Water treatment in dialysis- more than a Brita filter

And now for something totally exciting—a post on water treatment in dialysis. Dr Daniel Coyne of Washington University gave a great review on this topic at the Brigham Renal Board Review course this week. Here is the basic process of water treatment in HD:

1) water passes through filters for particle removal
2) it then passes over activated carbon, which removes chlorine and chloramines
3) next is a cation exchange resin that serves to “soften” hard water, i.e. exchange Ca and Mg for Na
4) then: reverse osmosis. Pressure is applied to the water and pushes it over a polyamide or cellulose acetate membrane. This process rids the water of organic matter, bacteria, and endotoxins.
5) next step: deionizers, resins that remove cations and anions.
6) water is then irradiated to kill any remaining pathogens.
7) then it is ultrafiltered to remove any remaining bacteria, viruses, and pyrogens.

Water is then continuously circulated to avoid stagnation, and siphoned off to different dialysis stations during treatment.

If you see the following signs in patients at a particular dialysis unit, consider the following water treatment problems:

Anemia- aluminum, chloramines, copper, zinc
Bone disease- aluminum, fluoride
Hemolysis- chloramines, copper, nitrates (3 C's from Nate's prior post)
Hypertension- calcium, sodium
Hypotension- bacteria, endotoxins, nitrates
Metabolic acidose- low pH, sulfates
Encephalopathy- aluminum
Nausea/vomiting- bacteria, endotoxins, low pH, nitrates, sulfates, zinc

Many thanks to Dr Coyne for the shameless pirating of several of his slides.