Testing The Waters – The Argument For Ultra-Purification In Home Hemodialysis
In most U.S. households, people think nothing of drinking a glass of water straight from the tap. After all, we have regulations in place to ensure it's clean enough to be consumed. When it comes to dialysis, however, the same water that’s fine for the dinner table needs extensive treatment before it’s safe for patients. Providing clean, ultra-purified water is an essential part of delivering high-quality dialysis therapy.
Efficiency, Exposure, Morbidity: 3 Reasons for Ultra-purification
Ultrapure water makes sense for dialysis because the therapy is meant to remove toxins from the patient’s blood. Fewer contaminants in the water improves the efficacy of the filter on the hemodialysis machine. Eliminating contaminants through ultrapure water production is therefore beneficial for both patients and machines.
Another reason why dialysis water should be ultrapure is patient safety. Bacteria and endotoxins in dialysis water are contributors to inflammation, and inflammation in dialysis patients can lead to complications such as atherosclerosis (the buildup of plaque on the arterial walls) and anemia, increasing mortality and morbidity. Filtering these harmful agents can help reduce inflammation risk.1
Seemingly innocuous substances like chlorine—often added to municipal water supplies to prevent bacteria growth—can also be dangerous for dialysis patients. While the average person drinks about two liters of water each day, dialysis patients come into contact with more than 200 liters of dialysis fluid each time they are treated. At this level of exposure, chlorine and other chemicals become toxic and can cause harm.2
Purification Standards and Technology
In the United States, tap water has to meet EPA standards. By comparison, ultrapure water for dialysis must go beyond EPA standards and exceed Association for the Advancement of Medical Instrumentation (AAMI) standards. According to AAMI, seasonal variations in source water may result in the need for additional testing when rejection rates fall below 90 percent.3
There are two water purification devices commonly used in the home to provide patients with ultrapure water for dialysis. One is a batch water purification system and the second is a reverse osmosis (RO) system. Depending on the incoming water quality, you may need to install an ultrafilter post-RO to achieve ultrapure water standards.
The purification process starts with prefiltration, which removes the largest particles, such as dirt, silt, and sediment. From there, smaller and smaller particles and contaminants are filtered out as the water moves through the system. Depending on the filtration device and the water quality, additional filters—such as softeners for removing calcium and magnesium—might also be necessary. Carbon filtration is another critical step in pretreatment, primarily used to remove chlorine that ROs or deionization (DI) systems cannot filter out. All of these stages prepare the water for the primary purification step, where the most critical part of the purification process occurs. Depending on the device, this takes place in either an RO or a DI system.
Reverse osmosis happens when, after the previously mentioned processes, water molecules are forced through semi-permeable membranes designed to reject dissolved contaminants that haven’t yet been filtered out. This results in the minimum of up to 99.0 percent of contaminates being filtered out, includes achieving <0.25 Endotoxin Unit and <10 Colony Forming Unit per mL for microbiological testing, leaving the clinician and patient with ultrapure dialysis water.4
Additional Safety Measures
Exposure to dialysis water that hasn’t been purified can result in acute and chronic health problems.5 Acute reactions are more apparent and can be treated at the point of care. However, because they are not as apparent, chronic issues may go untreated for longer periods and multiple exposures may compound the risks of morbidities and mortality. The following measures help ensure the quality of dialysis water, the efficacy of the purification device and the relative safety of the dialysis process:
Microbiological tests: These tests monitor dialysis water for the presence of microorganisms. Machines containing water that doesn’t pass inspection cannot be used for dialysis.
Disinfection: Using chemicals or heat, this procedure disinfects the equipment, that helps prevent microbiological growth and kills bacteria.
Additional Filtration Post-RO: The system may also contain an ultra-filter post-RO and/or an appropriate hemodialysis machine filter for an additional microbiological barrier.
Start-up readings: Before each treatment, a patient or care partner will take samples and readings to clear the entire system for use. Results must fall within specified parameters.
System alarms: If the purification device detects water below acceptable quality standards, it will display an alarm and stop. This helps to:
Prevent substandard water from coming into contact with patients
Signal that membranes may need disinfection or possibly replacement
Signals there may be a system issue requiring technical assistance
Note: System requirements may differ.
The importance of using ultrapure water for dialysis cannot be overstated. Most critical is the safety it provides to patients, preventing toxic substances from entering their bodies and/or sticking to the dialyzer and decreasing the efficacy of the dialysis process.
Ultrapure water also helps dialysis equipment run more efficiently, greatly reducing the contaminants these machines contend with and potentially extending their useful life.
All of these factors contribute to reliable solutions and processes that protect patients and the equipment that delivers their therapy.
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1 Di Iorio, B., Di Micco, L., Bruzzese, D. et al. Ultrapure dialysis water obtained with additional ultrafilter may reduce inflammation in patients on hemodialysis. J Nephrol 30, 795–801 (2017). https://doi.org/10.1007/s40620-017-0422-x; Kasparek T. and Rodriguez, OE. Clin J Am Soc Nephrol. 2015 Jun 5; 10(6): 1061– 1071.
2 Association for the Advancement of Medical Instrumentation. ANSI/AAMI RD62: 2001, Arlington, VA
3 Association for the Advancement of Medical Instrumentation. ANSI/AAMI RD52: 2004, Arlington, VA
4 Vivonic Membrane Data Sheet, 4-8Z20110609
5 Rainer Himmele MD, MSHM, Dixie N. Sawin. Water Purity in Hemodialysis. www.fmcna.com (2019). https://fmcna.com/insights/education/importance-of-fluid-management-during-dialysis/