Abstract:
Splitable-tip catheters are disclosed with bioresorbable adhesive to provide spatial separation of distal tip elements during use. The invention can be particularly useful in hemodialysis applications where it is desirable to separate blood extraction and return lumens. The adhesive facilitates insertion of the distal end of the catheter as an assembly, e.g., into a blood vessel using a single guidewire, while the bioresorbable nature of the adhesive allows the tip elements to separate in vivo.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional of U.S. patent application Ser. No. 10/874,298 filed on Jun. 9, 2004 and entitled “Splitable Tip Catheter With Bioresorbable Adhesive,” which is hereby incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention generally relates to catheters and preferably to multi-lumen catheters used for vascular access. 
       BACKGROUND OF THE INVENTION 
       [0003]    Multi-lumen catheters and, in particular split-tip catheters, are desirable for various treatment applications such as hemodialysis where fluid extraction and infusion occur simultaneously. Hemodialysis is the separation of metabolic waste products and water from the blood by diffusion through a semipermeable membrane. Typically, a hemodialysis unit is connected to a patient&#39;s body by a catheter. The catheter&#39;s distal end is placed in a blood vessel and its proximal end is connected to a hemodialysis unit. 
         [0004]    During hemodialysis, a patient&#39;s blood flows through a double lumen catheter to the hemodialysis unit which provides filtration and controls the flow of blood. A double lumen catheter has two lumens that independently allow fluid extraction and return. For example, one lumen can be used for removing blood from a patient for processing in the hemodialysis machine and the other lumen can be used for subsequently returning the processed blood back to the patient&#39;s circulatory system. 
         [0005]    Parameters that can be varied to achieve adequate hemodialysis include blood flow rate, dialysis solution flow rate, dialyzer competency, and temperature. Generally, raising the blood flow rate increases dialyzer clearance of small molecular weight solutes. Consequently, higher blood flow rates have been used to improve dialysis clearance efficiency. However, conditions such as access recirculation decrease clearance. Access recirculation is the recirculation of treated blood back into the hemodialysis unit causing inadequate dialysis. This problem effectively reduces blood flow rates thereby diminishing the efficiency of the hemodialysis process causing the duration of the treatment needed for dialysis to increase. Access recirculation can be particularly of concern when using a double lumen catheter due to the close proximity of the intake and outflow ports at the distal tip of the catheter. 
         [0006]    Various double lumen catheter designs have been suggested for the purpose of reducing access recirculation. The distal ends of intake and outflow lumens have been longitudinally spaced 20-30 mm apart to prevent recirculation. For example, Twardowski et al. U.S. Pat. No. 5,569,182 discloses that the lumen for return of blood back into the vein should terminate beyond the extraction lumen. The purpose of this is to prevent cleansed blood, exiting from the outlet point of the catheter, from re-entering the catheter&#39;s blood inlet point and returning to the dialysis machine. However, certain disadvantages have been noted by such large longitudinal spacing between the distal ends of the respective lumens. For example, blood flow stagnation in the region of the blood vessel between two widely separated tips can lead to clot formation. 
         [0007]    In addition to longitudinal spacing of the distal openings of the lumens for blood extraction and return, others have suggested that the distal end of a multi-lumen catheter can be split such that the distal tips of the lumens can independently move in the blood vessel to optimize the fluid dynamics of the different functions (blood extraction and blood return). 
         [0008]    In general, good catheter outcomes depend on proper positioning of the catheter in the blood vessel. Insertion complications include pneumothorax, hemothorax, and cardiac tamponade, as well as poor blood flow rates, poor clearances, and long-term complications such as catheter dysfunction and fibrin sheath formation. These complications are compounded by the use of double lumen catheters because of their size. 
         [0009]    Additional difficulties can be encountered when split distal tips must be inserted into a blood vessel. Typical insertion techniques of conventional double lumen catheters require the use of a peel-away sheath over a guidewire. Frequently there is a preference to insert the catheters without the use of a peel-away sheath to eliminate the risk of an air embolism by the use of two guidewires, or alternatively, inserting the guidewire through the one lumen and threading it through the side hole channels of the other lumen thus utilizing one guidewire, referred to as the “weave technique”. Moreover, precise positioning of a multi-lumen catheter can be challenging because the exact placement of the tips can not be assured. An improperly positioned multi-lumen catheter can further result in sub-optimal functionality requiring intervention. 
