IS DRINKING WATER THAT MEETS DRINKING WATER STANDARDS SUITABLE FOR KIDNEY DIALYSIS MACHINES TO REMOVE WASTES FROM A PERSON WHOSE KIDNEYS ARE FAILING?

Drinking water is made safe in this day and age due to diligent use of technology, data on water sources and strict regulations. This may give many the impression that your drinking water in the purest form you can possibly get, perhaps even pure enough to use for kidney dialysis machines or home dialysis. But this could not be further from the truth.

Kidney dialysis water must be ultra-pure in comparison to drinking water. That is why medical facilities are required to have their own water treatment systems and a technical support staff to monitor and troubleshoot such equipment. The level of heavy metals, unwanted electrolytes, bacteria or their toxins, and especially chloramines, have the potential to cross a semipermeable membrane and enter a patient's blood during dialysis. The result can be anemia, bone disease, hemolysis (rupture of red blood cells), low blood pressure, and in severe cases, death. The water used in a dialysis machine may come from a public drinking water system, but it receives further treatment on site as a primary component of the dialysate. The dialysate water is regulated as a drug under the Food and Drug Administration in this situation.

The main culprit of what makes drinking water unfit for use in a dialysis situation is the use of chloramines. Chloramines, derived from chlorine and ammonium, are added to water as disinfectants and may contaminate dialysis fluid and enter the blood of dialysis patients causing haemolytic anaemia. Depending on the number of chlorine atoms that bind to nitrogen in exchange for hydrogen, monochloramines, dichloramines or trichloramines are formed. The type of chloramine formed depends on the molar proportion of chlorine and nitrogen and the pH of the solution. If the pH is greater than 6 and if the molar proportion of chlorine is less than 5, monochloramines preferentially are formed. Since these conditions are present in the majority of city water supplies, monochloramines are most frequently encountered, and these have the least oxidative potential.

The chloramines react with the body fluids and liberate hypochloric acid, hypochlorite, and free oxygen radicals. They are all capable of modifying cellular proteins and lipids and of causing protein denaturation and haemolysis. The most obvious clinical manifestation in dialysed patients is haemolytic anemia . Oxidation of bivalent iron in haemoglobin to trivalent iron leads to the formation of methaemoglobin which is unable to transport either O₂ or CO₂. Methaemoglobin leads to the appearance of Heinz bodies, which are seen when chloramine concentrations exceed 0.5 mg/l. They increase in number and in proportion to the chloramine concentrations . This, and in addition oxidation of erythrocyte membrane phospholipids, leads to erythrocyte membrane fragility and reduced half-life of erythrocytes.

It is difficult to state at which chloramine concentration in the dialysis fluid clinical signs are seen in patients. Presumably the effect is gradual and increases with the concentration. At low concentrations, the effects are countered by the action of natural antioxidants which are generally diminished in uraemic patients. This interaction is suggested by the fact that plasma vitamin E concentrations are diminished in haemodialysed patients with exposure to chloramines compared to patients with no exposure . When the dialysate water is contaminated with chloramine at a concentration of 0.1–0.2 mg/l, erythrocyte half-life of dialysed patients is diminished and this translates clinically into a greater requirement of rhEpo.

The addition of chloramines to drinking water is one of the most commonly utilized procedures used to disinfect city water, and what largely makes it unsafe for dialysis. Not all water supplies used for haemodialysis contain significant chloramine concentrations. When chloramine is present in water, however, the best method to eliminate it is to use activated charcoal filters, preferably in series, and to monitor chloramine concentrations between the filters, where they should be less than 0.1 mg/l. Chloramine concentrations above 0.2–0.25 mg/l in the dialysis water may cause real `epidemics' of anaemia in dialysis units.