Patent Publication Number: US-6666839-B2

Title: Method of using reusable blood lines

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a division of application Ser. No. 09/664,432, filed Sep. 18, 2000, which is a division of application Ser. No. 08/892,685, filed Jul. 14, 1997, now U.S. Pat. No. 6,165,149, which is a division of application Ser. No. 08/504,457, filed Jul. 20, 1995, now U.S. Pat. No. 5,772,624. 
    
    
     BACKGROUND OF THE INVENTION 
     In the field of blood treatment, hemodialysis is the most widely used technique, although other techniques are also available such as plasmapheresis, hemoperfusion, blood oxygenation, and techniques for passing blood through blood treatment media such as an absorptive agent for the removal of toxins or the like. Typically, an arterial blood set delivers blood from the patient to the hemodialyzer or other desired blood treatment unit. After the blood has passed through the hemodialyzer, it is conveyed through a venous blood set back to the patient. 
     The arterial and venous blood sets typically each have about two meters of tubing, extending from patient connectors to other set components such as bubble removal chambers, a length of roller pump tubing or another pump device fitment, branch connection sites, a pressure pillow, and the like. Also, typically another meter of tubing extends between these various other set components and the dialyzer or other blood treatment device. Numerous other known devices may also be positioned on the blood sets, such as filters. 
     In the early days of dialysis, blood lines and dialyzers were hand-assembled before dialysis, and then disassembled, piece-by-piece, after dialysis for cleaning and resterilization. These early dialyzers were of the plate dialyzer form, and, generally, everything was reused except for the dialyzing membranes. Typically, glass chambers and various metallic fittings were press fit into latex blood tubing, with these components being reused a large number of times. 
     Since such a process was very expensive in terms of labor cost and time consumption, plastic, pre-sterilized dialyzers and blood lines were introduced in the late 1960&#39;s. Initially, these items were disposed of after a single use. However, in due course, the dialyzers particularly began to be reused, always on the same patient and typically for only four to six uses. In countries with less government funding and/or lower cost of labor the reuse of dialyzers, bloodlines, and even fistula needles has been and still is common, despite safety issues. 
     When U.S. government funding of dialysis began in the mid 1970&#39;s, dialyzer reuse substantially disappeared. However, since another funding change in 1982, U.S. dialyzer reuse has been once again increasing. 
     Particularly, hollow fiber dialyzers have been reused, especially since the introduction of non-cellulosic membranes such as polysulphone, which are more capable of exposure to oxidizing agents such as more concentrated liquid bleach, so that at the present time most hemodialyzers are reused, with the reuse typically being done with semi-automated equipment that controls the rinsing, bleach and antiseptic solution application, and other aspects of the disinfection process. Typically, in the more recent reuse techniques, the dialyzer is first disconnected from the arterial and venous blood sets, which are thrown away. Hollow fiber dialyzers have their headers removed in some cases so that the fiber manifolds can be swabbed and cleaned. Then, the dialyzers are connected by short reuse tubes which join its blood inlet, outlet, and dialysate ports to the respective ports on the reuse equipment. The blood and dialysate pathways are sequentially rinsed, followed by application of a bleach solution and another water rinse, following which the dialyzer is filled with a disinfectant solution. The dialyzer is then separated from the short reuse connecting tubes capped, and then stored until the patient&#39;s next dialysis. Dialyses are typically performed on a patient three times a week. 
     Immediately prior to the next use, the dialyzer is typically connected to a new arterial set that has been previously primed with sterile, physiological saline. Then a venous set is attached. The system is rinsed with sterile physiologic saline solution for essential elimination of the disinfectant. 
     Commonly, blood lines of the arterial and venous sets have not been reused, partly because the cost of blood lines is less than the cost of dialyzers, and also because blood lines are more difficult to reuse than dialyzers. This is because, contrary to the typical hollow fiber dialyzers, traditional blood lines have numerous branch lines, dead end spaces, and enlarged spaces such as are found in the bubble removal chambers and pressure pillows. Thus, efficient, effective cleaning of traditional arterial and venous sets is difficult or impossible. 
     Also, conventional arterial and venous sets are more difficult to set up for dialysis reuse than typical hollow fiber dialyzers, since the above mentioned components also cause difficulties in the removal of the chemical sterilant prior to reuse. The presence of filters, as are commonly found in the venous sets, presents a major obstacle to effective cleaning prior to reuse. Likewise, arterial and venous sets tend to be long and cumbersome after they have been unwound, making it difficult to manipulate the set during reuse, storage, and setup. 
     Additionally, unlike dialyzers, certain components of the prior art blood lines are subjected to repeated mechanical force which, as they are made from materials which degrade with use, and thus are not ideal for reuse. This also raises safety issues. For example, the roller pump tubing segment typically carried by blood sets can quickly suffer from a deterioration in elasticity, since the pump segment tubing is crushed and reexpanded thousands of times by the action of the roller pump. The functioning of the pump segment tubing depends upon its elastic “spring back” capability. With a loss of some of that characteristic to spring back from the crushing provided by the roller pump, the amount of blood pumped per rotation of the roller pump rotor decreases. To make matters worse, this can go unnoticed as blood flow rates are typically calculated indirectly in the blood pump by a measurement of the rotational speed of the pump rotor, so that the flow rate may decrease even though the pump rotor speed is maintained. This can take place in part because plasticizers of the typically PVC roller pump segment may have leached out or otherwise because of characteristics of the materials used. 
