Pulse amplitude and volume-pressure relationships in experimental hydrocephalus

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Abstract
Summary 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<0.01) and AMPo (p<0.001) were much higher in hydrocephalic animals and C decreased significantly (p<0.001). There were no statistical differences regarding PVI. A direct linear correlation was found between AMPo and ICPo (p<0.001) and between PVI and ICPo (p<0.05) but no correlations were found between PVI and AMPo. The regression analysis showed a non-linear correlation between C and ICPo (p<0.01) and between C and AMPo (p<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.