         [0010]    Thus, there remains a need for a multi-lumen catheter that addresses the problems of access recirculation yet retains the comparative ease of insertion of a single lumen catheter. 
       SUMMARY OF THE INVENTION 
       [0011]    Splitable-tip catheters are disclosed having tip elements that are joined with biodegradable or biosoluble adhesive to facilitate insertion and yet provide spatial separation of distal tip elements during use. The invention can be particularly useful in hemodialysis applications where it is desirable to separate blood extraction and return lumens. The adhesive facilitates insertion of the distal end of the catheter as an assembly, e.g., into a blood vessel using a single guidewire, while the biodegradable or biosoluble nature of the adhesive allows the tip elements to separate in vivo. The term “bioresorbable” as used herein encompasses both biodegradable and biosoluble materials. 
         [0012]    The biodegradable adhesive, applied to the contacting surfaces of the distal tips of the extraction and return lumens, can be formed from various polymer or copolymer compositions. Additionally, the adhesive can be composed such that the time in which the adhesive biodegrades or biodisolves can be in the range of about 1 second to 1 hour. More generally, the adhesives of the present invention can bio-resorb from about 1 second to about 7 days, or from about 1 second to about 1 day, or from about 1 second to about 1 hour, or from about 1 second to about 10 minutes, or from about 10 seconds to about 5 minutes. In another embodiment a splitable tip catheter is disclosed having distal fluid openings to accelerate dissolution. The biodegradable or biosoluble adhesive can be water soluble such that the introduction of saline or similar type fluid will dissolve the adhesive and facilitate the separation of the distal tip elements. 
         [0013]    An embodiment of the present invention provides a multi-lumen catheter device for hemodialysis having an elongate catheter body with at least one blood extraction lumen and one blood return lumen extending longitudinally therethrough. The proximal end of the instrument can be adapted for coupling to a hemodialysis apparatus and the distal end terminates in separable distal tip portions adapted for insertion into a blood vessel. The distal end of the catheter includes a distal extraction tip portion for fluid coupling of the extraction lumen with the blood vessel and a distal return tip portion for fluid coupling of the return lumen with the blood vessel, such that biodegradable or biosoluble adhesive joins the distal tip portions together prior to insertion into the blood vessel and facilitates the separation of the distal tip portions from each other following insertion. 
         [0014]    Another embodiment of the present invention provides a method for hemodialysis to include providing a multi-lumen catheter assembly with at least a blood extraction lumen and a blood return lumen extending longitudinally therethrough, each lumen having a proximal end adapted for coupling to a hemodialysis apparatus and a distal end terminating in separable distal tip portions for blood extraction and return where the tip portions are joined together by a biodegradable or biosoluble adhesive. The method further provides for inserting the distal end of the catheter assembly into a blood vessel and allowing the adhesive to degrade such that the distal tip portions separate from each other within the blood vessel. 
