Effect of Hypertonic Glucose, Urea and PVP on the Production and Absorption of Cerebrospinal Fluid

The effect of three different hypertonic solutions, 50 % glucose, 30 % urea and polivinylpyrrolidon (PVP), on the production and absorption of CSF was studied in the rabbit using the radioisotope, 32P. Experiments were performed in three groups of animals ; normal, immediately after brain compression, and after 24 hour period of compression. From the results obtained by measuring the turnover of 32P from blood to CSF (production rate) and from CSF to blood (absorption rate), an estimate was made of the effect of each solution upon CSF dynamics. Hypertonic glucose may produce a short lasting decrease in CSF pressure only in the acute compression group, while this effect may be negligible in the remaining two groups. On the other hand, hypertonic urea seems to produce a remarkable fall in the CSF pressure in all three groups, as a result of a conspicuous increase in the absorption of CSF which outweighs the slight increase inproduction. PVP however appeared to produce a consistent decrease in CSF pressure only in the group subjected to acute compression, since the rate of absorption increased gradually and progressively together with the slight decrease in production in this group. In the remaining two groups, the effect of PVP upon CSF may be negligible as with glucose. Following a 24 hour period of brain compression, it is suggested from the results that the function of the blood-CSF barrier recovers from the impairment caused by mechanical compression, at least after such very mild compression as was employed in this experiment. Likewise, there is no evidence of brain edema in this condition from the measurement of water content and histological study of the brain. The hydrodynamics of CSF is too complicated to be understood from the observation of a single phase in the CSF circulation. Any attempt to describe alteration of CSF dynamics must include a consideration of the phases of both production and absorption of CSF simultaneously.