DE3900119C1 - Apparatus for measuring the urea concentration in an extracorporeal circulation - Google Patents

Apparatus for measuring the urea concentration in an extracorporeal circulation

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Publication number
DE3900119C1
DE3900119C1 DE3900119A DE3900119A DE3900119C1 DE 3900119 C1 DE3900119 C1 DE 3900119C1 DE 3900119 A DE3900119 A DE 3900119A DE 3900119 A DE3900119 A DE 3900119A DE 3900119 C1 DE3900119 C1 DE 3900119C1
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Germany
Prior art keywords
filtrate
urea
cartridge
urease
conductivity
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Expired - Lifetime
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DE3900119A
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German (de)
Inventor
Siegfried Stiller
Udo 5100 Aachen De Schallenberg
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Priority to DE3900119A priority Critical patent/DE3900119C1/en
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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/021—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance before and after chemical transformation of the material
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M1/00—Suction or pumping devices for medical purposes; Devices for carrying-off, for treatment of, or for carrying-over, body-liquids; Drainage systems
    • A61M1/14—Dialysis systems; Artificial kidneys; Blood oxygenators ; Reciprocating systems for treatment of body fluids, e.g. single needle systems for hemofiltration or pheresis
    • A61M1/16—Dialysis systems; Artificial kidneys; Blood oxygenators ; Reciprocating systems for treatment of body fluids, e.g. single needle systems for hemofiltration or pheresis with membranes
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M1/00—Suction or pumping devices for medical purposes; Devices for carrying-off, for treatment of, or for carrying-over, body-liquids; Drainage systems
    • A61M1/14—Dialysis systems; Artificial kidneys; Blood oxygenators ; Reciprocating systems for treatment of body fluids, e.g. single needle systems for hemofiltration or pheresis
    • A61M1/16—Dialysis systems; Artificial kidneys; Blood oxygenators ; Reciprocating systems for treatment of body fluids, e.g. single needle systems for hemofiltration or pheresis with membranes
    • A61M1/1601—Control or regulation
    • A61M1/1603—Regulation parameters
    • A61M1/1605—Physical characteristics of the dialysate fluid
    • A61M1/1607—Physical characteristics of the dialysate fluid before use, i.e. upstream of dialyser
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M2230/00—Measuring parameters of the user
    • A61M2230/65—Impedance, e.g. conductivity, capacity

Abstract

A continuous stream of filtrate of about 2 millilitres per hour is removed from the extracorporeal circulation through a single capillary with a plasma filtration membrane and is passed successively through a first conductivity measurement cell, a cartridge with urease and a second conductivity measurement cell of the same design as the first. The stream of filtrate is maintained by the reduction in pressure generated by a syringe with retracted and locked plunger. The urea in the filtrate is chemically decomposed by the urease in the cartridge between the two conductivity measurement cells. This results in two millimole of NH3 and 1 mmol of CO2 per millimole of urea. NH3 is substantially dissociated at physiological pH so that the conductivity in the filtrate after passing through the cartridge with urease is increased. The difference between the conductivites determined by the first and the second measurement cell is therefore a measure of the urea concentration in the filtrate. This corresponds to the urea concentration in the blood (accurately in the plasma) in the extracorporeal circulation.

Description

Die Erfindung geht aus von einer Vorrichtung zum Messen der Harnstoffkonzentration nach dem Oberbegriff des Patentanspruchs 1, wie sie aus der DE 34 36 748 A1 bekannt ist.The invention is based on a device for measuring the urea concentration after Preamble of claim 1 as they is known from DE 34 36 748 A1.

Die ausreichende Elimination von Harnstoff ist eine notwendige Bedingung für eine erfolgreiche Behandlung des akuten und terminalen Nierenversagens mit der künstlichen Niere. Der Zeitbedarf für die Harnstoffelimination bestimmt auch im wesentlichen die durchschnittliche Dauer der Behandlung. Die Orientierung der Dauer der Behandlung an der Harnstoffausscheidung gilt als anerkannte Methode; vgl. dazu z. B. Lowry, E. G., Teehan, B. P., Principoles of prescribing dialysis therapy: implementing recomendations from the National Cooperative Dialysis Study. Kidney International, 23, Suppl. 13, 1983: s113; oder Gotch, F. A. Sargent, J. A., A mechanistik analysis of the National Cooperative Study Dialysis Study. Kidney Internationl. 28, 1985: s526.Adequate elimination of urea is necessary Condition for successful treatment of acute and terminal kidney failure with the artificial kidney. The Time required for urea removal also determined in the essentially the average duration of treatment. The orientation of the duration of the treatment on the urea excretion is considered a recognized method; see. to e.g. B. Lowry, E.G., Teehan, B.P., Principoles of prescribing dialysis therapy: implementing recomendations from the National Cooperative Dialysis Study. Kidney International, 23, Suppl. 13, 1983: s113; or Gotch, F.A. Sargent, J.A., A mechanistic analysis of the National Cooperative Study Dialysis study. Kidney International 28, 1985: s526.

