DE19806900C1 - Dialysis parameter provision method for blood dialysis device for treating kidney patients - Google Patents

Abstract

The method involves setting the dialysis fluid flow rate to a value at which the concentration of a substance in the dialysis fluid flowing from the dialysis chamber (6) corresponds to the concentration of the substance in the blood flowing into the blood chamber (4). The substance concentration in the dialysis fluid flowing from the dialysis chamber is measured, for determination of the required dialysis parameter.

Description

The invention relates to a method for determining parameters of the Hemodialysis during extracorporeal blood treatment as well as one Blood treatment device with a device for determining Hemodialysis parameters.

An essential task of the human kidneys is secretion urinary substances from the blood and the regulation of water and Electrolyte excretion. Hemodialysis provides a treatment procedure Compensation for kidney malfunctions in the removal of the urinary substances and the setting of the electrolyte concentration in the blood The water excretion is via an ultrafiltration device controlled.

During hemodialysis, the blood is conducted in an extracorporeal circuit through the blood chamber of a dialyzer, which is separated from a dialysis fluid chamber via a semipermeable membrane. The dialysis fluid chamber is flowed through by a dialysis fluid containing the blood electrolytes in a certain concentration. The substance concentration (c _d ) of the dialysis fluid corresponds to the concentration of a healthy person's blood. During the treatment, the patient's blood and the dialysis fluid are generally passed in countercurrent on both sides of the membrane at a predetermined flow rate (Q _b and Q _d ). The urinary substances diffuse through the membrane from the blood chamber into the chamber for dialysis fluid, while electrolytes present in the blood and in the dialysis fluid diffuse from the chamber of higher concentration to the chamber of lower concentration. The metabolism can also be influenced by applying a transmembrane pressure.

In order to optimize the blood treatment process, the determination is parameters of hemodialysis during extracorporeal blood treatment (in vivo) necessary. Of particular interest is the value for the Concentration of a substance in the blood at the entrance to the dialyzer or the Exchange performance of the dialyzer for a specific substance by the so-called "clearance" or "dialysance D" is shown.

As a clearance for a certain substance K, that becomes virtual (calculated) blood volume referred to that per minute below defined Conditions in the dialyzer completely freed from a certain substance becomes. Dialysance is another term used to determine the Performance of a dialyzer, in which the concentration of the eliminated substance in the dialysis fluid is taken into account. Next these parameters to describe the performance of the dialyzer other parameters are important, such as the values of the aqueous Proportion of blood, blood volume and blood inlet concentration etc.

The metrological-mathematical quantification of blood purification processes and the determination of the aforementioned dialysis parameters is relative complex. Regarding the calculation bases, Sargent, J.A., Gotch. F.A.,: Principles and biophysics of dialysis, in: Replacement of Renal Function by Dialysis, W. Drukker, F.M. Parsons, J.E Mower (ed.). Nijhoff, The Hague referred 1983.

The dialysance or clearance can be determined for a given electrolyte, for example sodium, at an ultrafiltration rate of zero as follows. The dialysance D is the ratio between the blood-side mass transport for this electrolyte (Q _b × (cbi - cbo)) and the concentration difference of this electrolyte between the blood and the dialysis fluid at the respective inlet of the dialyzer (cbi - cdi).

For mass balance reasons:

Q _b (cbi-cbo) = -Q _d . (Cdi-cdo) (2)

It follows from the two equations (1) and (2) above:

In (1) to (3) mean:
Q _b = effective blood flow
Q _d = dialysis fluid flow
cb = concentration of substances in the blood
cd = substance concentration in the dialysis fluid
i = input of the dialyzer
o = output of the dialyzer

The effective blood flow is the flow of the blood portion in which to be removed Substances are dissolved, d. that is, it relates to the (aqueous) solution volume for this stuff. Depending on the substance, this can be the plasma water flow or the Blood water flow, d. H. the total water content in whole blood. The Concentration cb refers to the corresponding blood percentage.

In the case of a special metabolic waste product, e.g. B. urea, cdi = 0, since this substance is not intended to be present in the fresh dialysis fluid. Then one no longer speaks of dialysance, but before clearance K for this metabolic product.

