DEVICE FOR EXTRACORPORAL BLOOD TREATMENT AND METHOD FOR BALANCE CONTROLLING A DIALYSIS FLUID IN EXTRACORPORAL BLOOD TREATMENT

Description

Technical area

[0001] The present disclosure relates to a device for extracorporeal blood treatment, in particular for hemodialysis, and a method for balancing a dialysis fluid in extracorporeal blood treatment. Background of the invention

[0002] In extracorporeal blood treatment (e.g., hemodialysis), a patient's blood is passed through a dialyzer, through which dialysis fluid is simultaneously passed. In the dialyzer, the blood and dialysis fluid are brought into contact via a semipermeable membrane, allowing a substance exchange between the patient's blood and the dialysis fluid. The goal of this type of dialysis treatment is to detoxify the blood of a patient with kidney failure and also to remove excess water from the body.

[0003] The dialysis fluid consists of ultrapure water, a basic first component (sodium bicarbonate (NaHCO3)), and an acidic second component. The latter is typically composed of sodium chloride (NaCl), potassium chloride (KCl), magnesium chloride (MgCl2), calcium chloride (CaCl2), acetic acid (CH3COOH), and glucose. Dosing pumps and conductivity probes are typically used to produce or proportion the dialysis fluid. One probe measures the conductivity after the sodium bicarbonate has been added using a first dosing pump. Another probe records the conductivity of the entire dialysis fluid after the acidic component has also been added using a further dosing pump. With conductivity-controlled proportioning, the amounts added are regulated based on the measured conductivities.

[0004] In volumetric proportioning, the conductivity probes serve only as a control. The proportioning is done directly via the dosing pump flow rates, which is why the exact composition of the components used must be known.

[0005] The correct composition of the dialysis fluid is crucial for a patient's well-being and life expectancy. Sodium, in particular, plays a significant role, as it is the most abundant cation in both the dialysis fluid and blood plasma. In patients with renal insufficiency, the regulation of water and electrolyte balance via the kidneys is severely limited. For this reason, patients are advised to limit their water and sodium intake to a minimum. Sodium is primarily absorbed in the form of table salt (NaCl). Dialysis patients compensate for increased sodium intake by consuming an appropriate amount of fluid.

[0006] However, increased fluid intake results in the patient requiring more excess fluid to be removed by ultrafiltration during the next dialysis treatment. However, studies have shown that increased ultrafiltration rates are associated with higher mortality rates (Flythe, JE; Kimmel, SE, Brunelli, SM: "Rapid fluid removal during dialysis is associated with cardiovascular morbidity and mortality," Kidney International, 2010, 79, 250-257).

[0007] During dialysis, high ultrafiltration rates can also cause symptomatic drops in blood pressure (Saran, R.; Bragg-Gresham, J.; Levin, N.; Twardowski, Z.; Wizemann, V.; Saito, A.; Kimata, N., Gillespie, B.: "Longer treatment time and slower ultrafiltration in hemodialysis: Associations with reduced mortality in the DOPPS", Kidney International, 2006, 69, 1222-1228).

[0008] To treat or prevent the latter, the patient is given NaCl injections or is dialyzed against a dialysis fluid with a relatively high sodium concentration. However, both of these treatments lead to increased water intake. A vicious cycle begins.

[0009] However, too low a sodium concentration in the dialysis fluid is also detrimental to the patient. Within the patient, the intracellular and extracellular spaces are in osmotic equilibrium. A low sodium concentration in the dialysis fluid would lead to a decrease in extracellular osmolarity (osmotic concentration) due to diffusion processes within the dialyzer. However, since both spaces are in equilibrium, water would diffuse from the intracellular space into the extracellular space. As a result, the cells would shrink, which can lead to dizziness, headaches, nausea, cramps, and also drops in blood pressure.

[0010] For the reasons stated above, it is therefore desirable to individually adjust the sodium concentration in the dialysis fluid so that the patient's plasma sodium concentration changes as little as possible, and ideally not at all, during treatment. This type of dialysis is referred to as isonatremic dialysis. (de Paula, FM; Peixoto, AJ; Pinto, LV; Dorigo, D.; Patricio, PJM; Santos, SFF: "Clinical consequences of an individualized dialysate sodium prescription in hemodialysis patients", Kidney International, 2004, 66, 1232-1238; and Basile, C., Lomonte, C.: "It is Time to Individualize the Dialysate Sodium Prescription", Seminars in Dialysis, 2016, 29, 24-27).