Neben der ausreichenden Ausscheidung von Harnstoff muß auch die ausreichende Ausscheidung von höhermolekularer Urämietoxine, sowie ein Ausgleich des Wasser-, des Elektrolyt- und des Säurebasenhaushaltes erzielt werden. Diese Bedingungen lassen sich jedoch in der Regel innerhalb der für die Harnstoffelimination notwendigen Zeit erreichen. Einzelheiten zur Hämodialyse anderer Verfahren der extrakorporalen Detoxifikation sind in Standardwerken enthalten, z. B. Replacement of Renal Function by Dialysis, Hrsg.: W. Drukker, F. M. Parson, J. F. Maher, M. Nÿhoff Publishers, Boston/The Hague/Lancater, 2. Aufl. 1983; oder Hämodialyse, Peritonealdialyse, Plasmapherese und verwandte Verfahren, Hrsg.: E. Wetzels, A. Colombi, P. Dittrich, H. J. Gurland, M. Kessel, H. Klinkmann.In addition to the sufficient excretion of urea, the sufficient excretion of higher molecular uraemia toxins, as well as a Balancing the water, electrolyte and acid base balance be achieved. However, these conditions can be found in the Usually within the time necessary for urea elimination to reach. Details of hemodialysis of other procedures of extracorporeal detoxification are in standard works included, e.g. B. Replacement of Renal Function by Dialysis, Ed .: W. Drukker, F. M. Parson, J. F. Maher, M. Nÿhoff Publishers, Boston / The Hague / Lancater, 2nd ed. 1983; or Hemodialysis, peritoneal dialysis, plasmapheresis and related Method, Ed .: E. Wetzels, A. Colombi, P. Dittrich, H. J. Gurland, M. Kessel, H. Klinkmann.

Die Messung der Harnstoffkonzentration im extrakorporalen Kreislauf gestattet es deshalb, die kürzest mögliche Behandlungszeit für jede einzelne Dialysebehandlung zu finden.The measurement of the urea concentration in the extracorporeal Circulation therefore allows the shortest possible Find treatment time for each individual dialysis treatment.

Die Behandlungszeit liegt heute bei der Hämodialyse und verwandten Verfahren (Hämofiltration, Hämodiafiltration) zwischen 2 und 7 Stunden 3mal in der Woche (6 bis 21 Stunden in der Woche). Die Behandlungszeit ist aus verschiedenen Gründen von großer Bedeutung. Eine kurze Behandlungszeit wird von einem Patienten eher akzeptiert, da ihm dann die soziale und berufliche Eingliederung leichter fällt. Auch das lange "Gefesseltsein" an der Dialysemaschine wird von den Patienten nicht geschätzt, manche fühlen sich in dieser Zeit nicht wohl.The treatment time today is hemodialysis and related Procedure (hemofiltration, hemodiafiltration) between 2 and 7 Hours 3 times a week (6 to 21 hours a week). The Treatment time is of great importance for various reasons. A short treatment time is more likely from a patient accepted, because then the social and professional integration is easier. Also the long "bondage" to the  Dialysis machines are not appreciated by patients, some don't feel comfortable during this time.

Die Dauer der Behandlung ist ein Kostenfaktor, da in dieser Zeit Behandlungsplätze, ärztliches Personal und Pflegepersonal bereit stehen müssen.The duration of the treatment is a cost factor since at this time Treatment places, medical staff and nursing staff ready have to stand.

Eine verkürzte Dialysezeit kann deshalb zur Rehabilitation der Patienten und zur Senkung der Kosten für die Behandlung beitragen.A shortened dialysis time can therefore be used for the rehabilitation of Patients and help reduce the cost of treatment.

Zum Messen der Harnstoffkonzentration sind eine Reihe von Verfahren bekannt, die entweder auf der Spaltung des Harnstoffs durch Urease und dem Nachweis von NH₃ beruhen (vgl. die eingangs genannte DE 34 36 748 A1) oder eine chromogene Reaktion herbeiführen und die Extinktion photometrisch messen; vgl. dazu: Clinical Chemistry: Principles and Techniques, Hrsg.: R. Henry, D. C. Cannon, J. W. Winkelmann, Harper and Row Publishers, New York 1974.A number of methods are known for measuring the urea concentration, either on the split of the Urea based on urease and the detection of NH₃ (see. The aforementioned DE 34 36 748 A1) or one Induce chromogenic reaction and the absorbance photometrically measure up; see. to: Clinical Chemistry: Principles and Techniques, Ed .: R. Henry, D. C. Cannon, J. W. Winkelmann, Harper and Row Publishers, New York 1974.