         [0015]    Therefore, the present invention addresses current problems associated with conventional split-tip catheter insertion by joining the distal tips of a split-tip catheter with biodegradable or biosoluble adhesive. After insertion of the catheter into the patient, the biodegradable or biosoluble adhesive dissolves and the distal tips of the split-tip catheter are free to move and function like conventional split-tip, double lumen, triple lumen, or multi-lumen catheters. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0017]      FIG. 1A  is a schematic, perspective view of an embodiment of the present invention showing distal tip portions joined together; 
           [0018]      FIG. 1B  is a schematic, perspective view of an embodiment of the present invention showing distal tip portions separated from one another; 
           [0019]      FIG. 1C  is a schematic view of an embodiment of the present invention in use in the body of a patient; 
           [0020]      FIG. 2A  is a cross-section view of an embodiment of the present invention showing opposed “D” shaped lumens inside an outer sheath; 
           [0021]      FIG. 2B  is a cross-section view of an embodiment of the present invention showing unibody construction utilizing opposed “D” shaped lumens; 
           [0022]      FIG. 2C  is a cross-section view of an embodiment of the present invention showing yet another unibody construction; 
           [0023]      FIG. 2D  is a cross-section view of an embodiment of the present invention showing individual lumens inside an outer sheath; 
           [0024]      FIG. 2E  is a cross-section view of an embodiment of the present invention showing a unibody construction utilizing individual lumens; 
           [0025]      FIG. 2F  is a cross-section view of a variation of an embodiment of the present invention showing opposed “D” shaped lumens; 
           [0026]      FIG. 2G  is a cross-section view of an embodiment of the present invention showing three lumens; 
           [0027]      FIG. 2H  is a cross-section view of a variation of an embodiment of the present invention showing three lumens; 
           [0028]      FIG. 2I  is a cross-section view of a yet another variation of an embodiment of the present invention showing three lumens; 
           [0029]      FIG. 3A  is a schematic, perspective view of an embodiment of the present invention showing an adhesive application using spots of adhesive; 
           [0030]      FIG. 3B  is a schematic, perspective view of an embodiment of the present invention showing an adhesive application using regions of adhesive; 
           [0031]      FIG. 4A  is a cross-section view near the distal end of a catheter according to the present invention showing distal tip portions adhered to one another; 
           [0032]      FIG. 4B  is an distal cross-sectional view of another embodiment of the present invention showing alternative adhesive disposition; 
           [0033]      FIG. 4C  is a distal cross-sectional view of yet another adhesive design; 
           [0034]      FIG. 5A  is a schematic, perspective view of another embodiment of the present invention showing distal tip portions joined and wound about one another; 
           [0035]      FIG. 5B  is a schematic, perspective view of yet another embodiment of the present invention; 
           [0036]      FIG. 5C  is a schematic, perspective view of an embodiment of the present invention showing one lumen wound about another lumen; 
           [0037]      FIG. 6A  is a schematic, perspective view of an embodiment of the present invention showing fluid openings in the distal tip portions; 
           [0038]      FIG. 6B  is a schematic, perspective view of an embodiment of the present invention showing a design having an additional center lumen; 
           [0039]      FIG. 6C  is a cross-sectional view of an embodiment of the present invention showing a design having an additional center lumen; 
           [0040]      FIG. 7A  is a schematic, perspective view of an embodiment of the present invention showing distal tip portions adhered to one another in a shape memory configuration; 
           [0041]      FIG. 7B  is a schematic, perspective view of the embodiment in  FIG. 6A  showing distal tip portions that are separated; and 
           [0042]      FIG. 8  is schematic, perspective view of an embodiment of the present invention showing distal tip portions in an alternate shape memory configuration. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0043]    As used herein, the term “bioresorbable” refers to materials that are biodegradable or biosoluble such that they degrade or break down by mechanical degradation upon interaction with a physiological environment into components that are metabolizable or excretable over a period of time. 
         [0044]    The present invention includes various embodiments of a multi-lumen catheter for hemodialysis and methods of use. As shown in  FIGS. 1A and 1B , one embodiment of catheter  10  includes an elongate body  20  having proximal and distal end  11  and  12 , and at least one blood extraction lumen  30  and at least one blood return lumen  40  extending longitudinally therethrough. Each lumen  30 ,  40  has a proximal end  30 ′,  40 ′ adapted to direct fluid to, or couple directly with, a hemodialysis apparatus (not shown), and a distal end  31 ,  41  for insertion into a blood vessel. Distal extraction and return tip portions  32 ,  42  of each lumen  30 ,  40  include a distal end opening  33 ,  43  formed therein to provide for simultaneous flow of blood in opposite directions during hemodialysis. The distal extraction and return tip portions  32 ,  42  are joined by bioresorbable adhesive  90  prior to being inserted into a blood vessel such that after insertion, the bioresorbable adhesive degrades sufficiently to allow the distal extraction and return tip portions of each lumen  30 ,  40  to separate from one another. 
         [0045]      FIGS. 1A and 1B  illustrate an outer sheath  50  which covers and encloses the lumens  30 ,  40 . The outer sheath  50  can be any shape and size and can be made of the same material as the lumens  30 ,  40  or other material compatible with insertion into a blood vessel. As illustrated in the embodiment shown in  FIGS. 1A and 1B , the outer sheath  50  terminates proximal to the distal ends  31 ,  41  of the lumens  30 ,  40  such that the distal extraction and return tip portions  32 ,  42  of each lumen can separate from one another after being inserted into a blood vessel.  FIG. 2A  shows a cross-section  2 - 2  of one embodiment of an outer sheath  50 . The outer sheath  50  can be any thickness and can have varying inner and outer shapes as well as varying inner and outer dimensions. 
