Abstract:
Multi-lumen catheter devices having at least one split-tipped end are disclosed, together with methods of forming such split tip catheters. In one aspect of the invention, the manufacturing methods can include the steps of: providing a catheter body having at least a first and a second internal lumen extending longitudinally through the catheter body; removing a distal portion of the catheter body to form a first distal tip segment such that the first lumen extends longitudinally within this tip segment beyond the second lumen; and joining a second lumen tip segment to the catheter body in communication with the second lumen. The second tip segment can be joined to the catheter body such that it is at least partially separated from the first tip segment and, in some embodiments, preferably diverges at an angle relative to the first tip segment.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the priority of U.S. Provisional Application Ser. No. 60/980,633 filed Oct. 17, 2007 entitled “Manufacture of Split Tip Catheters,” which is herein incorporated by reference in its entirety. This application is also related to commonly owned U.S. patent application Ser. No. ______ filed concurrently herewith entitled “Catheters With Enlarged Arterial Lumens” (Attorney Docket No. 101430-238), U.S. patent application Ser. No. ______ filed concurrently herewith entitled “Fusion Manufacture of Multi-Lumen Catheters” (Attorney Docket No. 101430-236), and U.S. patent application Ser. No. ______ filed concurrently herewith entitled “Manufacture of Fixed Tip Catheters” (Attorney Docket No. 101430-240), each of which are herein incorporated by reference in their entireties. 
     
    
     BACKGROUND 
       [0002]    The present invention generally relates to catheters and preferably to multi-lumen catheters used for vascular access. 
         [0003]    Multi-lumen catheters and, in particular split-tip catheters, are desirable for various treatment applications such as hemodialysis where fluid extraction and return occur simultaneously. Hemodialysis is the separation of metabolic waste products and water from the blood by filtration. 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 typically 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. Such catheters can also include additional lumens for flushing, administration of anticoagulants or the like. 
         [0005]    Parameters that can be varied to achieve adequate hemodialysis include blood flow rate, dialysis solution flow rate, and dialyzer competency. Generally, raising the blood flow rate increases dialysis efficiency. However, conditions such as access recirculation decrease efficiency. Access recirculation is the recirculation of treated blood back into the hemodialysis unit. Excess recirculation effectively reduces dialysis efficiency and lengthens the duration of the treatment needed for adequate dialysis. 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, others have suggested that the distal end of a multi-lumen catheter can be split such that the distal tip segments can independently move in the blood vessel to optimize the fluid dynamics of the different functions (blood extraction and blood return). The introduction of an angle between the extraction and return lumens of a split tip catheter can further reduce the likelihood of access recirculation due to greater separation between inflow and outflow lumens. 
         [0008]    Moreover, it can be desirable to have the maximum possible luminal cross-sectional areas to optimize catheter flow characteristics and also to maintain adequate flow over time since flow rates tend to decrease due to factors such as catheter clotting. However, a need can remain to maintain adequate physical and mechanical properties of the catheter, for instance tensile strength and kink-resistance, and to keep overall catheter dimensions small enough for insertion and proper physiological function. With these constraints in mind, it can be advantageous to have a different shape, e.g., greater luminal cross-section, for one or the other of the lumens or split tip segments, for example, to facilitate blood withdrawal or to diffuse returning cleansed blood. In particular, the arterial (or extraction) lumen is more prone to clogging and can benefit from having a larger cross-section. However, such geometric differences are difficult to incorporate into split-tip catheters using conventional manufacturing techniques. 
         [0009]    While various techniques are known for manufacturing split tip catheters, there exists a need for more efficient and more robust techniques, especially in manufacturing split tip catheters when the divergence of the tip elements at an angle is desired or a different shape or geometry is desired for one or the other of the lumens or tip segments. 
       SUMMARY OF THE INVENTION 
       [0010]    Multi-lumen catheter devices having at least one split end are disclosed, together with methods of forming such split tip catheters. In one aspect of the invention, the manufacturing methods can include the steps of: providing a catheter body having at least a first and a second internal lumen extending longitudinally through the catheter body; removing a distal portion of the catheter body to form a first distal tip segment such that the first lumen extends longitudinally within this tip segment beyond the second lumen; and joining a second lumen tip segment to the catheter body in communication with the second lumen. The second tip segment can be joined to the catheter body such that it is at least partially separated from the first tip segment and, in some embodiments, preferably diverges at an angle relative to the first tip segment. 