[0011] The simplest approach would be to take a blood sample from the patient before each treatment and analyze it to adjust the sodium concentration in the dialysis fluid based on this. However, this procedure is very time-consuming and costly, as well as requiring extensive equipment. For this reason, many dialysis centers use a standardized dialysis fluid composition for dialysis, even though plasma sodium concentrations can vary from patient to patient (Mendoza, J.M.; Sun, S.; Chertow, GM; Moran, J.; Dass, S., Schiller, B.: "Dialysate Sodium and Sodium Gradient in Maintenance Hemodialysis: A Neglected Sodium Restriction Approach?", Nephrol Dial Transplant, 2011, 26, 1281-1287).

[0012] A dialysis device with controlled dialysis fluid composition is disclosed in EP 0 097 366 A2. In this dialysis device, the electrolyte content of the dialysis fluid is measured by two detectors before it enters and after it leaves the dialyzer, and the composition of the dialysis fluid is controlled based on the difference between the measured values ​​obtained.

[0013] A dialysis device for performing isonatremic dialysis and a method for sodium balancing in the dialysate circuit are known from WO 2010 / 112223 A1. Specifically, the conductivity of the dialysis fluid before and after the dialyzer is determined and compared in a dialysate circuit. Additional parameters required include the concentrations of bicarbonate and potassium in the patient's blood, which must be determined beforehand using an external measuring device.

[0014] DE 699 16 053 T2 describes a method for determining waste products in a dialysis fluid emerging from a dialyzer, in which the content of one or a combination of substances in the dialysis fluid is determined spectrophotometrically using a suitable measuring cell.

[0015] Kuhlmann, U.; Maierhofer, A.; Canaud, B.; Hoyer, J., Gross, M., "Zero Diffusive Sodium Balance in Hemodialysis Provided by an Algorithm-Based Electrolyte Balancing Controller: A Proof of Principle Clinical Study", Artificial Organs, Wiley, 2018, describe an algorithm for controlling the sodium concentration in the dialysis fluid of hemodialysis or hemodiafiltration based on conductivity measurements of the dialysis fluid before and after the dialyzer.

[0016] A device and method for performing isonatremic dialysis are also known from DE 10 2017 116 097 A1. To minimize changes to the plasma sodium concentration in the patient's blood during dialysis treatment, this concentration is determined or estimated in advance by switching the dialysis machine to bypass mode at the start of the dialysis treatment. During this mode, fresh dialysis fluid no longer flows through the dialyzer, but the patient's blood continues to flow through the dialyzer. After a certain period of time, the sodium concentration of the dialysis fluid in the dialyzer correlates with the patient's plasma sodium concentration and can be measured using a suitable measuring device, such as a conductivity cell.

[0017] However, it was shown that conductivity measurements of the dialysis fluid flowing out of the dialyzer, i.e., the used dialysis fluid, are influenced by substances that have migrated from the blood into the dialysis fluid. Thus, a simple correlation between the measured conductivity value and the sodium concentration is not possible.

[0018] Although sodium and the associated anions of the corresponding sodium salts, particularly chloride and bicarbonate, make the largest contribution to the conductivity of a dialysis fluid, the conductivity measurement is influenced by other substances, making a simple conversion between conductivity and sodium concentration impossible. For example, increased potassium concentrations can increase conductivity. However, there are also substances that are not conductive per se but can nevertheless impair conductivity by reducing the mobility of the conductive ions. This effect is caused by toxins and other substances that are excreted in the urine. Especially at the beginning of dialysis treatment, many of these substances pass through the semipermeable membrane in the dialyzer and thus reach the dialysate side.If conductivity is reduced due to these substances, the proportioning of fresh dialysis fluid will result in too low a conductivity and thus too low a sodium concentration, resulting in undesirable sodium removal from the patient during the dialysis treatment. Even a rigid correction of conductivity by adding a fixed amount would be disadvantageous, as the toxin load can vary from patient to patient and from treatment to treatment.

[0019] The invention is therefore based on the object of providing a device for extracorporeal blood treatment, in particular for hemodialysis, with which the composition of the dialysis fluid can be automatically adjusted to suit the individual patient, so that, among other things, zero-diffusive sodium balancing can be achieved during dialysis. A further object of the present invention is to provide a simple yet precise method for balancing a dialysis fluid during extracorporeal blood treatment, using only measured values ​​recorded on the dialysate side.

