Movement of solutes across the blood brain barrier depends on the reflection coefficient of the solute. Reflection coefficient is defined as the selectivity of the blood brain barrier to a particular substance. Molecules with a reflection coefficient of 1 are excluded by the blood brain barrier. As shown in the table below, sodium chloride is effectively “reflected back” or excluded by the blood brain barrier compared to the other osmotic compounds listed.
Qureshi, Adnan I. and Jose I. Suarez. “Use Of Hypertonic Saline Solutions In Treatment Of Cerebral Edema And Intracranial Hypertension”. Critical Care Medicine 28.9 (2000): 3301-3313.