         [0046]      FIG. 1C  illustrates another embodiment showing a cross-section of an elongate body  20  having unibody construction  500  which incorporates the blood extraction and blood return lumens  308 ,  408  in a single elongate body  200 . The unibody catheter can be constructed such that sheath material  500 ′ separates the lumens  308 ,  408 . The amount of sheath material around each lumen  308 ,  408  and in-between each lumen can vary but preferably allows for blood extraction and blood return in accordance with hemodialysis. Separating the sheath material in-between both lumens  308 ,  408  along a vertical axis y at one end of the unibody construction can separate the lumens from one another into distinct distal portions. A variety of methods known to one skilled in the art can be used to separate the material such as for example cutting or scoring. 
         [0047]    In another embodiment of the present invention the elongate body  20 ′ can be formed such that the blood extraction and blood return lumens  300 ,  400  are non-circular to increase the areas of their outer surfaces  350 ,  450  that are in contact as shown in cross-section CC in  FIG. 2C . Here, the distal extraction and return tip portions  320 ,  420  of each lumen can have bioresorbable adhesive on all or any part of their facing surfaces  350 ,  450 . As shown in  FIG. 2C , the facing surfaces can be joined by spots  91  as well as regions  94  of adhesive (further described below). The configuration of the lumens in this embodiment allows the lumens, as joined, to resemble a single, circular lumen prior to insertion. After insertion of the distal extraction and return tip portions  320 ,  420 , into a blood vessel, the bioresorbable adhesive  90  can dissolve allowing the tip portions to separate and facilitate hemodialysis. 
         [0048]    The lumens  30 ,  40  can have a variety of cross-sectional shapes and sizes but preferably, as shown in the embodiment in  FIG. 1A , the lumens are “D” shaped. Alternately, each of the lumens  30 ,  40  can have a cross-sectional shape, size, or area that can be distinct from the other, as shown in  FIGS. 2A through 2I .  FIG. 2A  is a cross-section view of an embodiment of the present invention showing opposed “D” shaped lumens inside an outer sheath.  FIG. 2B  is a cross-section view of an embodiment of the present invention showing unibody construction utilizing opposed “D” shaped lumens.  FIG. 2C  is a cross-section view of an embodiment of the present invention showing yet another unibody construction.  FIG. 2D  is a cross-section view of an embodiment of the present invention showing individual lumens inside an outer sheath.  FIG. 2E  is a cross-section view of an embodiment of the present invention showing a unibody construction utilizing individual lumens.  FIG. 2F  is a cross-section view of a variation of an embodiment of the present invention showing opposed “D” shaped lumens.  FIG. 2G  is a cross-section view of an embodiment of the present invention showing three lumens.  FIG. 2H  is a cross-section view of a variation of an embodiment of the present invention showing three lumens.  FIG. 2I  is a cross-section view of a yet another variation of an embodiment of the present invention showing three lumens. The lumens  30 ,  40  can be made of any material consistent with materials presently known for catheters including any material which allows the distal tip portions  32 ,  42  of the lumens to be flexible and facilitate hemodialysis. 
         [0049]    The distal extraction and return tip portions  32 ,  42  of each lumen  30 ,  40  include distal end openings  33 ,  43  formed thereon for the extraction or return of blood or other bodily fluids. The openings are preferably sized to allow the carrying of blood to and from the hemodialysis unit. The distal extraction and return tip portions  32 ,  42  can be the same length or, as shown in  FIG. 1A , can be different lengths. As shown, the distal extraction tip portion  32  of the blood extraction lumen  30  terminates proximal to the distal return tip portion  42  of the blood return lumen  40 . However, in another embodiment, the distal return tip portion  42  of the blood return lumen  40  can terminate proximal to the distal extraction tip portion  32  of the blood extraction lumen  30 . The longitudinal distance d between the distal extraction and return tip portions  32 ,  42  of each lumen  30 ,  40  can vary but preferably allows for performing blood extraction and blood return in accordance with hemodialysis. Prior to the distal end  11  of the catheter being inserted into a blood vessel, the distal extraction and return tip portions  32 ,  42  of the lumens  30 ,  40  are joined to one another with bioresorbable adhesive  90 . After insertion into the blood vessel, bioresorbable adhesive  90  facilitates the separation of the distal extraction and return tip portions  32 ,  42  of the lumens  30 ,  40 . 
