Cerebral hemodynamics and viscoelastic property in brain edema

本研究旨在观察脑水肿时脑血流动力学和脑粘弹性的时程变化，分析甘露醇改善脑水肿时压力-容积状态的作用机制。采用Marmarou描述的直接灌注技术（0.25 ml/120 min）在右额叶白色物质中产生脑水肿。在脑水肿后静脉给予甘露醇2g/Kg/3 min。采用激光血流法监测脑血流量和脑血容量。测量ICP、PVIcsf、PVItissue和PVI-ratio（PVIcsf/PVItissue），水肿发生器的存在提示CBV持续降低和CBF短暂降低。随着水肿产生的机械力的停止，CBV和CBF恢复到控制状态。肺静脉指数在水肿形成后有下降趋势。Mandarin使CBF、CBF、PVIcsf和PVI比率增加。颅内压容积状态的改善可能是由于CBF的增加以及ICP的降低。虽然通过测量PVI比率来估计脑组织的粘弹性，但本实验中使用的组织压力测量方法不够灵敏，无法获得有意义的值。

The objective of this study was to examine the time course of cerebral hemodynamics and viscoelastic property in the brain edema, and to analyse the mechanism of mannitol effect on improving pressure-volume status in brain edema.Anesthetized cats were used for this study. Brain edema was produced in right frontal white matter by direct infusion technique (0.25ml/120min) described by Marmarou. Mannitol was administered 2g/Kg/3min intravenously following brain edema. CBF and CBV were monitored by Laser flow method. ICP, PVIcsf, PVItissue, and PVI-ratio (PVIcsf/PvItissue) were obtained.The presence of an edema generator elicits a continuous reduction of CBV and a transient reduction of CBF. With cessation of this mechanical force of edema production, CBV and CBF return to control. PVI-ratio tended to decrease after edema formation. Mannitol increased CBF, CBF, PVIcsf and PVI-ratio. The Improvement of the Intracranial Pressure volume status might be due to an increase in CBF as well as ICP reduction.Although viscoelastic property in the brain tissue was estimated by measuring PVI-ratio, the method of tissue pressure measurement used in this experiment was not enough sensitive to obtain significant values.