1. Dialysis dose is expressed by the single-pool Kt/V for urea (spKt/V)
2. Measurement of the dialysis dose is done at least once a month
3. Recommended delivered dialysis dose by spKt/V is the following:
(a) The minimal adequate dose is 1.2
(b) The target dose is 1.4 or higher
4. The recommended minimal dialysis time is 4 h or longer
8.4.1 Removal of β2M (Middle Molecules)
Since β2M has a larger molecular weight of 11.8 kD, permeability of the dialyzer is low , and in long-term dialysis cases, it accumulates and causes dialysis-related amyloidosis (Gejyo et al. 1985).
The JSDT guideline recommends β2M removal as shown in Table 8.2 (Watanabe et al. 2015). In the JSDT survey, the predialysis serum β2M concentration at the maximum interval (Monday and Tuesday) was significantly higher than 25–30 mg/L, above which the death rate was significantly high. Therefore, a predialysis maximum serum β2M concentration is required to achieve <30 mg/L.
JSDT guideline for β2M
1. Predialysis serum β2M level at the maximum intervals is a factor related to prognosis
2. The dialysis conditions are recommended to achieve the maximum predialysis serum β2M concentration of <30 mg/L
3. The dialysis conditions are preferred to achieve the maximum predialysis serum β2M concentration of 25 mg/L
4. Decreasing the concentrations of substances with greater than β2M can improve the prognosis of patients
The serum β2M concentration increases with inflammation and initial treatment to suppress the inflammatory state, and for further biological purification of the dialysis, fluid is important. As mentioned earlier, the factor that mostly affects the clearance of high-molecular-weight solutes such as β2M is the performance of the dialyzer, and the selection of a super high-flux membrane dialyzer and convective therapies is necessary. Additionally, since β2M has a low migration speed from the tissue into the blood, it is difficult to remove a sufficient amount if the dialysis time is short; therefore, dialysis should be performed for the maximum possible time.
Appendix 1: Kinetics Modeling of Dialysis: Reference for JSDT Guideline (Watanabe et al. 2015)
Indices of dialysis dose, solute removal , and the sampling methods of blood are mentioned below.
Kt/Vurea is an index of the degree to which urea is removed in one dialysis session (i.e., dialysis dose). Although various definitive equations of Kt/Vurea have been proposed as described below, no absolute equation has been selected. It is important to use one of these appropriate equations consistently for each patient.
Gotch and Sargent’s Equation (Kt/Vurea) (Gotch and Sargent 1985)
This model assumes the one-compartment model with no effect of fluid removal and urea production.
where BUNpre and BUNpost are the predialysis and post-dialysis BUN concentrations, respectively.
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