HEMODIALYSIS SYSTEM HAVING A FLOW PATH WITH A CONTROLLED COMPLIANT VOLUME

• US 20130199998A1
• Filed: 08/02/2012
• Published: 08/08/2013
• Est. Priority Date: 08/02/2011
• Status: Active Grant

• Current Assignee: Mozarc Medical US LLC
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Kelly, Thomas D., Lyu, SuPing, Pudil, Bryant J., Meyer, Thomas E.
• Granted Patent: US 10,695,481 B2
• Time in Patent Office: Days
• US Class Current: 210/646
• CPC Class Codes: A61M 1/1696 with dialysate regeneration
• CPC Class Codes: A61M 1/3482 by filtrating the filtrate using another cross-flow filter, e.g. a membrane filter
• CPC Class Codes: A61M 2202/0021 removed from and reintroduced into the body, e.g. after treatment
• CPC Class Codes: A61M 2202/0413 Blood

Abstract

Systems and methods for the performance of kidney replacement therapy having or using a dialyzer, control components, sorbent cartridge and fluid reservoirs configured to be of a weight and size suitable to be worn or carried by an individual requiring treatment are disclosed. The system for performing kidney replacement therapy has a controlled compliance dialysis circuit, where a control pump controls the bi-directional movement of fluid across a dialysis membrane. The dialysis circuit and an extracorporeal circuit for circulating blood are in fluid communication through the dialysis membrane. The flux of fluid moving between the extracorporeal circuit and the dialysis circuit is modified by the rate at which the control pump is operating such that a rate of ultrafiltration and convective clearance can be controlled. The system provides for the monitoring of an inlet and outlet conductivity of the sorbent cartridge to provide a facility to quantify or monitor the removal of urea by the sorbent cartridge.

Claims

1. A system for performing kidney replacement treatment or for performing kidney replacement treatment with enhanced convective clearance and reduced blood clotting risk, comprising:

a hemodialysis system having a controlled compliance dialysis circuit, a dialyzer with a dialysis membrane, a blood inlet end for receiving blood, a blood outlet end for allowing blood out of the dialyzer, a dialysate inlet end for receiving dialysate and a dialysate outlet end for allowing dialysate out of the dialyzer, wherein the blood and the dialysate contact different sides of the dialysis membrane;

an extracorporeal circuit having a conduit for receiving blood from a subject and a conduit for returning blood to the subject, and a blood pump for conveying blood from the subject, to the dialyzer and back to the subject;

a dialysis circuit having a sorbent cartridge for removing at least one impurity or waste species from the dialysate, one or more conduits for conveying dialysate between the sorbent cartridge and the dialyzer, and a dialysate pump for conveying dialysate from the sorbent cartridge, to the dialyzer and back to the sorbent cartridge, the sorbent cartridge having a dialysate inlet end and a dialysate outlet end;

a control pump for moving fluid bi-directionally between the dialysis circuit and the extracorporeal circuit, and wherein a flux of fluid moving between the extracorporeal circuit and the dialysis circuit is changed by the rate at which the control pump is operating;

a first control reservoir for storing fluid removed from the dialysis circuit by the control pump or for storing fluid that can be added to the dialysis circuit by the control pump; and

one or more controllers for controlling a rate of the control pump, a rate of the blood pump, and a rate of the dialysate pump.

2. The system of claim 1, with the proviso that the blood pump and the dialysate pump are not pulsatile pumps.

3. The system of claim 1, wherein a volume of fluid added to the dialysis circuit by the control pump results in substantially the same volume of fluid transferred to the body of the subject and wherein a net volume of fluid removed from the dialysis circuit by the control pump results in substantially the same volume of fluid transferred form the body of the subject to the system for performing kidney replacement treatment.

4. The system of claim 1, wherein the volume of the dialysate within the dialysis circuit is a substantially inflexible volume.

5. The system of claim 1, wherein a void volume space for accommodating the dialysate in the sorbent cartridge, the dialyzer, and conduits comprising the dialysis circuit has a substantially inflexible volume.

6. The system of claim 1, further comprising a relative blood volume monitor to determine the relative blood volume hydration status (RBVHS) of the blood in the extracorporeal circuit, the relative blood volume monitor configured to send information to the one or more controllers, wherein the relative blood volume monitor determines the level of one or more solutes in the blood at a first time (C₀) and determines the level of the one or more solutes in the blood at a second time later than the first time (C_t), and the relative blood volume hydration status is calculated by the formula RBVHS=C₀/C_t, wherein optionally the relative blood volume monitor is configured to determine the fluid volume of the blood at a position prior to the blood entering the dialyzer.

7. The system of claim 1, wherein the one or more controllers control operation of the control pump to intermittently switch between an efflux direction to move fluid across the dialysis membrane from the extracorporeal circuit to the dialysis circuit and a second influx direction to move fluid across the dialysis membrane from the dialysis circuit to the extracorporeal circuit.

8. The system of claim 1, wherein the one or more controllers control the blood pump and the dialysate pump such that a ratio of the flow rate of blood to dialysate through the dialyzer is from about 1:

1.5 to about 3;

1.