         [0011]    The second lumen tip segment can be joined to the device by various techniques. For example, the second segment can be joined to the catheter body by thermal or chemical fusion. Alternatively, the second lumen tip segment can be bonded to the catheter body with an adhesive or the like. 
         [0012]    In one embodiment of the invention, the second lumen tip segment can be oriented such that the first and second tip segments are separate and diverge from each other at an angle. The angle between the first and second tip segments can be formed before, during, or after the second tip segment is joined to the catheter body. For example, the angle can be formed after joining the segment to the catheter body by the application of heat. Alternatively, the catheter body and/or the second segment can present an angled interface such that an angle is formed at the joint itself. The angle between the first and second tip segments can change from a proximal end of the first and second tip segments to a distal end of the first and second tip segments, e.g., one or both of the separate tip segments can be a compound angle or formed in the shape of a simple or compound curve. 
         [0013]    In another embodiment of the invention, the second lumen tip segment can be oriented such that the first and second tip segments are separate but substantially parallel to each other. 
         [0014]    Split tip catheters according to the invention can be formed by removing a distal portion of the catheter body by slicing away one of the lumens. If an angled separation is desired, the method can further include trimming the lumen in a non-perpendicular direction with respect to a longitudinal axis of the catheter body to facilitate attachment of the second tip segment at an angle. Alternatively, if substantially parallel split tips are desired, the method can further include trimming the lumen in a direction that is substantially perpendicular to a longitudinal axis of the trimmed lumen. 
         [0015]    The catheters of the present invention can further include forming fluid passage holes in a side of at least one of the tip segments. In another aspect, the catheters of the present invention can further include coatings of at least a portion of the catheter body or the first and/or second tip segments with an antithrombotic agent, such as heparin, to reduce blood clotting or protein adhesion. In other aspects, the catheters of the present invention can include coatings of at least a portion of the body or the first and/or second tip segments with an antibacterial agent and/or an anti-inflammatory agent. 
         [0016]    Additionally, following (or during) formation of the split tip catheter, the first and second tip segments can be joined together with a bioresorbable adhesive to simplify vascular insertion. Following insertion, the tip segments can separate upon dissolution of the adhesive, e.g., over a period of time ranging from 1 second to several days, more preferably from about 1 minute to about 10 hours, or 5 hours or one hour. 
         [0017]    In another aspect of the invention, a method of forming a split tip catheter is disclosed including the steps of: (a) providing a multi-lumen catheter having at least a first inner lumen and a second inner lumen extending therethrough; (b) partially truncating a distal end of the multi-lumen catheter body to form a first distal lumen tube such that the first lumen of the catheter within the first distal tube longitudinally extends further than at least a second lumen of the catheter; and (c) attaching a second lumen tube to the severed end of the catheter such that a second distal lumen tube in fluid communication with the second lumen of the catheter is formed and extends longitudinally from the catheter separate from the first distal lumen tube. 
         [0018]    The method can further include forming a non-zero angle between the first distal tube and the second distal tube. A non-zero-angle can be formed, for example, by trimming the catheter body at an angle, e.g., in a non-perpendicular direction with respect to a longitudinal axis of the first distal lumen tube, and then fusing or bonding the second distal tube to the catheter body at this location. The term “fusing” is used interchangeably with “bonding” herein and, as used, both terms are intended to encompass thermal fusion, melt bonding, ultrasonic welding, chemical bonding, adhesive bonding and the like. 
         [0019]    Alternatively, the first and second distal end tubes can be formed with substantially a zero angle of divergence, e.g., the two end segments are substantially parallel to each other in a rest position. A zero-angle can be formed, for example, by trimming the catheter body in a perpendicular direction with respect to a longitudinal axis of the first distal lumen tube, and then fusing or bonding the second distal tube to the catheter body at this location. 
         [0020]    In certain embodiments, it may be preferable that the second distal tube (that is to be joined to the catheter body) have a different luminal cross-section than the second lumen within the catheter body or that the first and second lumens within the catheter body have a different luminal cross-section from one another. The invention is also applicable to catheters having three or more lumens. For example, a three lumen catheter body can be truncated such that only one distal lumen extends from the point of truncation and then two separate end tubes can be grafted onto the body to provide three independent distal tip segments. Alternatively, the two grafted segments can be attached together but joined to the body separately from the first segment (formed from the original catheter body). In another alternative, the three lumen catheter body can be truncated such that two of the lumens extend in a distal segment from the point of truncation with a separate end tube grafted onto the body to provide a separated third lumen. 
