Dialysis procedures have been optimized over the years. And, these procedures were greatly benefited when blood pumps became the norm (as opposed to letting our hearts pump the blood through the dialyzer), high flux dialyzers (membrane devices that were extremely adept at letting metabolic toxins be removed from blood), etc.
For normal dialysis in a clinic, dialysate flows ranged about 500 ml min. (Data demonstrated that the benefit of higher flows were too low to merit the significant cost factor of more water and saline concentrates.) Blood flow choices were centered around 200 ml min. With these parameters and a standard four hour treatment, it becomes clear that 120 liters of purified water (32 gallons) would be required for each treatment. These needs- plus the space requirement – limit the ability of many a dialysis patient to be treated at home.
Decades ago, a recirculating device, the ReDy, used a cannister that allowed for recycling of the dialysate (which employed flow rates of 250 ml/min). Last year, a newer device was introduced, the Tablo from Outlet Medical. It, too, has an integrated water purification system and an on-demand dialysate production scheme.
To minimize the water needs (right now this device is generally used in acute- and not chronic- settings) studies were effected to see the results if dialysate flow was reduced. A 300 ml/min dialysate flow means the total water needed for a treatment would be cut by 40% (which would mean only 19 gallons of purified water would be needed.) To adjust for a potential reduction in urea removal at the lower flow rate, a high flux dialyzer with large surface area was chosen.
Dr. Sevag Demirjian (Cleveland Clinic) led the study (Drs. Anne M. Huml, Michael W. George, Tracy Coates, J. Matthew Layne, Jonathan J. Taliercio comprised the rest of the team) of the Tablo unit that demonstrated the 300 ml dialysis flow actually bested the urea reduction ratio compared to the dialysate flow of 600 ml/min, with the blood flow rate 400 ml.min (2022 American Society of Nephrology (ASN) Annual Mofeeting in Orlando).
Proof that we don’t always remember what we promise. Today is the 7th of December- “a day that will live in infamy”. Pearl Harbor Day. Let us recall those who perished that day.
For my generation, it was 22 November 1963, when Kennedy was murdered. For my children, it was 9-11-2001.
I did not realize the amount of purified water was needed – 19 gallons still sounds like a lot but compared to 32 gallons, this is a major improvement. But right now just for acute use. One can hope for further improvement but our health system is broken in so many ways, I tend to be a pessimist.
Yes, that is among the reasons why home dialysis is so problematic, Alana.