The known methods for in-vivo determination of parameters of the Hemodialysis is based on the above considerations. Here is what Strive to get by without a direct measurement intervention in the blood side because this is a not inconsiderable source of danger. The too The determining variables must therefore only be taken from dialysate measurements be derived.

DE 39 38 662 C2 (EP 0 428 927 A1) describes a method for in Vivo determination of parameters of hemodialysis, in which the dialysate Electrolyte transfer in two different cases Dialysate input concentrations is measured. Assuming that the Blood input concentration is constant, according to the known method the dialysance is determined by the difference between the differences the dialysis fluid ion concentration on the input side and the Output side of the dialyzer at the time of the first and second measurement is determined by the difference in the dialysis fluid  Ion concentration on the input side at the time of the first measurement and the second measurement is divided and the quotient from this with the Dialysis fluid flow is multiplied.

EP 0 291 421 B1 describes a method for determining the Blood inlet concentration known, at which the ramp Dialysate input concentration is changed to determine the point where there is no more electrolyte transfer across the membrane. The known The process therefore works on the principle of input conductivity Change dialysis fluid to such an extent that it can no longer separate from the Output conductivity differs. In this case, it has Blood input conductivity assumed.

The above Processes prove to be disadvantageous in that they are relatively complex Devices for varying the dialysate input concentration are required are.

EP 0 330 892 A1 and EP 0 547 025 A1 describe another Procedure that aims to determine the blood inlet concentration. In this known method, the difference in the dialysis fluid Ion concentration at the input and output side of the dialyzer, d. H. the Electrolyte transfer rate, determined. The known method also works with different concentration settings in the dialysis fluid path, so that also a relatively complex device for varying the Dialysis fluid input concentration is required.

No. 5,110,477 A1 describes a method for determining the clearance known a dialyzer in which both the dialysate and Blood side calibration solutions are passed through the dialyzer. This too The process requires a relatively complex apparatus. Furthermore, it can  not in vivo, but only in vitro, d. H. outside the current Dialysis treatment.

WO 94/09351 describes a urea sensor for a Hemodialysis device used for analysis of the dialysis fluid path withdrawn used dialysis fluid. The dialysis fluid withdrawal requires a certain flow rate of the dialysis fluid.

From the article Clinical Validation of a Predictive Modeling Equation for Sodium, authors: Nguyen-Khoa Man et al .; Editor: Artificial Organs, 9 (2): 150-154 (1985), Raven Press, New York is a process for Determine the Na concentration in the bloodstream of an artificial kidney known, the measurement being carried out in the dialysis fluid circuit. In which known method is the leading to the dialyzer and from the dialyzer outgoing line of the dialysis fluid circuit shorted, so only a small amount of dialysis fluid from the Dialysis fluid pump is pumped through the dialyzer. This will achieved that a state of equilibrium is established and the Concentration values in the bloodstream in the Correspond to the dialysis fluid circuit.

A method is also known from EP 0 578 585 B1 in which the Measurement on the dialysis fluid side after setting a Equilibrium takes place. With this method, too, one recirculates only a small amount of dialysis fluid through the dialyzer until the Has set equilibrium.

The above Procedures in which only a small amount of Dialysis liquid is passed through the dialyzer are disadvantageous in that as a redirection of the dialysis fluid in the dialysis fluid path  is required. This is with additional equipment connected.

The invention has for its object a method for determining To specify parameters of hemodialysis, which is a very simple, dialysate side Measurement of the concentration at the mass exchange of the dialyzer participating substance in the blood as the parameter to be determined or as Intermediate value for the parameter to be determined during the extracorporeal blood treatment allowed and also a device for determining Parameters of hemodialysis to create such Measurement allowed.

This object is achieved with the method according to claim 1 or solved with the device according to claim 13.

