Views:0 Author:Site Editor Publish Time: 2021-01-25 Origin:Site
The dialyzer is an important part when patients doing their dialysis.
The choice of the dialyzer is a balance between dialyzer performance and cost. One size does not fit all. We will talk about the way to choose the dialyzer in 4 parts:
Design and clearance
Design and condensation
Membrane manufacturing and processing
Dialyzer selection for AKI and critical care
Dialyzers can be divided into head, body, and inlet, blood outlet, and dialysate.
Other clinically important components of the dialyzer are the fibrous capillaries and baffles that determine the flow path of blood and dialytic fluid. Blood enters and leaves the dialyzer through the dialyzer manifold and rapidly dissipates into a series of narrow diameter parallel capillary fibers. Instead, dialysate enters and leaves through ports in the dialyzer body. In addition to countercurrent blood flow, increased relative flow, concentration gradient resistance to solute channels, hydrophobicity, and charge, dialyzer design affects clearance rates.
Although adequate anticoagulation is the key to keeping the loop open, the design of the dialyzer may have an impact on condensation and clearance. The condensation reduction design focuses on reducing protein deposition on the surface of the capillary fiber of the dialyzer. Some of these include the undulating structure of the capillary fibers and produce inside the dialyzer to prevent the flow of protein deposits.
Membrane materials commonly used in the dialyzer include naturally substituted cellulose (cellulose acetate, diacetate, triacetate, since the addition of these side groups reduces biocompatibility) and synthetic membranes, including polysulfone, polyacrylonitrile, polycarbonate, polyamide, and polymethyl methacrylate. The negatively charged AN69 dialyzer increases bradykinin production, which may be exacerbated by the prescription of an angiotensin-converting enzyme inhibitor (ACE).
The dialyzer is described in terms of flux, mass transfer coefficient, hydraulic permeability, and biological incompatibility
The original dialyzer "flux" was defined by the ultrafiltration coefficient (Kuf), a high-throughput dialyzer Kuf >15 mL/h/mmHg. However, the dialysis flux was subsequently redefined in terms of β2 microglobulin clearance rather than hydraulic permeability, after improved toxicity was reported in the medium molecular weight uremia.
The biological incompatibility of the dialyzer membrane can be defined as the sum of the specific interactions between the blood and the dialyzer membrane or the absence of any interference in the blood components.
Biological incompatibility also includes the effects of disinfectants, irrigation compounds, and chemicals leach from extracorporeal circulation. Apart from the poor quality of the unmodified copper film, there does not seem to be any significant clinical difference in biocompatibility with current digitizers, so biocompatibility is no longer a controversial issue.
Mass transfer area coefficient
The mass transfer area coefficient (KoA) refers to the permeability between the blood and dialytic pathways through the diffusion mass transfer barrier. Ko is the mass transfer coefficient and A is the surface area of the dialysis membrane. The KoA of a dialysis membrane depends on pore density, pore size distribution, and resistance to solute passage. Higher values indicate more efficient dialyzers. The Kt/V measured in vitro during dialysis is generally much lower than the Kt/V obtained in clinical practice.
l Hydraulic permeability
The hydraulic permeability of a dialyzer or its ultrafiltration coefficient (Kuf) is a measure of the water flow rate and flow rate across the dialyzer membrane. Kuf is a limiting factor for ultrafiltration flow and volume, so it is very important when choosing a dialyzer for convection therapy. Ultrafiltration flux (Quf) is not linearly related to Kuf but follows a parabolic function. Thus, one vertex defines the optimal Quf for the dialyzer, rather than the maximum Quf, which is usually associated with blood concentration, increased coagulation, and decreased effective surface area of the dialyzer.
Membrane composition, dialyzer surface area, and membrane flux are three main factors that we considered when selecting a dialyzer for AKI patients. Compared with synthetic membranes, unmodified cellulose membranes are associated with a greater complement and inflammatory cell activation and have been reported to delay renal recovery. In a meta-analysis, unmodified cellulose dialyzers reduced survival and renal recovery, but neither modified cellulose nor synthetic membrane dialyzers did.
To prevent dialysis balance syndrome, a dialyzer with a smaller surface area is preferred, while a larger dialyzer is preferred to increase clearance when treating intoxication or drug toxicity. Dialyzer flux is also an important determinant of clearance, especially for medium molecules. High retention membranes and a new generation of intermediate retention membranes may play a role in the treatment of mild nephropathy as well as appropriate chemotherapy. However, the actual reported clinical outcomes for the use of these high-cutoff membranes remain inconclusive.