Hemodialysis system having a flow path with a controlled compliant volume

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.

1 - 22 . (canceled) 
     
     
         23 . A system for performing kidney replacement treatment, 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;   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;   at least a first pump in fluid communication with the controlled compliant flow path and at least a first reservoir;   at least a second pump in fluid communication with the controlled compliant flow path and either a fluid source or a reservoir;   the first and second pumps for selectively metering in and metering out fluid from the controlled compliant flow path; and   the first pump and second pump operable in concert to control net fluid movement across the dialysis membrane.   
     
     
         24 . The system of  claim 23 , wherein the second pump is selected from the group consisting of an infusate pump, a filtrate pump, a bicarbonate pump, and a water pump. 
     
     
         25 . The system of  claim 24 , further comprising a controller; the controller controlling each pump to accomplish a predetermined patient fluid balance. 
     
     
         26 . The system of  claim 23 , wherein the volume of the dialysate within the dialysis circuit is a substantially inflexible volume. 
     
     
         27 . The system of  claim 23 , 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. 
     
     
         28 . The system of  claim 27 , wherein the void volume space is between 0.1 and 5.0 L. 
     
     
         29 . The system of  claim 23 , further comprising a conductivity meter downstream of the sorbent cartridge. 
     
     
         30 . The system of  claim 23 , wherein the first reservoir is an isolated reservoir. 
     
     
         31 . The system of  claim 23 , further comprising a controller; the controller controlling 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. 
     
     
         32 . The system of  claim 23 , further comprising at least a second reservoir for storing fluid that can be added to the dialysis circuit by the second pump. 
     
     
         33 . The system of  claim 23 , 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.   
     
     
         34 . The system of  claim 33 , 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 Ca 2+ , Mg 2+ , 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 Ca 2+ , Mg 2+ , 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 NH 4   +  for Na +  ions by the sorbent cartridge by subtracting the starting conductivity from the corrected outlet conductivity.   
     
     
         35 . The system of  claim 34 , the controller further determining ammonium breakthrough in the sorbent cartridge 
     
     
         36 . The system of  claim 23 , 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 first pump, a rate of the second reservoir pump, a rate of the blood pump, and a rate of the dialysate pump. 
     
     
         37 . The system of  claim 23 , wherein the first pump is positioned on a conduit between the controlled compliant flow path and the first reservoir. 
     
     
         38 . The system of  claim 23 , wherein the sorbent cartridge contains zirconium phosphate, a urease-containing material, zirconium oxide, and activated carbon. 
     
     
         39 . The system of  claim 23 , further comprising a pH meter in the controlled compliant dialysis circuit. 
     
     
         40 . The system of  claim 23 , further comprising a microbial filter in the controlled compliant dialysis circuit. 
     
     
         41 . The system of  claim 23 , wherein the second pump is a water pump in fluid communication with a water reservoir, the water pump positioned upstream of the sorbent cartridge. 
     
     
         42 . The system of  claim 23 , further comprising one or more controllers; the one or more controllers controlling a pump rate of a blood pump, a dialysate pump, the first pump, and the second pump.