Fluids in Bags for Hemodiafiltration

Abstract

The objective of hemodiafiltration (HDF) is to increase the convective transport of solutes poorly removed by diffusion, and therefore ultrafiltration (UF) beyond the desired weight loss is prescribed. The excess UF is compensated for by infusion of a physiological solution which should be sterile and nonpyrogenic. This replacement solution can be provided either in bags containing commercially prepared infusion solution, i.e. so-called classic HDF, or by an integrated stepwise filtration of the dialysis fluid, i.e. so-called online HDF. In both cases the composition of the replacement solution should mirror that of plasma water. When the fluid is provided in bags, practical handling is a limiting factor, and the amount of convection that can be delivered is most often restricted to 10-12 l/session. Results from clinical studies show that the degree of convective transport obtained in classic HDF corresponds to what can be achieved in contemporary high-flux dialysis, where uncontrolled UF and backfiltration take place inside the dialyzer. Classic HDF with replacement fluid in bags offers the possibility of delivering an HDF treatment with controlled convective dose and fluid quality, albeit with a limited amount of convection.

Haemodiafiltration--optimal efficiency and safety

“…They both say that the fluid must be sterile and should contain <0.25 EU/ml. Considering the fluid volumes infused in modern versions of HDF, 4–6 l/h, the maximum recommended endotoxin exposure for healthy individuals (5 EU/kg body weight and hour) could be exceeded already at moderate infusion rates and body weights using this fluid [49]. It is therefore important that the substitution solution for HDF is of considerably higher microbiological quality than stipulated by the authorities.…”

Pulse Push/Pull Hemodialysis: Convective Renal Replacement Therapy

“…As shown in Fig. 1, resulting TMP gradients can be readily increased by increasing blood and/or dialysate pressure drops (Fiore & Ronco, 2004, 2007. For blood, the pressure drop is proportional to blood viscosity and tube length in accord with Poiseuille's equation (Eq.…”

“…HDF, which describes an intermittent renal supportive therapy of combined simultaneous diffusive and convective solute transport, is characterized by a large filtration volume that far exceeds the desired volume removal, and hence, external substitution is essential. In early HDF trials, a large number of sterile bags were used to supply substitution fluid, which was costly and complicated (Ledebo, 2007). However, technical advances made in the production of pyrogen-free ultrapure water allow sterile dialysate to be readily produced, which enables on-line based HDF to be used on a clinical basis.…”

Development of Hemodiafiltration Therapy - A Historical Perspective

“…In anticipation of future development to provide user-friendly and cost-effective systems for HDF that were registered and approved for on-line, the therapy was performed with infusion fluid in bags, today referred to as ‘classic HDF' [9,12]. Typical HDF treatments used 9 l of infusion fluid in postdilution mode, and thus provided 10-12 l of convective clearance, allowing for 1-3 l weight loss.…”