It has surprisingly been found that the concentration of a substance in the flowing out of the dialysing fluid chamber of the dialyzer Dialysis fluid essentially the concentration of the considered Substance in the blood flowing into the blood chamber is largely independent of the treatment conditions when the flow rate through the Dialysis fluid chamber flowing dialysis fluid starting from a predetermined value for the blood treatment to a certain value is reduced. Accordingly, it is not necessary to set one Equilibrium the dialysis fluid flow through the To interrupt the dialysis fluid chamber. Despite being variable Treatment conditions can be the concentration of a substance at the entrance  the blood chamber of the dialyzer by measuring the concentration of the Substance at the exit of the dialysis fluid chamber with sufficient Accuracy can be determined if the dialysis fluid rate during the extracorporeal blood treatment is reduced. After determining the Incoming blood concentration, d. H. the concentration of a substance in the Blood chamber of the dialyzer flowing blood, by measuring the Initial dialysis fluid concentration, d. H. the concentration of Substance in the fluid flowing out of the dialysis fluid chamber Dialysis fluid, as the parameter to be determined or as an intermediate value for the parameter to be determined, the dialysis fluid rate can be set to a value specified for the blood treatment can be set. Of The advantage is that not only a limited sample volume is available, but the liquid leaving the dialysis liquid chamber exactly as long as the concentrate level to be measured can be maintained as long as it is is required for the measurement. Ongoing ultrafiltration for peeling of the sample volume is not necessary, since the measurement state is solely via the diffuse compensation can come about. So that can claimed methods can also be used in situations where a continuation of ultrafiltration to a critical condition of the patient can lead. On the other hand, ultrafiltration to support the Measurement procedure to be continued at any time.

It is also advantageous that the treatment during the measurement process can continue, albeit with reduced efficiency. Still is it is advantageous that the dialyzer or the membrane also during the Measurement is flushed or flushed out. This prevents Form residues in the dialyzer during the measurement.

The subclaims indicate embodiments of the invention.

Setting the dialysis fluid flow rate to a value at which the Concentration of the substance in the dialysis fluid chamber essentially the concentration of these in the blood may increase at the beginning, during the course or  at the end of blood treatment. With an initial measurement immediately set the reduced dialysis fluid rate to then switch to the Treatment value to be increased. During blood treatment, the Dialysis fluid rate starting from one for treatment predefined value and after the measurement to the original Value increased again.

It has been shown that at a blood flow rate of <300 ml / min Dialysis fluid rate only set to a value of <100 ml / min are needed to establish a state of equilibrium, the one Measurement with sufficient accuracy allowed.

As the blood flow rate decreases, the dialysis fluid rate drops to one set lower value. At a blood flow rate of <150 ml / min Adequate equilibrium occurs when the dialysis fluid rate <75 ml / min.

In practice, it has surprisingly been found that largely regardless of the treatment conditions, e.g. B. the level of blood flow or the membrane surface of the dialyzer is always sufficient Equilibrium sets when the dialysis fluid rate is at a value of 40 to 60 ml / min, preferably 50 ml / min is set. Only in Exceptionally, a dialysis fluid flow rate may be required from 10 to 30 ml / min, preferably 20 ml / min.

The specified period for equilibrium can be set in the range from 1 to 5 min. lie. The response time can also be increased by other Measures, e.g. B. pressure surges in the dialysis fluid path and / or parallel Ultrafiltration, can be reduced. There is also an extrapolation of the final value based on measurements possible in a shorter period of time.  

Such methods find z. B. in electronic clinical thermometers Application.

The invention will now be described with reference to the drawings based on an embodiment of a blood treatment device with a Device for determining parameters of hemodialysis explained in more detail.

Show it:

Fig. 1 is a schematic diagram of a blood treatment apparatus with a device for determining parameters of the hemodialysis,

FIG. 2a is a diagram in which is shown, in a dialyzer having a membrane area of 0.7 m ² measured ratio of dialysatseitiger conductivity and blood mutual conductivity as a function of the dialysis-fluid,

Fig. 2b is a graph showing the ratio of dialysate-side conductivity and blood-side conductivity measured as a function of the dialysis fluid flow rate in a dialyzer with a membrane area of 1.8 m ²

Fig. 2c is a graph showing the change over time in the dialysate conductivity due to a change in the dialysis fluid flow rate.

