导致rCMRgk均一性降低，但仅导致rCBF在13个兴趣区中的7个降低。灰质区rCMR出及疋BF分别降低了32．4％±4．0％（P〈0．001）和14．8％±5．9％（P=0．007）；自质区rCMR出降低了10．9％±6．4％（P=0．030），而rCBF增加了9．2％±7．3％。在岛叶、扣带前回、扣带后回及躯体感觉皮质区rCBF／rCMR出比值增加最明显。结论在1MAC氙气麻醉时rCMR出的降低程度大于rCBF的降低，因而rCBF／rCMRgk比值增加。有趣的是氙气麻醉对脑代谢及脑血流的影响与挥发性麻醉药相似。

BACKGROUND： General anesthetics can alter the relationship between regional cerebral glucose metabolism （rCMRgk） and blood flow （rCBF）. In this positron emission tomography study, our aim was to assess both rCMRgk and rCBF in the same individuals during xenon anesthesia. METHODS：^18 F-labeled fluorodeoxyglucose and ^15 O-labeled water were used to determine rCMRgk and rCBF, respectively, in five healthy male subjects at baseline （awake） and during 1 minimum alveolar anesthetic concentration of xenon. Anesthesia was based solely on xenon. Changes in rCMRgk and rCBF were quantified using region-of-interest and voxel-based analyses. RESULTS： The mean （SD） xenon concentration during anesthesia was 67.2 （0.8）%. Xenon anesthesia induced a uniform reduction in rCMRgk, whereas rCBF decreased in 7 of 13 brain regions. The mean decreases in the gray matter were 32. 4 （4.0）% （P 〈 0. 001） and 14.8 （5.9）% （P = 0. 007） for rCMRglc and rCBF, respectively, rCMRgk decreased by 10.9 （6.4）% in the white matter （P = 0. 030）, whereas rCBF increased by 9.2 （7.3）% （P 0. 049）. The rCBF/rCMRgk ratio was especially increased in the insula, anterior and posterior cingulate, and in the somatosensory cortex. CONCLUSIONS： In general, the magnitude of the decreases in rCMRgk during 1 minimum alveolar anesthetic concentration xenon anesthesia exceeded the reductions in rCBF. As a result, the ratio between rCMRgk and rCBF was shifted to a higher level. Interestingly, xenon-induced changes in cerebral metabolism and blood flow resemble those induced by volatile anesthetics.