     Also, a worn pump segment or diaphragm may shed into the pumped blood excessive amounts of particles from the plastic of which the segment is made. 
     Also, blood filters and transducer protector filters are reused only with difficulty and inefficiency, because the blood tends to clog the openings of the respective filters. Likewise injection sites may quickly wear out due to repeated punctures and the loss of elasticity as a consequence of use in a dialysis procedure. Organic material that collects in the puncture sites of elastomeric injection site partitions is especially difficult to remove and decontaminate. 
     Currently, arterial and venous sets for dialysis are reused in some clinics. However, in such reused sets the arterial blood line is generally not equipped with an arterial chamber, which prevents accurate monitoring of arterial pre-pump or post-pump pressures, raising a significant safety issue. Likewise, venous blood lines that are reused generally do not include a filter, which raises another significant safety issue. Furthermore, the reusable arterial and venous blood lines generally lack injection sites and other branch lines, which creates a significant inconvenience and a safety issue. 
     The reason for these deficiencies in the above reusable blood lines lies in the difficulty of reusing blood lines which have chambers, filters, injection sites, dead end side ports, and branch lines. 
     Luther et al. U.S. Pat. No. 4,612,170 discloses a blood oxygenator which has a removable and reusable heat exchanger. The remainder of the oxygenator and the blood lines are apparently not intended not to be reused. 
     Also, the Medisystems Corporation offered for sale during the 1970&#39;s and 1980&#39;s a neonatal venous line for dialysis in which a central chamber with filter was removably connected at both ends to lengths of tubing which each carried a branching connector site. The purpose of this was to permit replacement of the filter in case the filter became severely clotted during dialysis, to which neonatal dialysis is sometimes prone. It is not believed that any suggestion was made about reuse of any of the components of the neonatal venous line. 
     DESCRIPTION OF THE INVENTION 
     By this invention, a blood treatment method is provided, which is typically a hemodialysis technique but may comprise other blood treatment methods as well. The method comprises the following steps: 
     One flows blood sequentially through connected members which comprise a first conduit; a first blood handling member comprising at least one of a first debubbling chamber and a pump device fitment; a second conduit; a blood treatment device such as a membrane dialyzer; a third conduit; a second blood handling member comprising at least one of a second debubbling chamber and pump device fitment; and a fourth conduit. In a preferred embodiment, the blood treatment device is a hemodialyzer. Typically, blood is withdrawn from the patient into the first conduit, and returned to the patient through the fourth conduit. The conduits are typically flexible plastic tubes of the arterial and venous blood sets, although rigid materials and/or non-tubular shaped conduits can preferably be employed in certain circumstance such as cassetted devices or conduits that are permanent or semi-permanent. Attachments to the treatment device or monitoring/supply device. Following such treatment, one terminates the flowing of blood and substantially removes the blood from the above components. 
     In accordance with this invention, at least one of the first and second blood handling members is disconnected from the respective flexible tubes and removed. One then connects ends of at least one of the first and second conduits and/or the third and fourth conduits together, to recreate a blood flow path with the absence of at least one the first and second blood handling members. At least one of the first and fourth conduits are then connected at a free end to a source of cleaning/storage solution, which may sequentially or otherwise include water for rinsing, bleach, and a disinfecting solution used for storage of the blood lines, either with the blood lines being connected to the blood treatment device (hemodialyzer) or separate therefrom if desired. One then flows the cleaning/storage solution through the first through fourth conduits and, optionally, the blood treatment device which in that circumstance is not disconnected from the tubes. 
     Prior to such connection, the ends of the first, second, third and fourth conduits are preferably treated with an antimicrobial agent such as liquid bleach, following which, the first and second, and the third and fourth, conduits may be connected, thus reducing the risk of microbial contamination. 
     It is preferred that the above blood treatment method is performed a plurality of times, for example a dozen or more times, with at least some of the same first through fourth conduits. This can save 65 percent or more of conventional, fully disposable plastic of the blood line sets (by weight) in each dialysis procedure, since the first through the fourth conduits may comprise the longest portions of the respective arterial and venous sets. Such a reuse, if universally used in all current United States dialysis procedures, could reduce the consumption of plastic up to four million kilograms per year, which must now be both paid for and then disposed of as biologically hazardous material. 
     It should also be added that, particularly in the situation where the blood lines remain connected to the dialyzer during cleaning and storage for reuse, the reuse of the first through fourth conduits can be accomplished at an extremely low increased cost compared to the reuse of the membrane dialyzer by itself. The reuse cycle with a conventional reuse machine can be practically the same whether the dialyzer is connected to the reuse equipment alone, or with attached long tube assemblies comprising the first through fourth conduits. Preferably, these long conduit assemblies are free of branch lines, dead end spaces associated with branch lines and other components, and other features that inhibit their reuse. 
     If desired, either or both of the second and third conduits may be permanently connected to the dialyzer. 