         [0021]    The present invention is advantageous, among other reasons, because only one distal tip segment is bonded to the catheter body (in contrast to prior art where two tip segments must be bonded), thus simplifying the process and shortening the manufacturing time. A further advantage is that bonding a single distal tip segment permits reduced septum thickness in the catheter body (and therefore increased luminal cross-sections) since the septum does not have to accommodate the attachment of two separate distal end tubes. 
         [0022]    The method is particularly useful when one or more of the lumens has a non-circular cross-section, e.g., a substantially D-shaped cross-section. For example, the catheter body can be formed in a “double-D” configuration, with two “D” shaped lumens back-to-back and separated by a septum. A catheter body with a septum between the lumens can be formed by various means, e.g., as an integral body by extrusion or by assembling two D-shaped single lumen elements and then surrounding them by a sheath of heat-shrink polymeric material, thereby forming an integral body. 
         [0023]    The method according to the invention can further include the step of partially truncating the catheter body further comprises truncating the body at a truncation point such that at least a portion of the septum (and preferably a major portion or all of the septum) is retained by the first distal lumen tube. Moreover, the method can further include attaching the second distal tube at least partially to the septum of the first distal tube. 
         [0024]    The method according to the invention can further include the step of attaching a second distal tube that has a different shape than the first or second lumens of the catheter body. (The term “shape” is used herein to encompass differences in geometry, e.g., circular, ellipsoid or D-shaped as well as differences in size, e.g., cross-sectional area of the lumens.) 
         [0025]    In another aspect of the invention, a method of forming a split tip catheter is disclosed, wherein the method can include the steps of: (a) truncating the catheter body at a septum dividing two of the lumens such that a first distal end tube is formed and the first tube surrounds a first lumen having a length that extends beyond a truncation point; and (b) attaching a second distal end lumen tube to the catheter body in fluid communication with a second lumen of the catheter body. 
         [0026]    In yet another aspect of the invention, another method of forming a split tip catheter is disclosed including the steps of: (a) removing a partial length of a lumen included in a catheter body to expose a septum between the lumen and another lumen included in the catheter body, wherein each lumen defines a separate fluid pathway extending longitudinally through the body; and (b) attaching a replacement lumen tube at a distal end of the catheter body such that a pathway extending longitudinally through the replacement lumen tube is in communication with the pathway of the lumen that was partially removed. Again, the two (or more) lumen tubes can be formed to either diverge at an angle or to remain parallel to each other. (The term “parallel,” as used herein, is intended to encompass configurations that nominally have a “zero” angle of divergence as well as slight angles that may exist due to practical constraints or machining tolerances. It should also be appreciated that the preferred materials for the catheters of this invention are polymeric materials, such as polyurethane or silicone, that will also exhibit flexibility or “floppiness,” in both their parallel and divergence configurations.) 
         [0027]    The step of removing the partial length of the lumen can further include trimming the lumen opening at a zero or non-zero angle in relation to an axis perpendicular to a longitudinal axis of the catheter. The end of the replacement lumen tube to be joined to the catheter body can also be cut at an angle. 
         [0028]    In another aspect of the invention, a method of forming a split tip catheter is disclosed including the steps of: (a) providing a multi-lumen catheter body having at least a first inner lumen and a second inner lumen extending therethrough; (b) partially truncating the multi-lumen catheter body such that a first distal lumen tube is formed to longitudinally extend the first lumen of the catheter further than at least the second lumen of the catheter; and (c) attaching a second lumen tube to the truncated end of the catheter such that a pathway separate from the first distal tube is formed in fluid communication with the second lumen of the catheter, wherein the first inner lumen has a different shape than the second inner lumen. 
         [0029]    In a further aspect of the invention, split tip catheter devices are disclosed. In one embodiment the split tip catheter can include a catheter body; a first lumen included in the catheter body, the first lumen having an inner pathway extending longitudinally through the catheter body; a second lumen included in the catheter body, the second lumen having an inner pathway extending longitudinally through the catheter body and a length less than a length of the first lumen; and a lumen tip segment attached to the second lumen and having a pathway extending longitudinally through the lumen tip segment such that the pathway of the lumen tip segment is in communication with the pathway of the second lumen. 
