METHOD AND DEVICE FOR EXTRACORPOREAL BLOOD TREATMENT

Abstract

A method for extracorporeal blood treatment using a medical device including at least a dialyzer device, with the following steps: start of blood treatment by means of hemodialysis on the basis of default values for the hemodialysis; determination of current values or ratios of at least one blood flow, an ultrafiltration quantity, a substitution quantity or a type of substitution; recording of a therapy progress on the basis of an output signal of a sensor means; determination of a time of formation of a secondary membrane on the dialyzer by determination of a cross rate in the dialyzer device; change from the hemodialysis to a hemodiafiltration with post-dilution after a predetermined period of time has elapsed; and regulation of the substitution quantity during hemodiafiltration with post-dilution. Corresponding tools for carrying out the method are arranged in a device for extracorporeal blood treatment.

Claims

1.-20. (canceled)

21. A device for performing hemodialysis or hemodiafiltration with post-dilution, the device comprising: a dialyzer; a user interface to be at least one of operated or read by a user for starting a blood treatment by means of hemodialysis on the basis of default values for the hemodialysis; at least one current determining unit configured to at least one of record or compute current values and/or ratios for at least one of blood flow, an ultrafiltration quantity, a substitution quantity, or a type of substitution; a sensor for recording a therapy progress; a first determination means configured to determine an ultrafiltration rate in the dialyzer; a second determination means configured to determining a time of formation of a secondary membrane in the dialyzer using the determined ultrafiltration rate; a switch for changing from hemodialysis to hemodiafiltration with post-dilution after a predetermined period of time has elapsed; and a regulator that regulates substitution quantity during hemodiafiltration with post-dilution.

22. The device of claim 21, wherein the predetermined period of time is a period of time after a first recording of a blood flow on the sensor, and the change from hemodialysis to hemodiafiltration with post-dilution occurs automatically, if at the predetermined time a predetermined cross rate is determined, wherein at the predetermined cross rate a predetermined treatment blood flow is assumed as having been achieved and the secondary membrane is assumed as having a predetermined state of formation.

23. The device of claim 22, wherein the predetermined period of time is initially 3 to 5 minutes, and the device is configured after a start of treatment to adjust an actual period of time on the basis of default values and currently calculated values, and to start hemodiafiltration with post-dilution in an automatically delayed manner.

24. The device of claim 22, wherein the sensor comprises a blood flow sensor arranged on an air detector and wherein the first recording of the blood flow occurs by the blood sensor and the assumed state of formation of the secondary membrane is derived from the determined cross rate.

25. The device of claim 21, wherein the regulator regulates the substitution quantity in accordance with a default of an application and wherein the substitution quantity does not exceed a predetermined maximum percentage portion of the blood flow.

26. The device of claim 21, wherein the regulator regulates the substitution quantity to a constant value or quantity.

27. The device of claim 25, wherein the predetermined maximum percentage portion is 25 to 30% of the blood flow.

28. The device of claim 25, wherein the regulator automatically reduces the substitution quantity, if the blood flow falls below a predetermined minimum quantity, and issues a message for a user informing on the reduced substitution quantity.

29. The device of claim 21, wherein the regulator automatically limits the substitution quantity, if a predetermined cross rate is reached, and issues a message for a user informing on the limitation of the substitution quantity.

30. The device of claim 21, wherein all necessary parameters can be predetermined by the user and the device is configured to reduce maximum quantities automatically.

31. A method for extracorporeal blood treatment using a medical device including a dialyzer, the method comprising: starting blood treatment by means of hemodialysis using default values for the hemodialysis; determining at least one of current values or ratios for at least one of blood flow, an ultrafiltration quantity, a substitution quantity and/or a type of substitution; recording a therapy progress using an output signal of a sensor; determining an ultrafiltration rate in the dialyzer; determining a time of formation of a secondary membrane in the dialyzer using the determined ultrafiltration rate; changing from the hemodialysis to a hemodiafiltration with post-dilution after a predetermined period of time has elapsed; and regulating substitution quantity during hemodiafiltration with post-dilution.

