HEMODIALYSIS SYSTEM WITH DIALYSATE RECYCLING

Abstract

The hemodialysis system with dialysate recycling uses a urea-adsorbing zeolite to remove urea from used dialysate, thus allowing the dialysate to be recycled. The hemodialysis system includes a housing and a dialyzer mounted on the housing. Similar to a conventional hemodialysis dialyzer, the dialyzer has blood inlet and blood outlet ports and dialysate inlet and dialysate outlet ports. The blood inlet port is adapted for receiving blood from the patient to be cleaned, and the blood outlet port is adapted for outputting cleaned blood, which is returned to the patient. A dialysate container may be mounted on the exterior of the housing and is adapted for receiving dialysate and the urea-adsorbing zeolite. Clean dialysate is fed from the dialysate container to the dialysate inlet port of the dialyzer, and used dialysate is recirculated from the dialysate outlet port of the dialyzer through the dialysate container.

Claims

1. A home-use dialysis system providing dialysate recycling in a portable device with dimensions of a medium-sized box of 35×40×25 cm, comprising: a housing containing electrical circuits that have light and compact components; a dialyzer mounted on the housing, the dialyzer having a blood inlet port and a blood outlet port, the blood inlet port being adapted for receiving uremic blood from a patient, and the blood outlet port being adapted for outputting cleaned blood to be returned to the patient, the dialyzer further having a dialysate inlet and a dialysate outlet; a dialysate container adapted for receiving dialysate, the dialysate container being connected to the dialysate inlet and dialysate outlet ports; a urea-adsorbing zeolite disposed in the dialysate container whereby clean dialysate is fed from the dialysate container to the dialysate inlet port of the dialyzer, and used dialysate is recirculated from the dialysate outlet port of the dialyzer through the dialysate container for removal of urea by the urea-adsorbing zeolite to provide clean dialysate, the dialysate container containing a blade to ensure continuous mixing of the dialysate and the urea-adsorbing zeolite in order to maintain a homogeneous suspension; an alarm system connected to a hospital to provide notification in case of complications; two pumps including a first pump connected to a blood inlet tube for driving the blood from the patient to be cleaned with 250-300 L/min as a speed; a second pump connected to the dialysate inlet for driving the clean dialysate through the dialyzer with 500-600 L/min as a speed; and an air bubble sensor located in a blood outlet for monitoring the cleaned blood carried by a blood outlet tube for the presence of air bubbles, wherein when an air bubble is detected the hemodialysis system turns off immediately.

2. The home-use hemodialysis system as recited in claim 1, further comprising: a dialyzer holder secured to the housing, the dialyzer holder having a horizontal orientation to avoid gravity effects during movement and ensure minimal variations oof a circulated speed, the dialyzer being removably held within the dialyzer holder.

3. The home-use hemodialysis system as recited in claim 1, wherein the dialysate has a composition of components to ensure a complete dialysis session without need for different adsorbents, the components having respective concentrations as follows: 142 mEq/L of Na+, 3 mEq/L of K+, 4 mEq/L of Ca++, 1.5 mEq/L of Mg++, 107 mEq/L of Cl—, 34 mEq/L of HCO3—, 1.2 mEq/L of Lactate, 0 mEq/L of HPO4—, 0 mEq/L of urate, 0 mEq/L of sulfate —, and 100 mEq/L of glucose.

4. (canceled)

5. (canceled)

6. The home-use hemodialysis system as recited in claim 1, further comprising a heater that maintains temperature at 37° C., and a temperature sensor located in the blood outlet tube that turns off the hemodialysis system of less than 35° C. are detected,

7. (canceled)

8. The home-use hemodialysis system as recited in claim 6, further comprising a flowrate sensor in the blood outlet for selectively monitoring a flowrate of cleaned blood carried by the blood outlet tube and as a result monitoring turning the alarm system on when the flowrate is less than 300 mL/min for the patient to consume anticoagulation pills, turning the alarm system off when the flowrate is more than 300 mL/min, and turning the home-use hemodialysis system off when the flowrate is less than 250 mL/min.

