Hydrogen exchange through the pial vessel wall and its meaning for the determination of the local cerebral blood flow

摘要

In anaesthetized cats clearances of inhaled hyrogen were measured by means of microelectrodes in the lumen and at the wall of pial vessels, in the surrounding subarachnoid space, as well as in the cerebral cortex. The following results were obtained:1.In the environment of pial arteries the H2-clearance takes place considerably faster than in the cerebral cortex or in the subarachnoid space without visible vessels.2.The liquor space covered by glass foils is washed out slowly. The desaturation process corresponds to an “apparent cerebral blood flow” of about 20 ml/100g×min.3.When veins and arteries are situated in narrow vicinity a shunt diffusion of hydrogen occurs, since in both types of vessels almost identical clearance curves were recorded.4.From the aorta to the small pial arteries (60 μm diameter) the clearance profile changes dependent on the localization. This is due to the hydrogen diffusion exchange with the surrounding tissue. When different arterial clearance curves are used as an input function for the determination of the local blood flow, tissue blood flow values differ from 25 to more than