WO2009083011A4

WO2009083011A4 - A method for dialysis fluid regeneration

Info

Publication number: WO2009083011A4
Application number: PCT/EG2007/000042
Authority: WO
Inventors: Khaled Mohamed Talaat Mohamed Fahim
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-12-30
Filing date: 2007-12-30
Publication date: 2009-10-15
Anticipated expiration: 2010-06-30
Also published as: WO2009083011A3; WO2009083011A2

Abstract

The present invention provides a method to extract a substantial portion of the water content of the spent dialysis fluid by simple osmosis in which water is extracted down a concentration gradient to dilute a concentrated electrolyte solution then by reverse osmosis in which more water is extracted and used to further dilute the concentrate to obtain a regenerated dialysis fluid. A complementary method for urea removal is added to the osmosis treatment. By eliminating the need for a large supply of exogenous water, the present invention allows the construction of portable and wearable dialysis units.

Claims

AMENDED CLAIMS received by the International Bureau on 15 August 2009

Claims What is claimed is:

Claim 1

A method for dialysis fluid regeneration wherein a substantial volume of the spent dialysis fluid water is extracted by simple osmosis (also known as forward osmosis) down a concentration gradient to dilute a concentrated electrolyte solution which is then passed back to the patient's dialysis unit to be used in the patient's dialysis process as regenerated dialysis fluid with or without further treatment. Claim 2 An osmosis unit comprising a simple (forward) osmosis device wherein the spent dialysis fluid water is extracted from the spent dialysis fluid by simple (forward) osmosis down a concentration gradient into a concentrated draw solution across a forward osmosis membrane or filter. Claim 3 The method of claim 1 wherein the spent dialysis fluid consists of the fluid used in the patient's dialysis process and/or the fluid extracted from the patient by ultrafiltration, the said dialysis process may be a conventional short dialysis session, a slow process, a nocturnal dialysis prescription, an ambulatory dialysis procedure or a combination of them. Claim 4

The said simple osmosis unit according to claim 2 comprising a water permeable but highly solute impermeable simple (forward) osmosis membrane [101 ], its housing and its support., the said membrane is made of polyamide thin-film composite or cellulose acetate, however, any membrane or filter with sufficiently high solute rejection and sufficient water flux may be used, the said membrane or filter may have a modified spiral, hollow fiber, tubular, plate and frame configuration or any other technically feasible configuration. Claim 5 The method in association with claim 1 wherein the said spent dialysis fluid is made to circulate along a simple (forward) osmosis membrane or filter [ 101] while on the other side of the said membrane or filter [1 1 1], a small volume of concentrate is made to circulate, water being then drawn from the spent dialysis fluid down the concentration gradient by simple (forward) osmosis into the concentrate side [1 1 1], the extracted water directly diluting the concentrate whose composition becomes more similar to the patient's extracellular fluid while water is extracted out of the spent dialysis solution which therefore looses a substantial portion of its volume leading to the formation of a concentrated spent solution with a substantially smaller volume and higher concentration of the uremic toxins which are mostly kept on the spent dialysis fluid side of the forward osmosis membrane or filter..

Claim 6

The method according to claim 1 wherein the osmolarity of the said concentrated electrolyte solution is substantially higher than the osmolarity of the patient's extracellular fluid, preferably, but not limited to, between 10 to 25 times the normal plasma osmolarity, the said concentrate is composed mainly of sodium chloride, optionally, other solutes like inorganic salts and untrients are added to the said concentrated solution to make the concentrate more physiological and to further increase its total osmolarity and consequently its efficiency in extracting water from the spent dialysis fluid. Claim 7

The method of claim 1 further comprising the optional addition of a reverse osmosis treatment of the spent dialysis fluid, where the said spent dialysis fluid is subjected to a hydraulic pressure while it is circulated alongside a reverse osmosis membrane or filter [ 102] to accomplish a reverse osmosis process and extract a permeate containing a low solute concentration which is then mixed with the fluid obtained on the concentrate side of the forward osmosis membrane [1 1 1 ] to increase its volume and decrease its concentration, alternatively, if the reverse osmosis treatment is placed so that it follows the forward osmosis treatment, the said permeate may be redirected into the spent dialysis fluid side of the forward osmosis membrane [105], in another arrangement both pressure driven osmosis and forward osmosis processes may be accomplished simultaneously across the same membrane or filter by applying both a hydraulic pressure gradient and a concentration gradient working in the same direction across the same membrane or filter. Claim 9 A method wherein the osmolarity of the said obtained solution formed on the concentrate side of the said simple (forward) osmosis membrane or filter [1 1 1] is brought to the desired therapeutic level by controlled dilution with exogenous water before reusing it in the patient' dialysis procedure, the said exogenous water may be introduced into the spent dialysis fluid side of the said simple osmosis membrane [1 1 1] or filter, or directly mixed with the said obtained solution using a feed back controlled pump.

Claim 11

A method for hypertonic low flow prolonged hemodialysis and ultrafiltration treatment wherein the obtained solution formed on the concentrate side of the simple osmosis membrane is not diluted down to the physiological level of the patient's plasma before its reuse and consequently the volume of the water used in diluting the said obtained solution is substantially reduced, in the said hypertonic low flow dialysis, the stimulation of thirst and increased oral water intake by the patient during the therapy correct the resulting hyperosmolarity and the resulting increase in the body fluid volume is corrected by ultrafiltration across the patient's dialyzer, in the said hypertonic low flow hemodialysis, the dialysis fluid flow through the dialyzer is set at a very low rate, preferably but not limited to between 1-3 liters/hour while the dialysis time is set at 7-12 hours/day to allow enough time for physiological correction of the resulting hyperosmolarity. Claim 13

The method of claim 1 where, optionally, a complementary process to remove urea from the said obtained solution on the concentrate side of the forward osmosis membrane [1 1 1] or directly from the patient's dialysis fluid circuit is added, the prescription and measurement of urea clearance are done independently while the prescription and measurement of the overall dialysis dose are done using the clearance of another marker e.g. creatinine.