[0020] The objects are achieved by a device for extracorporeal blood treatment according to claim 1, as well as a method for balancing a dialysis fluid according to claim 9.

[0021] The device according to the invention for extracorporeal blood treatment, in particular for hemodialysis, comprises: a dialyzer that enables a mass exchange between a patient's blood and a dialysis fluid, a proportioning unit that provides fresh dialysis fluid and is connected to the dialyzer via a supply line for supplying fresh dialysis fluid, wherein the dialyzer is further connected to a discharge line for discharging used dialysis fluid from the dialyzer, a first measuring device provided in the supply line for detecting the conductivity of the fresh dialysis fluid, a second measuring device provided in the discharge line for detecting the conductivity of the used dialysis fluid, and a control unit connected to the proportioning unit and the measuring devices for data exchange, characterized in that a third measuring device is provided in the discharge line,for measuring or estimating a load of the used dialysis fluid with substances that are excreted in the urine, and the third measuring device is connected to the control unit for data exchange and the control unit is designed, on the basis of the conductivities continuously recorded by the first measuring device and the second measuring device during the blood treatment and the load with substances that are excreted in the urine recorded or estimated by the third measuring device, to continuously control or regulate the concentration of a substance in the fresh dialysis fluid provided by the proportioning unit during the blood treatment so that it is equal to the concentration of the substance in the used dialysis fluid, or is greater or less than the concentration of the substance in the used dialysis fluid by a predetermined value.

[0022] The dialyzer of the device according to the invention is preferably a commercially available dialyzer such as those used for extracorporeal blood treatment. It contains several hollow-fiber capillaries characterized by a semipermeable membrane. Inside the dialyzer, the patient's blood flows through the capillaries, and the capillaries are surrounded from the outside by the dialysis fluid, which absorbs toxins and other harmful substances from the patient's blood.

[0023] The device according to the invention further comprises a proportioning unit in which the fresh dialysis fluid used in dialysis is prepared. Principles generally known in the prior art are preferably used for this purpose. Examples include the variants explained above, such as conductivity-controlled proportioning, volumetric proportioning, or a combination of both. Typically, ultrapure water, a basic first component, and an acidic second component are mixed together.

[0024] To distinguish between the dialysis fluids, in the present application the dialysis fluid provided by the proportioning unit and supplied to the dialyzer is referred to as "fresh dialysis fluid" and the dialysis fluid leaving the dialyzer is referred to as "used dialysis fluid".

[0025] The device according to the invention also comprises a supply line in the form of a fluid connection between the proportioning unit and the dialyzer for supplying the fresh dialysis fluid to the dialyzer. The dialyzer is further connected to a discharge line that serves to drain used dialysis fluid from the dialyzer and directs it to a drain.

[0026] A first measuring device is provided in the supply line for detecting the conductivity of the fresh dialysis fluid. The first measuring device is preferably a temperature-compensated conductivity cell, so that a temperature-compensated conductivity of the fresh dialysis fluid can be detected.

[0027] A second measuring device is provided in the discharge line to measure the conductivity of the used dialysis fluid. The second measuring device is also preferably a temperature-compensating conductivity cell.

[0028] Furthermore, a third measuring device is provided in the discharge line, which is arranged either upstream or downstream of the second measuring device in the direction of flow. The third measuring device is intended to determine or estimate the load of the used dialysis fluid with substances that are excreted in the urine. Preferably, the third measuring device is an optical sensor that detects the absorption property of the used dialysis fluid, such as the extinction. Preferably, the absorption property is detected in the ultraviolet range between 235 nm and 400 nm. More preferably, the absorption property of light with a wavelength of 285±15 nm is detected. Alternatively, an enzymatic or other electrochemical sensor is also conceivable.

[0029] The terms "loading of the used dialysis fluid with urinary substances" and "loading with urinary substances" refer to the sum of all substances that pass from the patient's blood into the dialysis fluid during dialysis and are thus contained in the used dialysis fluid discharged from the dialyzer. These substances collectively alter properties of the used dialysis fluid, such as its absorption properties, so that the extent of the loading of the used dialysis fluid with urinary substances can at least be estimated using the third measuring device.

[0030] The device according to the invention further comprises a control unit connected to the proportioning unit and the three measuring devices for data exchange. The connection can be implemented, for example, via suitable electrical lines and / or wirelessly. This allows the values ​​recorded by the measuring devices to be transmitted to the control unit, the proportioning unit to be controlled, and the status of all components connected to the control unit to be recorded.

