For a treatment of a patient suffering from renal failure, there have been proposed various blood purifying methods in which blood is taken out from the body of the patient to be purified and is then returned into the body. To purify the blood, hemodialyzers which accommodate a translucent membrane (hereinafter also referred to as “dialysis membrane”) such as a hollow yarn cellulose membrane, polyacrylonitrile membrane, or polysulfone membrane in a housing have been used. The purification method to be employed differs according to a state of a disease and conditions of a patient.
For example, inacaseofhemodialysis (HD), blood and a dialysis fluid are brought into contact with each other through the dialysis membrane of the hemodialyzer to remove urea, uric acid, and the like accumulated in the blood of a patient by the movement of substances caused by diffusion. In a case of hemofiltration (HF), water, body wastes, and toxins in the blood are removed by filtration through holes provided in the dialysis membrane.
In the above-mentioned treatment method, HD (hemodialysis) has an excellent property of removing small-molecular wastes and solutes, but has a disadvantage of lacking performance of the removal of medium molecules and large molecules. Meanwhile, HF (hemofiltration) has an excellent property of removing medium (or large) molecular wastes, but has disadvantages in that a performance of removing small molecules is low and that proteins in blood are apt to leak. Moreover, both the HD and HF are greatly affected by the characteristics of the hollow yarn membrane in the hemodialyzer.
As a treatment method having the advantages of both the HD and HF, that is, excellent removal characteristics of the HD and HF, there has been proposed a hemodiafiltration (HDF) method, and efficient removal of a solute has been expected. However, in a conventional bottle-type HDF system, only about 5 to 10 L of fluid substitution can be performed, and hence, a remarkable effect could not be exhibited. Therefore, large-quantity fluid substitution HDF by on-line HDF or Push & Pull HDF has come to attract attention, and the former on-line HDF capable of constructing a system relatively easily has widely come into use.
As prior art documents, JP 06-134031 A, JP 07-313589 A, and the like shown below have been disclosed.
However, in order to perform HDF (including on-line HDF and Push & Pull HDF), a dedicated blood circuit for injecting a supplemental fluid (i.e., substitution fluid) has been required, and furthermore, in bottle-type HDF, it has been required to prepare a dedicated supplemental fluid.
In contrast, the present invention provides a hemodialysis apparatus which does not require a dedicated blood circuit or the preparation of a dedicated supplemental fluid and the like, and in which the HD treatment can be shifted to the HDF treatment easily, or the HDF treatment can be shifted to the HD treatment easily.