Die Messung des freiwerdenden NH₃ über die Änderung der Leitfähigkeit wird von der Fa. Beckmann Instruments GmbH München in ihrem Gerät zur Messung der Harnstoffkonzentration im Blut angewandt; siehe "Blood Urea Nitrogen Chemistry Module", Operating and Service Instructions (015-5 55 587 A, 1981).The measurement of the released NH₃ on the change the conductivity is from Beckmann Instruments GmbH Munich in their device for measuring the urea concentration in the Blood applied; see "Blood Urea Nitrogen Chemistry Modules ", Operating and Service Instructions (015-5 55 587 A, 1981).

Aufgabe der Erfindung ist es danach, die Vorrichtung nach dem Oberbegriff des Anspruchs 1 dahingehend weiterzuentwickeln, daß das Messen kontinuierlich erfolgt, so daß weder eine mehrmalige Probenentnahme unter Verwendung von umschaltbaren Ventilen erforderlich ist, noch ein Durchmischen der Probe mit einer Verdünnungsflüssigkeit durch Verrühren.The object of the invention is then the device according to the preamble of claim 1 to further develop that Measure continuously takes place so that neither a repeated sampling under Use of switchable valves is still required mixing the sample with a dilution liquid by stirring.

Diese Aufgabe wird mit dem Gegenstand des Anspruchs 1 gelöst. Vorteilhafte Ausgestaltungen dieses Gegenstands sind in den Unteransprüchen angegeben.This object is achieved with the subject matter of claim 1. Advantageous developments of this object are specified in the subclaims.

Ein Ausführungsbeispiel der beanspruchten Vorrichtung ist in Abb. 1 dargestellt. In den arteriellen Schenkel des extrakorporaten Kreislaufs, hinter der Blutpumpe, vor dem Blutfilter (Dialysator, Hämofilter) ist eine einzelne Kapillare integriert. Die Anordnung im extrakorporalen Kreislauf bei der Hämodialyse ist in Abb. 2 dargestellt. Kapillaren mit einer symmetrischen Plasmafiltrationsmembran sind dafür geeignet. Entsprechende Kapillaren sind kommerziell verfügbar. Das offene Ende der Kapillaren ist über ein Y-Stück aus dem extrakorporalen Kreislauf herausgeführt, das geschlossene Ende schwimmt frei im Blutstrom.An embodiment of the claimed device is shown in Fig. 1. A single capillary is integrated in the arterial leg of the extracorporeal circuit, behind the blood pump, in front of the blood filter (dialyzer, hemofilter). The arrangement in the extracorporeal circuit during hemodialysis is shown in Fig. 2. Capillaries with a symmetrical plasma filtration membrane are suitable for this. Corresponding capillaries are commercially available. The open end of the capillaries is led out of the extracorporeal circuit via a Y-piece, the closed end floats freely in the blood stream.

Der Ausgang der Kapillaren ist mit einem Schlauch von geringen Lumen (Innendurchmesser <0,4 mm) mit der ersten Leitfähigkeitsmeßzelle M 1, wie sie z. B. aus der Zeitschrift Medizintechik, 105. Jg., Nr. 4/85, S. 124 bis 131, bekannt ist, verbunden. Über eine Patrone mit Urease-Granulat fließt das Filtrat in die zweite Meßzelle M 2 (mit der ersten gleich). Beide Zellen und die Patrone mit Urease sind von einer Kapsel umschlossen, die durch Umströmung mit der Dialysierflüssigkeit auf konstanter Temperatur gehalten wird. Die Temperatur der Dialysierflüssigkeit wird von der Dialysemaschine konstant gehalten.The exit of the capillaries is with a tube of small lumens (inner diameter <0.4 mm) with the first conductivity measuring cell M 1 , as z. B. from the journal Medizintechik, 105th vol., No. 4/85, pp. 124 to 131, is known. The filtrate flows into the second measuring cell M 2 (same as the first one) via a cartridge with urease granulate. Both cells and the cartridge with urease are enclosed in a capsule, which is kept at a constant temperature by the dialysis fluid flowing around it. The dialysis machine keeps the temperature of the dialysis fluid constant.

