DIALYSIS MACHINE HAVING A CONTROL UNIT FOR CARRYING OUT A CONDITIONING OF THE DIALYSIS MEMBRANE

Abstract

The present invention relates to a dialysis machine having an extracorporeal blood circuit; a dialyzer; and a dialysate circuit, wherein a blood pump is arranged in the extracorporeal blood circuit; wherein the dialyzer has a dialysate membrane which separates its blood side from its dialysate side; wherein the dialysis machine has a control unit which is configured to carry out a conditioning cycle which comprises a conditioning phase in which an ultrafiltration rate exceeds the blood flow through the dialyzer conveyed by the blood pump.

Claims

1. A dialysis machine having an extracorporeal blood circuit, a dialyzer, and a dialysate circuit, wherein a blood pump is arranged in the extracorporeal blood circuit; and wherein the dialyzer has a dialysis membrane which separates its blood side from its dialysate side, characterized in that the dialysis machine has a control unit which is configured to carry out a conditioning cycle which comprises a conditioning phase in which an ultrafiltration rate exceeds the blood flow through the dialyzer which is conveyed by the blood pump.

2. A dialysis machine in accordance with claim 1, characterized in that the conditioning cycle is carried out at the start of the treatment.

3. A dialysis machine in accordance with claim 1, characterized in that the ratio of the ultrafiltration rate to the blood flow rate caused by the blood pump amounts to between 1.5 to 1 and 2.5 to 1, preferably between 1.8 to 1 and 2.2 to 1, and preferably approximately 2 to 1.

4. A dialysis machine in accordance with claim 1, characterized in that little or no dialysate flows into the dialysate side of the dialyzer during the conditioning phase.

5. A dialysis machine in accordance with claim 1, characterized in that the duration of the conditioning phase amounts to 15 to 120 seconds, and preferably 30 to 60 seconds.

6. A dialysis machine in accordance with claim 1, characterized in that a fluid volume of between 20% and 70%, and preferably of between 30% and 60%, of the total volume of the blood side of the dialyzer is withdrawn through the dialysis membrane during the conditioning phase.

7. A dialysis machine in accordance with claim 1, characterized in that the conditioning cycle is repeated, preferably at least 3, and, for example, between 3 and 6, with the repetitions preferably directly following one another.

8. A dialysis machine in accordance with claim 1, characterized in that the conditioning cycle comprises a flushing phase which follows the conditioning phase and in which the blood flow through the dialyzer generated by the blood pump exceeds the ultrafiltration rate.

9. A dialysis machine in accordance with claim 8, characterized in that the blood volume used in the flushing phase to flush the blood chamber of the dialyzer amounts to 0.5 to 5 times, and preferably 1 to 2 times, the blood chamber volume.

10. A dialysis machine in accordance with claim 1, characterized in that the dialysis machine has a substitution line which preferably leads into the venous line of the extracorporeal blood circuit, with the control unit being configured such that the fluid volume withdrawn in the conditioning phase in the dialyzer is at least partly substituted using this line, preferably after the conditioning phase and during the flushing phase.

Description

[0030] Further details and advantages of the invention result from the Figures and embodiments discussed in the following. There are shown in the Figures:

[0031] FIG. 1: a schematic representation of the change process when the dialysis membrane comes into contact with blood proteins in an early treatment stage;

[0032] FIG. 2: extents of the hydrostatic pressures on the blood side and on the dialysate side, of the oncotic pressure and of the effective pressure along the dialyzer membrane;

[0033] FIG. 3: extents of the local filtration at the blood-side inlet and of the integral filtration over the path covered at the dialyzer membrane;

[0034] FIG. 4: time progressions of the instantaneous albumin concentration and of the cumulated albumin concentration in the dialysate;

[0035] FIG. 5: an experimental setup for the experimental testing of the invention;

[0036] FIG. 6 a schematic representation of the flow progressions and of the pressure progressions in the dialyzer at a ratio of the ultrafiltration rate to the blood flow rate of 2 to 1;

[0037] FIG. 7: a graphical representation of the time progressions of determined albumin concentrations in the ultrafiltrate; and

[0038] FIG. 8: a schematic representation of a dialysis machine in accordance with the invention.