9. The home-use hemodialysis system as recited in claim 1, further using a molecular sieve 13X zeolite that is distributed in a dialysate solution including a mass of

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 is a diagrammatic front view of a hemodialysis system with dialysate recycling.

[0016] FIG. 2 is a diagram of a conventional prior art hemodialysis machine.

[0017] FIG. 3 is a block diagram of the hemodialysis system with dialysate recycling of FIG. 1.

[0018] FIG. 4 is a plot of measured concentrations of urea adsorbed by a zeolite from a dialysate sample as a function of time for differing masses of the zeolite, and also comparing unstirred zeolite/dialysate suspensions against a stirred zeolite/dialysate suspension.

[0019] FIG. 5 is a plot of removal efficiency of the urea adsorption by the zeolite from the dialysate sample of FIG. 4 for the differing masses of the zeolite, and also comparing unstirred zeolite/dialysate suspensions against the stirred zeolite/dialysate suspension.

[0020] Similar reference characters denote corresponding features consistently throughout the attached drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The hemodialysis system with dialysate recycling, designated generally as 10 in the drawings, uses a urea-adsorbing zeolite to remove urea from used dialysate, thus allowing the dialysate to be recycled. As shown in FIG. 1, the hemodialysis system 10 includes a housing 13 and a dialyzer 12 mounted on the housing 13. A dialyzer holder 15 may be secured to the housing 13, such that the dialyzer 12 is removably held within the dialyzer holder 15, allowing the dialyzer 12 to be temporarily removed for replacement, cleaning, transport, or storage. It should be understood that the overall configuration and dimensions of the housing 13 and the dialyzer holder 15 are shown in FIG. 1 for exemplary purposes only. Since the recycling of the dialysate removes the need for large storage tanks, the hemodialysis system with dialysate recycling 10 may be used as a portable dialysis system. The housing 13 may be dimensioned for portability and home use. For example, the housing 13 may be configured as a box with dimensions of 35 cm×40 cm×25 cm. Additionally, it should be understood that any suitable type of hemodialysis dialyzer may be used. For example, the dialyzer 12 may use a polyethersulfone membrane to separate the dialysis compartment from the blood compartment within the housing of the dialyzer 12.

[0022] Similar to a conventional hemodialysis dialyzer, the dialyzer 12 has blood inlet and blood outlet ports 14, 16, respectively, and dialysate inlet and dialysate outlet ports 18, 20, respectively. The blood inlet port 14 is adapted for receiving blood B from the patient to be cleaned, and the blood outlet port 16 is adapted for outputting cleaned blood CB to be returned to the patient. A dialysate container 22 may be mounted on the exterior of the housing 13 and is adapted for receiving dialysate D and a urea-adsorbing zeolite. It should be understood that the overall dimensions and configuration of the dialysate container 22 are shown in FIG. 1 for exemplary purposes only.

[0023] Clean dialysate D is fed from the dialysate container 22 to the dialysate inlet port 18 of the dialyzer 12, and used dialysate UD is recirculated from the dialysate outlet port 20 of the dialyzer 12 through the dialysate container 22. The dialyzer 12 operates in a manner similar to that of a conventional dialyzer and may make use of counter-current flow, where the clean dialysate D flowing into the dialyzer 12 through the dialysate inlet port 18 flows in the opposite direction to the blood B flowing through the dialyzer 12. Counter-current flow maintains the concentration gradient across the semipermeable membrane inside the dialyzer 12 at a maximum and increases the efficiency of the dialysis. Fluid removal from the patient's blood B is performed by ultrafiltration, and is achieved by altering the hydrostatic pressure of the dialysate compartment within the dialyzer 12, causing free water and the dissolved solutes to move across the semipermeable membrane along the created pressure gradient.

[0024] As the used dialysate UD is circulated back through the dialysate container 22, the urea-adsorbing zeolite within the dialysate container 22 adsorbs the urea from the used dialysate UD, allowing it to be recycled as clean dialysate D, which is recirculated back through the dialyzer 12. It should be understood that any suitable type of urea-adsorbing zeolite may be used. An example of such a urea-adsorbing zeolite is the Molecular Sieve 13X (Na.sub.86[(AlO.sub.2).sub.86(SiO.sub.2).sub.106].Math.nH.sub.2O) zeolite. The urea-adsorbing zeolite may be, for example, in the form of a powder, and a mixer or stirrer 52 may be disposed within, or attached to, the dialysate container 22 to maintain a homogeneous mixed suspension of dialysate and zeolite powder within the dialysate container 22.