In Fig. 1 only the essential components of a dialysis machine are shown. The dialysis device essentially consists of a dialysis fluid part 1 and an extracorporeal blood circuit 2 . The extracorporeal blood circuit 2 comprises an arterial branch 3 , a blood chamber 4 of a dialyzer 7 divided into the blood chamber 4 by a semipermeable membrane 5 and a dialysis fluid chamber 6 , and a venous branch 8 . A blood pump 9 is arranged in the arterial branch 3 , with which a specific blood flow rate Q _b in the extracorporeal circuit can be predetermined.

The dialysis fluid chamber 6 of the dialyzer 7 is connected to a dialysis fluid source 11 via a feed line 10 . A discharge line 12 , into which a dialysing liquid pump 13 which specifies the flow rate Q _{d of} the dialysing liquid is connected, leads into an outlet 14 .

A measuring device 15 , 16 for determining the substance concentration of the dialysis fluid at the inlet of the dialyzer 7 and the substance concentration of the dialysis fluid at the outlet of the dialyzer is arranged in the feed line 10 and the discharge line 12 . The measuring device 15 is initially not necessary to carry out the claimed method. However, the presence of such a measuring device is advantageous for determining further parameters. The measuring devices 15 , 16 for determining the dialysis fluid inlet and outlet concentrations cdi and cdo have conductivity sensors arranged upstream and downstream of the dialyzer 7 , which preferably measure the temperature-corrected conductivity of the dialysis fluid, which is mainly caused by the Na concentration. Instead of conductivity sensors, optical sensors or enzyme sensors etc. for measuring the dialysis fluid concentration can also be arranged in the dialysis fluid path 1 . Instead of a conductivity sensor, the measuring device 16 downstream of the dialyzer 7 can also have a urea sensor, it being possible to dispense with a urea sensor upstream of the dialyzer if the clearance is to be determined. The measuring devices 15 , 16 are connected via data lines 17 , 18 to an evaluation unit 19 in which the output signals of the measuring devices are processed. The evaluation unit communicates with a control unit 21 via a data line 20 . The control unit 21 is connected via control lines 22 , 23 to the blood pump 9 and the dialysis fluid pump 13 , so that the blood flow rate Q _b or the dialysis fluid flow rate Q _{d can be} set and varied.

During the dialysis treatment, the dialysis fluid provided in the dialysis fluid source 11 flows through the dialysis fluid chamber 6 of the dialyzer 7 at a flow rate Q _d predetermined by the delivery rate of the dialysis fluid pump 13 , while the patient's blood to be treated flows through the blood chamber 4 of the dialyzer 7 with a blood pump 9 flows through predetermined flow rate Q _b .

The program sequence predetermined by the control unit 21 for determining the blood inlet concentration cbi is explained below.

During the hemodialysis treatment, the dialysis fluid flow rate is reduced to 40 to 60 ml / min, preferably 50 ml / min. The flow rate is reduced in that the control unit 21 controls the dialysis fluid pump 13 accordingly. After a period of 2 to 3 minutes, which is predetermined by a timer provided in the control unit, the control unit controls the evaluation unit 19 in such a way that the evaluation unit detects the dialysis fluid output concentration cdo measured with the measuring device 16 . The measured dialysis fluid outlet concentration cdo then essentially corresponds to the blood inlet concentration cbi as the parameter to be determined. The control unit 21 then uses the dialysis fluid pump 13 to reset the dialysis fluid flow rate to the original value.

The blood inlet concentration cbi determined can be used as an intermediate value for the determination of further parameters. The dialysance of the dialyzer 7 can thus be determined by two further measurements. For this purpose, the control unit 21 controls the evaluation unit 19 in such a way that it detects the dialysis fluid inlet concentration cbi measured with the measuring device 15 at a predetermined dialysis fluid flow Q _d and the dialysis fluid outlet concentration cdo which is now established and which is measured with the measurement device 16 . In the evaluation unit, the previously determined blood inlet concentration cdi and the dialysis fluid inlet and outlet concentration cdi, cdo as well as the predetermined dialysis fluid rate Q _d according to the equation

the dialysance D determines.

The parameters to be determined can be on a not shown Display unit output or used for further process control become.

