Vascular components of cerebrospinal fluid compensation.
Czosnyka M., Richards HK., Czosnyka Z., Piechnik S., Pickard JD., Chir M.
OBJECT: The aim of the study was to assess how cerebrospinal fluid (CSF) pressure-volume compensation depends on cerebrovascular tone. METHODS: In 26 New Zealand White rabbits, intracranial pressure (ICP), arterial blood pressure, and basilar artery blood flow velocity were measured continuously. Saline was infused into the cranial subarachnoid space to assess CSF compensatory parameters: the resistance to CSF outflow, the elastance coefficient, and the amplitude of the ICP pulsatile waveform. Infusions were repeated on two different levels of CO2 concentration in the arterial blood (PaCO2), at normotension and hypotension, and after the death of the animal. 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 pressure from a mean of 100 to 51 mm Hg caused a 25% decrease in CSF outflow resistance (p<0.01) but did not affect the elastance coefficient. Postmortem, 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 impact on CSF infusion studies. The vascular component of ICP may be identified as a significant factor contributing to this phenomenon. During infusion studies, physiological parameters influencing vascular conditions should be maintained as stable as possible.