     Also, the performance standards of the first through fourth conduits on reuse can remain high through a dozen reuses or more, providing performance that is substantially equivalent to the original equipment specifications. It is generally preferred, to enhance reuse capability, that the first, second, third, and fourth (first through fourth) conduits are tubes made of a plastic which is substantially free of plasticizers, or at least leachable plasticizers. For example, polyurethane, silicone, polycarbonate and similar materials may be used. Also, thermoplastic elastomer materials may be used such as Kraton, sold by The Shell Chemical Company. 
     Typically, with each reuse of the first through fourth conduits, new first and second blood handling members may be respectively connected between the first and second, and the third and fourth, conduits. Priming solution may be passed through the connected conduits blood handling members, and blood treatment device (dialyzer), followed by flowing blood sequentially therethrough in accordance with the original method described above. 
     Further in accordance with this invention, an arterial or venous set for blood handling is provided, usable in the above method. The set comprises of a first typically flexible tube having ends which respectively carry a first connector (typically a dialyzer connector) and a second connector. A central assembly comprises a pathway conduit having at least one of a blood degassing chamber, a connected branch tube, a pump device fitment, and an injection site. The central assembly carries a third connector which is connected with the second connector, and a fourth connector. 
     A second typically flexible tube is also provided to the set, having ends which respectively carry a fifth connector and a sixth connector (typically a patient access connector). The fifth connector is connected to the fourth connector of the central assembly. At least the second and fifth connectors are of the type which permit repeated connection and disconnection to permit repeated, sealed blood flow through the set while the connectors are connected, so that they may be reused time after time, while the central assembly may be replaced. 
     The first flexible tube may correspond exactly to the previously discussed second or third conduits. The second flexible tube may correspond exactly to the first or fourth conduits, depending on usage. 
     Also, it is preferred for at least the second connector and the fifth connector to define first sealing surfaces that respectively sealingly abut against other sealing surfaces of the third and fourth connectors, to which they are respectively connected. The second and fifth connectors also have second sealing surfaces, the latter two connectors being also connectable with each other to form a sealed connection by contact of the second sealing surfaces while the first sealing surfaces are positioned in exposed manner within the connected second and fifth connectors. This latter condition is accomplished after the central assembly has been removed, and the first and second tubes are connected together for cleaning and reuse. The second sealing surfaces form a sealed connection between the second and fifth connectors by sealing contact together, while the first sealing surfaces in this condition are positioned in exposed manner within the connected second and fifth connectors, so that antimicrobial solution in the joined first and second flexible tubes can be in contact with the first sealing surfaces. Thus, upon desired reuse of the first and second tubes, they may be connected again with the third and fourth connectors of a new central assembly under aseptic conditions since the first sealing surfaces have been cleaned and rendered aseptic. 
     The second and fifth connectors may each define a threaded sleeve of differing diameter compared with the other sleeve, to permit telescoping, threaded interengagement for a locking connection while the second sealing surfaces are in sealing abutment. 
     Also, the threaded sleeve of at least one of the second and fifth connectors may be threaded both inside and out to provide engagement between the second and fifth connectors, and also to alternatively provide engagement with the connectors of the central assembly. 
     Alternatively, an O-ring connector system may be used in which at least one O-ring comprises at least one first or second sealing surface. 
     Further in accordance with this invention, a flow through blood treatment device and a connected blood set portion comprises a housing, a blood inlet, a blood outlet, and at least one membrane in the housing. The housing defines a blood flow path between the blood inlet and outlet on one side of the membrane, and a second flow path defined on the other side of the membrane. The blood inlet and the blood outlet are each respectively connected to lengths of first blood flow tubing by first connectors positioned at one end of each of the respective lengths of first blood flow tubing, which connectors may provide permanent connection if desired. 
     The first blood flow tubing carries on its other end a second connector which is connected to a fifth connector (similar to that previously described) carried on one end of a second blood tube. Each length of the second blood tube is connected to a sixth connector, typically a patient access connector, on its end opposed to the end which carries the fifth connector. Thus, a blood treatment device such as a dialyzer may be connected to one or both of the arterial and venous blood sets, in which each of the inlet and outlet tubing assemblies comprises first and second lengths of tubing which are removable one from the other by disengagement of the respective connectors. 
     Such an arrangement may be cleaned and stored for reuse. Then, when reuse is desired, the respective lengths of first and second tubings can be disconnected, a central assembly containing, for example one or more blood degassing chambers and/or a blood pumping device such as roller pump tubing, may be connected between the respective first and second tubes so that the blood treatment device becomes ready for use. 
     The respective arterial and venous sixth connectors on the free ends of the second tubes may be connected to each other so that the flow path of the blood treatment device is formed into a closed loop, for storage purposes. Alternatively, the respective sixth connectors may be connected to opposed ends of a short shunt tube or an overconnector for the same purpose. 
     Particularly, the second and fifth connectors of the above device may have the design previously described, where the connectors define first and second sealing surfaces and where the second and fifth connectors are connectable with each other, with abutment together of the second sealing surfaces while the first sealing surfaces are positioned in exposed manner within the connectors, so that the first sealing surfaces may be cleaned and rendered aseptic for subsequent sealing contact with a sealing surface of another connector. 