[0031] In addition, the control unit is designed such that, on the basis of the conductivities detected by the first measuring device and the second measuring device and the load with urinary substances detected or estimated by the third measuring device, it controls or regulates the concentration of a substance in the fresh dialysis fluid provided by the proportioning unit during the blood treatment in such a way that it is equal to the concentration of the substance in the used dialysis fluid, or is greater or less than the concentration of the substance in the used dialysis fluid by a predetermined value.

[0032] The device according to the invention is preferably used to carry out a sodium balance control, wherein according to a further preferred embodiment, a zero-diffusive sodium balance can also be realized with high accuracy during dialysis.

[0033] According to a preferred embodiment of the device according to the invention, it further comprises: a first valve provided in the supply line, a second valve provided in the discharge line, a bypass line connecting the supply line upstream of the first valve to the discharge line downstream of the second valve, bypassing the dialyzer, and a third valve provided in the bypass line, wherein the first measuring device is provided in the supply line upstream of the bypass line and the second measuring device and the third measuring device are provided in the discharge line downstream of the bypass line, and the valves are connected to the control unit for data exchange.

[0034] In this embodiment, a first valve is provided in the supply line and a second valve is provided in the discharge line. Furthermore, a bypass line is provided as a fluid connection between the supply line and the discharge line to bypass the dialyzer. The bypass line is connected to the supply line upstream of the first valve and to the discharge line downstream of the second valve. A third valve is also provided in the bypass line.

[0035] The three valves are connected to the control unit for data exchange, so that, for example, the valves can be controlled and their status recorded.

[0036] The bypass line is arranged such that the first measuring device is provided in the supply line upstream of the bypass line and the second measuring device and the third measuring device are provided in the discharge line downstream of the bypass line.

[0037] The first, second and third valves can each independently control and / or regulate the fluid flows in the supply line, the discharge line and the bypass line.

[0038] During blood treatment and thus also during the recording of conductivities by means of the first and second measuring devices and during the recording or estimation of the load of the used dialysis fluid with urinary substances by means of the third measuring device, the valves are controlled by the control unit in such a way that the first and second valves are opened and the third valve in the bypass line is closed.

[0039] As already stated above, in the device according to the invention the control unit is designed such that, on the basis of the conductivities detected by the first measuring device and the second measuring device and the load with urinary substances detected or estimated by the third measuring device, the concentration of a substance in the fresh dialysis fluid provided by the proportioning unit can be controlled or regulated such that it is equal to the concentration of the substance in the used dialysis fluid, or is greater or less than the concentration of the substance in the used dialysis fluid by a predetermined value.

[0040] Since, as explained above, the conductivity measurement in the used dialysis fluid can be influenced by various substances contained therein, such as toxins, in such a way that an incorrect value for the concentration of the substance to be determined is obtained, the device according to the invention uses the third measuring device to measure or estimate the load of the used dialysis fluid with urinary substances. When calculating the concentration of the substance in the used dialysis fluid, the control unit takes the degree of load with urinary substances into account, thus enabling a more precise concentration determination. Based on this more precise concentration value, the proportioning unit is able to provide fresh dialysis fluid with improved accuracy, which, for example, contains the same concentration of the substance as the used dialysis fluid.This can ensure, for example, more precise isonatremic dialysis. Alternatively, if desired, a predefined concentration difference of the substance can be set between fresh and used dialysis fluid, allowing the concentration of this substance in the patient's blood to be adjusted specifically and, above all, with improved accuracy.

[0041] Thus, the device according to the invention enables improved balance control of the dialysis fluid during dialysis, allowing for more precise determination of whether a substance dissolved in the dialysis fluid, or how much of it, passes into the patient's blood as it passes through the dialyzer. It is also possible to determine more precisely whether a substance dissolved in the patient's blood, or how much of it, passes into the dialysis fluid as it passes through the dialyzer. This ensures a more gentle dialysis treatment, as high ultrafiltration rates can be avoided in the medium and long term, and allows for more gentle changes to the patient's water and electrolyte balance.

[0042] The advantage of the device and method according to the invention lies, among other things, in the fact that the concentration of a substance in the fresh dialysis fluid can be controlled or regulated during dialysis, i.e., continuously and without interruption. For this purpose, measured values ​​are continuously recorded during dialysis using the three measuring devices and transmitted to the control unit. The control unit continuously determines the composition of the fresh dialysis fluid based on the obtained measured values.

