Role of pressure gradients and bulk flow in dynamics of vasogenic brain edema

Abstract

The authors present the results of an investigation of the vasogenic type of brain edema using cold injury in cats as a model. Their findings indicate that bulk flow and not diffusion should be considered the main mechanism for the spread of edema through the white matter. This conclusion is based on: 1) comparison of the distances actually traveled by various substances during edema spread with those calculated theoretically for migration of the substances by diffusion; 2) coincidence in the speed of movement by two substances (sucrose and albumin) with widely different diffusion coefficients; 3) measurement of interstitial fluid pressure (IFP) at various distances from the lesion showing the presence of increased IFP in the lesion area and decreasing pressures along the edema pathway toward the normal tissue; and 4) the fact that spreading of edema can be significantly impeded by inducing before the cold lesion an intracellular type of brain edema that reduces the size of the extracellular space (ECS) and increases the resistance to flow of edema fluid. The pressure-volume curve of the brain ECS, as derived from determinations of IFP and tissue water content, indicates that initial steep slope in IFP probably represents the high resistance to fluid mobility through the small diameter extracellular channels and the counteracting resistance of the intermingled structures of brain parenchyma to be separated. Once the IFP exceeds these opposing forces, the ECS dilates, fluid mobility increases, and the edema front advances.

An atlas-based method to compensate for brain shift: Preliminary results

“…Conversely, elevated capillary pressures increase local tissue volume, resulting in tissue stress and distortion. A pressure elevation of 20-30 mmHg has been measured in experimental brain edema and shown to be capable of driving edema fluid through the brain (Reulen et al, 1977) (for this work, a value of 27 mmHg was used). The term k c (p − p c ) is intended to model these fluid exchanges.…”

Salirasib (farnesyl thiosalicylic acid) for brain tumor treatment: a convection-enhanced drug delivery study in rats

“…Fluid convection (bulk flow), which occurs in the brain interstitial fluid under normal conditions (1), in cases of vasogenic edema (2), and after infusion of solutions directly into the brain parenchyma (3), is a promising technique for the distribution of solutions into brain tissue. The fluid convection established by maintenance of a pressure gradient during interstitial infusion has been shown to greatly enhance the distribution of various molecules in the brain (4,5).…”

Dexamethasone Effects on [125I]Albumin Distribution in Experimental RG-2 Gliomas and Adjacent Brain

“…Even though a lymphatic system does not exist in brain, a clearance mechanism for albumin and other pro teins apparently exists that maintains the differ ences between brain extracellular fluid and plasma protein concentrations (Cserr and Ostrach, 1974;Blasberg, 1976;Cserr et al ., 1981;Vorbrodt et al ., 1985). When the influx of albumin and other plasma solutes into brain tissue is increased in pathological conditions, such as brain tumors , it is likely that the capacity of the normal mechanisms for clearing plasma proteins, ions, and water from brain extra cellular fluid are exceeded (Reulen, 1976;Reulen et al ., 1977Reulen et al ., , 1978Klatzo et al ., 1980;Hossmann et al ., 1980Hossmann et al ., ,1983aKuroiwa et al ., 1985). Under these conditions, vasogenic brain edema may de velop.…”