Vascular components of cerebrospinal fluid compensation

Object. The aim of the study was to assess bow cerebrospinal fluid (CSF) pr essure-volume compensation depends on cerebrovascular tone. Methods. In 26 New Zealand White rabbits, intracranial pressure (ICP), arte rial blood pressure, and basilar artery blood flow velocity were measured c ontinuously. Saline was infused into the cranial subarachnoid space to asse ss CSF compensatory parameters: the resistance to CSF outflow, the elastanc e coefficient, and the amplitude of the ICP pulsatile waveform. Infusions w ere repeated on two different levels of CO2 concentration in the arterial b lood (PaCO2), at normotension and hypotension, and after the death of the a nimal. An increase in PaCO2 from a mean of 27 to 48 mm Hg was accompanied by an 18 %; increase in the resistance to CSF outflow (p < 0.005) and a 64% increase (p < 0.05) in the elastance coefficient. A decrease in arterial blood pres sure from a mean of 100 to 51 mm Hg caused a 25% decrease in CSF outflow re sistance (p < 0.01) but did not affect the elastance coefficient. Postmorte m, a 23% decrease in the CSF outflow resistance was associated with a 102% decrease in the elastance coefficient. Conclusions. Cerebrovascular parameters have a limited but significant impa ct on CSF infusion studies. The vascular component of ICP may be identified as a significant factor contributing to this phenomenon. During infusion s tudies, physiological parameters influencing vascular conditions should be maintained as stable as possible.