         [0050]    The bioresorbable adhesive  90  used to join the distal extraction and return tip portions,  32 ,  42  of the lumens  30 ,  40  to one another can be a composition selected from the group of polymers consisting of polylactides, polyglycolides, polylactones, polyorthoesters, polyanhydrides, and copolymers and combinations thereof. In general, bioresorbable adhesives have bonding elements and degradable elements. The degradable elements can have the components of polylactide, polyglycolide and polylactones (polycaprolactone). The bonding elements can have hydrogen bonding strength (polyvinyl alcohol, polysaccharides) or can be able to polymerize as a single component (cyanoacrylates) or as two componets (epoxy compound plus amino compounds, or radical(light) initiators of acrylate compounds). 
         [0051]    Proteins, sugars, and starch can also be used as an adhesive. By way of non-limiting example, antithrombotic agents such as heparin and hirudin, citrate, antithrombin-heparin complex, and albumin heparin complex as well as anti-infective agents such as chlorohexidine, silver, antibiotics, and antiseptic agents may be added to the adhesive. 
         [0052]    In an embodiment of the present invention, polymers which can be useful include polyurethane, generally described as a copolymer of polyethylene glycol with polylactide or polyglycolide end capped with methacrylates. Another embodiment can include a two component composition, one component preferably including a low molecular weight polyurethane end capped with methacrylates, and the other component preferably including polylactide, polyglycolide, or polycaprolactone end capped with methacrylate. 
         [0053]    In another embodiment of the present invention, one or more components can be used from styrene, methyl methacrylate, methyl acrylate, ethylene dimethacrylate, ethylene diacrylate, acrylamide, diurethane dimethacrylate, polyisoprenegraft-maleic acid monomethyl ester, azobis(cyanovaleric acid), azobiscyclohexanecarbonitrile, azobisisobutyronitrile, benzoyl peroxide, iron(II) sulfate, polyvinyl alcohol, dextran, polysaccharide, epichlorohydrin, ethylenediamine, diaminocyclohexane, diamino propane, copolymers with polylactide and polyethylene oxide as the blocks and acrylate, methacrylate as the end groups, cyanoacrylates, ethyl-2cyanoacrylate, propyl-2-cyanoacrylates, pentyl-2-cyanoacrylate, hexyl-2-cyanoacrylate, and octyl-2-cyanoacrylate, ammonium persulfate and/or polyethylene glycol methacrylate when water, organic solvent such as dichloromethane, chloroform, tetrahydrofuran, acetone, petroleum ether, acetyl acetate, dimethylformamide, or the mixture thereof, is combined with the aforementioned solvents. 
         [0054]    As shown in  FIG. 1A , bioresorbable adhesive can be applied along a facing surface  35 ,  45  of either, or both, distal extraction and return tip portions  32 ,  42  of the lumens  30 ,  40  to facilitate the joining of the lumens along their longitudinal length l prior to insertion of the distal end  11  of the catheter  10  into a blood vessel. (As used throughout, “catheter  10 ” refers to the various embodiments of the present invention.)  FIG. 1A  shows bioresorbable adhesive  90  applied along a longitudinal length l of the distal extraction and return tip portions  32 ,  42  of each lumen  30 ,  40 . However, the bioresorbable adhesive  90  need not be applied along the entire length of the facing surfaces  35 ,  45  of each lumen  30 ,  40  but is preferably applied such that the adhesive facilitates the joining of the distal extraction and return tip portions  32 ,  42  of the lumens  30 ,  40  prior to insertion into a blood vessel and allows the distal extraction and return tip portions of the lumens to separate after insertion. 