     Because the long first through fourth tubes may be reused many times, they may be made of larger inner cross-sectional area at a very small cost increase, especially when factored over the many separate dialyses in which they are used. Larger inner cross-sectional areas, for example about 0.17 to 0.4 cm 2 , can desirably reduce the flow pressure drop, which is particularly of advantage in the higher flows of modern dialysis procedures. 
     Preferably, new first and second blood handling members may be incorporated into the blood treatment device which is to be reused after the antimicrobial agent has been completely removed from the system and replaced with normal saline solution. Thus, setup can be fast and efficient, because the greater part of the blood sets are already primed. 
    
    
     DESCRIPTION OF DRAWINGS 
     FIG. 1 is plan view of a connected dialyzer, arterial blood set, and venous blood set in accordance with this invention; 
     FIG. 2 is a generally schematic elevational view showing the dialyzer and blood sets of FIG. 1 connected to a reuse machine for cleansing of the system for later reuse, with certain set components removed; 
     FIGS. 3 and 4 are enlarged, detailed longitudinal sectional views illustrating one embodiment of joined connectors as used in FIG. 1; 
     FIG. 5 is an enlarged longitudinal sectional view illustrating two of the connectors of FIGS. 3 and 4 joined together as shown in FIG. 2; 
     FIG. 6 is an enlarged, exploded longitudinal sectional view showing another embodiment of connectors as they may be joined together in the manner of FIG. 3; 
     FIG. 7 is an enlarged, longitudinal sectional view showing another embodiment of connectors which are joined together for use in the configuration of FIG. 2; 
     FIG. 8 a  is an enlarged, exploded longitudinal sectional view, showing another connector embodiment in the configuration of FIG. 1; 
     FIG. 8 b  is an enlarged longitudinal sectional view showing two connectors of FIG. 8 a  in the configuration of FIG. 2; 
     FIG. 8 c  is a longitudinal sectional view of an overconnector used in FIG. 8 b;    
     FIG. 8 d  is a perspective view, with portions broken away, of another embodiment of overconnector for use similar to the overconnector of FIG. 8 c;    
     FIG. 9 is a longitudinal sectional view of another embodiment of joined connectors as shown in FIG. 2; 
     FIG. 10 is a sectional view of the connection of the patient connectors to the reuse machine as shown in FIG. 2; and 
     FIG. 11 is a plan view of another embodiment of a dialyzer connected to a combined arterial-venous blood set in another embodiment of this invention. 
    
    
     DESCRIPTION OF SPECIFIC EMBODIMENTS 
     Referring to FIG. 1, the blood flow portions of a hemodialysis system are shown. A conventional hemodialyzer  10  has a blood inlet  12  which is connected by a conventional luer lock system to first connector  20  at an end of arterial blood set  14 . Dialyzer  10  also has a blood outlet  16 , which is connected to a first connector  52  of venous set  18 . These sets  14 ,  18  and dialyzer  10  are of conventional design except as otherwise indicated herein in accordance with this invention. 
     First connector  20  is carried by first branchless, flexible tube  22  of arterial set  14 , which first tube terminates in second connector  24 . Second connector  24  communicates with a third connector  26 , which is carried by central assembly  28  of arterial set  14 . While first flexible tube  22  is preferably without branches or other components except for approximately 100 cm. of plastic tubing, (preferably having an inner diameter of 4.5 to 7 mm. or a lumen cross-sectional area of 0.17 to 0.38 cm2) central assembly  28  may comprise a substantial number of branching and other components carried with tubing segments  29 ,  30  and  31 . A length of roller pump tubing  32  is provided, shown to be in a roller pump track  33  and being retained in line by a pair of pump tubing connectors  34 ,  36 , designed to accommodate the differing diameters of the respective lines. Connector  34  may have a branch connecting line  38  which comprises an anti-backup heparin line, as an optional feature. Between tubings  30 ,  31  a debubbling chamber  40  may be provided having conventional branch or side arm lines, one of such lines carrying a transducer protector  42  for conventional pressure measurements. At line  31 , another conventional branch line  44  may be provided for connection with a source of phisiological saline solution. Other designs of central assembly  28  may also be used. 
     Central assembly  28  terminates in a fourth connector  46 , which communicates with fifth connector  48  of a second length of flexible tubing  50 , comprising a single, unbranched tubing length of about 180 cm. length, and having a lumen cross section typically similar to first flexible tube  22 . 
     Finally, arterial set  14  may be terminated with a conventional sixth connector  53  of luer lock type. 
     If desired, components may be added or subtracted to the arterial and venous sets shown. For example, an injection site  54  of conventional design may be placed on the arterial set in the position shown, or any other desirable position, including on reusable tubing conduits  14 ,  50 ,  72 , or  18 . 
     A significant difference in the arterial set  14  of this invention over the prior art arterial sets lies in the presence and design of connectors  24 ,  26 , and  46 ,  48 . Arterial set  14  may be used in a conventional dialysis procedure. Then, at the end of the procedure, after the blood has been substantially rinsed from set  14 , connectors  24  and  26 , and connectors  46 ,  48  may be respectively disconnected, and central assembly  28  may be removed. Then, connectors  24  and  48  may be connected together in the manner to be shown below. Preferably, the mode of connection between connectors  24  and  48  is different from the mode of connection between connectors  24 ,  26  and  46 ,  48 , so that the first sealing surfaces utilized in sealing contact between the respective connectors  24 ,  26  and  46 ,  48  are open and exposed within the connected connectors  24 ,  28 , so that the application of cleaning/storage solution through the set causes cleaning and antibacterial action on these first sealing surfaces. 