32. The method of claim 31, wherein the predetermined period of time is a period of time after a first recording of a blood flow by the sensor, and the change from the hemodialysis to the hemodiafiltration with post-dilution occurs automatically, if at the predetermined time a predetermined cross rate is determined, wherein at the predetermined cross rate a predetermined treatment blood flow is assumed as having been achieved and the secondary membrane is assumed as having a predetermined state of formation.

33. The method of claim 32, wherein the predetermined period of time is initially approximately 3 to 5 minutes and the method further comprises, after start of treatment, adjusting an actual period of time on the basis of default values and currently calculated values, and starting the hemodiafiltration with post-dilution in an automatically delayed manner.

34. The method of claim 32, wherein the first recording of the blood flow is by a blood sensor arranged on an air detector and the assumed state of formation of the secondary membrane is derived from the determined cross rate.

35. The method of claim 31, wherein the substitution quantity is regulated in accordance with a default of an application wherein the substitution quantity does not exceed a predetermined maximum percentage portion of the blood flow.

36. The method of claim 31, wherein the substitution quantity is regulated to a constant value or quantity.

37. The method of claim 35, wherein the predetermined maximum percentage portion is 25 to 30% of the blood flow.

38. The method of claim 35, wherein the substitution quantity is reduced automatically, if the blood flow falls below a predetermined minimum quantity, and the method further comprises issuing a message to a user informing of the reduced substitution quantity.

39. The method of claim 31, wherein the substitution quantity is limited automatically, if a predetermined cross rate is reached, and the method further comprises issuing a message to a user informing on the limitation of the substitution quantity.

40. The method of claim 31, wherein all necessary parameters are predetermined by the user and the medical device is configured to reduce maximum quantities automatically.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The invention is best understood from the following detailed description when read in connection with the accompanying drawings. Included in the drawings are the following figures:

[0028] FIG. 1 is a schematic view of a blood circulation with post-dilution and/or pre-dilution during online hemodiafiltration (online HDF) arranged in an embodiment of the method and the device for extracorporeal blood treatment;

[0029] FIG. 2 is a schematic view for explanation of the formation of a secondary membrane in a dialyzer device;

[0030] FIG. 3 is a schematic view for illustration of flow ratios during online HDF inside a dialyzer; and

[0031] FIG. 4 is a schematically and highly simplified flow chart of the method for extracorporeal blood treatment according to an embodiment

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] In the following description of the figures the same elements and/or components or elements and/or components having the same effect can be designated in the same way or with the same reference numerals and can be expediently described non-redundantly. Where a subsequent embodiment corresponds functionally at least to a previous embodiment, i.e. corresponding functions, assemblies and/or process sequences or operating procedures are equally covered, expediently only differences are treated.

[0033] FIG. 1 shows a schematic view of a blood circulation with post-dilution and/or pre-dilution during online hemodiafiltration (online HDF) used and/or arranged in an embodiment of the method and the device for extracorporeal blood treatment.

[0034] A device for extracorporeal blood treatment such as, for example, a dialyzer machine for cleaning the blood of a patient, if, for example, his or her renal function is impaired or ceased, comprises a dialyzer, through which on the one hand the patient's blood to be cleaned flows and through which on the other hand dialysis fluid or dialysis solution flows, preferably according to the countercurrent principle, wherein certain dissolved substances (for example, urea) from the blood pass into the dialysis fluid.

[0035] Moreover, the device for extracorporeal blood treatment has an arterial blood circulation in which a blood pump is arranged, a venous blood circulation, a dialysis fluid supply line supplying fresh dialysis fluid to the dialyzer, a dialysis fluid discharge line, which discharges and/or purges used dialysis fluid from the dialyzer, a substitution line and a substitution pump which supplies substituate (electrolyte solution) flowing in the substitution line to a dilution point located upstream (pre-dilution) or downstream (post-dilution) of the dialyzer in the arterial and/or venous blood circulation. Furthermore, a control unit measures the concentration of blood, for example, in a predetermined dilution channel section, and controls the substituate quantity supplied by the substitution pump for preventing excessive blood thickening and for continuous compensation of ultrafiltration exceeding the necessary elimination of liquid and thus avoiding volume losses, on the basis of the measured or an evaluated blood concentration. A device for extracorporeal blood treatment of the above mentioned type can be designed for preparing, supplying and substituting substituate according to the principle of online hemodiafiltration (online HDF) or online hemofiltration. In the case of an online HDF method, the substitution fluid and/or the substituate is extracted from the dialysis fluid and infused either upstream or downstream of the filter.

