Artificial kidney with moderate exchange rates

• US 4,950,395 A
• Filed: 11/27/1987
• Issued: 08/21/1990
• Est. Priority Date: 11/28/1986
• Status: Expired due to Term

• Current Assignee: Industries Gambro
• Original Assignee: Hospal Industrie
• Inventors: Richalley, Gerard
• Primary Examiner(s): JONES, WILLIAM G
• Application Number:
  US07/126,018
• Time in Patent Office: 998 Days
• Field of Search: 604/4, 604/5, 210/195.2, 210/257.1, 210/257.2, 210/259, 210/321.65, 210/321.71, 210/321.72, 210/321.75
• US Class Current: 210/195.2
• CPC Class Codes: A61M 1/16 with membranes
• CPC Class Codes: A61M 1/1611 Weight of the patient
• CPC Class Codes: A61M 1/1643 with weighing of fresh and used dialysis fluid
• CPC Class Codes: A61M 1/3431 upstream of the filter
• CPC Class Codes: A61M 1/3646 Expelling the residual body fluid after use, e.g. back to the body
• CPC Class Codes: A61M 2202/0498 Urea
• CPC Class Codes: A61M 2205/15 Detection of leaks

Abstract

An artificial kidney capable of operating without a dialysis machine for the treatment of chronic renal failure in discontinuous sessions consisting essentially of:

a. a source of a prepackaged dialysis liquid;

b. a hemodialyzer with a high permeability membrane continuously traversed by the blood and the dialysis liquid;

c. means for collecting the used dialysis liquid and possibly the ultrafiltrate;

d. means for measuring the patient'"'"'s variations in weight; and

e. possibly means for injecting a sterile and apyrogenic liquid into the extracorporeal blood circuit.

This artificial kidney is particularly intended for operating in a non-hospital environment.

Claims

1. An artificial kidney capable of ensuring the treatment of a patient'"'"'s chronic renal failures by discontinuous sessions of a weekly total of less than or equal to about 24 hours, consisting essentially of:

a source of dialysis liquid;

means for collecting the used dialysis liquid and ultrafiltrate;

a high permeability membrane exchanger of the hemodialyzer type comprising two compartments separated by a membrane, the first compartment adapted to be traversed by the blood and connected to the arterio-venous system of the patient by an extracorporeal blood circuit, and means for preventing the clotting of blood in said circuit, the second compartment being adapted to be continuously traversed by said dialysis liquid, to collect any ultrafiltrate, and to be connected at one end via a first conduit to said dialysis liquid source and at the other end via a second conduit to said means for collecting said used dialysis liquid and any ultrafiltrate;

means for continuously flowing sterile and apyrogenic dialysis liquid using the force of gravity through said second compartment at a rate of between about 50-200 ml/minute;

means for continuously flowing blood through said first compartment during said treatment session using the pressure of the patient'"'"'s arterio-venous system;

means for continuously maintaining a higher pressure in said first compartment than in said second compartment during said treatment session; and

means for measuring the variation of the weight of the patient due to the balance of the quantities of the liquids injected and withdrawn during said treatment;

wherein said membrane exchanger simultaneously provides a dialysis capacity exceeding or equal to about 40 ml/minute for the clearance of urea and an ultrafiltration capacity exceeding or equal to about 8 ml/h/mmHg.

2. An artificial kidney according to claim 1, wherein said source of the dialysis liquid is constituted by fresh dialysis liquid prepackaged in at least one reservoir whose total capacity for one session is less than or equal to 60 liters.

3. An artificial kidney according to claim 1, wherein said exchanger is of the flat membrane type.

4. An artificial kidney capable of ensuring the treatment of a patient'"'"'s chronic renal failures by discontinuous sessions of a weekly total of less than or equal to about 24 hours, consisting essentially of:

a source of dialysis liquid;

means for collecting the used dialysis liquid and ultrafiltrate;

a high permeability membrane exchanger of the hemodialyzer type comprising two compartments separated by a membrane, the first compartment adapted to be traversed by the blood and connected to the arterio-venous system of the patient by an extracorporeal blood circuit, and means for preventing the clotting of blood in said circuit, the second compartment being adapted to be continuously traversed by said dialysis liquid, to collect any ultrafiltrate, and to be connected at one end via a first conduit to said dialysis liquid source and at the other end via a second conduit to said means for collecting said used dialysis liquid and any ultrafiltrate;

