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 (AJVDO(2)), 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%O(2) versus 70%N(2)/30%O(2) 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. AJVDO(2), 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, AJVDO(2), AJVDG, and AJVDL. DISCUSSION: Short-term inhalation of 70% Ar does not affect global cerebral circulation or metabolism in male humans under general anaesthesia.