FACTORS INFLUENCING THE EXCHANGE OF SODIUM BETWEEN PLASMA AND CEREBROSPINAL FLUID*†

Abstract

The exchange of Na24 between plasma and cerebrospinal fluid (CSF) has been studied in anesthetized dogs. The average exchange time (half-time) in 27 normal dogs was 143 [plus or minus] 38 min. (S. D.) The administration of vasopressin resulted in a decrease in the exchange time. The intravenous administration of acetazoleamide resulted in an increase in the exchange time and in a marked increase in intracranial pressure. Both increased intracranial pressure secondary to an epidural mass and decreased intracranial pressure secondary to CSF drainage resulted in a decrease in the exchange time. The exchange time was not affected by the following drugs and procedures: cortisone, desoxycorticosterone or corticotropin, hypertonic or hypotonic intravenous solutions, 10% CO2, norepinephrine, insulin hypoglycemia, diphenylhydantoin, chlorthiazide, meralluride or neostigmine. There was not direct correlation between change in intracranial pressure and the Na exchange time. The significance of these data with regard to the blood-CSF barrier has been discussed.