Hinter der zweiten Leitfähigkeitsmeßzelle ist ein Steckkontakt für eine Spritze mit Luer-Ansatz. Vor dem Beginn der Messung wird der Kolben der Spritze zurückgezogen und arretiert. Durch den Unterdruck wird ein kontinuierlicher Filtratstrom durch die Leitfähigkeitsmeßzellen und die Patrone mit Urease erzeugt, der sich in der Spritze sammelt. Die Länge der Kapillaren und der Unterdruck in der Spritze werden so gewählt, daß ca. 2 Milliliter pro Stunde Filtrat erzeugt wird. Da der Druck in der Spritze mit der Zeit sinkt, nimmt der Filtratfluß mit der Zeit zu. Deshalb wird das Volumen der Spritze so groß gewählt, daß auch am Ende der Behandlung noch ein ausreichender Filtratfluß besteht.A plug contact is located behind the second conductivity measuring cell for a syringe with a Luer neck. Before the start of the measurement the syringe plunger is retracted and locked. By the Vacuum is a continuous flow of filtrate through the Conductivity cells and the cartridge with urease are generated collects in the syringe. The length of the capillaries and the Negative pressure in the syringe is selected so that approx. 2 milliliters per hour of filtrate is generated. Because the pressure in the syringe with time decreases, the filtrate flow increases with time. That's why the volume of the syringe is chosen so large that even at the end of the Treatment there is still a sufficient flow of filtrate.

Die Messung der Leitfähigkeitsdifferenz erfolgt nach der üblichen Technik. Widerstandsmessung mit ca. 1000 Hz Wechselstrom. Zur Sicherheit wird die Stromversorgung des Gerätes (12 Volt) durch einen Trenntransformator galvanisch entkoppelt.The conductivity difference is measured according to the usual Technology. Resistance measurement with approx. 1000 Hz alternating current. To Security is the power supply of the device (12 volts) an isolation transformer galvanically decoupled.

Bei der Passage des Filtrates durch die Patrone mit Urease wird der Harnstoff im Filtrat chemisch zerlegt, dabei werden je Millimol Harnstoff 2 mmol NH₃ und 1 mmol CO₂ frei. Bei physiologischem pH (ca. 7,4) dissotiiert NH₃ und CO² weitgehend: When the filtrate is passed through the cartridge with urease the urea in the filtrate is chemically broken down, each time Millimoles of urea free 2 mmol NH₃ and 1 mmol CO₂. At Physiological pH (approx. 7.4) largely dissotiates NH₃ and CO²:  

Die Spaltung von Harnstoff führt zu einer Erhöhung der Ionenstärke und damit zu einer Erhöhung der Leitfähigkeit proportional zur Harnstoffkonzentration. Die Leitfähigkeit, die in der zweiten Meßzelle gemessen wird, ist deshalb höher als in der ersten. Die Differenz der Leitfähigkeit in der zweiten und der ersten Meßzelle ist der Harnstoffkonzentration im Filtrat proportional.The splitting of urea leads to an increase in the ionic strength and thus to an increase in conductivity proportional to Urea concentration. The conductivity in the second Measuring cell is measured is therefore higher than in the first. The Difference in conductivity in the second and the first measuring cell is proportional to the urea concentration in the filtrate.

Claims (4)

1. Vorrichtung zum Messen der Harnstoffkonzentration in einem extrakorporalen Kreislauf, die Urease zum Zersetzen des Harnstoffs enthält, dadurch gekennzeichnet, daß vor und nach einer kontinuierlich von Filtrat durchströmten Patrone mit der Urease je eine Leitfähigkeitsmeßzelle angeordnet ist.1. Device for measuring the urea concentration in an extracorporeal circuit, which contains urease for decomposing the urea, characterized in that a conductivity measuring cell is arranged with the urease before and after a cartridge through which the filtrate flows continuously. 2. Vorrichtung nach Anspruch 1, dadurch gekennzeichnet, daß das Filter zum Erzeugen des Filtratstroms aus einer einzelnen Kapillaren besteht, die an einem Ende verschlossen ist und mit diesem Ende frei im Blutstrom schwimmmt.2. Device according to claim 1, characterized, that the filter to generate the filtrate stream consists of a single capillary, the one end is locked and free with this end swims in the bloodstream. 3. Vorrichtung nach Anspruch 1 oder 2, gekennzeichnet durch eine Spritze, deren Kolben zurückgezogen und arretiert ist, um den Unterdruck, der den Filtratstrom erzeugt, hervorzurufen. 3. Device according to claim 1 or 2, featured through a syringe, whose pistons are retracted and locked is to the negative pressure that the filtrate flow generated to evoke.   4. Vorrichtung nach einem der Ansprüche 1 bis 3, gekennzeichnet durch eine Einrichtung zum Umströmen der Leitfähigkeitsmeßzellen und der Patrone mit Dialysierflüssigkeit von konstanter Temperatur.4. Device according to one of claims 1 to 3, characterized by a device for flowing around the Conductivity cells and the Cartridge with Dialysis fluid of constant Temperature.
DE3900119A 1989-01-04 1989-01-04 Apparatus for measuring the urea concentration in an extracorporeal circulation Expired - Lifetime DE3900119C1 (en)