[0036] System, structure, components and functioning of the above mentioned device for extracorporeal blood treatment are in itself fundamentally known, and are therefore included herein and not described further.

[0037] The blood circulation with post-dilution and/or pre-dilution shown in FIG. 1 is part of an device for extracorporeal blood treatment as described above. From an online, i.e. substituate originating during a current therapy from a substituate source 2 in or on the device for extracorporeal blood treatment is transported from an online substituate pump 4 through a dilution line to an air detector means 6. A venous blood line coming from a dialyzer 8, a high flux dialyzer in the present embodiment, opens out into the air detector means 6. Moreover, a venous pressure transducer 10 is connected with the air detector means 6. An arterial blood line coming from a patient opens out into the dialyzer 8, in the course of which blood line are arranged an arterial pressure transducer 12, an arterial blood pump 14, another pressure transducer 16 on an arterial expansion chamber upstream of the dialyzer 8 and a point of introduction for a pre-dilution. Moreover, arterially also a heparin addition (anticoagulant) controlled by the device for preventing blood coagulation can be provided.

[0038] FIG. 2 shows a schematic view for explanation of the formation of a secondary membrane in a dialyzer device. A secondary membrane occurs as a diffusion layer 22 on the hollow membranes 20 in the dialyzer 8 during a current blood treatment by attaching, for example, cellular blood components and proteins and/or plasma proteins to the dialyzer membrane. Formation of a secondary membrane is coupled with the transmembrane pressure TMP. The transmembrane pressure TMP in the dialyzer 8 is a hydrostatic pressure gradient between the blood side and dialysis fluid side which is used by the ultrafiltration.

[0039] Function and integrity of the dialyzer 8 can be monitored on the machine side by measurement of the dynamic inlet and outlet pressures. For example, by assuming a linear pressure drop a mean pressure for the blood side and a mean pressure for the dialysis fluid side can be determined from the inlet and outlet pressures the difference of which results in a mean transmembrane pressure TMP. Said mean transmembrane pressure TMP can then be used for monitoring as to whether the filter is blocked by deposits and formation of a secondary membrane.

[0040] As is shown on the right side of FIG. 2, the transmembrane pressure TMP rises at first at the beginning of an HDF dialysis and during formation of a secondary membrane and then reaches at least approximately a plateau.

[0041] Although the transmembrane pressure TMP rising at the beginning is accompanied by a blocking or clogging of the pores of the dialyzer, for example, by accumulating proteins and this virtually corresponds to a decrease of the filter surface, whereby the efficiency of the entire therapy may be decreased, also advantages result due to the formation of the secondary membrane and/or diffusion layer, such as, for example, a suppression of complement activation, a decrease of thrombogenicity, a suppression of thrombocyte activation and a decrease of protein absorption.

[0042] In the present embodiment it is assumed that a sufficient secondary membrane has formed after approximately 3 to 5 minutes after start of therapy at low blood flow and minimum ultrafiltration.

[0043] In an example, a hematocrit level of approx. 35% at the dialyzer inlet and a hematocrit level of approx. 50% at the dialyzer outlet can occur at the beginning of the HDF dialysis at a dialysis fluid flow of approx. 30% of the blood flow and post-dilution. Due to formation of the secondary membrane and/or along with the increase of the transmembrane pressure TMP, these amounts can change, for example, when assuming a decrease of the blood volume by 15% to approx. 41% on the dialyzer inlet and approx. 59% on the dialyzer outlet. The hematocrit increase is inversely proportional to the change of blood volume, i.e. the decrease of the relative blood volume is characterized by the increase of the hematocrit level. By measuring the hematocrit level a relative change of the (relative) blood volume can be detected.