         [0055]    In the embodiments described herein, the bioresorbable adhesive  90  preferably dissolves after insertion into a blood vessel to provide separation of the distal extraction and return tip portions  32 ,  42  of the lumens  30 ,  40  in a time period ranging from 1 minute to 1 hour. This range can be controlled by using different compositions of the bioresorbable adhesive  90  as well as by the amount of adhesive applied to join the distal extraction and return tip portions  32 ,  42  of the lumens  30 ,  40  together. In another embodiment with opposed distal fluid openings  80  (further described below), the bioresorbable adhesive  90  can be water soluble such that the introduction of saline or similar type fluid will effectuate the separation of the distal extraction and return tip portions  32 ,  42  of the lumens  30 ,  40 . In this instance, the adhesive will not dissolve until a time after the introduction of the soluble solution into the lumens  30 ,  40 . 
         [0056]    As shown in another embodiment in  FIG. 3A , the bioresorbable adhesive can also be applied to the facing surfaces of the distal extraction and return tip portions  32 ,  42  of the lumens  30 ,  40  in form as discrete spots  91 . The spots  91  of bioresorbable adhesive  90  can be applied continuously along the entire longitudinal length l of the distal extraction and return tip portions  32 ,  42  of the lumens  30 ,  40  or selectively in an assortment of areas thereof. Preferably, the bioresorbable adhesive  90  is applied such that the spots  91  of adhesive facilitate the joining of the distal extraction and return tip portions  32 ,  42  of the lumens  30 ,  40  prior to insertion into a blood vessel and allow the distal extraction and return tip portions of the lumens to separate after insertion. The spots  91  of bioresorbable adhesive  90  can vary in number and size in order to facilitate the joining of the tip portions of the lumens. 
         [0057]      FIG. 3B  shows yet another embodiment of the application of the bioresorbable adhesive  90  in the form of discrete regions  94 . Discrete regions  94 , like the spots  91  stated above, of bioresorbable adhesive  90  can be applied to the facing surfaces of the distal extraction and return tip portions  32 ,  42  of the lumens  30 ,  40 . The discrete regions  94  of bioresorbable adhesive  90  can also be different lengths and can be applied in addition to discrete spots  91  of adhesive such that the adhesive facilitates the joining of the distal extraction and return tip portions  32 ,  42  of the lumens  30 ,  40  prior to insertion into a blood vessel and allows the distal extraction and return tip portions of the lumens to separate after insertion. 
         [0058]      FIGS. 4A-4C  show cross-sections of the distal extraction and return tip portions  32 ,  42  of the lumens  30 ,  40  detailing alternate embodiments of the bioresorbable adhesive  90  application.  FIG. 4A  shows bioresorbable adhesive  90  applied at the contact point  70  of the facing surfaces  35 ,  45  of the lumens  30 ,  40 .  FIG. 4B  shows another embodiment of an application of the bioresorbable adhesive  90  such that the adhesive, as applied, joins non-contacting surfaces  36 ,  46  of the distal extraction and return tip portions  32 ,  42  of the lumens  30 ,  40 .  FIG. 4C  shows a variation on the embodiment shown in  FIG. 4B  where the bioresorbable adhesive  90  surrounds the distal extraction and return tip portions  32 ,  42  of the lumens  30 ,  40  forming a continuous cross-section of adhesive coating notwithstanding the distal extraction and return tip portions of the lumens extending therethrough. As stated above, the bioresorbable adhesive  90  need not be applied along the entire length of the distal extraction and return tip portions  32 ,  42  of each lumen  30 ,  40  but is preferably applied such that the adhesive facilitates the joining of the distal extraction and return tip portions of the blood extraction and blood return lumens prior to insertion into a blood vessel and allows the distal extraction and return tip portions of the lumens to separate after insertion. It should be noted that because the lumens  30 ,  40  can be various shapes, as stated above, the bioresorbable adhesive  90  need not be applied to all of the contact area  95  of the facing surfaces  35 ,  45  of each lumen  30 ,  40 , as shown in  FIG. 2C . In this embodiment, the bioresorbable adhesive  90  can be applied as a region  94 , spot  91 , or other shape, to a section of the contact area  95  and need only be applied to facilitate the joining function. 
