JP2010082068A - Blood circuit and circulation system for evaluation and inspection of blood compatibility - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a blood circuit with smooth blood flow, made of a base material with anticoagulant activity, and enabling an accurate evaluation or inspection on the performance and quality of medical devices such as an external blood circulation module; a blood circulation system including the medical device and the blood circuit; and an in-vitro evaluation method using this blood circulation system. <P>SOLUTION: In the blood circuit for the evaluation or inspection on the blood compatibility of a material containing a compound with anticoagulant activity, when an analysis is made on a dispersion model in a tracer response test, the ratio of 2 or more of standardized dimensionless time ϕ to the area below the response curve is 0.2 or less. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a blood circuit and a circulatory system, and an evaluation method using them, mainly used for in vitro evaluation and testing of blood compatibility of a material imparted with anticoagulant activity.

High blood compatibility is required not only for blood circuits used in the medical field but also for blood circuits used for performance evaluation and quality testing in the development of materials with anti-coagulant activity. There is a need to reduce thrombus formation. Thrombus formation is caused not only by contact between blood and a circuit board, but also by flow field problems such as stagnation. Existing blood circuits used in the medical field are made up of various parts such as connectors and chambers, and stagnation occurs in parts where the connection between the parts and the circuit inner diameter change. Since anticoagulants such as heparin and nafamostat mesylate are used in medical settings, activation of blood components due to contact between blood and circuit substrate and retention in stagnation is suppressed, and circulation without coagulation is possible. it can. However, in the evaluation / inspection of anticoagulant materials, anticoagulants cannot be used to examine the anticoagulant performance of the material itself, and existing blood circuits used in medical settings are used for material evaluation / inspection. When used as is, solidification occurred in the circuit, making evaluation and inspection impossible. In order to solve such a problem, for example, a technique is disclosed in which the inner diameter and the thickness of the connecting portion in the circuit are the same, the end faces are brought into close contact with each other, the step is eliminated, and blood stays in the connecting portion. (See Patent Document 1). In addition, a technique for making blood compatible and antithrombogenic by coating the blood circuit with heparin is also disclosed (see Patent Document 2). On the other hand, as an in vitro evaluation of cardiopulmonary bypass, a method of circulating human blood to which heparin as an anticoagulant is added to an open or closed circuit has been reported (see Non-Patent Document 1). In addition to the in vitro evaluation using heparin-added blood, the evaluation of a medical connector base material to which anticoagulant activity is imparted has been reported (see Non-Patent Document 2). As described above, various attempts have been made to improve the blood compatibility of the blood circuit, but it is difficult to say that these techniques are sufficient, and in these techniques, the addition of an anticoagulant to the evaluation makes it difficult for coagulation to occur. Blood is used, and there is a disadvantage that the condition is not close to that of a living body. From the above, a circuit and an evaluation method that do not form a thrombus suitable for performance evaluation and quality inspection of an anticoagulant material are not yet known.
JP 2003-320037 A JP 2004-8893 A Artificial organs. 1999 23 (6), pp.547-551 Journal of biomaterials applications. 2002 17 (1), pp.5-17

A medical device made using a base material with anti-coagulant activity is attached to the circuit, and blood circulation is performed mainly in vitro under conditions without adding an anticoagulant such as heparin or nafamostat mesylate. In this case, there is a problem that thrombus formation occurs in the circuit, and it is impossible to correctly evaluate or test the performance and quality of the base material. For this reason, it was required to prevent thrombus formation in the circuit. The present invention improves such drawbacks, and has a good blood flow that can correctly evaluate or test the performance and quality of a medical device such as an extracorporeal circulation module comprising a base material having anticoagulant activity. It is an object of the present invention to provide a circuit, a circulation system including the device, the circuit, and an evaluation method using the system.