means for continuously flowing sterile and apyrogenic dialysis liquid using the force or gravity through said second compartment at a rate of between about 50-200 ml/min;

means for continuously flowing blood through said first compartment during said treatment session using the pressure of the patient'"'"'s arterio-venous system;

means for continuously maintaining a higher pressure in said first compartment than in said second compartment during said treatment session;

means for measuring the variation of the weight of the patient due to the balance of the quantities of the liquids injected and withdrawn during said treatment;

wherein said membrane exchanger simultaneously provides a dialysis capacity exceeding or equal to about 40 ml/minute for the clearance of urea and an ultrafiltration capacity exceeding or equal to about 8 ml/h/mmHg;

wherein said source of the dialysis liquid is constituted by fresh dialysis liquid prepackaged in at least one reservoir whose total capacity for one session is less than or equal to 60 liters; and

including means for sterilizing said dialysis liquid before it enters into said exchanger.

5. An artificial kindney capable of ensuring the treatment of a patient'"'"'s chronic renal failures by discontinuous sessions of a weekly total of less than or equal to about 24 hours, consisting essentially of:

a source of dialysis liquid;

means for collecting the used dialysis liquid and ultrafiltrate;

a high permeability membrane exchanger of the hemodialyzer type comprising two compartments separated by a membrane, the first compartment adapted to be traversed by the blood and connected to the arterio-venous system of the patient by an extracorporeal blood circuit, and means for preventing the clotting of blood in said circuit, the second compartment being adapted to be continuously traversed by said dialysis liquid, to collect any ultrafiltrate, and to be connected at one end via a first conduit to said dialysis liquid source and at the other end via a second conduit to said for collecting said used dialysis liquid and any ultrafiltrate;

means for continuously flowing sterile and apyrogenic dialysis liquid using the force of gravity through said second compartment at a rate of between about 50-200 ml/min;

means for continuously flowing blood through said first compartment during said treatment session using the pressure of the patient'"'"'s arterio-venous system;

means for continuously maintaining a higher pressure in said first compartment than in said second compartment during said treatment session;

means for measuring the variation of the weight of the patient due to the balance of the quantities of the liquids injected and withdrawn during said treatment;

wherein said membrane exchanger simultaneously provides a dialysis capacity exceeding or equal to about 40 ml/minute for the clearance of urea and an ultrafiltration capacity exceeding or equal to about 8 ml/h/mmHg; and

including means for purifying the liquid collected at the outlet of said exchanger at least partly, so that it can be reused.

6. An artificial kidney capable of ensuring the treatment of a patient'"'"'s chronic renal failures by discontinuous sessions of a weekly total of less than or equal to about 24 hours, consisting essentially of:

a source of dialysis liquid;

means for collecting the used dialysis liquid and ultrafiltrate;

a high permeability membrane exchanger of the hemodialyzer type comprising two compartments separated by a membrane, the first compartment adapted to be traversed by the blood and connected to the arterio-venous system of the patient by an extracorporeal blood circuit, and means for preventing the clotting of blood in said circuit, the second compartment being adapted to be continuously traversed by said dialysis liquid, to collect any ultrafiltrate, and to be connected at one end via a first conduit to said dialysis liquid source and at the other end via a second conduit to said means for collecting said used dialysis liquid and any ultrafiltrate;

means for continuously flowing sterile and apyrogenic dialysis liquid using the force of gravity through said second compartment at a rate of between about 50-200 ml/min;

means for continuously flowing blood through said first compartment during said treatment session using the pressure of the patient'"'"'s arterio-venous system;

means for continuously maintaining a higher pressure in said first compartment than in said second compartment during said treatment session;

means for measuring the variation of the weight of the patient due to the balance of the quantities of the liquids injected and withdrawn during said treatment;

wherein said membrane exchanger simultaneously provides a dialysis capacity exceeding or equal to about 40 ml/minute for the clearance of urea and an ultrafiltration capacity exceeding or equal to about 8 ml/h/mmHg; and

including a reservior filled with a physiological, sterile and apyrogenic liquid and means for connecting said reservoir to said extracorporeal blood circuit to allow at least oen of the following operations to be performed;

preliminarily rinsing said exchanger, initially filling said extracorporeal blood circuit, compensating at least partly the ultrafiltrate withdrawn from the patient, complementarily feeding the patient, detoxification of the patient, or restoring the blood to the patient at the end of the session.

