AN INDEX OF PLASMA REFILLING IN HEMODIALYSIS-PATIENTS

During hemodialysis therapy, a large amount of water is removed from t he patient's blood in a short time; however, blood pressure remains st able in most patients. As water is removed, the circulating serum prot eins become more concentrated, resulting in a marked increase in the d riving force which pulls water from the extravascular space into the b lood vessels, by a process called plasma refilling. However, since a m ethod for studying plasma refilling has not previously been proposed, it is not known what determines the plasma refilling capacity of hemod ialysis patients. To evaluate the plasma refilling capacity of patient s, we propose here a method for calculating an index of plasma refilli ng capacity, which we have called the plasma-refilling coefficient (Kr ). In 14 patients receiving maintenance hemodialysis therapy, total se rum protein was measured before hemodialysis, and hematocrits were mea sured hourly during hemodialysis. From the changes in the hematocrits, we estimated the changes in the circulating plasma volume and in the intracapillary oncotic pressure at each time point. The water removal rate was also measured hourly. From these values, we calculated Kr. An averaged volume of 2,692 +/- 219 ml of water was removed from each pa tient resulting in a decrease in the estimated circulating blood volum e, while the hematocrit and the estimated intracapillary oncotic press ure increased gradually. Kr calculated after 1 h of hemodialysis varie d widely between patients, 140.3-1,744.2 ml/mm Hg/h, and decreased gra dually as water removal continued. The average Kr of 14 patients was 6 98.9 +/- 15.2 ml/mm Hg/h at the beginning of water removal, and it dec reased to 405.3 +/- 75.4, 203.9 +/- 39.5, 130.2 +/- 20.5 and 93.9 +/- 14.3 each hour thereafter. The index of plasma refilling proposed in t his paper is useful for examining capillary water permeability and the degree of plasma refilling in hemodialysis patients.