Changes of frequency spectrum of the CSF pulse wave caused by supratentorial epidural brain compression
Journal of Neurology, Neurosurgery and Psychiatry
The frequency spectrum of the CSF pulse wave and amplitude transfer function from arterial to CSF pressure were estimated in the lateral ventricle and cisterna magna during the course of supratentorial epidural compression of brain in anaesthetised ventilated cats. Ventricular fluid pressure, the amplitude of spectral components of the CSF pulse and the amplitude of transfer function in the supratentorial compartment were increased in an exponential manner as epidural compression advanced. A
... nstentorial pressure gradient developed when epidural compression exceeded a critical level. Conduction of the CSF pulse through the tentorial hiatus decreased in an exponential manner when plotted against the transtentorial pressure gradient. Transtentorial conduction of the CSF pulse may serve as a sensitive indicator of the development of tentorial herniation. Changes of the waveform of the CSF pulse associated with changes in intracranial pressure (ICP) are often noted during continuous monitoring. Several authors have proposed that waveform analysis of the CSF pulse may be a useful means to estimate intracranial pressure dynamics."5 Detailed study of the CSF pulse waveform under controlled experimental conditions, however, is still necessary before assessing the practical value of pressure waveform analysis in the management of patients with raised ICP. This study was planned to determine the behaviour of the CSF pulse wave when ICP was raised experimentally by epidural compression of the brain under controlled conditions. Materials and methods Twelve mongrel cats of both sexes, weighing between 4-2 and 4 8 kg, were used for these experiments. Each animal was anaesthetized by ketamine 20 mg/kg IM after premedication by atropine 0-05 mg/kg subcutaneously. Tracheotomy and intubation were performed, then anaesthesia was maintained by mixed gases of 30% 02 and 70% N20. The animal was paralysed by pancuronium bromide 0-05 mg/kg IV and respiration was maintained mechanically (Harvard respiratory Model 665 A made by Harvard Apparatus, South Natick, Massachusetts, USA). The left femoral vein and artery were cannulated for the drip infusion of Hartmann's solution and for monitoring of blood gases (blood gas analyser IL system 1302 made by Instrument Laboratory, Milano, Italy), respectively. A catheter was placed in the left subclavian artery for monitoring of systemic blood pressure. The animal was fixed in a stereotaxic frame in the sphinx position. A midline incision was made in the suboccipital region and a 22-gauge spinal needle was placed in the cisterna magna through the foramen magnum. A small rubber balloon was placed in the epidural space of the right parietal region through a drill hole in the skull. Another spinal needle of the same gauge was inserted into the left lateral ventricle stereotaxically through a drill hole. The sites of insertion of spinal needles and epidural balloon were sealed by cyanoacrylate adhesive or dental acrylic. The catheter placed in the subclavian artery and spinal needles in the CSF space were connected to pressure transducers (pressure transducers made by Bentley Laboratories, Irvine, California, USA) by tubes of high pressure type and of equal length for recording by a polygraph and a FM tape recorder (FM tape recorder Model MR-10 made by TEAC Corporation, Tokyo, Japan). All pressure transducers were calibrated by a water column and positioned halfway between the tip of dorsal spine and the sternum. Pulsatile components of arterial pressure and CSF pulse were selectively magnified by a four channel AC amplifier with preset gain from twice to 100 times, and recorded by a FM tape recorder. After stabilisation of the animal, the CSF pulse and blood pressure were recorded under baseline conditions. Then the epidural balloon was inflated at the rate of 0-038 ml/min and all pressures were recorded. Sizes of both pupils were Protected by copyright. on 26 April 2019 by guest.