Measurement of the effective dialyzer Na diffusion gradient in vitro and in vivo

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    ABSTRACT: A computer model was developed to simulate sodium and water kinetics during hemodiafiltration (HDF), acetate-free biofiltration (AFB) and hemodialysis (HD). Multiple regression analysis of the results of 3,240 simulated applications of the model (1,620 HDF, 1,080 AFB, 540 HD) showed that, during HDF and AFB, there is a close correlation (R2 = 0.92 and 0.91) between plasma water sodium concentration [( Na+P]) and a set of three variables: 1) the sodium gradient between plasma water and dialysate, 2) the sodium concentration of the substitution fluid and 3) ultrafiltration (UF) rate. With HD, a close correlation (R2 = 0.94) was found between changes in [Na+P] and combined changes in sodium gradient and the UF rate. On this basis, a regression equation was formulated for each procedure which allowed a reliable prediction of final [Na+P] to be made on the basis of knowledge of the imposed Na gradient, the programmed infusion (during HDF and AFB), and the UF rate. Clinical validation of the model was obtained in 12 patients: predicted final [Na+P] agreed well with the values measured by means of direct potentiometry (141.9 vs. 142.1 mEq/liter; P = NS), with a mean difference (-0.16 mEq/liter) and limits of agreement (+0.8 to -1.03 mEq/liter) fully acceptable for clinical purposes.(ABSTRACT TRUNCATED AT 250 WORDS)
    Kidney International 10/1991; 40(3):525-32. DOI:10.1038/ki.1991.241 · 8.56 Impact Factor
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    ABSTRACT: Intermittent dialysis therapy is used in chronic uremia to re-establish body water solute concentrations that cannot be achieved by the natural organ. In this sense, the dialyzer becomes an artificial kidney and it is through the transport of substances by this device that chemical and biophysical control consistent with continued survival is achieved. This chapter is organized as shown in Figure 1 and consists of two basic lines of development: 1. Consideration of the dialyzer and its operating principles 2. Application of mass balance principles to various solute systems and the effect of dialyzer use on solute control during intermittent dialysis therapy
    Replacement of Renal Function by Dialysis, 12/1995: pages 34-102;
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    ABSTRACT: Sodium modeling. The most serious side effects induced hemodialysis therapy are caused by changes in sodium concen and subsequent water shift between the intracellular and extracellular fluid compartment. Because of inadequate precision of proportioning, a certain sodium concentration in the measurement of sodium concentration in dialysis fluid and plasma water, an error of up to 10 g in the diffusive exchange of sodium chloride remains in most dialysis sessions. Common side effects occur within this sodium balance error. Sodium modeling is a simplified mathematical method to describe quantitatively the fluid exchange in the body caused by changes in extracellular sodium concentration. It is based on fundamental physiologic properties of sodium and its per-meability through the corresponding membranes. It also explains the different working mechanisms of sodium- and urearelated changes in osmolarity. Sodium modeling is a helpful tool for the illustration of the effects of changes in sodium concentration and ultrafiltration rate on sodium balance during one dialysis session. Sodium profiling is a method employed to avoid unwanted side effects of hemodialysis therapy by deliberately changing the sodium concentration in dialysis fluid during the course of a dialysis session. Clinical reports on practicing sotions dium profiling are unsatisfactory, involving only short trial periods in most cases. Most of the studies reported positive sodium balance with temporary decreases in intradialytic hypotension reand less blood volume reduction, but with increases in thirst and body weight. To date, no validated studies with suitable control of sodium balance have been published that clearly demonmuscle strate the long-term benefits of this mode of therapy compared with the use of constant dialysate sodium concentrations.
    Kidney international. Supplement 09/2000; 76(76):S72-8. DOI:10.1046/j.1523-1755.2000.07609.x
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