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0549341A1 (en) * 1991-12-24 1993-06-30 W.R. Grace & Co.-Conn. Hollow fiber plasma sampler
EP0614081A1 (en) * 1993-03-01 1994-09-07 BELLCO S.p.A. A method and a system for measuring the concentration of a substance in a fluid, and the use thereof
EP0621046A1 (en) * 1993-03-05 1994-10-26 Gambro Ab Method of measuring the effect of a dialysis treatment
DE4401400A1 (en) * 1994-01-19 1995-07-20 Ernst Prof Dr Pfeiffer Method and arrangement for continuously monitoring the concentration of a metabolite
WO1996004401A1 (en) * 1994-07-29 1996-02-15 Gambro Ab Method and device for measuring the concentration of a substance in a solution
WO1997025615A1 (en) * 1996-01-11 1997-07-17 Cambridge Consultants Limited Method and apparatus for measuring an electrical parameter of a fluid
NL1006711C2 (en) * 1997-08-04 1999-02-08 Nedap Nv System for monitoring and controlling protein utilization in animals.
WO1999062574A1 (en) * 1998-06-04 1999-12-09 Althin Medical Ab Method for determining waste products in the dialysis liquid in dialysis treatment
EP1338891A1 (en) * 2002-02-22 2003-08-27 Toyo Engineering Corporation Method and apparatus for determining urea concentration

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3436748A1 (en) * 1983-12-22 1985-07-04 VEB Meßgerätewerk Zwönitz, DDR 9417 Zwönitz Device for automatic determination of the efficacy of haemodialysis

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3436748A1 (en) * 1983-12-22 1985-07-04 VEB Meßgerätewerk Zwönitz, DDR 9417 Zwönitz Device for automatic determination of the efficacy of haemodialysis

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
DE-Z.: Medizintechnik, 105.Jg. Nr.4/85, S.124-131 *
Firmendruckschrift: "Blood Urea Nitrogen ChemistryModule", Operating and Service-Instructions (015-555587A, 1981) *

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0549341A1 (en) * 1991-12-24 1993-06-30 W.R. Grace & Co.-Conn. Hollow fiber plasma sampler
EP0614081A1 (en) * 1993-03-01 1994-09-07 BELLCO S.p.A. A method and a system for measuring the concentration of a substance in a fluid, and the use thereof
EP0621046A1 (en) * 1993-03-05 1994-10-26 Gambro Ab Method of measuring the effect of a dialysis treatment
DE4401400A1 (en) * 1994-01-19 1995-07-20 Ernst Prof Dr Pfeiffer Method and arrangement for continuously monitoring the concentration of a metabolite
EP1182264A2 (en) * 1994-07-29 2002-02-27 Gambro Lundia AB Method and device for assay of urea
WO1996004401A1 (en) * 1994-07-29 1996-02-15 Gambro Ab Method and device for measuring the concentration of a substance in a solution
EP1182264A3 (en) * 1994-07-29 2003-06-11 Gambro Lundia AB Method and device for assay of urea
WO1997025615A1 (en) * 1996-01-11 1997-07-17 Cambridge Consultants Limited Method and apparatus for measuring an electrical parameter of a fluid
NL1006711C2 (en) * 1997-08-04 1999-02-08 Nedap Nv System for monitoring and controlling protein utilization in animals.
EP0896222A3 (en) * 1997-08-04 2001-03-14 N.V. Nederlandsche Apparatenfabriek NEDAP System for monitoring and controlling protein utilization in animals
EP0896222A2 (en) * 1997-08-04 1999-02-10 N.V. Nederlandsche Apparatenfabriek NEDAP System for monitoring and controlling protein utilization in animals
WO1999062574A1 (en) * 1998-06-04 1999-12-09 Althin Medical Ab Method for determining waste products in the dialysis liquid in dialysis treatment
EP1338891A1 (en) * 2002-02-22 2003-08-27 Toyo Engineering Corporation Method and apparatus for determining urea concentration
US7153693B2 (en) 2002-02-22 2006-12-26 Toyo Engineering Corporation Method and apparatus for determining urea concentration

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