[0044] FIG. 3 shows a schematic view for illustration of flow ratios during online HDF inside a dialyzer, for example, of the dialyzer 8 according to FIG. 1. Moreover, in FIG. 3 with a DF filter 32 and/or dialysis fluid filter as a first filter stage and with a HDF filter 34 as a second filter stage in the dialysis fluid flow are designated which are likewise arranged in the device for extracorporeal blood treatment. Moreover, Q.sub.D designates a dialysis fluid flow, Q.sub.B designates a blood flow, Q.sub.UF designates an ultrafiltration flow and Q.sub.S designates a substituate flow for the pre-dilution or post-dilution.

[0045] As is shown in FIG. 3, the entire original dialysis fluid flow, in the present embodiment for example Q.sub.D=600 ml/min, is directed through the DF filter 32. Downstream of the DF filter 32 part of the dialysate flow Q.sub.D, for example an amount of 520 ml/min, is directed through the dialyzer 8. The remaining part of the dialysis fluid flow Q.sub.D is in addition directed through the HDF filter 34 and downstream of said filter provided as a substituate flow Q.sub.S=80 ml/min for pre-dilution or post-dilution.

[0046] Countercurrently to the dialysis fluid flow through the dialyzer 8, the blood flow Q.sub.B flows through the dialyzer which blood flow in the present embodiment is, for example, at the dialyzer inlet Q.sub.B=300 ml/min and at the dialyzer outlet still Q.sub.B=210 ml/min. From this a cross rate or cross rate of ultrafiltration of Q.sub.UF=90 ml/min or approx. 27% is calculated in the present embodiment. In other words, Q.sub.UF=90 ml/min of fluid pass through the membrane of the dialyzer 8 (convective transport). As is indicated on the right side of the HDF filter, the substituate flow Q.sub.S=80 ml/min is added post-dilutively to blood flow Q.sub.B=210 ml/min on the dialyzer outlet so that a venously flowing off blood flow Q.sub.B=290 ml/min results.

[0047] Since in the case of post-dilution the ratio of blood to total ultrafiltration should be 25 to 30% maximum, and at the same time the total substitution volume should be approximately one third of the body weight of the patient, in one example the following calculated values result for post-dilution for a patient with a body weight of 81 kgs: [0048] body weight: 81 kgs [0049] weight loss: 3 kgs [0050] treatment time: 5 hours [0051] 30% of 81 kgs=27 l substitution volume [0052] 27 l substitution volume+3 l weight loss=30 l net ultrafiltration quantity 30 l in 5 hours treatment time yields an ultrafiltration rate of 6 l/h or 100 ml/min. The entire ultrafiltration quantity is thus 3 l, and the blood flow Q.sub.B should be at least approx. 350 ml/min.

[0053] In accordance with the above description a delayed hemodiafiltration treatment start in connection with a regulation to maximum cross rate of ultrafiltration within the scope of a hemodiafiltration treatment, preferable an online hemodiafiltration treatment, is carried out in the method and the device for extracorporeal blood treatment of the present embodiment.

[0054] For this purpose, prior to treatment and as indicated above by way of an example on the basis of practical scales, at first applicable ratios from blood flow, ultrafiltration quantity, substitution quantity and type of substitution are determined or calculated.

[0055] FIG. 4 shows a schematically highly simplified flow chart of the method. After determination of the necessary treatment or therapy parameters and selection or determination of the form of therapy, in a step S01 therapy is started by a user, for example, a nurse in a dialysis station, by means of hemodialysis on the basis of the default values for the hemodialysis. Subsequently, the procedure advances to a step S02.

[0056] In step S02 current values and/or parameters and/or ratios at least of blood flow, ultrafiltration quantity, substitution quantity and/or type of substitution are determined or adjusted. The values determined can be modified via the user interface of the device for extracorporeal blood treatment. The user in this stage tries to achieve the predetermined blood flow as fast as possible in order to be able to start the actual therapy. The user can enter all values and parameters but maximum quantities are reduced by the device in an appropriate manner, if necessary. The procedure advances to a next step S03.

