Stepwise achievement of high convection volume in post‐dilution hemodiafiltration: A prospective observational study

Abstract

High‐volume online hemodiafiltration (HDF) has been reported to reduce the patient's mortality. However, achieving a high convection volume is challenging. In this prospective study, we investigated the feasibility of achieving high‐volume HDF with ≥21 L substitution volume via modification of blood flow rate (BFR), needle size, and dialysis membrane. In 30 patients undergoing hemodialysis, we followed a stepwise protocol and gradually increased the BFR (280→300→330 ml/min; steps 1, 2, and 3) and needle size (16→15 G; step 4). After changing dialyzer surface area (1.8 m2→2.5 m2), the BFR and needle size were similarly increased stepwise (steps 5, 6, 7, and 8). The mean substitution volume was 18.7 ± 2.2 L at step 1 and it significantly increased to 25.1 ± 2.6 L by step 8. A substitution volume of 21 L was achieved by 13.3% of patients in step 1 and by 96.7% after step 8. The substitution volume was higher for the dialyzer with a large surface area and for the larger needle (15 G). Between steps 1 and 8, the Kt/V and β2 microglobulin reduction ratios also improved significantly. High‐volume HDF is feasible through a stepwise increase in the BFR, needle size, and surface area of the dialysis membrane.

Why should we focus on high-volume hemodiafiltration?

“…After changing the dialyzer surface area, the blood flow rate and needle size were increased sequentially in the same manner (steps 5-8). In step 1, 13.3% of patients reached a substitution volume of ≥21 L, while 96.7% of patients achieved a high convection volume after step 8 [65]. In conclusion, it is not difficult to obtain an appropriate level of convection volume for high-volume HDF in the real world by increasing the treatment time, blood flow rate, needle size, dialyzer surface area, and filtration fraction using a stepwise protocol.…”

“…1). Recently, Kim et al [65] reported in a prospective observational study that a sufficiently high convection volume could be obtained by appropriately adjusting the blood flow rate, needle size, and dialyzer surface area. In this prospective observational study, an 8-step stepwise protocol was applied to 30 patients receiving postdilution HDF.…”

Prescription of online hemodiafiltration (ol‐HDF)

“…Several clinical factors are implicated in this endeavor. For practical reasons, these factors are described analytically and then implemented synthetically in a stepwise clinical approach 3,14,15 . Baseline patient's clinical condition represents the guiding factor of HDF prescription and initiation.…”

“…A stepwise approach for implementing online HDF has been successfully achieved in several recent studies. 3,14,15 For practical reasons, prescription and clinical implementation of HDF is discussed according to three clinical conditions: first, in an incident dialysis patient; second, in a prevalent, stable, and regularly dialysis patient; third, in unstable patient or in case of unusual treatment schedule. This is presented in Figure 1.…”

Who is the winner, pre-, post-, or mixed-dilution hemodiafiltration?

“…Hemoconcentration generally limits the filtration fraction to 20%–25% of the blood flow rate in postdilution HDF [ 3 ]. However, modern HDF machines have the option to run TMP-controlled mode during HDF by adapting the substitution flow according to the blood viscosity in the dialyzer [ 4 ]. Filtration fraction up to 30% can be achieved with TMP-controlled mode without excessive hemoconcentration.…”