         [0059]      FIG. 5A  illustrates another embodiment of the present invention. As shown, the lumens  30 ,  40  are twisted about, or otherwise wrapped, around one another. The wrapped lumens can be twisted about one another such that there are non-contact areas  96 , along the longitudinal length l of the distal extraction and return tip portions of each lumen  30 ,  40  as shown in  FIG. 5A . In  FIG. 5B , the distal tip elements are shown in a separated state. The distal extraction and return tip portions of each lumen  30 ,  40  can wrap around one another any number of times, as well as wrap such that one lumen  30  is wound around the other lumen  40  as shown in  FIG. 5C , or visa versa. In  FIG. 5A , bioresorbable adhesive  90  can be applied where the distal extraction and return tip portions of the lumens  30 ,  40  contact one another. As stated above, the bioresorbable adhesive  90  can be applied in discrete spots or regions where the distal extraction and return tip portion surfaces contact one another. However, the bioresorbable adhesive need not be applied to all contact points of the twisted lumens  30 ,  40  so long as the joining of the distal extraction and return tip portions of the lumens  30 ,  40  can be facilitated. The various compositions and methods of application of the bioresorbable adhesive  90  application previously described above can also be used with the twisted embodiment catheter design as well. 
         [0060]    In another embodiment of the present invention,  FIG. 6A  shows distal fluid openings  80 , in formed in the distal extraction tip portion  32  of lumen  30 . It should be understood from the drawings that in the embodiment shown, the distal fluid openings  80  can either be in addition to, or in place of, the distal end opening  33  located on the distal extraction tip portion  32  of lumen  30 . The distal fluid openings  80  can be any shape and size and can be located in a variety of places on lumen  30  as illustrated. However,  FIG. 6A  shows the distal fluid openings  80  located on facing (contacting) surface  35  of the distal extraction tip portion  32  of lumen  30 . In this embodiment, the distal fluid openings  80  can be filled or covered with fluid activated bioresorbable adhesive  900  and joined to lumen  40  along its facing surface  45 . After insertion of the catheter into a blood vessel, saline or similar type fluid can be introduced into lumen  30  at its proximal end  30 ′ such that the fluid travels through the lumen to the distal fluid openings  80  and dissolves the fluid activated bioresorbable adhesive  900  thereby separating the distal extraction and return tip portions  32 ,  42  along their longitudinal length l to facilitate hemodialysis. Bioresorbable adhesive  90  can also be applied to the contact surfaces  35 ,  45  of each lumen as previously described above in addition to the distal fluid openings  80  being filled or covered with fluid activated bioresorbable adhesive  900 . 
         [0061]      FIG. 6B  shows yet another embodiment in which the catheter  10  can be designed to facilitate separation of its distal tips  325 ,  425  after insertion into a blood vessel. Catheter  10  can include a center lumen  60  extending in-between lumens  300 ,  400  from a proximal end  120  to a separation point  62  and can be used to carry saline or a similar type fluid. At the separation point  62 , the center lumen splits into two center lumen halves  63 ′,  64 ′ each half located in a facing surface  350 ,  450  of each lumen  300 ,  400 . The center lumen  60  can be made of a variety of cross-sectional shapes but is preferably circular. As shown, the center lumen halves  63 ′,  64 ′ terminate proximal to the distal ends  310 ,  410  of lumens  300 ,  400 . (It should be noted that a mirrored portion of center lumen half  64 ′ is located in the facing surface  450  of distal return tip  425 , out of view in  FIG. 5B .) and can extend at the proximal end  120  of catheter  10  anywhere outside the patient so long as the center lumen  60  can be accessible for saline fluid introduction. As shown in  FIG. 5C , the center lumen  60  and the center lumen halves  63 ′,  64 ′ are not in fluid communication with either of the lumens  325 ,  425 . Distal extraction and return tip portions  325 ,  425  can have fluid activated bioresorbable adhesive  900  applied anywhere within center lumen halves  63 ′,  64 ′ distal of a center lumen gap  65 . The adhesive  900  can also be applied at or beyond a center lumen half end  61 , to facilitate separation of the distal tip portions  325 ,  425 . The center lumen gap  65 , of any desirable length, should remain free of fluid activated bioresorbable adhesive  900  and in fluid communication with a blood vessel in order to allow any extraneous saline or similar type fluid to be displaced between the facing surfaces  350 ,  450  and into the bloodstream during the dissolving process. 