7. An artificial kidney capable of ensuring the treatment of a patient'"'"'s chronic renal failures by discontinuous sessions of a weekly total of less than or equal to about 24 hours, consisting essentially of:

a source of dialysis liquid;

means for collecting the used dialysis liquid and ultrafiltrate;

a high permeability membrane exchanger of the hemodialyzer type comprising two compartments separated by a membrane, the first compartment adapted to be traversed by the blood and connected to the arterio-venous system of the patient by an extracorporeal blood circuit, and means for preventing the clotting of blood in said circuit, the second compartment being adapted to be continuously traversed by said dialysis liquid, to collect any ultrafiltrate, and to be connected at one end via a first conduit to said dialysis liquid source and at the other end via a second conduit to said means for collecting said used dialysis liquid and any ultrafiltrate;

means for continuously flowing sterile and apyrogenic dialysis liquid using the force of gravity through said second compartment at a rate of between about 50-200 ml/min;

means for continuously flowing blood through said first compartment during said treatment session using the pressure of the patient'"'"'s arterio-venous system;

means for continuously maintaining a higher pressure in said first compartment than in said second compartment during said treatment session;

means for measuring the variation of the weight of the patient due to the balance of the quantities of the liquids injected and withdrawn during said treatment;

wherein said membrane exchanger simultaneously provides a dialysis capacity exceeding or equal to about 40 ml/minute for the clearance of urea and an ultrafiltration capacity exceeding or equal to about 8 ml/h/mmHg; and

including means for maintaining the dialysis liquid at temperatures approximating that of the patient'"'"'s blood.

8. An artificial kidney capable of ensuring the treatment of a patient'"'"'s chronic renal failures by discontinuous sessions of a weekly total of less than or equal to about 24 hours, consisting essentially of:

a source of dialysis liquid;

means for collecting the used dialysis liquid and ultrafiltrate;

a high permeability membrane exchanger of the hemodialyzer type comprising two compartments separated by a membrane, the first compartment adapted to be traversed by the blood and connected to the arterio-venous system of the patient by an extracorporeal blood circuit, and means for preventing the clotting of blood in said circuit, the second compartment being adapted to be continuously traversed by said dialysis liquid, to collect any ultrafiltrate, and to be connected at one end via a first conduit to said dialysis liquid source and at the other end via a second conduit to said means for collecting said used dialysis liquid and any ultrafiltrate;

means for continuously flowing sterile and apyrogenic dialysis liquid using the force of gravity through said second compartment at a rate of between about 50-200 ml/min;

means for continuously flowing blood through said first compartment during said treatment session using the pressure of the patient'"'"'s arterio-venous system;

means for continuously maintaining a higher pressure in said first compartment than in said second compartment during said treatment session;

means for measuring the variation of the weight of the patient due to the balance of the quantities of the liquids injected and withdrawn during said treatment;

wherein said membrane exchanger simultaneously provides a dialysis capacity exceeding or equal to about 40 ml/minute for the clearance of urea and an ultrafiltration capacity exceeding or equal to about 8 ml/h/mmHg; and

wherein the effective surface area fo said membrane of said exchanger is between 0.3 and 1.5 m².

9. An artificial kidney capable of ensuring the treatment of a patient'"'"'s chronic renal failures by discontinuous sessions of a weekly total of less than or equal to about 24 hours, consisting essentially of:

a source of dialysis liquid;

means for collecting the used dialysis liquid and ultrafiltrate;

a high permeability membrane exchanger of the hemodialyzer type comprising two compartments separated by a membrane, the first compartment adapted to be traversed by the blood and connected to the arterio-venous system of the patient by an extracorporeal blood circuit, and means for preventing the clotting of blood in said circuit, the second compartment being adapted to be continuously traversed by said dialysis liquid, to collect any ultrafiltrate, and to be connected at one end via a first conduit to said dialysis liquid source and at the other end via a second conduit to said means for collecting said used dialysis liquid and any ultrafiltrate;