         [0030]    Catheter devices according to the invention can be formed such that at least a part of one of the lumen tip segments is composed of a material different than a material of the catheter body. In certain embodiments, the first lumen and the lumen tip segment are separate and diverge from each other at an angle at a distal end of the catheter body. In other embodiments, the first lumen and the lumen tip segment are separate but substantially parallel to each other. 
         [0031]    In yet another embodiment, a split tip catheter device is disclosed including a catheter body; a first distal tip segment integral with the catheter body, the first distal segment having an inner pathway extending longitudinally through a first lumen of the catheter body; and a second distal tip segment separate from the first distal segment and joined to the catheter body to provide a fluid pathway from a second lumen of the catheter body and extending longitudinally through the second tip segment. 
         [0032]    Other advantages and features will become apparent from the following description and from the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0033]    The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which like reference numerals designate like parts throughout the figures, and wherein: 
           [0034]      FIG. 1  is a schematic, partially cutaway, side view of a catheter according to the present invention; 
           [0035]      FIG. 2  is a cross-section view of an embodiment of the present invention showing a catheter construction formed from opposed D-shaped lumen bodies inside an outer sheath; 
           [0036]      FIG. 3  is a cross-section view of an embodiment of the present invention showing a unibody catheter construction utilizing opposed D-shaped lumens; 
           [0037]      FIG. 4  is a cross-section view of a variation of an embodiment of the present invention showing opposed D-shaped lumens of different cross-sectional areas; 
           [0038]      FIG. 5  is a cross-section view of an embodiment of the present invention showing yet another unibody construction with lumens of different shape and size; 
           [0039]      FIG. 6  is a cross-section view of an embodiment of the present invention showing a unibody construction formed from two individual circular lumens inside an outer sheath; 
           [0040]      FIG. 7  is a cross-section view of an embodiment of the present invention showing a unibody construction with two individual circular lumens; 
           [0041]      FIG. 8  is a cross-section view of an embodiment of the present invention showing a unibody construction with three lumens; 
           [0042]      FIG. 9  is a cross-section view of a variation of an embodiment of the present invention showing a unibody construction with three lumens; 
           [0043]      FIG. 10  is a cross-section view of an embodiment of the present invention showing an elliptical-shaped unibody construction; 
           [0044]      FIG. 11  is a schematic, perspective view of a catheter according to the present invention in an initial, pre-trimmed configuration; 
           [0045]      FIG. 12  is a schematic, perspective view of another catheter in an initial, pre-trimmed configuration; 
           [0046]      FIG. 13  is a schematic, perspective view of an embodiment of the present invention showing a trimmed catheter; 
           [0047]      FIG. 14  is a schematic, perspective view of a variation of an embodiment of the present invention showing a trimmed catheter; 
           [0048]      FIG. 15  is a schematic, perspective view of an embodiment of the present invention showing a lumen tube attached to a catheter; 
           [0049]      FIG. 16  is a schematic, perspective view of a variation of an embodiment of the present invention showing a lumen tube attached to a catheter; 
           [0050]      FIG. 17  is a schematic, perspective view of a variation of an embodiment of the present invention showing a lumen tube attached to a catheter; 
           [0051]      FIG. 18  is a schematic, perspective view of a variation of an embodiment of the present invention showing a lumen tube attached to a catheter, where the lumen tube is attached to at least a portion of the septum; 
           [0052]      FIG. 19  is a schematic, perspective view of a variation of an embodiment of the present invention showing a lumen tube attached to a catheter, where the lumen tube is attached to at least a portion of the septum using an alternative method; 
           [0053]      FIG. 20  is a schematic, perspective view of an embodiment of the present invention showing an adhesive application; 
           [0054]      FIG. 21  is a distal cross-sectional view of another embodiment of the present invention showing alternative adhesive disposition; 
           [0055]      FIG. 22  is a distal cross-sectional view of yet another adhesive design; 
           [0056]      FIG. 23  is a schematic, perspective view of an embodiment of the present invention showing fluid openings in the distal tip; 
           [0057]      FIG. 24  is a cross-section view of a variation of an embodiment of the present invention showing a trimmed catheter; 