[0039] An experimental setup for the experimental testing of the invention is shown in FIG. 5. A vessel is marked by reference numeral 14 in which blood can be located at a body temperature of approximately 37 C. in a volume of, for example, 2000 ml. A dialyzer is marked by reference numeral 15; a simulated extracorporeal blood circuit by reference numeral 16; and a simulated dialysate circuit by reference numeral 17. In the experimental arrangement, the dialysate circuit 17 having the outflow line 18 for the substitution of the dialysate is subsequent to the venous line 19 of the blood circuit 16, and admittedly at a drip chamber 20. A throttle valve 21 is located between the drip chamber 20 and the vessel 14.

[0040] Pressure sensors 22, 23 an 24 serve the determination of the pressures P.sub.ven, P.sub.PP and P.sub.f. Reference numerals 25, 26 and 27 mark measurement points for the concentrations C.sub.in, C.sub.out and C.sub.f. A blood flow Q.sub.b of, for example, 300 ml/min can be produced using the blood pump 28 arranged downstream of the dialyzer 15 in the blood circuit 16. A dialysate flow or a substitute flow Q.sub.f can be produced using the ultrafiltration pump 29 arranged downstream of the dialyzer 15 in the dialysate circuit 17, with the it simultaneously being a substitution pump or syringe in the experimental setup.

[0041] The venous hose system 19 has to be connected to the (patient) volume free of air so that a volume flow of, for example, 40 ml/min can be withdrawn over the venous branch. The pressure P.sub.ven can amount, for example, to 150 mmHg.

[0042] The following experiments were carried out with this arrangement. The following parameters were approximately identical in all experiments:

[0043] Dialyzer type: FX600 (V.sub.b=95 mL)

[0044] Screening coefficient: S.sub.alb=0.032%

[0045] Blood flow: Q.sub.b=300 ml/min

[0046] Hematocrit: Hkt=36%2%

[0047] Albumin: C.sub.alb3.0 g/dL

EXAMPLE 1

[0048] The experimental setup was first prepared in accordance with FIG. 5 (step 1). The dialyzer 15 was filled and flushed with NaCl solution at the blood side and at the dialysate side and residual air was completely removed at both sides of the dialyzer 15 by knocking. The blood side was subsequently filled with blood (step 3).

[0049] In accordance with the invention, the blood pump 28 was then stopped (step 4) to reduce pressure drops along the capillaries of the dialyzer 15.

[0050] Approximately of the volume on the blood side was withdrawn over the membrane using a substitution pump 29 (step 5). The value for V.sub.uf amounted to 30 ml. The ultrafiltration volume V.sub.uf is thus drawn uniformly over the membrane. The procedure was as follows: The substitution pump 29 draws at the dialysate side at Q.sub.uf=60 ml/min until the desired ultrafiltration (UF) volume of 30 ml per cycle has been withdrawn (duration approximately 30 s to 60 s). The blood pump 28 runs in this phase at half the UF rate at Q.sub.b=30 ml/min. The residual volume flow (approximately 30 ml/min) is taken back over the venous hose system 19.

[0051] The ratio of the UF rate Q.sub.uf (60 ml/min to the lead flow rate of the blood Q.sub.b,in (30 ml/min) amounts to exactly 2/1 in this example. FIG. 6 schematically shows the flow development 40 and the pressure drop 41 in the dialyzer 15 which results at such a ratio. Half of the flow Q.sub.d,out of the filtrate withdrawn from the blood, which corresponds exactly to the ultrafiltration rate Q.sub.uf at a dialysate inflow rate Q.sub.d,in of 0 ml/min, comes from the arterial line where the blood pump 28 resupplies blood. Since the blood chamber of the dialyzer 15 is openly connected to the venous line 19, blood is also sucked in from the venous line 19 (30 ml/min). Pressure conditions which are as uniform as possible are achieved for a layer which is as uniform as possible by the symmetrical distribution. The pressure gradient on the blood side of the dialyzer is thus the lowest.