means for continuously flowing sterile and apyrogenic dialysis liquid using the force of gravity through said second compartment at a rate of between about 50-200 ml/min;

means for continuously flowing blood through said first compartment during said treatment session using the pressure of the patient'"'"'s arterio-venous system;

means for continuously maintaining a higher pressure in said first compartment than in said second compartment during said treatment session;

means for measuring the variation of the weight of the patient due to the balance of the quantities of the liquids injected and withdrawn during said treatment;

wherein said membrane exchanger simultaneously provides a dialysis capacity exceeding or equal to about 40 ml/minute for the clearance of urea and an ultrafiltration capacity exceeding or equal to about 8 ml/h/mmHg; and

including means for allowing the blood to flow into said exchanger at a flow rate between 80 and 200 ml/minute.

10. An artificial kidney capable of ensuring the treatment of a patient'"'"'s chronic renal failures by discontinuous sessions of a weekly total of less than or equal to about 24 hours, consisting essentially of:

a source of dialysis liquid;

means for collecting the used dialysis liquid and ultrafiltrate;

a high permeabilty membrane exchanger of the hemodialyzer type comprising two compartments separated by a membrane, the first compartment adapted to be traversed by the blood and connected to the arterio-venous system of the patient by an extracorporeal blood circuit, and means for preventing the clotting of blood in said circuit, the second compartment being adapted to be continuously traversed by said dialysis liquid, to collect any ultrafiltrate, and to be connected at one end via a first conduit to said dialysis liquid source and at the other end via a second conduit to said means for collecting said used dialysis liquid and any ultrafiltrate;

means for continuously flowing sterile and apyrogenic dialysis liquid using the force of gravity through said second compartment at a rate of between about 50-200 ml/min;

means for continuously flowing blood through said first compartment during said treatment session using the pressure of the patient'"'"'s arterio-venous system;

means for continuously maintaining a higher pressure in said first compartment than in said second compartment during said treatment session;

means for measuring the variation of the weight of the patient due to the balance of the quantities of the liquids injected and withdrawn during said treatment;

wherein said membrane exchanger simultaneously provides a dialysis capacity exceeding or equal to about 40 ml/minute for the clearance of urea and an ultrafiltration capacity exceeding or equal to about 8 ml/h/mmHg; and

including means for regulating the flow rate of the fresh dialysis liquid traversing said exchanger.

11. An artificial kidney capable of ensuring the treatment of a patient'"'"'s chronic renal failures by discontinuous sessions of a weekly total of less than or equal to about 24 hours, consisting essentially of:

a source of dialysis liquid;

means for collecting the used dialysis liquid and ultrafiltrate;

a high permeability membrane exchanger of the hemodialyzer type comprising two compartments separated by a membrane, the first compartment adapted to be traversed by the blood and connected to the arterio-venous system of the patient by an extracorporeal blood circuit, and means for preventing the clotting of blood in said circuit, the second compartment being adapted to be continuously traversed by said dialysis liquid, to collect any ultrafiltrate, and to be connected at one end via a first conduit to said dialysis liquid source and at the other end via a second conduit to said means for collecting said used dialysis liquid and any ultrafiltrate;

means for continuously flowing sterile and apyrogenic dialysis liquid using the force of gravity through said second compartment at a rate of between about 50-200 ml/min;

means for continuously flowing blood through said first compartment during said treatment session using the pressure of the patient'"'"'s arterio-venous system;

means for continuously maintaining a higher pressure in said first compartment than in said second compartment during said treatment session;

means for measuring the variation of the weight of the patient due to the balance of the quantities of the liquids injected and withdrawn during said treatment;

wherein said membrane exchanger simultaneously provides a dialysis capacity exceeding or equal to about 40 ml/minute for the clearance of urea and an ultrafiltration capacity exceeding or equal to about 8 ml/h/mmHg; and

including means for measuring the flow rate of the dialysis liquid traversing said exchanger.