[0025] In order to test the efficacy of molecular sieve 13X in removing urea, urea concentration in a sample dialysate was measured, both before and after addition of Molecular Sieve 13X zeolite. Using the non-linear multiple regression test, the results showed that as the mass of the zeolite adsorbent added to the sample dialysate increased, the urea concentration decreased by almost 0.18 g/mol. Based on these results, it was found that the required mass of the adsorbent over a period of time estimated for a normal human male with no other related diseases is 275 g of zeolite for each 1 liter of dialysate. This calculation is based on the flow required for each patient, where the typical blood flow rate is estimated to be in the range of 250-400 mL/min, while for the dialysate, the estimated flow rate is 500-800 mL/min. As a result, the dialysate must be twice the volume of blood to be purified. Thus, through the addition of the zeolite, far less dialysate must be used than in conventional hemodialysis. The addition of the adsorbent to the diffusion and ultrafiltration process also accelerates the purification of the blood, reducing the average time for hemodialysis to between one and two hours per session.

[0026] With regard to the other components removed from the blood, the various component concentrations in the dialysate may be adjusted relative to those of normal plasma and/or the uremic fluid. Table 1 below shows exemplary desired ratios to be used for each component to be removed from a patient's blood. The figures in Table 1 are based on an adult human male with kidney failure, but no additional conditions or diseases. As an example, in Table 1, in order to maintain glucose at 100 mEq/L, the diffusion process must be stopped, requiring the dialysate to have the same glucose concentration. As another example, the calcium concentration in the uremic fluid is 2 mEq/L but the desired concentration in normal plasma is 3 mEq/L. Thus, the dialysate should be prepared to have 4 mEq/L in order to achieve proper purification of the patient's blood.

TABLE-US-00001 TABLE 1 Dialysate Ratios for Blood Component Removal Normal Plasma Uremic fluid Dialysate Component (mEq/L) (mEq/L) (mEq/L) Na.sup.+ 142 142 142 K.sup.+ 5 7 3 Ca.sup.++ 3 2 4 Mg.sup.++ 1.5 1.5 1.5 Cl.sup.− 107 107 107 HCO.sub.3.sup.− 24 14 34 Lactate.sup.− 1.2 1.2 1.2 HPO.sub.4.sup.− 3 9 0 Urate.sup.− 0.3 2 0 Sulfate.sup.− 0.5 3 0 Glucose 100 100 100 Urea 26 200 0 Creatinine 1 6 0

[0027] Similar to a conventional hemodialysis system, a blood inlet tube 28 is provided for carrying the blood B from the patient to be cleaned to the blood inlet port 14 of the dialyzer 12, a blood outlet tube 30 is provided for carrying the cleaned blood CB from the blood outlet port 16 of the dialyzer 12 to the patient, a dialysate inlet tube 34 is provided for carrying the clean dialysate D from the dialysate container 22 to the dialysate inlet port 18 of the dialyzer 12, and a dialysate outlet tube 32 is provided for recirculating the used dialysate UD from the dialysate outlet port 20 of the dialyzer 12 to the dialysate container 22. A first pump 24 selectively and controllably drives the blood B from the patient to be cleaned through the blood inlet tube 28 to the blood compartment of the dialyzer 12, and back to the patient through the blood outlet tube 30. A second pump 26 selectively and controllably recirculates the used dialysate UD from the dialysate compartment of the dialyzer 12 back to the dialysate container 22 through the dialysate outlet tube 32, and the clean dialysate D is recycled in dialysate container 22 back to the dialysate compartment through the dialysate inlet tube 34.

[0028] As shown in FIG. 3, the first pump 24 and the second pump 26 may be in communication with a controller 48, which may be programmed and/or operated manually to control the action of each of pumps 24, 26. It should be understood that controller 48 may be any suitable type of controller, such as a microprocessor, a programmable logic controller, logic circuitry, a personal computer, a microcontroller, or the like. Controller 48 may be contained within housing 13 or may be externally or remotely located with respect to housing 13.