     Venous blood set  18  also comprises a first connector  52 , which connects to or is integral with the blood outlet of dialyzer  10 , and is carried by a first length of tubing  56 , which may be about 80 cm long and is preferably free of branches in a manner similar to the previously described first tubing  22 . 
     First tubing  56  terminates at its other end to second connector  58  which, in turn, communicates with a third connector  60  carried by the central assembly  62  of this blood set  18 . Central assembly  62  comprises a filter-carrying debubbling chamber  64  and preferably branch lines as desired, one of said branch lines carrying a transducer protector  66  in a manner similar to the previous arterial set  14 . 
     Central assembly  62  also carries a fourth connector  68  which is in sealed, connected relation to a fifth connector  70  which is carried upon second length of tubing  72 . Second length of tubing  72  is similar in length and diameter to the other second tubing  50 , being also preferably free of branch connections, pressure pillows, injection sites, and other chambers. On-off clamps  74  are preferably externally carried on the tubings adjacent the respective connectors, and are not deemed an integral feature thereof. 
     Second tubing  72  of the venous set  18  terminates in a conventional sixth connector  76  of the luer lock type, for patient access connection. 
     Here also, at the termination of dialysis and the removal of all possible blood from the system, connectors  58 ,  60  and  68  and  70  may be disconnected, and the preferably specially designed connectors  58 ,  70  may be connected to each other, preferably in a manner as described above where the original sealing surfaces providing the sealed connection between connectors  58 ,  60  and  68 ,  70  are exposed to the connectors&#39; interior for washing and contact with the cleaning/storage solution in preparation for reuse. 
     Thus, first and second tubings  22 ,  50 ,  56 ,  72 , comprising in this embodiment about eighteen feet of tubing, can be reused in an indefinite number of dialysis procedures, resulting in substantial savings of plastic and reduced problems of the disposal of biohazard waste. With each use, it is typically contemplated that new central assemblies  28 ,  62  are connected into the respective sets between the respective first and second tubes  22 ,  50 ,  56 ,  72 , but if necessary and as possible, central assemblies  28 ,  62  may be cleaned and rehabilitated for reuse also. 
     FIG. 2 shows the set of this invention after disconnection of the central assemblies  28 ,  62 , and reconnection of the respective long tubes  22 ,  50 ,  56 ,  72 , with the dialyzer  10 , and the connected long tubes and dialyzer being mounted on a conventional reuse machine  80 . Sixth patient connectors  53 ,  76  of each set may be connected to special reuse connectors  82 ,  84  which hold connectors  53 ,  76  in sealed relation to provide cleaning/storage solution to the system with their first sealing surfaces exposed to the solution so that the surfaces are cleaned. As is conventional, short tubes  88  from reuse machine  80  connect to the dialysis ports  90  of dialyzer  10 , so that cleaning/storage solution, typically a sequence of various types of washing, sterilizing and storage solutions, are applied to the dialyzer and the tubular set components. 
     If desired, after such washing, connectors  53 ,  76 , may be connected together using an interconnector or an overconnector; the dialysis ports  90  may be closed; and the dialyzer and connected tubing may be removed from reuse machine  80  for storage until the next desired use. 
     At least some of the connectors used in this invention define first sealing surfaces that seal with one type of connector, and second sealing surfaces which seal with another type of connector in such a manner that the first sealing surfaces are positioned in exposed manner within the connectors so that antimicrobial solution in the joined connectors can be in contact with the first sealing surfaces. This later condition corresponds with the situation in FIG. 2, so that the first sealing surfaces can be exposed to the antimicrobial effect of the cleaning agents of reuse machine  80  or any reuse program desired. Thus, when new central assemblies  28 ,  62  are provided, the first sealing surfaces are placed back into sealing operation and do so under aseptic conditions, having been cleaned and subjected to antimicrobial action. 
     In illustration of this, FIG. 3 is an enlarged, longitudinal sectional view of connectors  46 ,  48  of arterial set  14 , showing the connection and the first sealing surface  92  which is generally circular in cross section and formed with screw threads  95  on male portion  94  of connector  46 , in sealing relation with surface  92   a  on female portion  98  of connector  48 . 
     FIG. 4 shows another design of connector system of the arterial set, namely connectors  24  and  26  in their connected relationship. Threaded male sleeve  100  of connector  24  is in screw-threaded engagement with female sleeve  102  of connector  26 , providing a first sealing surface  104  on male sleeve  100  and in sealing relation with female sleeve  102  at its first sealing surface  104   a.  Connector  24  also carries an outer sleeve  106  with inner threads, for use in its second connection. 
     The corresponding connectors of venous set  18  may be of similar design. 
