Dialysis is a medical procedure that takes over the function of failing kidneys. This process removes waste products and excess fluid from the blood, which the kidneys can no longer adequately filter. The quality and purity of the water used in dialysis are extremely important, directly influencing patient safety and treatment effectiveness. This article explores water’s role in dialysis, from its necessity to its purification and application in different methods.
What is Dialysis and Why it is Necessary
Dialysis replaces the filtering capabilities of the kidneys when they no longer function properly due to conditions like end-stage renal disease or acute kidney injury. Healthy kidneys filter approximately 200 quarts of blood daily, removing waste products and excess fluid to produce urine. They also maintain mineral levels, regulate blood pressure, and produce red blood cells.
When kidney function declines significantly, harmful waste products like urea and creatinine, along with excess fluid, build up in the body. This accumulation can lead to symptoms like fatigue, shortness of breath, and swelling. If left unaddressed, these dangerous levels can severely impact health and be fatal. Dialysis filters these substances and fluids from the blood, preventing severe complications and allowing individuals with kidney failure to manage their condition.
The Essential Role of Water Quality
The purity and specific composition of the water used in dialysis are extremely important for patient safety and treatment effectiveness. Patients undergoing hemodialysis are exposed to very large volumes of water, as it makes up about 95% of the dialysate solution. Unlike drinking water, dialysis water directly contacts a patient’s blood across a semipermeable membrane. This direct exposure means even trace impurities can diffuse into the bloodstream, posing serious health risks.
Tap water is unsuitable for dialysis without extensive treatment because it contains various impurities such as minerals, chemicals, bacteria, and endotoxins. Contaminants like aluminum or chloramine can cause toxicity, leading to complications such as seizures or hypotension. Bacterial or endotoxin contamination can cause fever, shock, and contribute to chronic inflammation, worsening cardiovascular disease. Rigorous water purification processes are implemented to remove these substances, ensuring treatment safety and effectiveness.
Preparing Water for Dialysis
Preparing water for dialysis involves a multi-stage purification process to meet stringent quality standards, such as those set by the Association for the Advancement of Medical Instrumentation (AAMI) and the International Standards Organization (ISO). This comprehensive treatment system begins with pre-treatment, preparing incoming tap water. During this initial phase, raw water is mixed to achieve a consistent temperature, usually around 77°F (25°C), optimizing the efficiency of subsequent purification steps.
Following temperature regulation, the water undergoes preliminary filtration to remove larger suspended particles. Water softening then occurs, where calcium and magnesium ions, which contribute to water hardness and can damage reverse osmosis membranes, are exchanged for sodium ions. Activated carbon filters adsorb chlorine, chloramines, and other dissolved organic contaminants, protecting the primary purification membrane. Hydrochloric acid may also be injected to adjust pH if water is excessively alkaline, which can interfere with carbon beds and RO membranes.
Primary treatment, primarily reverse osmosis (RO), forms the core of the purification system. In this process, hydrostatic pressure forces water through a semi-permeable membrane, effectively removing over 90% of contaminants, including ionic substances, bacteria, endotoxins, and viruses, while sending impurities to the drain. While RO is highly effective, some systems include post-treatment for further purification. Deionization (DI) can be used as a backup or additional purification measure, removing ionic contaminants by exchanging cations for hydrogen ions and anions for hydroxide ions. However, DI systems can promote bacterial growth, requiring subsequent bacterial control filters like ultrafilters or UV sterilization units to maintain purity.
Water in Different Dialysis Methods
Water is used distinctly in the two main types of dialysis: hemodialysis and peritoneal dialysis. In hemodialysis, purified water combines with concentrates to create a specialized solution called dialysate. This dialysate, approximately 95% water, then flows through an artificial kidney, known as a dialyzer. Inside the dialyzer, the patient’s blood flows on one side of a semipermeable membrane, while the dialysate flows on the other. This allows waste products and excess fluid to diffuse from the blood into the dialysate, requiring a substantial volume of purified water; a single four-hour treatment can use up to 150 liters.
Peritoneal dialysis uses a different approach, relying on a water-based solution where a sterile dialysate solution, composed of water, salts, and other additives, is introduced into the patient’s peritoneal cavity through a catheter. The peritoneum, the lining of the abdomen, acts as a natural filter, allowing waste products and excess fluid to pass from blood vessels into the dialysate. The solution remains in the peritoneal cavity for a prescribed “dwell time,” absorbing impurities. After the dwell time, the used solution, laden with waste, is drained and replaced with fresh dialysate. While purified water is not directly infused into the bloodstream as in hemodialysis, it forms the basis of the solution that facilitates internal filtering.