           [0058]      FIG. 25  is a cross-section view of a variation of an embodiment of the present invention showing another trimmed catheter; and 
           [0059]      FIG. 26  is a schematic side view of a catheter according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0060]    In  FIG. 1  an embodiment of a split tip catheter  100  according to the invention is shown having a catheter body  102  with two internal lumens  104   a ,  104   b  (collectively, the lumens  104 ). The lumens  104  include respective inner lumen pathways  106   a ,  106   b  (collectively, the pathways  106 ) extending longitudinally through the catheter body  102 . The catheter body  102  has a split-tip distal end  108  in which the catheter body  102  (and the lumens  104 ) separate into two distal lumen tip segments,  110   a ,  110   b  (collectively, the lumen tips  110 ). One of the lumens  104   b  has been trimmed to a length less than the other lumen  104   a . A lumen tip segment  114  has been joined to the trimmed lumen  104   b  such that the lumen tip  110   b  includes the lumen tip segment  114  and such that the lumen tip segment  114  is in fluid communication with the trimmed lumen  104   b . The lumen tip  110   b  forms an angle α with respect to the other lumen tip  110   a . The value of α can be zero or non-zero and is preferably in the range of zero to ninety degrees. The lumen tips  110  can, but need not, have one or more fluid passage holes  112   a ,  112   b  (collectively, the fluid passage holes  112 ) in fluid communication with their respective lumen  104  to facilitate fluid removal (typically through lumen  104   b ) and return (typically through lumen  104   a ), e.g., blood removal and return during hemodialysis. Alternatively, or in conjunction with the fluid passage holes  112 , one or both distal ends  116   a ,  116   b  (collectively, the distal ends  116 ) of the lumens  104  can be open to provide fluid passageways through the pathways  106 , e.g., for blood removal and return. A proximal end  118  of the catheter body  102  can also be split into separate segments  118   a ,  118   b  and terminate with two access ports  120   a ,  120   b , which can include couplings, such as Luer-locks or the like, to couple the catheter  100  to a hemodialysis machine in which blood is circulated and purified. The catheter body  102  is typically a very flexible silicone, polyurethane, or other biocompatible composition (e.g., having a stiffness in the range of about 65 to about 85 durometer), and can include any type of catheter (e.g., a hemodialysis catheter or a central venous catheter). 
         [0061]    The catheter body  102  can include an outer sheath  122  which partially or entirely covers and encloses the lumens  104 . The outer sheath  122  can be any shape and size and can be made of the same material as the lumens  104  or other material compatible with insertion into a blood vessel. As illustrated in this embodiment, the outer sheath  122  terminates proximal to the distal ends  116  of the lumens  104  such that the lumen tips  110  of each lumen  104  are separate or can separate from one another after being inserted into a blood vessel. 
         [0062]      FIG. 2  shows a cross-section c 1 -c 1  of one embodiment of the outer sheath  122 . The outer sheath  122  can be of any thickness and can have varying inner and outer shapes as well as varying inner and outer dimensions. The catheter body  102  can be constructed such that sheath material  200  encases the lumens  104   a  and  104   b  and no space remains between the sheath and the lumens. For example, the sheath can be fused to the lumens or heat-shrunk around them. 
         [0063]    The lumens  104  can have a variety of cross-sectional shapes and sizes but preferably, as shown in the embodiment in  FIG. 1 , the catheter body  102  has a substantially elliptical (circular or oval) shape and the lumens  104  are each D-shaped. However, one or both of the lumens  104  can transition from one shape to another along at least a portion of its length, e.g., transition from a D-shaped cross-section to a circular cross-section. Furthermore, each of the lumens  104  can have a cross-sectional shape, size, or area that can be the same or distinct from the catheter body  102  and/or the other lumen, as shown in examples of c 2 -c 2  cross-sections in  FIGS. 3-10 . 
         [0064]      FIG. 3  is a cross-section view of an embodiment showing unibody construction utilizing opposed D-shaped lumens  104  having substantially the same size of pathways  106 . This configuration eliminates the sheath as a distinct element. The device of  FIG. 3  can be formed, for example, by extrusion molding of a catheter body with a plurality of lumens integrated therein. In one embodiment according to the invention the end portion of the catheter body  102  can be truncated by splitting the body along either the center line γ of the longitudinal axis or along an off-center longitudinal axis γ′. In certain applications, truncation along off-center line γ can be preferably because it preserves most or all the septum  202 , while sacrificing part of the other lumen  104   a  (e.g., the part extending distally beyond the cut point  124  as shown in  FIG. 1 ). 
