The Economics Behind Dialyzers

Not only that, the physicians are choosing synthetic dialyzers that have undergone a sterilization process that lessens risks to patients, she continued. “At Baxter, our dialyzers—including our latest Xenium synthetic dialyzer and Exeltra, a modified cellulose dialyzer—are sterilized using a unique oxygen-free sterilization process, which helps prevent the oxidation of free radicals. In some parts of the world, oxygen-free gamma sterilization has already been established as the standard. The United States continued to use ethylene oxide (ETO), but physicians are beginning to widely recognize the advantages of gamma irradiation,” she said.

The improved biocompatibility trend is also driving interest in ultra-pure dialysate and cleaner water sources, Prichard added. “What is interesting in the market is that we feel we may be approaching a point in the development of dialyzers where we are reaching the theoretical maximum clearance performance, yet patient outcomes have not substantially improved. Mortality rates remain in excess of 15 percent per year in many countries, including the United States. Therefore, the nephrology community is looking at other ways to improve patient outcomes. For example, daily and/or longer hemodialysis sessions are being evaluated in current NIH trials. Dialyzers are only one part of the story, and it’s becoming clear that the next chapter will be increasing time on therapy, ideally in the home where it can be done safely, frequently and conveniently,” she observed.

Basic Functions— A Primer on Dialyzers

The dialyzer functions like an artificial kidney, removing waste products and excess fluid from the blood through a semi-permeable membrane. Rasin and Bosch explained that early-generation dialyzer membranes were made from cellulose, a naturally occurring organic compound found in the cell walls of many plants. “These membranes were less biocompatible and sometimes caused adverse patient reactions,” Rasin and Bosch said. “The recent generations of synthetic dialyzer membranes are man-made and represent a wide range of chemical structures. These synthetic membranes are considered more biocompatible and do not cause adverse patient reactions to the same extent.”

In addition to filtering out toxins and extra fluid from the bloodstream, the dialyzer also maintains the homeostasis of the circulatory system. “Think of it as a very sophisticated toxin filter for patients who have lost much of the use of their kidneys,” said Prichard. “The filtering membrane itself is composed of tens of thousands of individual fibers integrated into fiber bundles. When the blood passes through these straw-like fibers, toxins and excess fluid are filtered out through their walls into a chamber that holds the dialysate. The dialysate is formulated to draw out the toxins and excess fluid, while maintaining homeostasis in the blood,” she said.

In the past, the filtering membrane of the dialyzer was composed of cellulose materials. The high-flux synthetic dialyzers of today offer improved biocompatibility for patients, as well as a much more even flow distribution in the dialysate compartment. They perform with much greater efficiency. As discussed before, we are also seeing a shift towards more biocompatible sterilization methods such as oxygen-free gamma irradiation. And, of course, improved middle-molecule clearance is an area of greater focus in the literature and clinical practice.”