The inventive method is based on the fact that when the Flow rate of the dialysis fluid despite variable treatment conditions Blood inlet concentration can be determined by the Dialysis fluid output concentration is measured. This has the Advantage that an intervention in the extracorporeal blood circulation is not necessary is. The accuracy of the measurement method has changed in the following Experiments confirmed.

The coupled dialysate and Blood circulation modeled. Because of diffusion behavior and dialyzer clearances for electrolytes and for urea were almost identical, instead of  Urea NaCl can be used as a test substance. This is about the Conductivity measurement a simple, highly accurate method for Concentration measurement available. On the blood side, a 15 millimolar NaCl Solution used. This concentration is of the order of magnitude typical urea concentration. Pure water became dialysate side used. The conductivity cells were upstream and downstream of the Dialysing fluid chamber of the dialyzer arranged.

The measurements were carried out with different dialyzer types, which differ from each other in their membrane area. Measurement curves for some blood flows were recorded for each dialyzer. The minimum blood flow that is clinically common was set at 200 ml / min. For a given blood flow Q _b , the dialysate flow Q _{d was} gradually changed from 500 ml / min to 0 ml / min, after each change in the dialysate flow Q _d the setting of a stable state was waited for and the ratio of the conductivity on the dialysate side to the blood side was determined. FIG. 2a shows the ratio X / X _{0 of} the conductivity on the dialysate side to the blood-side conductivity as a function of the dialysis fluid flow rate Q _d in a dialyzer with a membrane area of 0.7 m ² , while FIG. 2b shows the ratio of the dialysate-side conductivity on the blood-side conductivity as a function of the dialysis fluid flow rate shows in a dialyzer with a membrane area of 1.8 m ² . The dialysate-side conductivity or blood-side conductivity corresponds to the dialysis fluid outlet or blood inlet concentration. As the measurements show, the equilibrium _is almost completely reached at a dialysis fluid flow rate Q _d of 50 ml / min. In the dialyzer with a membrane area of 0.7 m ² , the ratio X / X ₀ <0.97 for Q _b ≧ 200 ml / min and in the case of a dialyzer with a membrane area of 1.8 m ² , X / X ₀ < 0.99 for Q _b ≧ 200 ml / min. With higher blood flows there is an even better concentration balance.

Claims (14)