[0043] Furthermore, no additional process steps are required to determine the concentration of the substance in the patient's blood in order to adjust the proportioning of the fresh dialysis fluid accordingly. Thus, patient-specific dialysis is possible even without collecting and analyzing the patient's blood. The bypass mode required in DE 10 2017 116 097 A1 for determining or estimating the sodium concentration in the patient's blood can also be eliminated with the device according to the invention. Furthermore, it is not necessary to interrupt dialysis if the concentration of the substance needs to be determined again.

[0044] According to a further preferred embodiment, the control unit is designed such that, based on the measured or estimated load of the used dialysis fluid with urinary substances and the detected conductivity of the used dialysis fluid, a corrected conductivity of the used dialysis fluid can be calculated. Based on the corrected conductivity of the used dialysis fluid, the composition of the fresh dialysis fluid can be determined such that the conductivity of the fresh dialysis fluid is equal to the corrected conductivity of the used dialysis fluid. Thus, with the device according to the invention, for example, isonatremic dialysis can be performed with improved accuracy.

[0045] The correction of the measured conductivity of the spent dialysis fluid can be carried out, for example, by mathematically combining the conductivity C DO measured by the second measuring device and the absorbance A measured by the third measuring device to obtain the corrected conductivity C DO,corr: C DO , corr = ƒ C DO , A

[0046] In the simplest case, a linear equation is suitable. However, higher-degree polynomials or an equation determined using an artificial neural network are also conceivable. An alternative option is the use of a lookup table.

[0047] For example, if a zero-diffusive sodium-balanced dialysis is to be performed, the dialysis fluid is mixed by the proportioning unit so that its conductivity C DI corresponds to the corrected conductivity of the used dialysis fluid C DO,corr: C DI = C DO , corr

[0048] If both conductivities are equal, no diffusive exchange of sodium ions occurs between the blood and dialysate sides in the dialyzer. The conductivity C DI or C DO,corr thus also corresponds to the plasma water conductivity C BI , which is proportional to the plasma sodium concentration in the patient's blood. Therefore, after initially determining the plasma sodium concentration, it is also possible to adjust the dialysis fluid so that a defined amount of sodium can be removed from or administered to the patient. The sodium flow Δ J is calculated as follows: Δ J = k ⋅ Q D ⋅ C DI − C DO , corr + k ⋅ Q UF ⋅ C DO , corr with the dialysis fluid flow Q D , the ultrafiltration rate Q UF and a factor k, with which the conductivity is converted into a sodium concentration, although more complex conversions can also be used here.

[0049] Furthermore, the present invention makes it possible to determine the absolute amount of sodium removed. This can be done either using a previous equation taking into account the duration of treatment or: Given a known ultrafiltration volume and the plasma sodium concentration during the course of the dialysis treatment, the amount of sodium removed corresponds to the product of the ultrafiltration volume and the plasma sodium concentration.

[0050] If the first and second valves of the device according to the invention are closed and the third valve is opened, the device is in bypass mode. The dialysis fluid then flows unaffected by the dialyzer through the third valve, past the second and third measuring devices, and into the drain. In this state, the same fluid flows through the first and second measuring devices, so that the state of the bypass can be used to compare the functioning of both sensors and to zero any differences by means of a calibration. Furthermore, the state of the bypass can be used to calibrate the third measuring device, since fresh dialysis fluid is required for calibration.

[0051] The device according to the invention can also comprise a balancing unit designed to determine how much water is removed from the patient's blood during blood treatment. The balancing unit can ensure, for example, by comparing and, if necessary, adjusting the flow rate of the dialysis fluid, that exactly the prescribed amount of excess water is removed from the patient.

[0052] In the unclaimed method for extracorporeal blood treatment, in particular for hemodialysis, by means of a dialyzer which enables a substance exchange between a patient's blood and a dialysis fluid, the conductivities of a fresh dialysis fluid supplied to the dialyzer and of a used dialysis fluid discharged from the dialyzer are recorded during the blood treatment, and a load of the used dialysis fluid with substances which are excreted in the urine is measured or estimated.Furthermore, a control unit determines the composition of the fresh dialysis fluid based on the conductivity data and the load with urinary substances such that the concentration of a substance in the fresh dialysis fluid is equal to the concentration of the substance in the used dialysis fluid, or is greater or less than the concentration of the substance in the used dialysis fluid by a predetermined value, and a proportioning unit provides a fresh dialysis fluid with the composition determined by the control unit for supply to the dialyzer.

