The heart of hemodialysis is the dialyzer. A very large and competive market, with several manufacturers, serves the needs of the hemodialysis community. A typical specification flyer for hemdialyzers is shown in the picture immediately following (this is not an endorsement for Fresenius products).
The back side of the flyer typically contains dialyzer specifications, as shown here.
The most common dialyzers are hollow fiber devices that contain thousands of hollow fibers housed in a hard plastic, typically polycarbonate, shell. Blood flows through the dialyzer on the interior (lumen) of the fibers. Dialysate flows through the dialyzer on the exterior (shell-side) of the fibers.
Depending upon the manufacturer, the fibers are made from such biocompatible materials as cellulose acetate or polysulfone. The fibers have a microporous structure that permit the diffusion of small molecular weight species from the blood to the dialysate. The diffusion rate can be expressed in terms of the dialyzer clearance of the molecule. The specification sheet above shows the clearances of various molecules for indicated dialyzers under different blood and dialysate flow rate conditions. The large variety of dialyzers permits physicians to appropriately specify a hemodialysis treatment to meet the needs of a patient.
The web addresses for three of the larger vendors in the United States are:
www.fmc-ag.com (Fresenius Medical Care)
www.baxter.com (Baxter Healthcare Corporation)
www.gambro.com (Gambro AB)
Copyright © 2001, John F Patzer II
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