     Referring to FIG. 5, this shows the situation when central assembly  28  is removed from arterial set  14 , and connectors  24 ,  48  are connected together as illustrated in FIG.  2 . Sleeve  98  of connector  48 , threaded both inside and out, is capable of receiving outer sleeve  106  of connector  24  in threaded relation as shown in FIG.  5 . In this configuration, the outer surface  104  of sleeve  100  of connector  24  is inwardly spaced from the inner surface of sleeve  98 , so that the first sealing surfaces  92   a,    104  of the respective connectors that form the first sealing area are open and accessible to the antimicrobial cleaning/storage solution that is provided in the configuration of FIG. 2 for cleaning of those surfaces  92   a,    104  of the respective connectors  24 ,  48  that participate in the first sealing surface. The remaining connectors  46 ,  26  are respectively connected to central assemblies  28 ,  62 , which are removed, and do not participate in the process of this invention any further. Annular, second sealing surfaces  108 ,  108   a  are provided between the inner surface of outer sleeve  106  and the outer surface of sleeve  98 , as shown. 
     Thus, upon reuse of arterial set  14 , when a new, sterile central assembly  28  is provided, one can be confident that the new first sealing surface  92  that is formed with new connectors  26 ,  46  will be aseptic. Similarly, the same procedure assures aseptic conditions for first sealing surfaces  104  of the connectors of venous set  18 . 
     Referring to FIG. 6, a preferred connector arrangement for the connectors of FIG. 3 is shown. In this embodiment, the reusable fifth patient connector  48   a,  corresponding to connector  48  of FIG. 1, can be seen to comprise a female tapered first sealing area  92   a ′ corresponding in function to the threaded seal area  92   a  of FIG.  3 . Connector  48   a  may carry an outer sleeve  110  surrounding most of the taper area and connected at an annular connection  112  with the structure  114  defining female taper surface  92   a ′. Outer sleeve  110  carries external threads  116 . 
     The mating disposable connector  46   a  corresponds in function to connector  46  of FIG. 1, so that the respective two connectors  48   a,    46   a  connect the second flexible tube  50  with the central assembly  28  of a blood set in accordance with this invention as specifically disclosed in FIG.  1 . The design of connector  46   a  varies from connector  46 . First sealing surface  118  comprises a male tapered sleeve. Outer sleeve  120  carries internal threads  122 . Male taper surface  118  of connector  46   a  can seal with female luer surface  92   a ′ of connector  48   a.  Outer sleeve  120  has internal threads  122  which engage threads  116  of connector  48   a  in locking relation. 
     Also, FIG. 6 can represent a detailed view of a preferred design for mating connectors  58 ,  70  in FIG.  1 . 
     Also shown is a disposable third connector  26   a  which is similar in function and position to third connector  26  of FIG. 1 but with a different design. Male tapered sleeve  109  comprises the first sealing surface, mating with surface  124  of second connector  24   a,  which corresponds in function to connector  24  of FIG.  1 . Thus, male tapered connector  26   a  seals at respective first sealing surfaces  111 ,  124  at conical taper  124  of connector  24   a.  Sleeve  113  of third connector  26   a  carries threads  115  for engaging the threads  127  of connector  24   a.    
     Thus it can be seen that four different connectors are used in this modification of FIG. 1 to permit central assembly  28  to be removed and replaced. 
     Then, in accordance with this invention, when it is desired to remove a central assembly  28  from between the respective first and second conduits or flexible tubes for the purposes described above, connector  48   a  may be separated and then rejoined with connector  24   a  as in FIG. 7, to link together the respective first and second tubes  22 ,  50  of the device of FIG.  1 . 
     As stated, connector  24   a  defines a female taper surface  124 , used as the first sealing surface for initial locking with a male connector  26   a  of central assembly  28  as in FIG.  1 . Now, outer sleeve  126 , having internal threads  127 , locks with the external threads  116  of outer sleeve  110 . At the same time, at least the distal end of outer sleeve  110  of connector  48   a  may comprise a female taper surface  128  which engages with male tapered surface  130  which is defined by projecting member  132  of connector  24   a.  Thus projecting member  132  defines a female taper surface  124  on the inside and a male taper surface  130  on its exterior, forming the respective second sealing area  130 ,  128  that provides the second seal between connectors  24   a,    48   a.    
     In this latter connection, the first luer taper areas  92   a ′ and  124 , as well as adjacent surfaces  129  and  129   a,  are exposed to fluid flow through the connectors and the respective tubes  22 ,  50  as shown in FIG. 7 for cleaning and antibacterial action. Accordingly, upon reuse of tubes  22 ,  50  by reconnection with another central assembly, the connectors  24   a,    48   a  can form an aseptic seal in their respective first sealing areas  92   a ′,  124 . 
     FIG. 8 a  shows a detailed modification of FIG. 1, in which the first tube  22  is terminated by connector  24   b,  which is shown to be a male luer lock-type connector capable of connecting with connector  26   b  in a manner analogous to the previously described connectors  24 ,  26 . 
     Second tubing  50  connects with fourth connector  48   b,  which is a female-type luer lock connector and which connects with connector  46   b  in a manner similar to the previous connectors  46 ,  48 . 