As a result of studying a circuit with no blood retention and a good flow, the inventors controlled a circuit configuration and a linear velocity, thereby creating a blood circuit that does not form a thrombus without adding an anticoagulant to the blood. I found it. The present invention has the following configuration.
1. When the analysis by the diffusion model is performed in the tracer response test, the ratio of 2 or more of the normalized dimensionless time φ to the area under the curve of the response curve is 0.2 or less. A blood circuit for evaluating and testing blood compatibility of materials containing compounds.
2. 2. The blood circuit for blood compatibility evaluation / testing according to 1 above, wherein the volume other than the main circuit is 1.5 or less when the main circuit volume in the circuit is 1.
3. 3. A circulation system comprising a module using a blood compatibility evaluation / test circuit according to 1 or 2 above and a base material to which anticoagulant activity is imparted.
4). 4. A method for evaluating or testing blood compatibility of a material containing a compound having anticoagulant activity, which is obtained by circulating blood containing sodium citrate and calcium gluconate in the circulation system according to 3 above.
5). 5. The method for evaluating or testing the blood compatibility of a material containing a compound having anticoagulant activity, wherein the linear velocity of the fluid flowing in the circulation system is 120 to 230 cm / min.

With the good flow blood circuit provided by the present invention, it is possible to correctly evaluate or test the blood compatibility of materials having anticoagulant activity even in vitro, and as a result, stable quality products can be obtained. Not only can it be supplied to the market and provide safe and reliable diagnosis and treatment to the medical field, it can also lead to the creation of higher performance medical materials and medical devices.

  When the analysis by the diffusion model is performed in the tracer response test in the present invention, the blood circuit in which the ratio of 2 or more of the normalized dimensionless time φ to the area under the curve of the response curve is 0.2 or less It is a blood circuit with a good flow with few blood retention parts. The blood circuit used in the clinic is composed of components such as a chamber and a connector for avoiding air mixing into the blood vessel in addition to the tube. The more the components, the more the blood retention portion increases. Blood stagnation occurs in the blood retention portion, blood coagulation factors are activated, and coagulation in the circuit is promoted. Further, the contact between blood and air in the chamber and the change in the inner diameter at the connecting portion between the component and the tube also cause activation of blood coagulation factors in the circuit. In the present invention, it has been found that the blood compatibility of a material having anticoagulant activity can be evaluated using blood to which no anticoagulant is added, by making these components as small as possible and forming a circuit in which the ratio of the tube is large. It came to solve a problem.

  In the present invention, the main circuit volume refers to the tube volume, and the volume other than the main circuit refers to a volume other than the tube, such as a chamber. If the volume other than the main circuit is too large, for example, if the volume of the chamber is large or the number of chambers is large, the chance of blood coming into contact with air in the chamber increases, and the circuit inner diameter changes at the connection between the chamber and the main circuit. And blood stagnation occurs. Since both contact with air and stagnation cause blood coagulation in the circuit, the ratio of the volume other than the main circuit to the volume of the main circuit is preferably 1.5 or less, and preferably 1 or less. Further preferred. In conventional blood circuits, if the chamber or connector is used as usual, the ratio of the volume other than the main circuit to the volume of the main circuit will exceed the above numerical range, and as a result, the circuit is likely to come into contact with air and stagnation. It was. This was based on the common sense that a significant amount of air in the blood circuit would necessarily affect the circulation time. However, in the examination of the present invention, the fact that even if a considerable amount of air enters the circuit does not affect the circulation time, conventionally prevents the evaluation module from entering the air and promoting solidification. It was confirmed that the circuit could be used even if there was no chamber used to do this. Furthermore, by setting the end point of circulation in the human blood circulation test as “the time when circulation is impossible” (for example, the time when the part connecting both ends of the tube is released due to pressure rise), the module or circuit pressure measurement, coagulation factor, etc. The above-mentioned range can be achieved by eliminating the need for time-dependent measurement and by reducing the number of connectors required for tube connection to a circuit for pressure measurement and sampling. The material of the tube used in the blood circuit of the present invention is not particularly limited, but is preferably one that can withstand long-term contact with the pump. Moreover, the inner diameter and outer diameter of the tube used in the blood circuit of the present invention can be determined according to the pump to be used, the module to be connected, and the blood flow rate, and are not particularly limited.

