Measurement of Cerebral Hemispheric Blood Flow by Intracarotid Injection of Hydrogen Gas: VALIDATION OF THE METHOD IN THE MONKEY

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Abstract
To develop a reliable method for measuring hemispheric blood flow and metabolism in man, the clearance of hydrogen was measured in the cerebral lateral sinus blood of macaque monkeys after intracarotid injection. Hydrogen is an inert gas and its clearance from cerebral venous blood depends solely on arterial inflow, and since it is highly diffusible, rapid equilibrium is maintained between brain tissue and its capillary-venous blood. Cerebral venous clearance curves for hydrogen appeared to provide accurate and reproducible measures of cerebral blood flow. A bolus of 0.2 to 0.3 ml of saline saturated with hydrogen was injected rapidly into the internal carotid artery. Electrodes placed on the cortex showed that the bolus was almost exclusively distributed to the ipsilateral cerebral hemisphere. Blood flow of each hemisphere was calculated by Meier and Zierler's formula based on the Stewart-Hamilton principle, as well as by compartmental analysis. The values obtained for hemispheric blood flow were in good agreement with average cerebral blood flow measured by inhalation of hydrogen using the Fick principle. Values for hemispheric blood flow were the same whether the intracarotid injection of hydrogen was rapid or slow.