Blood‐brain barrier permeability during shortlasting intravascular hyperosmolality

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Abstract
Blood‐brain barrier permeability for 24Na+and 36Cl‐ ions and for 3HOH was studied during isoosmolality and during shortlasting intravascular hyperosmolality in twenty‐five patients using the double indicator single injection method. Hyperosmolality was induced by a rapid injection into the internal carotid artery of 8 ml of one of the following hypertonic solutions: 5% saline, 25% mannitol or a contrast medium of the metrizoat group (Isopaque‐amine 280®. The extractions of the small sodium and chloride ions remained unchanged and essentially zero indicating that ‘opening’ of the blood‐brain barrier did not occur. The blood‐brain barrier permeability to water remained unchanged during hyperosmolality, but the extraction of 3HOH increased when mannitol and especially when Isopaque‐amine 280®was used as hypertonic agent corresponding to the lower water concentration in these solutions.