[0053] If, according to a preferred embodiment of the method, the composition of the fresh dialysis fluid is to be determined such that the concentration of the substance in the fresh dialysis fluid is equal to the concentration of the substance in the used dialysis fluid, such as in isonatremic dialysis, the control unit calculates a corrected conductivity of the used dialysis fluid based on the measured or estimated load of the used dialysis fluid with urinary substances and the recorded conductivity of the used dialysis fluid and determines the composition of the fresh dialysis fluid such that the conductivity of the fresh dialysis fluid is equal to the corrected conductivity of the used dialysis fluid.

[0054] In the extracorporeal blood treatment method, the concentration of the substance in the dialysis fluid is preferably a sodium concentration. This allows for more accurate sodium balancing, preferably zero-diffusive sodium balancing, during dialysis.

[0055] The method for extracorporeal blood treatment achieves the same advantages as those mentioned above in the explanation of the device for extracorporeal blood treatment according to the invention.

[0056] According to the present invention, a method for balancing or monitoring a dialysis fluid during extracorporeal blood treatment, in particular hemodialysis, in which the dialysis fluid flows through a dialyzer is further provided. In this method, the conductivities of a fresh dialysis fluid supplied to the dialyzer and a used dialysis fluid discharged from the dialyzer are continuously recorded during the blood treatment, and the concentration of urinary substances in the used dialysis fluid is measured or estimated.In addition, based on the data of the conductivities and the load with substances excreted in the urine, the composition of the fresh dialysis fluid is continuously determined by means of a control unit during the blood treatment in such a way that the concentration of a substance in the fresh dialysis fluid is equal to the concentration of the substance in the used dialysis fluid, or is greater or less than the concentration of the substance in the used dialysis fluid by a predetermined value, and based on the composition determined by the control unit, a proportioning unit provides a fresh dialysis fluid with this composition for feeding to the dialyzer.

[0057] If the composition of the fresh dialysis fluid is determined for the dialysis to be carried out such that the concentration of the substance in the fresh dialysis fluid is equal to the concentration of the substance in the used dialysis fluid, as for example in isonatremic dialysis, according to a preferred embodiment of the method for balance control of a dialysis fluid, the control unit calculates a corrected conductivity of the used dialysis fluid based on the measured or estimated load of the used dialysis fluid with urinary substances and the recorded conductivity of the used dialysis fluid and determines the composition of the fresh dialysis fluid such that the conductivity of the fresh dialysis fluid is equal to the corrected conductivity of the used dialysis fluid.

[0058] In the method according to the invention for balancing or monitoring a dialysis fluid during extracorporeal blood treatment, the concentration of the substance in the dialysis fluid is preferably a sodium concentration. Thus, a more precise sodium balance, preferably a zero-diffusive sodium balance, can be achieved during dialysis.

[0059] The method according to the invention for balancing or monitoring a dialysis fluid in an extracorporeal blood treatment achieves the same advantages as those mentioned above in the explanation of the device according to the invention for extracorporeal blood treatment.

[0060] The method for extracorporeal blood treatment explained above as well as the method for balancing a dialysis fluid in an extracorporeal blood treatment is preferably carried out using the device for extracorporeal blood treatment according to the invention.

[0061] According to a preferred embodiment, both methods can also include the implementation of a bypass mode, in which the first and second valves are closed and the third valve is opened. In this state, the same fluid flows through the first and second measuring devices, so that the state of the bypass can be used to compare the functionality of both sensors and to zero any differences through calibration. Furthermore, the state of the bypass can be used to calibrate the third measuring device, since fresh dialysis fluid is required for calibration.

[0062] According to preferred embodiments, both in the device according to the invention and the method according to the invention, data from the measuring devices and / or characteristics of the dialysis fluid mixed by the proportioning unit can be displayed on a screen or a data management system in order to make the processes transparent for the medical personnel and / or the user. This particularly applies to conductivities, concentrations, extinctions, pH values, temperatures and / or pressures. According to a further embodiment, it can be provided that certain data is only made available as a recommendation. Thus, based on this recommended data, the medical personnel can decide for themselves whether or not to follow the recommendation, i.e., hypo-, iso-, or hypernatremic dialysis does not take place automatically according to this embodiment.