[0029] An air bubble sensor 38, also in communication with controller 48, may be mounted on the housing 13 for monitoring the cleaned blood carried by the blood outlet tube 30 for the presence of air bubbles. It should be understood that any suitable type of air bubble sensor may be utilized. If air bubble sensor 38 detects the presence of air bubbles in the cleaned blood CB, the controller 48 may actuate a visible and/or audio alarm 50 to warn a technician or user and/or stop pumps 24 and 26 from operating to prevent the cleaned blood from flowing back to the patient.

[0030] A temperature sensor 40 in communication with the controller 48 may also be mounted on the housing 13 for measuring the temperature of the cleaned blood CB carried by the blood outlet tube 30. If the cleaned blood has a temperature below a pre-set threshold, controller 48 may actuate the alarm 50 and/or stop the pumps 24 and 26 from operating to prevent the cleaned blood CB from flowing back to the patient. Alternatively, a heater 46, also in communication with controller 48, may be provided for selectively raising the temperature of the cleaned blood CB carried by the blood outlet tube 30 to the desired threshold temperature. For example, the threshold temperature may be set to 37° C., the average body temperature of an adult human. Additionally, a flow rate sensor 42 in communication with the controller 48 may also be mounted on the housing 13 for selectively monitoring the flow rate of the cleaned blood CB carried by the blood outlet tube 30.

[0031] By monitoring and controlling both temperature and fluid flow rate, there is no need to use anticoagulants, such as heparin, in the hemodialysis system 10 with dialysate recycling. Anticoagulation is achieved through maintaining the temperature constant at the 37° C. threshold with a high rate of flow. For example, the blood flow rate may be set at approximately 250-300 mL/min. Based on the measurements from temperature sensor 40 and/or flow rate sensor 42, if the controller 48 determines that there is a low level of risk to the patient, the alarm 50 may be actuated and the patient may be given an additional anticoagulant, for example. If the controller 48 determines that there is a high risk to the patient, the blood flow can be stopped. Further, since low temperature blood returning to the patient can cause harm to the patient, the heater 46 can be actuated accordingly. Heater 46 can be controlled by the controller 48 to maintain a constant temperature of the cleaned blood CB at, for example, 37° C.

[0032] As discussed above, a stirrer/mixer 52 may be disposed in the dialysate container 22 to maintain a homogeneous suspension of the zeolite. In order to test the efficacy of stirring, an experiment was performed to test urea concentration in a sample dialysate when masses of 9 g, 12 g and 15 g of the zeolite were added, where there was no stirring, and also when a mass of 11 g of zeolite was added, but with stirring. Table 2 shows the results of measured concentrations of urea measured between a start time (shown as 0 minutes) and an end time of 120 minutes.

TABLE-US-00002 TABLE 2 Urea Concentrations Following Adsorption Urea Urea Urea Urea concentration concentration concentration concentration (mg/dL) for 9 g (mg/dL) for 12 g (mg/dL) for 15 g (mg/dL) for 11 g Time of zeolite, of zeolite, of zeolite, of zeolite, (min.) not stirred not stirred not stirred with stirring 0 19 19 19 19 15 14 10 9.087 7.917 30 10 9 8.261 6.333 45 9 8 7.435 4.750 60 8 7 6.609 3.167 120 8 7 6.609 3.167

[0033] It can be seen in Table 2 above that the urea concentration not only decreases with addition of more zeolite, but the stirring of the zeolite has a significant effect on the adsorption of the urea. These results are also plotted in FIGS. 4 and 5, where FIG. 4 shows the measured urea concentration as a function of time, and FIG. 5 shows the corresponding removal efficiency as a function of time.

[0034] It is to be understood that the hemodialysis system with dialysate recycling is not limited to the specific embodiments described above, but encompasses any and all embodiments within the scope of the generic language of the following claims enabled by the embodiments described herein, or otherwise shown in the drawings or described above in terms sufficient to enable one of ordinary skill in the art to make and use the claimed subject matter.