         [0065]      FIG. 4  is a cross-section view of another embodiment showing opposed D-shaped lumens  104  where one lumen  104   a  is of a smaller size (e.g., smaller cross-sectional area) than the other lumen  104   b .  FIG. 5  is a cross-section view of an embodiment showing yet another unibody construction.  FIG. 6  is a cross-section view of an embodiment showing individual, elliptical lumens inside an outer sheath  122 .  FIG. 7  is a cross-section view of an embodiment showing a unibody construction utilizing individual, elliptical lumens  104 .  FIG. 8  is a cross-section view of an embodiment showing three lumens  104 , at least one of which (here, lumen  104   c ) having a different size and/or shape from at least one other lumen (here, lumens  104   a ,  104   b ).  FIG. 9  is a cross-section view of a variation of an embodiment showing three lumens  104  having substantially the same size and shape.  FIG. 10  is a cross-section view of another embodiment showing two elliptical-shaped lumens  104 . 
         [0066]    The lumens  104  can be made of any biocompatible material, including any material which allows the lumen tips  110 ,  114  of the lumens  104  to be flexible and facilitate hemodialysis. Furthermore, the lumen tip segment  114  can be made from a material different from a material of the cut lumen  104   b . The different material can be one more or less flexible than the material of the cut lumen  104   b . Using different materials for the lumen tip segment  114  and the cut lumen  104   b  can allow the catheter body  102  to be used more efficiently or to be used at all in an application where it would not be preferable or possible having material of the cut lumen  104   b  at the distal end  116   b.    
         [0067]    The distal extraction and return tip portions  110  of each lumen  104  include pathways  106  formed therein for the extraction or return of blood or other bodily fluids. The pathways  106  are preferably sized to allow the carrying of blood to and from a hemodialysis unit, although the pathways  106  can be any size and the catheter  100  can be used in any application. The distal extraction and return tip portions  110  can be the same length or, as discussed further below, can be different lengths. 
         [0068]    An exemplary method of forming a split tip catheter is described with reference to  FIGS. 11-26 . Although described with reference to these figures (and related ones of  FIGS. 1-10 ), this method (or a similar method) can be implemented to form any of the split tip catheter devices described herein. 
         [0069]      FIG. 11  shows a circular catheter body  102  in an initial untrimmed configuration (e.g., without separate distal tip segments) having two “D-shaped” lumens  104   a ,  104   b .  FIG. 12  shows another, elliptical catheter body  102  with circular lumens  104   a ,  104   b  in an initial configuration (e.g., prior to trimming and joinder of a second distal lumen tip segment  114 ). Although the lumens  104  are shown having equal lengths in  FIG. 12 , the lumens  104  can have different lengths in this initial configuration. 
         [0070]      FIG. 13  shows the catheter body  102  in a trimmed configuration where a distal portion of the catheter body  102  has been removed, as compared to the initial configuration in  FIG. 11  or  12 . The catheter body  102  of  FIG. 13  can also be formed by extending the lumens  104   a ,  104   b  in a staggered, step configuration such that one of the lumens  104   a  is extended longer than the other lumen  104   b  by a length L 1 . The lumens  104   a ,  104   b  can be aligned in this way while hot and can bond together in this formation as they cool. However formed, in this configuration, one of the lumens  104   a  (herein referred to as “the uncut lumen  104   a ”) extends longitudinally beyond the other lumen  104   b  (herein referred to as “the cut lumen  104   b ”) by a length L 1 . In an initial configuration such as in this embodiment where the lumens  104  initially have equal lengths, length L 1  equals the amount of lumen trimmed from the cut lumen  104   b . The length L 1  can be in the range of about 1-3 inches, which is a preferable, but only an example, length of lumen to trim. 
         [0071]    The sacrificed lumen  104   a  can be trimmed in a variety of ways. In a preferred example, one of the lumens  104   b  can be sliced (e.g., cut or scored) widthwise across its circumference at a location  124 . Then a length L 1  of the cut lumen  104   b  can be trimmed from the catheter body  102 . When the length L 1  of the cut lumen  104   b  has been removed, a septum between the cut lumen  104   b  and the uncut lumen  104   a  can thereby be at least partially exposed. 
         [0072]    Referring again to  FIG. 4  where one lumen  104   a  is smaller than the other lumen  104   b , the larger lumen  104   b  is typically the arterial lumen because that is the one of the lumens  104  more prone to clogging in a hemodialysis setting, and a larger size pathway  106   b  can help reduce clogging. Truncation of the end portion according the invention typically involves sacrificing part of the larger lumen  104   b  and joining a new distal tip segment in its place. The catheter body  102  can again be split along an off-center longitudinal axis γ′, thereby preserving most or all the septum  202 , sacrificing part of lumen  104   b  (e.g., the part extending distally beyond the cut point  124 ). Following truncation, a new distal tip segment  114  (as shown in FIG.  1 ) can then be joined to the second lumen of the catheter body. The distal tip segment  114  can be similar in size and shape to the sacrificed lumen or can be different in size and/or shape. 