[0063] According to preferred embodiments of the device or method, collected data can be stored on a patient card, in the dialysis machine, and / or in a data management system. Studies conducted in recent years have shown that a patient's plasma sodium concentration is relatively constant compared to other parameters (setpoint theory): Peixoto, A.J.; Gowda, N.; Parikh, CR, Santos, SFF: "Long-Term Stability of Serum Sodium in Hemodialysis Patients", Blood Purif, 2010, 29, 264-267, Keen, ML, Gotch, FA: "The association of the sodium setpoint to interdialytic weight gain and blood pressure in hemodialysis patients", The International Journal of Artificial Organs, 2007, 30, 971-979, and Hecking, M.; Kainz, A.; Hörl, WH; Herkner, H., Sunder-Plassmann, G.: "Sodium Setpoint and Sodium Gradient: Influence on Plasma Sodium Change and Weight Gain", Am J Nephrol, 2011, 33, 39-48 .

[0064] Thus, the stored data, in particular the conductivities C DI and the corrected conductivity C DO.corr as well as the resulting difference and the extinction A can be evaluated using descriptive statistics (e.g. mean, standard deviation, temporal correlations) in order to detect possible changes that could indicate a general change in the state of health. Short description of the characters

[0065] Fig. 1 is a schematic representation of an embodiment of the device for extracorporeal blood treatment according to the invention. Description of the embodiments

[0066] A schematic implementation of the device according to the invention is shown in FIG. 1Blood is withdrawn from a dialysis patient 1 via the arterial tubing system 2 using a pumping device 3. The blood enters a dialyzer 4, where it is freed of toxins and excess water by diffusion and / or ultrafiltration. It is then returned to the patient via the venous tubing system 5. Withdrawal and return via a shared cannula is also conceivable.

[0067] Dialyzer 4 is a commercially available dialyzer as described above, such as those used for extracorporeal blood treatment. The dialysis fluid is prepared in the proportioning unit 6. The first measuring device 12, located in the supply line 14, measures a temperature-compensated conductivity of the fresh dialysis fluid.

[0068] During main flow, i.e., when the dialysis fluid flows through the dialyzer 4, the third valve 10, which is provided in a bypass line 16 connecting the supply line 14 upstream of the first valve 7 with the discharge line 15 downstream of the second valve 9, bypassing the dialyzer 4, is closed. The fresh dialysis fluid thus flows through the supply line 14 with the first measuring device 12 and through the first valve 7 into the dialyzer 4, where it absorbs the contaminants from the blood and, if necessary, releases other substances, in particular bicarbonate and / or other electrolytes or non-electrolytes, into the blood. After passing through the dialyzer 4, the used dialysis fluid passes the second valve 9 as well as the second measuring device 8 and the third measuring device 13 in the discharge line 15. The measuring device 8 is the same measuring device as the first measuring device 12.The third measuring device 13 is intended to determine or estimate the concentration of urinary substances in the used dialysis fluid. In the present embodiment, it is an optical sensor that measures the absorption properties of the used dialysis fluid in the ultraviolet range between 235 nm and 400 nm. Preferably, the absorption properties of light with a wavelength of 285 ± 15 nm are measured. Alternatively, an enzymatic or other electrochemical sensor is also conceivable.

[0069] The control unit 11 records the measured values ​​and states of the measuring devices 8, 12 and 13, the proportioning unit 6 and the valves 7, 9 and 10. Furthermore, it issues commands to the proportioning unit 6 and to the valves 7, 9 and 10.

Claims

1. A device for extracorporeal blood treatment, in particular for hemodialysis, comprising: a dialyzer (4) rendering possible an exchange of substances between a patient's blood and a dialysis fluid, a proportioning unit (6), which provides fresh dialysis fluid and is connected to the dialyzer (4) via a supply line (14) for supplying fresh dialysis fluid, the dialyzer (4) further being connected to a discharge line (15) for discharging used dialysis fluid from the dialyzer (4), a first measuring apparatus (12) provided in the supply line (14) for detecting the conductivity of the fresh dialysis fluid, a second measuring apparatus (8), provided in the discharge line (15), for detecting the conductivity of the used dialysis fluid, a control unit (11) connected to the proportioning unit (6) and the measuring apparatuses (8, 12) for data exchange, and wherein a third measuring apparatus (13) is provided in the discharge line (15) for measuring or estimating a loading of the used dialysis fluid with urophanic substances, and the third measuring apparatus (13) is connected to the control unit (11) for data exchange, characterized in that the control unit (11) is designed to continuously control in open-loop or closed-loop fashion, on the basis of the conductivities detected continuously during blood treatment by the first measuring apparatus (12) and the second measuring apparatus (8), and the loading with urophanic substances detected or estimated by the third measuring apparatus (13), the concentration of a substance in the fresh dialysis fluid provided by the proportioning unit (6) during the blood treatment in such a way that it is equal to the concentration of the substance in the used dialysis fluid or is greater or less than the concentration of the substance in the used dialysis fluid by a predetermined value.

