Fresenius Medical Care Completes Acquisition of NxStage Medical
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Rainer Himmele MD, MSHM, Vice President, Medical Information and Education, Fresenius Medical Care North America & Dixie N. Sawin, Sr. Director, Medical Information and Communications, Fresenius Medical Care North America
Water for dialysis requires a higher level of purity than drinking water for a number of reasons5,6:
Exposure to improperly treated water dialysate can result in both acute and chronic problems (Table 1). Although acute reactions are usually clinically evident and can be treated as they occur, chronic issues resulting from inadequately purified water can be missed and go untreated for long periods of time. This may lead to compounding of symptoms following each exposure and increased risks of morbidity and mortality.
Adequate water purification is available for patients dialyzing at home. There are currently two options to purify water at home:
Home water purification is an active field of research for even more efficient and innovative options7,8 including sorbent-based technologies with continuous regeneration of small volumes of municipal water in closed-loop systems.9
Even though dialysis uses large amounts of ultrapure water to remove accumulated metabolites and waste products, this water is not perfused into the patient. On the contrary, hemodialysis uses negative pressure to ultrafiltrate water across the dialyzer from the body to compensate for the impaired water removal by the kidneys. Ultrafiltration (UF) aims to reduce the patient’s fluid overload (FO) and return to the prescribed dry weight (DW) or slightly below.9 In addition to the absolute amount of fluid removed, the rate of removal (ultrafiltration rate, UFR) is important. As fluid is removed from the blood compartment, vascular or plasma refill occurs by shifting fluid from the tissues and organs into the vasculature to maintain blood volume. A slow UFR can prevent target weight attainment, which may lead to FO11,12. A fast UFR may cause a severe reduction in blood volume, resulting in intradialytic events.
To prevent the latter, the Centers for Medicare & Medicaid Services proposed a maximum UFR of 13 mL/hr. Although appropriate for many, the UFR should be optimized for each patient through close monitoring during dialysis. Blood volume monitoring devices provide information on how the patient is tolerating the dialysis session by showing the relationship between the UFR and the vascular/plasma refill rate. In some instances, the excess water may not be adequately removed during one session, and longer or additional dialysis sessions are needed to ensure that the patient reaches the dry weight.
Tap water contains contaminants that may not be harmful through ingestion but cause harm to the hemodialysis patient if not inactivated or removed. Thus, tap water must be appropriately and adequately purified prior to its use for dialysate preparation. This can be achieved in the dialysis center or the patient’s home. While dialysate is needed for the removal toxins and waste products it does not enter the body. Adequate UF is pivotal to the patient’s overall fluid management. Close attention must be paid to the appropriate amount of fluid removal as well as to balancing the UF rate with the patient’s vascular refill to ensure reaching the dry weight while preventing intradialytic symptoms.