Characteristic profiles of circulating blood volume during dialysis therapy.

From continuous measurements of the hemoglobin concentration in the arterial blood line during 50 hemodialysis sessions in 20 stable dialysis patients, the influence of the amount of ultrafiltered fluid, the ultrafiltration rate, and overhydration of the patient upon the circulating blood volume was derived. If ultrafiltration is stopped, blood volume increases until equilibrium is obtained. The amount of refilling is proportional to the ultrafiltration rate [2.5%/(L/hr)]. The decrease of blood volume after re-equilibration depends upon the ultrafiltered amount and the degree of overhydration. The mean decrease of blood volume per liter of ultrafiltrate was found to be 5.5% for an average overhydration of 3 L.