         [0073]    In certain applications it can be preferable to sacrifice the smaller lumen  104   a  instead. In such instances, the truncation line can be moved to the other side of the septum  202 . 
         [0074]    Dimensions of the lumens  104   a  and  104   b  can vary between embodiments. In this example embodiment, dimensions allow the catheter body  102  to be used with standard hemodialysis equipment and lumen tip segments. Maximum width w 2  of the smaller lumen pathway  106   b  is about 0.06 in. and maximum width w 1  of the larger lumen pathway  106   a  is about 0.08 in. The septum  202  has a width w 3  of about 0.02±0.002 in., while the lumens  104  have an exterior width w 4  of about 0.022±0.003 in. Maximum height h 2  of the smaller pathway  106   a  is about 0.14 in. and maximum height h 1  of the larger pathway  106   b  is about 0.15 in. 
         [0075]    The cut distal end  124  of the cut lumen  104   b  can be trimmed in a perpendicular direction or a non-perpendicular direction with respect to a longitudinal axis P of the cut lumen  104   b .  FIG. 13  shows the cut distal end  124  trimmed in a perpendicular direction with respect to axis β. Alternatively,  FIG. 14  shows the cut distal end  124  trimmed in a non-perpendicular direction with respect to axis β. The non-perpendicular direction can result in any non-zero angle θ between the cut distal end  124  and axis β. As shown in  FIGS. 13 and 14 , the distal extraction tip portion  110   b  of the blood extraction lumen  104   b  terminates proximal to the distal return tip portion  110   a  of the blood return lumen  104   a . However, also including the lumen tip segment  114  attached to the distal tip return portion  110   b  as shown in  FIG. 15 , the two distal lumen tip segments  110  have the same length, although even including the lumen tip segment  114 , one or the other of the lumen tips  110  can be longer than the other. 
         [0076]    With a distal portion of the catheter body  102  removed, the lumen tip segment  114  can be joined to the catheter body  102  as shown in  FIG. 15 . The lumen tip segment  114  has been joined to the lumen tip  110   b  of the cut lumen  104   b  at the cut distal end  124  such that the pathway of the cut lumen  104   b  is in communication with the pathway of the lumen tip segment  114 , thereby forming a single pathway  106   b  through the cut lumen  104   b  and the lumen tip segment  114 . 
         [0077]    The lumen tip segment  114  can be attached to the catheter body  102  in a variety of ways. For example, the lumen tip segment  114  can be fused to the lumen tip  110   b  at the cut distal end  124 . Any fusion technique can be used, e.g., thermal fusion where elements to be joined (here, the lumen tip segment  114  and the lumen tip  110   b ) are heated along any or all portions of their perimeters or other areas to a desired temperature and fused together by application of a desired force or by inserting one lumen tube over the other (e.g., with an overlap by about 1 cm) and allowing them to melt/cool together. In another example, the lumen tip segment  114  can be bonded to the lumen tip  110   b  at the cut distal end  124 . Any bonding technique can be used, e.g., applying a bonding material such as an adhesive to one or more of the elements to be bonded and, if necessary, heating the bonding material to bond it to the elements. In some embodiments, the lumen tip segment  114  can be attached in such a way as to provide a gradual transition between the luminal walls of the catheter body  102  and the luminal walls of the lumen tip segment  114 , for instance via the insertion of a mandrel and the application of heat. 