     Then, in FIG. 8 b,  a detail from the situation of FIG. 2 is shown, where central assembly  28  and second and third connectors  26   b,    46   b  have been removed, with connectors  24   b,    48   b  being brought together in connected but spaced relationship by an overconnector  136 . Each of connectors  24   b,    48   b  respectively carry an integral locking ring  132  and sleeve  134 . Connector  48   b  may be of the conventional design for a female luer connector but with this added, integral outer sleeve  134 . Locking ring  132  has internal threads  132   a,  while sleeve  134  may be without threads. 
     It should be noted that the respective connectors  24   b,    48   b  can engage each other in conventional luer lock relation. However, in the configuration shown in FIG. 8 b  they do not. Rather, overconnector  136  is provided, being of generally tubular form, to enclose and to retain the respective locking rings  132 ,  134  of the connectors in sealed, spaced relation as shown. Overconnector  136  may be made of a somewhat resilient material so that the respective connectors  24   b,    48   b  may be each connected to it in snap-fit relation. Also, overconnector  136  defines an inner, annular spacing member  142  to provide inner spacing for connectors  24   b,    48   b  by engagement of the sleeves  132 ,  134  with member  142 . 
     The respective second seal area of connector  24   b  may comprise the outer surface  133  of sleeve  132 , while the second seal of connector  48   b  comprises the outer surface  135  of sleeve  134 . It can be seen that the first seal area for connector  24   b  is the conventional male luer taper surface  144 , while the first sealing surface for connector  48   b  is the female luer taper surface  146 . 
     One advantage of this system lies in the fact that only three different types of connectors need to be provided. Connector  26   b  can be seen to be of identical design to connector  48   b,  while connector  46   b  may be identical in design to connector  24   b.  This simplifies both the molding cost and the manufacture of the system, since the number of designs is reduced. 
     The third connector, which is overconnector  136 , is shown in FIG. 8 c  in its longitudinal cross section. Overconnector  136  may have optional end retaining members  138 ,  140 , performing as snap-fit detents, which may be continuously annular or interrupted projections as desired, for retention of the respective connectors pressing inwardly against inner annular spacing member  142 . Overconnector  136  may also be of differing end diameters as shown to accommodate the differently sized sleeves  132 ,  134 . Also, overconnector  136  may carry integral sealing rings  143 ,  143   a  to press against the respective outer surfaces  133 ,  135  of sleeves  132 ,  134  to provide the desired second seal in the second sealing area. 
     Thus a sealed connection can be provided between the respective connectors  24   b,    48   b,  by the use of overconnector  136 , so that a sealed connection is provided without the use of the respective luer taper surfaces  144 ,  146  of the respective connectors. Rather, these surfaces  144 ,  146  are exposed to the flow of fluid through the respective flexible tubes  22 ,  50  so that these first sealing areas  144 ,  146  can be cleaned and exposed to antimicrobial activity. Thus they may be reused in an aseptic seal with a new central assembly  28 . 
     Referring to FIG. 8 d,  a perspective view of another overconnector  136   a  is shown. While it is shown to be tubular in nature, it may be molded of a single shot of plastic having a plastic living hinge  150  so that it forms two pivotable semicylindrical halves  152 ,  154  connected together by a conventional clasp  155 . Retaining, annular endwalls  154  may be provided at each end, plus a central, inner ring  157  or the like to space the connectors in the overconnector. Thus, overconnector  136  may be applied laterally to the respective connectors  24   b,    48   b  and snapped together to form the desired sealed connection for the processing phase of the set prior to reuse, per FIG.  2 . 
     Alternatively, overconnector  136  may simply comprise an interference fit tube, optionally with inner, annular sealing member  142 , to provide second seal areas  141 ,  143 . Such a tube may be elastomeric, for example silicone or thermoplastic elastomer. 
     Referring to FIG. 9, another embodiment for the connectors shown in the connections of FIG. 2 is shown. 
     Connectors  24   c,    48   c  may be used as replacements for connectors  24 ,  48 , and also connectors  58 ,  70  as shown in FIG.  2 . These connectors have been previously connected as correspondingly shown in FIG. 1 with other connectors which may be disposable. Now, the respective first and second tubes  22 ,  50  are brought together as in FIG. 2 for the purposes described above. 
     In this embodiment, connector  24   c  defines an aperture having a first, outer bore  200  of a diameter which is greater than inner bore  202  of the aperture shown. A first O-ring  204  is provided in the inner bore portion  202 , while a second O-ring  206  is provided to the outer bore portion  200 . 
     Connector  48   c  defines a lumen  207  extending through it, and a tubular projection having an inner portion  208  of a diameter that is greater than the diameter of an outer projection portion  210 . Outer projection portion  210  carries another O-ring  212 . 
     Alternatively, O-ring  206  may be carried on the first projection portion  208  rather than the inner surface of bore portion  200 . The technology used with respect to the specific O-rings with respect to their securance and the materials of which they are formed may be conventional. 