1. A method for determining parameters of hemodialysis during an extracorporeal blood treatment, in which the blood to be treated in an extracorporeal blood circuit flows through the blood chamber of a dialyzer divided by a semipermeable membrane into the blood chamber and a dialysis fluid chamber with a predetermined blood flow rate and dialysis fluid in a dialysis fluid path Flow through the dialysis fluid chamber of the dialyzer with a predetermined dialysis fluid flow rate, with the following method steps:
Setting the dialysis fluid flow rate Q _d to a value at which the concentration cdo of a substance in the dialysis fluid flowing out of the dialysis fluid chamber essentially assumes the concentration cbi of the substance in question in the blood flowing into the blood chamber, and
Measuring the concentration of the substance in the dialysis fluid flowing out of the dialysis fluid chamber as the parameter to be determined or as an intermediate value for the parameter to be determined. 2. The method according to claim 1, characterized in that the dialysis fluid rate Q _d at the end of the blood treatment is reduced from a value specified for the blood treatment to the value at which the concentration cdo of the substance in the dialysis fluid essentially the concentration cbi thereof in Blood. 3. The method according to claim 1, characterized in that the dialysis fluid rate Q _{d is set} at the beginning of the blood treatment to the value at which the concentration cdo of the substance in the dialysis fluid essentially assumes the concentration cbi of the same in the blood, and after measuring the Concentration of the substance in the dialysis fluid is increased to a value specified for the blood treatment. 4. The method according to claim 1, characterized in that the dialysis fluid rate Q _d during the blood treatment is reduced from a value specified for the blood treatment to the value at which the concentration cdo of the substance in the dialysis fluid essentially the concentration cbi thereof in the blood assumes, and after measuring the concentration of the substance in the dialysis fluid is increased back to the original value. 5. The method according to any one of claims 1 to 4, characterized in that the concentration cdo of the substance in the dialysis fluid after the setting of the equilibrium state is measured. 6. The method according to claim 5, characterized in that the predetermined period of time for equilibrium adjustment in the range of 1-5 min. 7. The method according to any one of claims 1 to 6, characterized in that the dialysis fluid flow rate Q _{d is set} at a blood flow rate Q _b of <300 ml / min to a value of <100 ml / min. 8. The method according to any one of claims 1 to 6, characterized in that the dialysis fluid flow rate Q _{d is set} at a blood flow rate Q _b of <150 ml / min to a value of <75 ml / min. 9. The method according to any one of claims 1 to 6, characterized in that the dialysis liquid flow rate Q _{d is set} to a value of 40-60 ml / min, preferably 50 ml / min. 10. The method according to any one of claims 1 to 6, characterized in that the dialysis liquid flow rate Q _{d is set} to a value of 10-30 ml / min, preferably 20 ml / min. 11. The method according to any one of claims 4 to 10, characterized in that after increasing the dialysis fluid rate Q _d to the original value at the predetermined blood flow rate Q _b and the predetermined dialysis fluid rate, the concentration cdi of the substance in the dialysis fluid flowing into the dialysis fluid chamber and the Concentration cdo of the substance can be measured in the dialysis fluid flowing out of the dialysis fluid chamber, and according to the equation
the dialysance D is determined as a parameter. 12. The method according to any one of claims 1 to 11, characterized in that the concentration measurement by a conductivity measurement he follows.   13. Blood treatment device with
a dialyzer ( 7 ) which has a blood chamber ( 4 ) which is connected to an extracorporeal blood circuit ( 2 ) and which is separated by a semipermeable membrane ( 5 ) from a dialysis fluid chamber ( 6 ) which is connected to a dialysis fluid path ( 1 ), wherein in the extracorporeal blood circuit a blood pump ( 9 ) and in the dialysis fluid path a dialysis fluid pump ( 13 ) is connected, and
a device for determining parameters of hemodialysis during extracorporeal blood treatment,
characterized in that
the device for determining parameters of hemodialysis has:
a measuring device ( 16 ) arranged in the dialysis fluid path ( 1 ) downstream of the dialysis fluid chamber ( 6 ) for measuring the concentration cdo of the substance in the dialysis fluid flowing out of the dialysis fluid chamber,
a control unit ( 21 ) which is designed such that the delivery rate of the dialysis fluid pump ( 13 ) can be reduced during the dialysis treatment from a predetermined value for a predetermined period of time to a value at which the concentration cdo of the substance measured with the measuring device ( 16 ) in the dialysis liquid flowing out of the dialysis liquid chamber essentially assumes the concentration cbi of the substance in question in the blood flowing into the blood chamber ( 4 ) and
an evaluation unit ( 19 ) receiving the output signal of the measuring device ( 16 ), which is controlled by the control unit ( 21 ) in such a way that the evaluation unit detects the concentration cdo of the substance under consideration as the parameter to be determined or as an intermediate value for the parameter to be determined before the control unit increases the delivery rate to the original value. 14. Blood treatment device according to claim 13, characterized in that the device for determining parameters of hemodialysis, a second in the dialysis fluid path ( 1 ) upstream of the dialysis fluid chamber ( 6 ) arranged measuring device ( 15 ) for measuring the concentration cdi of the substance flowing into the dialysis fluid chamber Dialysis fluid, the output signal of which receives the evaluation unit ( 19 ), the evaluation unit being controlled by the control unit ( 21 ) in such a way that the evaluation unit determines the concentration cdi of the substance in question in the dialysis fluid flowing into the dialysis fluid chamber ( 6 ) and the concentration cdo of the substance in the dialysis fluid flowing out of the dialysis fluid chamber after the predetermined time has elapsed, when the control unit has increased the delivery quantity to the original value and that the evaluation unit ( 19 ) is designed in such a way that ß they at the predetermined blood flow rate Q _b and the predetermined dialysis fluid rate Q _d and the measured concentration cdi of the substance in the dialysis fluid flowing into the dialysis fluid chamber and the concentration cdo of the substance in the dialysis fluid flowing out of the dialysis fluid chamber, the evaluation unit according to the equation
the dialysance D determines.