         [0062]    In this embodiment, the catheter  10  is inserted into a patient and saline or other type fluid can be introduced into the center lumen  60  at its proximal end  120  which dissolves the fluid activated bioresorbable adhesive  900  applied at or beyond center lumen gap  65 . Once separated, the distal tip portions  325 ,  425  can facilitate blood extraction and blood return in accordance with hemodialysis through distal end openings  333 ,  433 . 
         [0063]    In  FIGS. 7A and 7B , another embodiment of the present invention is shown in which one or both of the lumens  30 ,  40  can be made of a shape memory material such that after insertion of the distal end  11  of the device into a blood vessel, and upon the bioresorbable adhesive  90  dissolving, the lumens, and more preferably the distal extraction and return tip portions  32 ,  42  thereof, can separate to a pre-adhesive position. The distal extraction and return tip portions  32 ,  42  of the lumens  30 ,  40  can be made of polymer material or other material as needed or combined to facilitate the shape memory in the described embodiment.  FIGS. 7A and 7B  illustrate the lumens  30 ,  40  in this configuration. The distal extraction and return tip portions  32 ,  42  of each lumen  30 ,  40  are joined with bioresorbable adhesive  90  prior to insertion into a blood vessel. A memory gap  93  can be located between the lumens and distal of the outer sheath  50 . The memory gap can be any length and width but preferably allows for a configuration such that the lumens  30 ,  40  are not pinched after joining. As shown, each lumen  30 ,  40  exits the outer sheath  50  in a non-parallel, diverging direction. The relative angle α at which the lumens  30 ,  40  exit the outer sheath  50  can vary. Bioresorbable adhesive  90  can be applied, in any manner described herein, to join the lumens  30 ,  40  distal of the memory gap  93 .  FIG. 7B  shows the lumens  30 ,  40  in roughly a “pre-adhesive” configuration as well as in an “after insertion into a blood vessel” configuration. It should be noted that the lumens  30 ,  40  illustrated in  FIG. 7B , can separate more or less, after being inserted into a blood vessel, as compared to their pre-adhesive state. 
         [0064]    In another embodiment, the distal extraction and return tip portions  32 ,  42  of each of the lumens  30 ,  40  can be pre-formed to exit the outer sheath  50  in a substantially parallel direction and then angularly diverge from one another, at a location distal from the outer sheath, upon the degradation of the bioresorbable adhesive  90 , as shown in  FIG. 8 . The distal extraction and return tip portions  32 ,  42  of each lumen  30 ,  40  shown in  FIG. 8 , exit the outer sheath  50  in a distal direction and are substantially parallel relative to one another. As the bioresorbable adhesive  90 , applied in any manner described herein, dissolves, the distal extraction and return tip portions  32 ,  42  of the lumens  30 ,  40  substantially separate and angularly diverge from one another along a longitudinal axis b. Distal extraction and return tip portions  32 ,  42  of each lumen  30 ,  40  can be pre-formed from polymer or similar type polymer materials to effectuate this divergence. As further shown in  FIG. 7 , the distal extraction and return tip portions  32 ,  42  can re-converge toward each other if desired or can continue diverging as shown in  FIG. 6B . 
         [0065]    In use, a catheter  10  is provided having distal extraction and return tip portions  32 ,  42  which are joined to one another using any of the bioresorbable adhesive applications described throughout this specification. The proximal end  12  of the catheter  10  can be attached to a hemodialysis apparatus using various attachment means known to one skilled in the art. The distal end  11  of the catheter  10  can be inserted into a blood vessel wherein the bioresorbable adhesive  90  is allowed to dissolve in a time in the range of 1 minute to 1 hour, such that the distal extraction and return tip portions  32 ,  42  of the blood extraction lumen  30  and the blood return lumen  40  separate from each other within the blood vessel. Blood extraction and blood return can be subsequently commenced through each lumen  30 ,  40  according to hemodialysis methods and practices. 
         [0066]    Accordingly, the embodiments of the present invention are not limited by what has been particularly shown and described, except as indicated by the appended claims. All publications and references cited herein are expressly incorporated herein by reference in their entirety.