[0052] Subsequently a determination of the albumin loss in the ultrafiltration volume takes place using the formula m.sub.alb=C.sub.alb*V.sub.uf (step 6). The withdrawn sample ultrafiltration volume V.sub.uf is again led back into the storage vessel 14.

[0053] The blood pump 28 is then started again at Q.sub.b=300 ml/min (step 7). The thickened blood is thus flushed out of the dialyzer 15 again.

[0054] After 2 min (600 ml blood volume), the blood pump 28 is stopped again (step 8).

[0055] After step 8, either the conditioning cycle of steps 5 to 8 can be repeated or a transition to step 9 can take place. In the present embodiment, the conditioning cycle of steps 5 to 8 is run through a total of 5 times; that is, the total V.sub.uf in the conditioning cycle amounts to 150 ml and a total of 5 samples are taken.

[0056] In the final step 9, a post HF treatment is simulated having a substitution rate of Q.sub.sub=100 ml/min and a duration of T=180 min. Samples are taken from the ultrafiltrate (C.sub.f, measurement point 25) and from the storage vessel (C.sub.in; measurement point 27) at test times (t=0 min; t=2 min 30 sec; t=5 min; t=7 min 30 sec; t=10 min; t=15 min; t=20 min; t=30 min; t=45 min; t=60 min; t=90 min; t=120 min; t=150 min; t=180 min) and the undisturbed pressures P.sub.ven, P.sub.PP and P.sub.f are noted.

[0057] The evaluation detected (a) the albumin loss and myoglobin loss during the conditioning phase, i.e. during the 5 times repetition of steps 5 to 8; and (b) the albumin loss during the 3-hour treatment.

EXAMPLE 2

[0058] This example was largely identical to Example 1, the conditioning cycle, i.e. steps 5 to 8 were, however, repeated 15 times, that is, the total V.sub.uf in the conditioning cycle amounts to 450 mL and the procedure of step 5 was as follows: The substitution pump 29 draws at the dialysate side at Q.sub.uf=90 ml/min until the desired ultrafiltration (UF) volume of 30 ml per cycle has been withdrawn (duration approximately 30 s to 60 s). The blood pump 28 runs in this phase at half the UF rate at Q.sub.b=45 ml/min. The residual volume flow (approximately 45 ml/min) is taken back over the venous hose system 19.

[0059] The evaluation took place as in Example 1.

[0060] In accordance with a modified Example 2, a setting of Q.sub.b at 40 ml/min would also be conceivable, which would result in a return flow rate from the venous line of 50 ml/min at an ultrafiltration rate Q.sub.uf=90 nil/min.

EXAMPLE 3

[0061] This example was also largely identical to Example 1, but here approximately of the volume on the blood side was withdrawn over the membrane with the syringe or substitution pump 29 in step 5, that is, V.sub.uf=45 ml, with a 5 running through of the conditioning cycle of steps 5 to 8, that is 225 m.

[0062] The evaluation again took place as in Example 1.

COMPARISON EXAMPLE 4

[0063] After carrying out steps 1 to 3 in accordance with Example 1, steps 4 to 8 were omitted and a post-HF treatment was simulated as in step 9 with a substitution rate of Q.sub.sub=100 ml/min.

[0064] The evaluation again took place as in Example 1.

[0065] The same experiments as in Examples 1 to 4 could also be carried out using alternative dialyzers, for example with an FX800 (V.sub.b=115 ml) or an FX1000 (V.sub.b=136 ml). In Example 1, step 5, the ultrafiltration volume V.sub.uf would then amount to 37 ml (FX800) or 44 ml (FX1000) and with a 5 time repetition of the conditioning cycle a total V.sub.uf of 185 ml (FX800) or 220 ml (FX1000) would result. In Example 2, that is, with a 15 time repetition of the conditioning cycle this would result in a total V.sub.uf of 555 ml (FX800) or 660 ml (FX1000). In Example 3, the ultrafiltration volume V.sub.uf would then amount to 55 ml (FX800) or 65 ml (FX1000) and with a 5 time repetition of the conditioning cycle a total V.sub.uf of 275 ml (FX800) or 325 ml (FX1000) would result.