12. An artificial kidney capable of ensuring the treatment of a patient'"'"'s chronic renal failures by discontinuous sessions of a weekly total of less than or equal to about 24 hours, consisting essentially of:

a source of dialysis liquid;

means for collecting the used dialysis liquid and ultrafiltrate;

a high permeabilty membrane exchanger of the hemodialyzer type comprising two compartments separated by a membrane, the first compartment adapted to be traversed by the blood and connected to the arterio-venous system of the patient by an extracorporeal blood circuit, and means for preventing the clotting of blood in said circuit, the second compartment being adapted to be continuously traversed by said dialysis liquid, to collect any ultrafiltrate, and to be connected at one end via a first conduit to said dialysis liquid source and at the other end via a second conduit to said means for collecting said used dialysis liquid and any ultrafiltrate;

means for continuously flowing sterile and apyrogenic dialysis liquid using the force of gravity through said second compartment at a rate of between about 50-200 ml/min;

means for continuously flowing blood through said first compartment during said treatment session using the pressure of the patient'"'"'s arterio-venous system;

means for continuously maintaining a higher pressure in said first compartment than in said second compartment during said treatment session;

means for measuring the variation of the weight of the patient due to the balance of the quantities of the liquids injected and withdrawn during said treatment;

wherein said membrane exchanger simultaneously provides a dialysis capacity exceeding or equal to about 40 ml/minute for the clearance of urea and an ultrafiltration capacity exceeding or equal to about 8 ml/h/mmHg; and

including means for regulating the flow of any ultrafiltrate extracted from the blood through said membrane of said exchanger.

13. An artificial kidney capable of ensuring the treatment of a patient'"'"'s chronic renal failures by discontinuous sessions of a weekly total of less than or equal to about 24 hours, consisting essentially of:

a source of dialysis liquid;

means for collecting the used dialysis liquid and ultrafiltrate;

a high permeability membrane exchanger of the hemodialyzer type comprising two compartments separated by a membrane, the first compartment adapted to be traversed by the blood and connected to the arterio-venous system of the patient by an extracorporeal blood circuit, and means for preventing the clotting of blood in said circuit, the second compartment being adapted to be continuously traversed by said dialysis liquid, to collect any ultrafiltrate, and to be connected at one end via a first conduit to said dialysis liquid source and at the other end via a second conduit to said means for collecting said used dialysis liquid and any ultrafiltrate;

means for continuously flowing sterile and apyrogenic dialysis liquid using the force of gravity through said second compartment at a rate of between about 50-200 ml/min;

means for continuously flowing blood through said first compartment during said treatment session using the pressure of the patient'"'"'s arterio-venous system;

means for continuously maintaining a higher pressure in said first compartment than in said second compartment during said treatment session;

means for measuring the variation of the weight of the patient due to the balance of the quantities of the liquids injected and withdrawn during said treatment;

wherein said membrane exchanger simultaneously provides a dialysis capacity exceeding or equal to about 40 ml/minute for the clearance of urea and an ultrafiltration capacity exceeding or equal to about 8 ml/h/mmHg; and

including means for recirculating the dialysis liquid in said exchanger.

14. An artificial kidney capable of ensuring the treatment of a patient'"'"'s chronic renal failures by discontinuous sessions of a weekly total of less than or equal to about 24 hours, consisting essentially of:

a source of dialysis liquid;

means for collecting the used dialysis liquid and ultrafiltrate;

a high permeability membrane exchanger of the hemodialyzer type comprising two compartments separated by a membrane, the first compartment adapted to be traversed by the blood and connected to the arterio-venous system of the patient by an extracorporeal blood circuit, and means for preventing the clotting of blood in said circuit, the second compartment being adapted to be continuously traversed by said dialysis liquid, to collect any ultrafiltrate, and to be connected at one end via a first conduit to said dialysis liquid source and at the other end via a second conduit to said means for collecting said used dialysis liquid and any ultrafiltrate;

means for continuously flowing sterile and apyrogenic dialysis liquid using the force of gravity through said second compartment at a rate of between about 50-200 ml/min;

means for continuously flowing blood through said first compartment during said treatment session using the pressure of the patient'"'"'s arterio-venous system;

means for continuously maintaining a higher pressure in said first compartment than in said second compartment during said treatment session;

means for measuring the variation of the weight of the patient due to the balance of the quantities of the liquids injected and withdrawn during said treatment;

wherein said membrane exchanger simultaneously provides a dialysis capacity exceeding or equal to about 40 ml/minute for the clearance of urea and an ultrafiltration capacity exceeding or equal to about 8 ml/h/mmHg;

wherein said exchanger is of the flat membrane type; and

, including means for allowing a concurrent circulation of the blood and dialysis liquid in said exchanger.

