Plasma volume in isosmotic hypervolaemia.

The Evans-blue distribution volume, haematocrit, and plasma protein concentration were investigated in non-hydrated (control), hydrated, and acutely nephrectomized hydrated, anaesthetized dogs. In control anaesthetized dogs a decrease of the plasma protein level was observed as part of the plasma proteins was lost into the extravascular space and did not return into the circulating plasma during the experimental period. Under the effect of hydration, the Evans-blue distribution volume increased significantly, while the haematocrit and plasma volume did not change. The phenomenon was ascribed to an increase in capillary permeability. During hydration following acute nephrectomy, the Evans-blue distribution volume increased but the haematocrit disecreased and the circulating plasma volume increased. It is concluded that a material (or materials) orginating from the kidney may influence capillary permeability.