ARTIFICIAL KIDNEY FUNCTION: KINETICS OF HEMODIALYSIS 1

Abstract

An artificial kidney (Brigham-Kolff type) was used to study kinetics of hemodialysis in vitro and in man. Its operation is described quantitatively, and parallels to human renal excretion are formulated. Equations governing exchanges in the artificial kidney are compared with equations governing natural renal excretion. The concept of dialysance, or the minute rate of net exchange of a substance between blood and bath per unit blood-bath concn. gradient, is introduced as a parameter in artificial kidney function corresponding to the clearance in natural kidney function. Its value is relatively characteristic for different molecular and ionic species although for any one species it increases with blood flow and cellophane surface area. Using the urea dialysance as a reference, relative dialysances have been detd. under various conditions for several non-electrolytes and ions. The volume of circulating fluid contained in the cellophane casing is proportional to the rate of flow. From this relation circulation times through the machine were deduced. A method is presented for stabilizing a patient''s blood volume during therapy and reducing the likelihood of occurrence of pulmonary edema. The effect of various concns. of glucose in the bath fluid on fluid balance in the artificial kidney was studied quantitatively. To maximize the exchange of hemodialyz-able solutes during some total operating time, the bath may be drained and refilled with fresh fluid at an intermediate time. It is concluded that, for any given total operating time and any chosen number of changes of bath fluid, operating time intervals between changes are optimum if equal. The effects of dialysance, blood flow, and bath volume on the exchange of material during hemodialysis are quantified.