15. An artificial kidney capable of ensuring the treatment of a patient'"'"'s chronic renal failures by discontinuous sessions of a weekly total of less than or equal to about 24 hours, consisting essentially of:

a source of dialysis liquid;

means for collecting the used dialysis liquid and ultrafiltrate;

a high permeability membrane exchanger of the hemodialyzer type comprising two compartments separated by a membrane, the first compartment adapted to be traversed by the blood and connected to the arterio-venous system of the patient by an extracorporeal blood circuit, and means for preventing the clotting of blood in said circuit, the second compartment being adapted to be continuously traversed by said dialysis liquid, to collect any ultrafiltrate, and to be connected at one end via a first conduit to said dialysis liquid source and at the other end via a second conduit to said means for collecting said used dialysis liquid and any ultrafiltrate;

means for continuously flowing sterile and apyrogenic dialysis liquid using the force of gravity through said second compartment at a rate of between about 50-200 ml/min;

means for continuously flowing blood through said first compartment during said treatment session using the pressure of the patient'"'"'s arterio-venous system;

means for continuously maintaining a higher pressure in said first compartment than in said second compartment during said treatment session;

means for measuring the variation of the weight of the patient due to the balance of the quantities of the liquids injected and withdrawn during said treatment;

wherein said membrane exchanger simultaneously provides a dialysis capacity exceeding or equal to about 40 ml/minute for the clearance of urea and an ultrafiltration capacity exceeding or equal to about 8 ml/h/mmHg; and

including at least one absorption cartridge containing active charcoal disposed in said extracorporeal blood circuit in series with said exchanger.

16. An artificial kidney capable of ensuring the treatment of a patient'"'"'s chronic renal failures by discontinuous sessions of a weekly total of less than or equal to about 24 hours, consisting essentially of:

a source of dialysis liquid;

means for collecting the used dialysis liquid and ultrafiltrate;

a high permeability membrane exchanger of the hemodialyzer type comprising two compartments separated by a membrane, the first compartment adapted to be traversed by the blood and connected to the arterio-venous system of the patient by an extracorporeal blood circuit, and means for preventing the clotting of blood in said circuit, the second compartment being adapted to be continuously traversed by said dialysis liquid, to collect any ultrafiltrate, and to be connected at one end via a first conduit to said dialysis liquid source and at the other end via a second conduit to said means for collecting said used dialysis liquid and any ultrafiltrate;

means for continuously flowing sterile and apyrogenic dialysis liquid using the force of gravity through said second compartment at a rate of between about 50-200 ml/min;

means for continuously flowing blood through said first compartment during said treatment session using the pressure of the patient'"'"'s arterio-venous system;

means for continuously maintaining a higher pressure in said first compartment than in said second compartment during said treatment session;

means for measuring the variation of the weight of the patient due to the balance of the quantities of the liquids injected and withdrawn during said treatment;

wherein said membrane exchanger simultaneously provides a dialysis capacity exceeding or equal to about 40 ml/minute for the clearance of urea and an ultrafiltration capacity exceeding or equal to about 8 ml/h/mmHg;

means for recirculating the dialysis liquid in said exchanger; and

including means for accomplishing treatment by hemofiltration wherein quantities of a sterile and apyrogenic liquid are adapted to be injected into the blood in amounts equivalent to the quantities of liquid withdrawn from the blood by hemofiltration less a desired variation of the patient'"'"'s weight.

17. An artificial kidney capable of ensuring the treatment of a patient'"'"'s chronic renal failures by discontinuous sessions of a weekly total of less than or equal to about 24 hours, consisting essentially of:

a source of dialysis liquid;

means for collecting the used dialysis liquid and ultrafiltrate;

a high permeability membrane exchanger of the hemodialyzer type comprising two compartments separated by a membrane, the first compartment adapted to be traversed by the blood and connected to the arterio-venous system of the patient by an extracorporeal blood circuit, and means for preventing the clotting of blood in said circuit, the second compartment being adapted to be continuously traversed by said dialysis liquid, to collect any ultrafiltrate, and to be connected at one end via a first conduit to said dialysis liquid source and at the other end via a second conduit to said means for collecting said used dialysis liquid and any ultrafiltrate;