  In the evaluation using the blood circuit of the present invention, the method of introducing blood into the circuit is not particularly limited. For example, one end of a circuit tube is placed in a container containing blood, and blood is introduced into the circuit using a pump. When the blood reaches one end on the opposite side, the pump may be stopped and the ends of the circuit may be connected. Such a method eliminates the need for adding blood from the chamber, and makes it possible to further reduce the number of chambers used.

The tracer response test of the present invention is based on the impulse response method which is one of the evaluation methods of the fluid mixing characteristics. The tracer response test is performed by instantaneously injecting the tracer from the inlet of the circuit where the fluid is constantly flowing in and out at a constant flow rate, and measuring the concentration of the tracer discharged from the circuit outlet over time. The measurement is performed by the following method. Using a pump, 0.35 g / L xanthan gum aqueous solution (hereinafter, xanthan gum aqueous solution) is passed through the circuit at a flow rate of 5.6 mL / min, and the flow is temporarily stopped. Vitamin B ₁₂ as a tracer was dissolved in aqueous xanthan gum solution at a concentration of 0.1 g / L solution (hereinafter, vitamin B ₁₂ solution) for 5 seconds from the circuit inlet at the same flow rate as above, to liquid permeation. Again, the xanthan gum aqueous solution is passed through the circuit at the same flow rate as above, and the solution discharged from the circuit outlet is sampled for 10 seconds per container at 0 seconds when the injection of the tracer is started. The absorbance of the collected solution at 360 nm is measured. The absorbance at 360 nm of a vitamin B ₁₂ solution prepared in advance at an arbitrary concentration is measured, and the result is used as a calibration curve to calculate the vitamin B ₁₂ concentration in the solution collected from the calibration curve.
For analysis in the tracer response test, a diffusion model known in chemical engineering is used. That is, from the result of the tracer response test, the change in the tracer concentration discharged from the circuit outlet is expressed as a function E (φ) using the dimensionless time φ obtained by normalizing the time after the tracer injection with the average residence time in the circuit. To express.

The dimensionless time φ and the dimensionless concentration E (φ) are calculated by the following procedure. That is, assuming that the circuit volume is V (cm ³ ), the flow rate is v (cm ³ / S), and the time after the tracer injection is t, the average residence time t _m of the circuit is represented by t _m = V / v, dimensionless time normalized by t _m is represented by φ = _t / t _m. If the tracer concentration from the circuit outlet is c, the dimensionless concentration E (φ) is expressed by E (φ) = c / c ₀ . However,

And Next, a response curve is drawn with the dimensionless concentration E (φ) as the vertical axis and the dimensionless time φ as the horizontal axis. The ideal flow of the blood circuit is a piston flow in which the entire amount of tracer flows out instantaneously at φ = 1. Another ideal flow is complete mixing, where the tracer is thoroughly mixed in the device. The actual flow in the circuit is intermediate between piston flow and complete mixing.
When there is a stagnant part in the blood circuit, tailing is seen in the response curve. The following calculations are performed to quantify the degree of tailing. That is, the area under the curve of the response curve obtained by the tracer response test is approximately obtained as a trapezoid area. For example, if the dimensionless concentration E (phi) _b of the dimensionless concentration E (phi) _a point b at a certain point a dimensionless time, area under the curve S from a to b is

Is approximately calculated. Subsequently, the ratio of the area under the two or more curves of the dimensionless time φ to the area under the entire curve is calculated. The area ratio of 2 or more of the dimensionless time φ indicates the degree of retention of the blood circuit, and if this ratio is too large, the retention part of the blood circuit increases and blood coagulation in the circuit is likely to occur. It is preferably 0.2 or less, and more preferably 0.15 or less. The module according to the present invention is formed by incorporating a material containing the above-mentioned compound having anticoagulant activity into a plastic case or the like in the form of a hollow fiber or the like. As shown in FIG. Similar to a thread type dialyzer, a module case having two ports (blood ports) that communicate with the inside of the hollow fiber and two ports (dialysate ports) that communicate with the outside, and a hollow that is fixed to both ends of the case by a potting agent The thing which comprises a thread | yarn is illustrated. The circulation system in the present invention comprises the blood circuit, the module, and the pump.