2. The device according to claim 1, further comprising: a first valve (7) provided in the supply line (14), a second valve (9) provided in the discharge line (15), a bypass line (16) connecting the supply line (14) upstream of the first valve (7) to the discharge line (15) downstream of the second valve (9), bypassing the dialyzer (4), and a third valve (10) provided in the bypass line (16), wherein the first measuring apparatus (12) is provided in the supply line (14) upstream of the bypass line (16), and the second measuring apparatus (8) and the third measuring apparatus (13) are provided in the discharge line (15) downstream of the bypass line (16), and the valves (7, 9, 10) are connected to the control unit (11) for data exchange.

3. The device according to claim 2, wherein the control unit (11) is designed to drive the valves during the blood treatment and during the detection of the conductivities by means of the first and second measuring apparatuses (12, 8), and during the detection or estimation of the loading of the used dialysis fluid with urophanic substances by means of the third measuring apparatus (13) in such a way that the first and second valves (7, 9) are open and the third valve (10) in the bypass line (16) is closed.

4. The device according to any of the preceding claims, wherein the control unit (11) is designed to calculate a corrected conductivity of the used dialysis fluid on the basis of the measured or estimated loading of the used dialysis fluid with urophanic substances and the detected conductivity of the used dialysis fluid, and determine the composition of the fresh dialysis fluid on the basis of the corrected conductivity of the used dialysis fluid so that the conductivity of the fresh dialysis fluid is equal to the corrected conductivity of the used dialysis fluid.

5. The device according to any of the preceding claims, wherein the first measuring apparatus (12) and the second measuring apparatus (8) detect temperature-compensated conductivities.

6. The device according to any of the preceding claims, wherein the third measuring apparatus (13) is an optical sensor, an enzymatic sensor or another electrochemical sensor.

7. The device according to claim 6, wherein the third measuring apparatus (13) is an optical sensor that detects light absorption in the wavelength range from 235 nm to 400 nm.

8. The device according to any of the preceding claims, wherein the device further comprises a balancing unit designed to determine how much water is removed from the patient's blood during blood treatment.

9. A method for balance control or monitoring of a dialysis fluid in an extracorporeal blood treatment, in particular a hemodialysis, in which the dialysis fluid flows through a dialyzer (4), wherein, during the blood treatment, the conductivities of a fresh dialysis fluid supplied to the dialyzer (4) and of a used dialysis fluid discharged from the dialyzer (4) are detected continuously, and a loading of the used dialysis fluid with urophanic substances is measured or estimated, on the basis of the data of the conductivities and the loading with urophanic substances by means of a control unit (11), the composition of the fresh dialysis fluid during blood treatment is determined continuously in such a way that the concentration of a substance in the fresh dialysis fluid is equal to the concentration of the substance in the used dialysis fluid, or is greater or less than the concentration of the substance in the used dialysis fluid by a predetermined value, and on the basis of the composition determined by the control unit (11), a proportioning unit (6) provides a fresh dialysis fluid with this composition for supply to the dialyzer (4).

10. The method according to claim 9, wherein, when the composition of the fresh dialysis fluid is determined such that the concentration of the substance in the fresh dialysis fluid is equal to the concentration of the substance in the used dialysis fluid, the control unit (11) calculates on the basis of the measured or estimated loading of the used dialysis fluid with urophanic substances and the detected conductivity of the used dialysis fluid, a corrected conductivity of the used dialysis fluid and determines the composition of the fresh dialysis fluid in such a way that the conductivity of the fresh dialysis fluid is equal to the corrected conductivity of the used dialysis fluid.

11. The method according to claim 9 or 10, wherein the concentration of the substance in the dialysis fluid is a sodium concentration.

12. The method according to any of claims 9 to 11, wherein the method is carried out using the device according to any of claims 1 to 7.