Pulse amplitude and volume-pressure relationships in experimental hydrocephalus

The bolus injection test was used to study the intracranial volume pressure relationships in an experimental population of normal and hydrocephalic dogs. Hydrocephalus was developed by means of an intracisternal injection of a kaolin powder solution. Hydrocephalic animals were tested a mean of 15 days after kaolin injection. The intraventricular pressure (ICPo) and amplitude of intraventricular pulse wave (AMPo) were measured at baseline steady-state. Pressure-volume index (PVI) and intracranial compliance (C) were calculated from bolus injection tests. The ICPo (p less than 0.01) and AMPo (p less than 0.001) were much higher in hydrocephalic animals and C decreased significantly (p less than 0.001). There were no statistical differences regarding PVI. A direct linear correlation was found between AMPo and ICPo (p less than 0.001) and between PVI and ICPo (p less than 0.05) but no correlations were found between PVI and AMPo. The regression analysis showed a non-linear correlation between C and ICPo (p less than 0.01) and between C and AMPo (p less than 0.001). The results of our experimental study suggest that: 1) pulse amplitude relates to the intracranial compliance, and 2) the intracranial compliance is a better parameter of the volume-pressure response than PVI.