Home Dialysis in Japan

H. Suzuki

• Editore: S. Karger
• Anno: 2012
• ISBN:
  9783318021103
• Argomento: Medicine
• Categoria: Medical Technology & Supplies

Despite the various advantages of home dialysis compared to in-center hemodialysis, only a fraction of patients in Japan currently opt for peritoneal dialysis or home hemodialysis. However, considerable advances in research and technical improvements have been made lately, advancing the practice of home dialysis therapy in Japan.Japanese research is well-known for its ingenuity and creative energy with regard to the development of new machines and systems for dialysis. New insights regarding peritoneal dialysis and home hemodialysis are presented in the publication at hand: Contributions by leading Japanese experts discuss topics such as educational methods, techniques, tools, novel systems and organization of patients. The book will be of great interest to clinical physicians involved in dialysis care; Moreover, the expertise collected in this volume may contribute to the advancement of home dialysis therapy in a global context.

Peritoneal Dialysis

Suzuki H (ed): Home Dialysis in Japan.
Contrib Nephrol. Basel, Karger, 2012, vol 177, pp 3-12

______________________

A Kinetic Model for Peritoneal Dialysis and Its Application for Complementary Dialysis Therapy

Akihiro C. Yamashita

Department of Human Environmental Sciences, School of Engineering, Shonan Institute of Technology, Tsujido-Nishikaigan, Fujisawa, Kanagawa, Japan

______________________

Abstract

Kinetic models have been used in both hemodialysis (HD) and peritoneal dialysis (PD) therapies. Since many different theoretical models are available, users should choose one of these models along with the purpose of their studies. In general, simple models are useful for clinical investigations as well as clinical research, while rigorous models may be useful for engineers and cannot be utilized without an aid of computers. Several pieces of commercial software that include rigorous models are available for evaluation of peritoneal permeabilities as well as for constructing prescriptions. One of these pieces was clinically evaluated and high correlations with correlation coefficients >0.98 were found between clinical and recalculated values of total Kt/V for urea, total creatinine clearances and the ultrafiltration volume. Although the overall mass transfer-area coefficients (MTAC) of the peritoneal membrane is a diffusive parameter, it may become a useful tool for predicting peritoneal ultrafiltration by defining an index for peritoneal diffusive selectivity, the ratio of MTAC for urea to that for creatinine. It is recommended to use super high-flux dialyzers in PD+HD (complementary) combined therapy because it is the opportunity in a week to remove much middle and/or large molecules greater than ß₂-microglobulin. Kinetic models are especially useful in treatments with relatively complex prescriptions such as PD+HD combined therapy, and may be a key to the further success of these modalities performed at home.

Copyright © 2012 S. Karger AG, Basel

There are several modalities available for treating end-stage renal disease patients. Each patient is required to choose one of these modalities after understanding features of each treatment. Peritoneal dialysis (PD) is used to be known as the first choice of the treatment because it was believed that PD could preserve the residual renal function (RRF) longer than hemodialysis (HD). However, since the choice of so-called super high-flux dialyzers that has high hydraulic permeability and high solute permeability as well as high biocompatibility [1] has become a standard with the use of ultrapure dialysis fluid [2], no significant difference has been reported in terms of preservation of RRF [3, 4]. Studies showed that local inflammation may greatly influence the preservation of RRF [5, 6]. There were so many factors that may directly or indirectly induce the local inflammation in classic HD treatment such as bioincompatibility of the dialysis membrane, water quality of dialysis fluid, etc.; however, most of these problems have already been solved in modern HD treatment. On the contrary, bioincompatibility of the dialysate for PD, including low pH, high glucose concentration and the existence of glucose degradation products, still remains a problem. Then there is the choice of PD as the initiation is becoming controversial for the purpose of preserving RRF.

Under such circumstances the choice of another modality is becoming more and more popular these days in Japan, that is, PD+HD combined therapy, also known as complementary dialysis recommended by an ad-hoc committee of the International Society for Peritoneal Dialysis (ISPD) in 2005. Although this modality is just a combination of PD and HD, the prescription may be even much more complicated than that for PD or for HD. This paper discusses a peritoneal transport model for PD and its application for complementary dialysis for the clinical use of prescription. How the kinetic model should be applied is also discussed for the further success of PD and PD-related modalities that are basically performed at home.

Theoretical

The first peritoneal transport model for PD was proposed by Henderson and Nolph [7], assuming only the diffusion would occur from the body compartment to the dialysate. Under such circumstances, the rate of mass transfer across the peritoneal membrane ṁ [mg/min] may be written in the following form:

(1)

where Ρ is the peritoneal permeability [cm/min] and A is the effective surface area [cm²] of the peritoneal membrane, C_B and C_D are the concentrations in blood and dialysate (mg/ml), respectively. In this model, a uniform structure of the peritoneal membrane as well as no stagnant layer adjacent to it was taken into account. Considering these effects, Ρ should be replaced by the overall mass transfer coefficient K_o and equation 1 becomes:

(2)

where the product of K_o and A is called the overall mass transfer-area coefficient (MTAC) [ml/min]. Babb et al. [8] and later Garred et al. [9] modified equation 2 by introducing convective mass transfer for small solutes from the blood to dialysate as follows:

(3)

where Q_u is the ultrafiltration rate across the peritoneum [ml/min]. Another modification was made by Yamashita and Hamada [10], co...