[0066] The absolute and relative albumin losses and myoglobin losses measured for Examples 1 to 4 over the total treatment time (determined in the ultrafiltrate at measurement point 27) are shown in Table 1.

TABLE-US-00001 TABLE 1 Myoglobin Myoglobin Albumin loss, Albumin loss, loss, loss, Example absolute relative absolute relative V4 1.08 g 22.3 mg V4 1.24 g 20.7 mg (double) 1 0.85 g 26% 21.2 mg 1% 2 0.77 g 33% 21.2 mg 1% 3 0.68 g 41% 20.3 mg 6%

[0067] The time progressions of the albumin concentrations in the ultrafiltrate determined at the measurement point 27 are shown in FIG. 7, wherein reference numeral 30 shows the curve for comparison example 4; reference numeral 31 shows the curve for the double of comparison Example 4; reference numeral 32 shows the curve for Example 1; reference numeral 33 shows the curve for Example 2; and reference numeral 34 shows the curve for Example 3.

[0068] The averages of the transmembrane pressures TMP measured over the treatment time and differences P.sub.PPP.sub.ven are shown in Table 2.

TABLE-US-00002 TABLE 2 Example TMP P.sub.PP-P.sub.ven V4 V4 (double) 190 mmHg 161 mmHg 1 150 mmHg 150 mmHg 2 174 mmHg 161 mmHg 3 160 mmHg 158 mmHg

[0069] In summary, it can be stated with reference to the examples that the albumin losses during the conditioning cycle were negligible due to the small exchanged volumes (V.sub.uf=5*30 ml=150 ml; C.sub.alb,max=0.5 mg/ml; m.sub.alb=75 mg). Example 3 delivered the best conditioning with a value for V.sub.uf of 5*45 ml (50% of the blood volume) and with a reduction of the albumin loss by 41%. The conditioning cycle lasts approximately 2 to 3 min per repetition including flushing; that is 10 to 15 min with a 5-fold repetition.

[0070] FIG. 8 shows a schematic representation of a dialysis machine in accordance with the invention.

[0071] In FIG. 8, the blood system of the patient is marked by reference numeral I; the extracorporeal blood circuit of the machine by reference numeral II; and the dialysate side of the machine by reference numeral III.

[0072] The principle in the sense of the invention can be implemented at such a machine using the experiment setup described in more detail above.

[0073] The blood system I of the patient comprises an artery A, a vein V and a fistula F.

[0074] The extracorporeal blood circuit is connected to the fistula using the needles 101 and 110. The arterial line 102 which has a blood pump 103 and opens downstream into the dialyzer 104 adjoins the arterial needle 101. The venous line 109 runs to the venous needle 110 from the dialyzer 104. The extracorporeal blood circuit comprises arterial and venous pressure sensors 113 and 114 as well as clamps 129, 143, 142 and 111.

[0075] The dialyzer 104 comprises a dialyzer membrane 105 by which the blood chamber 106 is separated from the dialysate chamber 107.

[0076] The dialysate system III comprises a dialysate source 116. a balancing device 127 and an infeed 115 which leads into the dialysate chamber 107 of the dialyzer 104. The ultrafiltration pump and dialysis fluid pump 108 and 119 are arranged in a drain line 117 from the dialysate chamber 107. The return is marked by the reference numeral 118.

[0077] A substitution fluid system 121 comprises a substitution fluid source 122 as well as a predilution line and predilution pump 123 and 124 and a post-dilution line and post-dilution pump 125 and 126.

[0078] The dialysis machine shown, unlike FIG. 5, does not only represent an experimental setup, but rather a real machine in accordance with the invention at which the inventive principle can be used.