Exchange of Cerebrospinal Fluid Potassium With Blood and Brain

Abstract

INITIAL STUDIES in unanesthetized rhesus suggested a rapid exchange of potassium between brain and CSF.^1,2In order to explore this relationship quantitatively, the exchange of potassium between blood, CSF, and brain has been measured in anesthetized cats, utilizing a technique of continuous perfusion of the animals' ventriculocisternal system with synthetic CSF.^3-7By adding potassium chloride K 42 (⁴²K) to either the perfusate or blood it is possible to calculate the flux of⁴²K into or out of the CSF.^3,4Since brain potassium exchanges very slowly with plasma K,⁵it is possible to determine the flux into CSF of potassium from brain and blood separately. These measurements provide information regarding the mechanisms present in mammalian species including man which maintain CSF potassium within the range of 2.6 to 3.2 mM despite variations in serum potassium.^6,8,9In the present experiments the exchange of CSF