The linear velocity calculation method in the present invention is obtained by dividing the flow rate by the cross-sectional area. For example, in the case of a circuit using a tube having a diameter of 2 mm, since the cross-sectional area is 0.0314 cm ² , the linear velocity is calculated as 178 cm / min if the flow rate is 5.6 mL / min.

If the linear velocity is too large, the contact time between the material or device and blood decreases when applied to the evaluation of the material or device, and the antithrombogenicity of the material or device is not exhibited. On the other hand, if it is too small, the portion other than the material or device, that is, the time for contact with the circuit is increased, and blood coagulation in the circuit is likely to occur, so that it is preferably 120 cm / min or more and 230 cm / min or less, More preferably, it is 210 cm / min or less.
A material containing a compound having anticoagulant activity, which is evaluated or examined using the blood circuit of the present invention, can be suitably used as a medical device. Examples of medical devices include artificial kidneys and catheters.

  Hereinafter, the blood circuit, the circulation system, and the in vitro evaluation method of the present invention will be described with reference to examples, but the present invention is not limited to these examples.

(Production of hollow fiber mini-module)
5 parts by weight of iso-PMMA and 20 parts by weight of syn-PMMA were added to 75 parts by weight of dimethyl sulfoxide and stirred at 110 ° C. for 8 hours to obtain a film forming stock solution. This film-forming stock solution was discharged from an orifice-type double-cylindrical die, allowed to pass through 300 mm in air, and then introduced into a 100% water coagulation bath to obtain a hollow fiber. At this time, dry nitrogen was used as the internal injection gas. The resulting hollow fiber had an inner diameter of 0.2 mm and a film thickness of 0.03 mm. 50 hollow fibers were bundled, and both ends thereof were fixed to the module case with an epoxy potting agent while paying attention not to block the hollow portion of the hollow fiber, so that a mini module (FIG. 1) shown in FIG. 1 was produced. The mini-module has a diameter of about 7 mm and a length of about 12 cm. Like a general hollow fiber type dialyzer, two ports (blood ports) that communicate with the inside of the hollow fiber and ports that communicate with the outside (dialysate port) ). The hollow fiber of the mini-module and the inside of the module were washed with distilled water, and four ports were sealed and irradiated with γ-rays in a state filled with distilled water. At this time, the absorbed dose of γ rays was 25 kGy. Thereafter, the hollow fiber of the mini module and the inside of the module are washed by flowing 300 mL each of distilled water and physiological saline at a temperature of 25 ° C. using a peristaltic pump at a flow rate of 10 mL / min. Abbreviated as module). Distilled water washing and physiological saline washing are not simultaneous.
(Tracer response test)
A tracer response test was performed using the circuits (1) to (3) shown below. That is, the tube was connected to a pump, and 0.346 g / L xanthan gum aqueous solution was allowed to flow at a flow rate of 5.6 mL / min. The liquid in which the vitamin B ₁₂ is dissolved in aqueous xanthan gum solution at a concentration of 0.1 g / L from one end of the tube and 0.47mL injected, and the liquid coming out of the other end was taken by 10 seconds. The absorbance of the collected solution was measured at a wavelength of 360 nm, and the vitamin B ₁₂ concentration was calculated from the calibration curve. The dimensionless concentration E (φ) and dimensionless time φ were calculated by the following equations.
E (φ) (concentration) (μg / mL) = vitamin B ₁₂ injection amount (μg) / priming volume of circuit (mL)
φ = real time (sec) / (priming volume of circuit (mL) / flow rate (mL / min) × 60)
E (φ) = actual concentration / E (φ) (concentration)
(Human blood circulation experiment)
Human blood circulation experiments were performed using circuits (1) to (3). That is, human blood is introduced from one end of the circuit (1) using a pump at a flow rate of 5.6 mL / min, and when the blood is filled in the entire circuit, the tips of the circuits are connected to circulate human blood. It was. Human blood is collected from healthy volunteers, sodium citrate is mixed at a ratio of 1: 9 to the blood, and 8.5% calcium gluconate solution is added at a ratio of 43.6 μL to 1 mL of blood immediately before circulation. did. In the circuit, the average of the circulation time until the blood could not be circulated by blood coagulation was determined as “average circulation time”.
Example 1
A silicon tube having an inner diameter of 2 mm and an outer diameter of 4 mm was cut into a length of 61.5 cm to produce a circuit (1) (FIG. 2). The volume of the silicon tube as the main circuit was 2.6 cm ^{3 in} the circuit (1). Since the volume of the chamber, which is a part other than the main circuit, was 4 cm ³ , the volume of the part other than the main circuit when the tube volume was 1 was as shown in Table 1.

