A fall of plasma osmolality created at dialyzer and its possible effect on circulating blood volume.

A mathematical analysis of fluid exchange during hemodialysis therapy was performed in order to determine which factors affect the circulating blood volume, and hence the circulatory stability. It was found that both fluid removal and also the fall of plasma osmolality during the passage of blood through the dialyzer can affect the circulating blood colume profoundly. The later was found to accelerate the decrease of circulating blood volume by an indirect action on capillary refilling. Some treatment systems such as those involving recirculation or ultrafiltration were found to show a small fall in osmolality with a correspondingly small fall in blood pressure. This result seems to be compatible with clinical experiences reported earlier and may explain why some methods of treatment are accompanied by stable circulatory function in spite of rapid removal of large amounts of fluid.