means for continuously flowing sterile and apyrogenic dialysis liquid using the force of gravity through said second compartment at a rate of between about 50-200 ml/minute;

means for continuously flowing blood at a natural flow rate through said first compartment during said treatment session using the pressure of the patient'"'"'s arterio-venous system;

means for continuously maintaining a higher pressure in said first compartment than in said second compartment during said treatment session;

means for measuring the variation of the weight of the patient due to the balance of the quantities of the liquids injected and withdrawn during said treatment; and

pump means for flowing blood through said first compartment when blood flow through said first compartment falls below said natural flow rate;

wherein said membrane exchanger simultaneously provides a dialysis capacity exceeding or equal to about 40 ml/minute for the clearance of urea and a ultrafiltration capacity exceeding or equal to about 8 ml/h/mmHg.

18. An artificial kidney capable of ensuring the treatment of a patient'"'"'s chronic renal failures by discontinuous sessions of a weekly total of less than or equal to about 24 hours, consisting essentially of:

a source of dialysis liquid;

means for collecting the used dialysis liquid and ultrafiltrate;

a high permeability membrane exchanger of the hemodialyzer type comprising two compartments separated by a membrane, the first compartment adapted to be traversed by the blood and connected to the arterio-venous system of the patient by an extracorporeal blood circuit, and means for preventing the clotting of blood in said circuit, the second compartment being adapted to be continuously traversed by said dialysis liquid, to collect any ultrafiltrate, and to be connected at one end via a first conduit to said dialysis liquid source and at the other end via a second conduit to said means for collecting said used dialysis liquid and any ultrafiltrate;

means for continuously flowing sterile and apyorgenic dialysis liquid using the force of gravity through said second compartment at a rate of between about 50-200 ml/minute;

means for continuously flowing blood through said first compartment during said treatment session using the pressure of the patient'"'"'s arterio-venous system;

means for continuously maintaining a higher pressure in said first compartment than in said second compartment during said treatment session;

means for measuring the variation of the weight of the patient due to the balance of the quantities of the liquids injected and withdrawn during said treatment; and

pump means for flowing said dialysis liquid through said second compartment when gravity cannot be relied upon to provide a necessary flow rate;

wherein said membrane exchanger simulataneously provides a dialysis capacity exceeding or equal to about 40 ml/minute for the clearance or urea and an ultrafiltration capacity exceeding or equal to about 8 ml/h/mmHg.

19. An artificial kidney capable of ensuring the treatment of a patient'"'"'s chronic renal failures by discontinuous sessions of a weekly total of less than or equal to about 24 hours, consisting essentially of:

a source of dialysis liquid;

means for collecting the used dialysis liquid and ultrafiltrate;

a high permeability membrane exchanger of the hemodialyzer type comprising two compartments separated by a membrane, the first compartment adapted to be traversed by the blood and connected to the arterio-venous system of the patient by an extracorporeal blood circuit, and means for preventing the clotting of blood in said circuit, the second compartment being adapted to be continuously traversed by said dialysis liquid, to collect any ultrafiltrate, and to be connected at one end via a first conduit to said dialysis liquid source and the other end via a second conduit to said means for collecting said used dialysis liquid and any ultrafiltrate;

means for continuously flowing sterile and apyrogenic dialysis liquid using the force of gravity through said second compartment at a rate of between about 50-200 ml/minute;

means for continuously flowing blood at a natural flow rate through said first compartment during said treatment session using the pressure of the patient'"'"'s arterio-venous system;

means for continuously maintaining a higher pressure in said first compartment than in said second compartment during said treatment session;

means for measuring the variation of the weight of the patient due to the balance of the quantities of the liquids injected and withdrawn during said treatment;

first pump means for flowing blood through said first compartment when blood flow through said first compartment falls below said natural flow rate; and

second pump means for flowing said dialysis liquid through said second compartment when gravity cannot be relied upon to provide a necessary flow rate;

wherein said membrane exchanger simultaneously provides a dialysis capacity exceeding or equal to about 40 ml/minute for the clearance of urea and an ultrafiltration capacity exceeding or equal to about 8 ml/h/mmHg.