9. The system of claim 1, further comprising a second control reservoir for storing fluid that can be added to the dialysis circuit by the control pump when the first control reservoir is used only for storing fluid from the dialysis circuit by the control pump.

10. The system of claim 1, further comprising a first conductivity meter for measuring the conductivity of the dialysate at a position between the dialyzer and the dialysate inlet end of the sorbent cartridge;

a second conductivity meter for measuring the conductivity of the dialysate at a position between the dialysate outlet end of the sorbent cartridge and the dialyzer; and

one or more controllers for comparing the conductivity measured by the first conductivity meter and the second conductivity meter and calculating the amount of urea absorbed by the sorbent cartridge.

11. The system of claim 10, wherein the one or more controllers calculates the amount of urea absorbed by the sorbent cartridge by:

calculating a starting conductivity by subtracting a conductivity attributed to a substantially constant concentration of Ca²⁺, Mg²⁺, and K⁺ ions in the dialysate from a conductivity measured by the first conductivity meter;

calculating a corrected outlet conductivity by subtracting an increase in conductivity attributed to an exchange Ca²⁺, Mg²⁺, and K⁺ ions for Na⁺ ions by the sorbent cartridge from a conductivity measured by the second conductivity meter; and

calculating a conductivity increase from the exchange of NH₄⁺ for Na⁺ ions by the sorbent cartridge by subtracting the starting conductivity from the corrected outlet conductivity.

12. The system of claim 1, further comprising a second reservoir and a second reservoir pump wherein the second reservoir holds a fluid that can be added to the dialysis circuit by operation of the second reservoir pump, wherein addition of the fluid by the second reservoir pump causes the movement of fluid from the dialysis circuit to the extracorporeal circuit, wherein the one or more controllers control a rate of the control pump, a rate of the second reservoir pump, a rate of the blood pump, and a rate of the dialysate pump.

13. A method for performing enhanced convective clearance with reduced risk of blood clotting, comprising:

attaching the vasculature of a subject to a system for kidney replacement therapy having an extracorporeal circuit having a first end that draws blood from the subject and a second end that returns blood to the subject, wherein the extracorporeal circuit is in fluid communication with a controlled compliance dialysis circuit through a dialysis membrane housed in a dialyzer;

conveying blood from the subject through the extracorporeal circuit and the dialyzer and returning the blood to the subject;

conveying a dialysate through the dialysis circuit such that the dialysate moves from a sorbent cartridge, to the dialyzer and back to the sorbent cartridge, where at least one waste species diffuses from the blood to the dialysate through the dialysis membrane and the sorbent cartridge substantially removes at least one impurity or waste species from the dialysate; and

operating a control pump that adds fluid from a control reservoir to the dialysis circuit in an influx direction via a conduit or removes fluid from the dialysis circuit to the control reservoir in an efflux direction via the conduit, and intermittently switching the control pump between the efflux direction to move fluid across the dialysis membrane from the extracorporeal circuit to the dialysis circuit and the influx direction to move fluid across the dialysis membrane from the dialysis circuit to the extracorporeal circuit.

wherein the intermittent switching of the pump accomplishes the convective clearance of at least one waste species.

14. The method of claim 13, wherein the intermittent switching of the pump accomplishes the convective clearance of at least one waste species.

15. The method of claim 14, wherein the waste species has a molecular weight less than about 66000 g/mol

16. The method of claim 13, wherein the control pump is intermittently switched between the efflux direction and the influx direction such that the pump is not operated continuously in either the efflux or influx direct for a time period exceeding about 2 minutes.

17. The method of claim 13, wherein a volume of fluid added to the dialysis circuit by the control pump results in substantially the same volume of fluid transferred to the body of the subject;

and

wherein a volume of fluid removed from the dialysis circuit by the control pump results in substantially the same volume of fluid transferred from the body of the subject to the system for performing kidney replacement treatment.

18. The method of claim 13, further comprising measuring the conductivity of the dialysate using a conductivity meter.

19. A system for performing kidney replacement treatment, comprising:

a hemofiltration system having a controlled compliance filtration circuit, a hemofilter with a hemofiltration membrane, a blood inlet end for receiving blood, a blood outlet end for allowing blood out of the hemofilter, and an ultrafiltration outlet for allowing an ultrafiltrate out of the hemofilter;

an extracorporeal circuit having a conduit for receiving blood from a subject and a conduit for returning blood to the subject, and a blood pump for conveying blood from the subject, to the hemofilter and back to the subject;

a hemofiltration circuit having a sorbent cartridge for removing at least one impurity or waste species from the ultrafiltrate to generate a replacement fluid, wherein the ultrafiltrate enters an inlet end of the sorbent cartridge and a replacement fluid exits an outlet end of the sorbent cartridge, the hemofiltration circuit having one or more conduits and a filtrate pump for conveying the ultrafiltrate from the hemofilter to the sorbent cartridge and for infusing the replacement solution into the extracorporeal circuit; and

one or more controllers for controlling a rate of the blood pump and a rate of the filtrate pump.

20. The system of claim 19, wherein a rate of conveyance of the replacement solution is substantially equal to the rate of operation of the filtration pump.