     Thus, while connectors  24   c  and  48   c  may replace connectors  24 ,  48  (and connectors  58 ,  70 ) in the embodiment of FIG. 2, they are also capable of connecting with other connectors as indicated in the embodiment of FIG. 1 so that the desired central assembly may be placed between the respective connectors. The connectors of the central assembly may be proportioned to form a seal with the respective O-rings  204 ,  212 , so that these seals define the respective first sealing areas (as previously discussed) for the connectors  24   c,    48   c.  Then, when the central assembly is to be disconnected and removed, the respective connectors  24   c,    48   c  may be brought together as shown in FIG. 9, with O-ring  206  comprising the second seal area (discussed previously) while the respective first O-rings  204 ,  212  are exposed as is desired for the first seal areas to contact with antiseptic solution passing through conduits  22 ,  50 , to permit their restoration back into aseptic condition for reuse, along with tubes  22 ,  50 . 
     Referring to FIG. 10, sixth connector  53  is shown in its connected relation with reuse port connector  82  which, in turn, is connected to the reuse apparatus  80  as shown in FIG.  2 . The connection of connector  76  with reuse port connector  84  may be of similar design. 
     After the extracorporeal circuit comprising tubes  50 ,  22 ,  56  and  72  and dialyzer  10  have been essentially cleared of blood, the central assemblies  28 ,  62  removed, and the respective tubes interconnected as previously discussed, the remaining set portion is connected to the reuse apparatus  80  for cleaning and preparation for storage, prior to reuse. 
     Reuse port  82  has a first annular sealing surface  81  and an annular stop  83 . 
     Connector  53  defines a conventional first annular sealing surface  77  comprising a male taper, for use in its connection with a fistula needle set or the like while blood is being circulated through the system. 
     Connector  53  also carries a conventional sleeve  78  having locking threads  78   a.  The outer annular surface  79  of sleeve  78  may then serve as the second sealing surface in accordance with this invention, engaging with the annular sealing surface  81  of reuse port  82 , for sealing engagement while in the configuration of FIGS. 2 and 10. Thus, as cleaning/disinfecting fluid passes from reuse device  80  through reuse connector  82  and sixth connector  53 , the male taper first sealing area  77  may also be cleaned and disinfected prior to storage and reuse of the set. 
     Reuse port  82  may be somewhat flexible and resilient so that connector  53  can snap-fit into and out of recess  81   a  defined by connector  82  at the sealing surface area  81 . 
     Referring to FIG. 11, a different embodiment of the blood conduits of a dialysis system in accordance with this invention is disclosed. As before, dialyzer  10  may be identical to the dialyzer of FIG.  1 . The first tubing  22  of the arterial set may connect through first connector  20  to blood inlet  12  of the dialyzer. First tubing  22  may be identical to the tubing of FIG. 1, connecting by connector  24  to a different central assembly. 
     Specifically, central assembly  160  serves the function of both of the central assemblies of FIG. 1, with respective first and second lines  22 ,  50 ,  56 , and  72  being connected thereto, the latter four blood lines being identical if desired to those of FIG.  1 . 
     Connector  161  connects to roller pump tubing  32   a  of central assembly  160 , with a branching heparin line  38   a  being provided if desired. Roller pump  32   a  connects to double chamber unit  162 , typically made of a blow molded plastic parison, and being made of a substantially stiff plastic although more resilient material may be used if desired. 
     The blood from pump segment  32   a  passes into chamber  164 . A branch connector line  166  is defined by structure  162  to connect to a saline line  168 . A top port  167  permits connection to a transducer line  169 . An outlet port  170  communicates with tubing  172  that carries an injection site  174  and outlet connector  176 , which may correspond in structure and function to connector  46  of FIG.  1 . Connector  176  may connect with fifth connector  48  of second flexible tubing  50 , which may be identical to the corresponding second tube of FIG.  1 . Second flexible tube  50  terminates in a sixth patient connector  52 , shown to be connected to a fistula needle and tube  178  of conventional design. Thus the arterial set is shown. 
     Turning now to the venous side, blood outlet  16  of dialyzer  10  is connected to connector  52  of the first venous tubular portion  56 , identical if desired with the corresponding structure of FIG.  1 . First tube  56  terminates in second connector  58  as before, and communicates with third venous connector  180  of the central assembly  160 , communicating with conduit  182  that leads to second chamber  184 . Chamber  184  also has branch ports providing communication with the chamber for transducer protector line  186  and another line  188 . 
     Chamber  184  has a bottom exit through filter  190  which may be integrally attached and of a design similar to that shown in U.S. Pat. No. 5,328,461. Bottom exit port communicates with tubing  192  which carries an injection site and fourth connector  196 , which may be similar in structure and function to connector  68  of FIG.  1 . 
     Connector  70  is carried by second venous tube  72 , which may be identical to tube  72  of FIG.  1 . Second venous tube  72  is terminated by a sixth connector  76 , shown to be in communication with another fistula needle and tube  198 . 
     Thus, this system may function in the manner similar to the arrangement of FIG. 1, using any of the connector designs shown herein and others as well, to provide dialysis to a patient, the blood access being through fistula sets  178 ,  198 . At the termination of dialysis, as in the previous embodiment, connectors  24 ,  48  may be separated and connected to each other, while connectors  58 ,  70  may be similarly separated and connected to each other, so that the multiple chamber central assembly  162  is removed, and the system assumes the configuration of FIG. 2 for washing, sterilization, and storage until reuse is again desired of the dialyzer and tubing. 
     The above has been offered for illustrative purposes only, and is not intended to limit the scope of the invention of this application, which is as defined in the claims below.