A solute is the solid that is dissolved in a liquid. The solvent is the liquid in which something is dissolved in. Water is the most abundant solvent there is. It will dissolve almost any solid particle to some extent, in varying times. We get most of our water from rain. As rain water passes through the air toward our reservoirs, it picks up impurities like sulfur dioxide and carbon dioxide gases. Since water makes up about 90% of dialysate, its proper treatment used for hemodialysis prevents any complications for the patients. Providing safe water, which is one of the best water guide tips for dialysis technicians to learn, also prevents potential damage to our equipment.
Established in 1974, the “safe drinking water act” is rooted on an average daily intake of 2 liters, or approximately 14 liters of water per week. 14 liters of water, along with its associated contaminants, pass through people with healthy kidneys each week. Meanwhile, in the same week, patients undergoing 3-4 hour dialysis treatments are exposed to about 360 liters of water and all the contaminants it could possibly hold. A healthy person can effectively handle some of the contaminants in drinking water. Since healthy kidneys remove most of these contaminants, people with end-stage renal disease do not have that protection. To be safe, water used for dialysis should pass through a water treatment system. This system, comprising a series of devices, takes out specific contaminants.
Water Guide Tips for Dialysis Technicians #1: Know your local water source and the types of contaminants in your water source.
Thoroughly examining the local water source, the water, and its possible contaminants beforehand will help determine the needed pretreatment components. What contaminants will you need to remove from the water? Bear in mind that the recommended standards set by the Association for the Advancement of Medical Instrumentation (AAMI) for water used in Hemodialysis (RD52) are more detailed than drinking water standards. Only limited traces of elements, metals, salts, bacteria and fragments of dead bacteria are allowed, according to the guidelines. Generally, organic/inorganic chemical contaminants and microbial limits are periodically tested, usually once a month. The chart below lists the possible chemical contaminants present in water, their maximum allowable limits, and the symptoms patients may exhibit if contaminant levels are high.
Water Guide Tips for Dialysis Technicians #2: Pretreatment, water purification, and distribution are the three processes that make up the water treatment system for hemodialysis.
Each process of water treatment requires monitors in place to guarantee the safety for dialysis patients exposed to high volumes of water. These monitors provide alarms that alert staff members when contaminants in the water are too high for dialysis use. Periodic monitoring of water quality and temperature is very important if you want to keep your patients free from harm. Sampling of water to be tested are usually prescribed in intervals depending on the facility you work in. For instance, when testing for total chlorine, water samples are collected prior to first patient treatment and then every 4 hours. On the other hand, total water hardness, which could cause scaling of the membranes if too high, is collected at the end of each treatment day. Microbial cultures are tested at least once a month, inorganic chemical contaminants are tested once a year.
Water Guide Tips for Dialysis Technicians #3: Know the typical pretreatment components.
Water Guide Tips for Dialysis Technicians #4: Master your purification terminology.
Osmosis is a phenomenon that occurs naturally. It is responsible for the movement of fluid from an area of low solute concentration to an area of high solute concentration. Reverse osmosis is the exact opposite. RO causes fluid to move from an area of high solute concentration to an area of low solute concentration. Since this movement of particles is unnatural, we need to add a pump to achieve RO. This pump provides the energy needed to force the water across the membrane. As a result, we end up with one side of the membrane having most of the contaminants. The permeate RO water, is the product water that made it through the membrane.
• Osmotic pressure – the pressure that builds when two liquids having different solute concentrations, are separated by a semi-permeable membrane.
• Percent Rejection – measures how effective the RO membranes are. The ability of the membranes to get rid of contaminants.
• Product TDS (Total Dissolved Solid) – describes all ions, organic and inorganic matter remaining in product water after passing through RO membranes.
• Feed TDS (Total Dissolved Solids) – describes all ions, organic and inorganic matter in the feed water entering the RO membranes.
• Percent rejection – measures the percent of total dissolved solids (TDS) in the product water compared to the feed water.
• Deionization (DI) – the collection of contaminants and which is then exchanged for H20 – water molecules. Done in tanks, DI does not remove microbial contaminants but rather backup water purification.
• Ultrafilter – lesser known as the pyrogen or endotoxin filter, ultrafilters are filters placed at the end of the water system before the first point of use. These filters are capable of removing all viruses, bacteria, and most endotoxins.
Water Guide Tips for Dialysis Technicians #5: Keep the distribution loop clean.
The distribution loop sends purified water to all its points of use. This loop functions by transporting water from the water treatment room to each point of use in the dialysis facility and back to the RO unit. Since a slime made by microorganisms, called Biofilm, can build up in the distribution loop, make sure there’s a continuous adequate flow of water through it. However, the design of the distribution loop will ultimately dictate the prevention of biofilm buildup and the control of microbial formation. Actions are required when samples go beyond the allowable or action levels. Samples for cultures and endotoxin should also be drawn when trends indicate increase in contamination.