[0057] In step S03 therapy progress is recorded on the basis of an output signal of a sensor means. For example, the therapy progress can be recorded by recording arrival of a first blood quantity with a blood sensor in or on the air detector equipment 6. If sufficient therapy progress is recorded (YES in step S03), the procedure advances to a next step S04. If therapy has not yet progressed far enough (NO in step S03), the procedure returns to step S02.

[0058] In step S04 the ultrafiltration rate and/or the ultrafiltration cross-flow is determined by the membrane in the dialyzer device 8. In other words, a cross rate calculation is carried out. Then the procedure advances to a step S05.

[0059] In step S05 it is checked as to whether a cross rate consistent with the other parameters, i.e. the desired treatment blood flow, is reached, and as to whether the secondary membrane is sufficiently formed. If the treatment blood flow is reached and the secondary membrane is sufficiently formed (YES in step S05), the procedure advances to a step S06. If the treatment blood flow is not yet reached and/or the secondary membrane is not yet sufficiently formed (NO in step S05), the procedure returns to step S02. Alternatively it can be provided that the procedure returns to step S04.

[0060] In step S06 a delayed start of hemodiafiltration with post-dilution and/or HDF (post) occurs which is carried out automatically in accordance with specifications and calculation. The automatic start of HDF (post), i.e. the change from the initial hemodialysis to hemodiafiltration is to be expected in practice approx. 5 minutes after the first contact with blood on the air detector equipment 6, if an appropriate cross rate has been achieved, i.e. the treatment blood flow is achieved, and the secondary membrane is sufficiently formed. Then, the procedure advances to a step S07.

[0061] In step S07 the substitution quantity, i.e. the quantity of the substituate supplied with post-dilution, is adjusted according to default of the application and to 25% to 30% max. of the blood flow.

[0062] For example, the substitution quantity can be regulated to a constant value, which is 25% to 30% max. of the blood flow, if the blood flow remains constant, or regulated to a value, which is constantly 25 to 30% max. of the blood flow, if the blood flow changes. In the case of a changing blood flow which is, where applicable, insufficient then, it is provided that the substitution quantity is likewise reduced accordingly in order to maintain the above mentioned percentage amount. In this case the method and the device are configured to issue, for example, via the user interface of the device or the like an indication for the user that the substitution quantity has been automatically reduced.

[0063] Subsequent to step S07, in a step S08 shown in a highly simplified manner, further therapy or blood treatment is carried out, and the method and/or its process(es) end at the end of therapy in a step S09.

[0064] As has been described above, according to aspects of the invention the maximum performance of the dialyzer is used and maintained. If, for example, by a possibly sub-optimally adjusted parameter intervention of a user, a calculable (massive) worsening of the therapy result could occur, an intervention by the system can be made. Causes for interventions by the system can be varied and, for example, be due to the complexity and diversity of types of application requiring increasingly expert knowledge, a respective personnel key and qualification of operating personnel, no instant availability of the responsible physician, and be the reasons for a reduced therapy result.

[0065] The method according to aspects of the invention and the device according to aspects of the invention support the user in applications which directly impair the performance of the dialyzer. Necessary parameters are corrected automatically in the process. In addition, also a note is issued but at any rate in such a case due to the inventive limitation of the substitution to a maximum factor the performance capability of the dialyzer is not impaired. Due to the limitation to a maximum factor, i.e., the constant value regulation of the substitution flow, the dialyzer is no longer burdened beyond limit.

[0066] When the cross rate is reached, the substitution quantity is automatically limited and the user is informed accordingly. For example, a display or message can issued as follows:

[0067] “Caution: The infused quantity is reduced, the therapeutic goal may possibly not be reached any more.” The substitution target quantity can be modified by the user at any time. Likewise he or she can switch on and switch off warnings with respect to the target.

[0068] It should be understood that the invention is not limited to the embodiments described and its modifications but that combinations nevertheless obvious for the person skilled in the art of at least parts of said embodiments, modifications and equivalents may result within the scope of protection defined by the subsequent patent claims.