Argon does not affect cerebral circulation or metabolism in male humans

Objective
Accumulating data have recently underlined argon´s neuroprotective potential. However, to the best of our knowledge, no data are available on the cerebrovascular effects of argon (Ar) in humans. We hypothesized that argon inhalation does not affect mean blood flow velocity of the middle cerebral artery (Vmca), cerebral flow index (FI), zero flow pressure (ZFP), effective cerebral perfusion pressure (CPPe), resistance area product (RAP) and the arterio-jugular venous content differences of oxygen (AJVDO2), glucose (AJVDG), and lactate (AJVDL) in anesthetized patients.
Materials and methods
In a secondary analysis of an earlier controlled cross-over trial we compared parameters of the cerebral circulation under 15 minutes exposure to 70%Ar/30%O2 versus 70%N2/30%O2 in 29 male patients under fentanyl-midazolam anaesthesia before coronary surgery. Vmca was measured by transcranial Doppler sonography. ZFP and RAP were estimated by linear regression analysis of pressure-flow velocity relationships of the middle cerebral artery. CPPe was calculated as the difference between mean arterial pressure and ZFP. AJVDO2, AJVDG and AJVDL were calculated as the differences in contents between arterial and jugular-venous blood of oxygen, glucose, and lactate. Statistical analysis was done by t-tests and ANOVA.
Results
Mechanical ventilation with 70% Ar did not cause any significant changes in mean arterial pressure, Vmca, FI, ZFP, CPPe, RAP, AJVDO2, AJVDG, and AJVDL.
Discussion
Short-term inhalation of 70% Ar does not affect global cerebral circulation or metabolism in male humans under general anaesthesia.

研究目的
近年来日益积累的研究数据证实了氩气（argon）的神经保护潜力。然而，据我们所知，目前尚无关于氩气（Ar）对人体脑血管效应的相关研究数据。本研究假设，在麻醉患者中，吸入氩气不会对大脑中动脉平均血流速度（mean blood flow velocity of the middle cerebral artery，Vmca）、脑血流指数（cerebral flow index，FI）、零血流压（zero flow pressure，ZFP）、有效脑灌注压（effective cerebral perfusion pressure，CPPe）、阻力面积乘积（resistance area product，RAP）以及动-颈静脉血氧含量差（arterio-jugular venous content differences of oxygen，AJVDO2）、动-颈静脉血糖含量差（arterio-jugular venous content differences of glucose，AJVDG）与动-颈静脉血乳酸含量差（arterio-jugular venous content differences of lactate，AJVDL）产生影响。
材料与方法
本研究对一项既往对照交叉试验开展二次分析，纳入29例接受冠状动脉手术前、采用芬太尼-咪达唑仑联合麻醉的男性患者，比较其在吸入70%氩气（Ar）/30%氧气（O2）与70%氮气（N2）/30%氧气（O2）各15分钟时的脑循环参数。通过经颅多普勒超声（transcranial Doppler sonography）测量大脑中动脉平均血流速度（Vmca）；通过对大脑中动脉的压力-血流速度关系进行线性回归分析，估算零血流压（ZFP）与阻力面积乘积（RAP）；有效脑灌注压（CPPe）通过平均动脉压与零血流压（ZFP）的差值计算得到；动-颈静脉血氧含量差（AJVDO2）、动-颈静脉血糖含量差（AJVDG）与动-颈静脉血乳酸含量差（AJVDL）通过动脉血与颈静脉血中氧、葡萄糖及乳酸的含量差值计算得出。统计学分析采用t检验与方差分析（ANOVA）。
结果
吸入70%氩气（Ar）进行机械通气未对平均动脉压、Vmca、FI、ZFP、CPPe、RAP、AJVDO2、AJVDG及AJVDL产生任何显著影响。
讨论
短期吸入70%氩气（Ar）不会对全身麻醉男性患者的全脑循环与代谢产生影响。