Subsequently, using the circuit (1), a tracer response test and a human blood circulation experiment were performed. Subsequently, a human blood circulation experiment was conducted by connecting to a mini-module. The results are shown in Table 1.
(Example 2)
A polyvinyl chloride chamber was attached to a position 10 cm from one end of a tube made of the same material as in Example 1, and a circuit (2) having a total length including the chamber of 61.5 cm was produced (FIG. 3). The volume of the silicon tube as the main circuit was 2.4 cm ³ in the circuit (2). Since the volume of the chamber, which is a part other than the main circuit, was 4 cm ³ , the volume of the part other than the main circuit when the tube volume was 1 was as shown in Table 1.

Subsequently, using the circuit (2), a tracer response test and a human blood circulation experiment were performed. Subsequently, a human blood circulation experiment was conducted by connecting to a mini-module. The results are shown in Table 1.
(Example 3)
Two polyvinyl chloride chambers are attached at a position 10 cm from one end of the tube of the same material as in Example 1 and 12.5 cm from the opposite end, so that the total length including the chamber is 61.5 cm. A simple circuit (3) was produced (FIG. 4). The volume of the silicon tube as the main circuit was 2.2 cm ³ in the circuit (3). Since the volume of the chamber, which is a part other than the main circuit, was 4 cm ³ , the volume of the part other than the main circuit when the tube volume was 1 was as shown in Table 1.

  Subsequently, using the circuit (3), a tracer response test and a human blood circulation experiment were performed. Subsequently, a human blood circulation experiment was conducted by connecting to a mini-module. The results are shown in Table 1.

It is a schematic side view which shows a minimodule. It is a schematic system diagram which shows the circuit (1) used by a tracer response test. It is a schematic system diagram which shows the circuit (2) used by a tracer response test. It is a schematic system diagram which shows the circuit (3) used by a tracer response test.

Explanation of symbols

1, 1 ': Blood port 2, 2': Dialysate port 3: Module case 4: Hollow fiber 5: Potting part 6: Pump 7: Silicon tube 8: Tracer collection container 9: Container containing xanthan gum aqueous solution 10: Chamber

Claims (5)

  When the analysis by the diffusion model is performed in the tracer response test, the ratio of 2 or more of the normalized dimensionless time φ to the area under the curve of the response curve is 0.2 or less. A blood circuit for evaluating and testing blood compatibility of materials containing compounds.   The blood circuit for evaluation / testing of blood compatibility according to claim 1, wherein the volume other than the main circuit is 1.5 or less when the main circuit volume in the circuit is 1.   A circulation system comprising a blood compatibility evaluation / test circuit according to claim 1 and a module using a base material to which anticoagulant activity is imparted.   A method for evaluating or testing blood compatibility of a material containing a compound having anticoagulant activity, which is obtained by circulating blood containing sodium citrate and calcium gluconate in the circulation system according to claim 3.   5. The method for evaluating or testing the blood compatibility of a material containing a compound having anticoagulant activity, wherein the linear velocity of the fluid flowing in the circulation system is 120 to 230 cm / min.

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