         [0078]    The lumen tip segment  114  can be oriented at any angle with respect to the longitudinal axis β of the cut lumen  104   b . Moreover, one or both of the lumen tip segment  114  and the lumen tip  110   a  can have a convex shape with respect to the other tip over at least some portion of its length. For example, the lumen tip segment  114  can be attached to the lumen tip  110   b  at a ninety degree angle θ′ with respect to axis P as shown in  FIG. 15 . In such a configuration, the lumen tips  110  are separate but are substantially parallel to each other.  FIG. 16  shows another embodiment where the lumen tips  110  are separate and substantially parallel to each other in an angled spit tip configuration, e.g., as described in U.S. Pat. No. 6,482,169, which is hereby incorporated by reference in its entirety. Alternatively, as shown in  FIG. 17 , the lumen tip segment  114  can be oriented to the cut lumen  104   b  at an angle θ′ less than ninety degrees. In such a configuration, the lumens  104  are separate and diverge from each other at an angle σ. When the angle θ′ is less than ninety degrees, it is typically in configurations where the cut distal end  124  has been trimmed in a non-perpendicular direction with respect to axis β, and the angle σ is formed when the lumen tip segment  114  is joined to the cut lumen  104   b . However, the angle σ can be formed after the lumen tip segment  114  has been joined to the cut lumen tip  110   b , e.g., by the application of heat. In another example, the design in  FIG. 17  can be formed by first attaching the lumen tip segment  114  to the cut lumen tip  110   b  and then heating the lumens  104  to form the angle σ. Alternatively, the lumen tips  110  such as those in  FIG. 17  can have an initial configuration where they are at the angle θ′ with respect to axis β. 
         [0079]    The apex of angle σ can be located either at the junction of the cut lumen  104   b  and the lumen tip segment  114 , as shown in  FIG. 17 , or further toward the distal end of the catheter body  102 . In the case that angle σ is further toward the distal end of the catheter body  102 , the lumen tip segment  114  can be bonded to the septum along a length L 5  of the uncut lumen  104   a , as shown in  FIG. 18 . Alternatively, the lumen tip segment  114  can be bonded to the septum along the length L 5  of uncut lumen  104   a  and attached to the cut lumen  104   b  at an angle θ′, as shown in  FIG. 19 . Typically, in these or other embodiments, the lumen tip segment  114  can also be bonded along the circumference at the junction with the cut lumen  104   b.    
         [0080]    Whether substantially parallel or diverging from one another, the lumens  104  are separate (at least before application of any adhesive, discussed further below).  FIG. 17  shows the lumens  104  separate for the length L 1 , and  FIG. 18  shows the lumens  104  separate for the length L 4 .  FIG. 17  also shows an embodiment where one of the lumens  104  is longer than the other, with the distal end  116   a  of the lumen tip  110   a  extending beyond the distal end  116   b  of the lumen tip segment  114  by a length L 3 . 
         [0081]    Referring again to  FIG. 15 , the lumens  104  shown in this embodiment are substantially parallel and can be secured together with an adhesive  1600  for a length L 1 . Prior to the distal ends  116  of the catheter body  102  being inserted into a blood vessel, a full or partial portion of the lumen tips  110  of the lumens  104  can be joined to one another with the bioresorbable adhesive  1600 . After insertion into the blood vessel, the bioresorbable adhesive  1600  facilitates separation of the lumen tips  110  of the lumens  104 . 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. 
         [0082]    The bioresorbable adhesive  1600  used to join the lumen tips  110  of the lumens  104  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 components (epoxy compound plus amino compounds, or radical (light) initiators of acrylate compounds). 
         [0083]    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. 
         [0084]    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. 
         [0085]    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, dirnethylformamide, or the mixture thereof, is combined with the aforementioned solvents. 
         [0086]    As shown in  FIG. 15 , the bioresorbable adhesive  1600  can be applied along a facing surface of either, or both, the lumen tips  110  of the lumens  104  to facilitate the joining of the lumen tips  110  along their longitudinal lengths prior to insertion of the distal ends  116  of the catheter body  102  into a blood vessel. (As used throughout, “the catheter body  102 ” and its components refers to the various embodiments of the present invention.)  FIG. 15  shows the bioresorbable adhesive  1600  applied along a longitudinal length L 1 . However, the bioresorbable adhesive  1600  need not be applied along the entire length of the facing surfaces of each lumen  104  but is preferably applied such that the adhesive  1600  facilitates the joining of the lumen tips  110  of the lumens  104  prior to insertion into a blood vessel and allows the lumen tips  110  of the lumens  104  to separate after insertion. Furthermore, the bioresorbable adhesive  1600  can be applied along more than length L 1  if, for example, the lumens  104  were separated an additional length L 2 , in which case the adhesive  1600  can be applied along a length equal to L 1 +L 2 . 
         [0087]    In an embodiment shown in  FIG. 20 , bioresorbable adhesive can be applied to facing surfaces of the lumen tips  110  of the lumens  104  as discrete spots or regions  2000 . (Assume in this example that the lumen tip segment  114  has already been attached to the cut lumen tip  110   b .) The spots  2000  of the bioresorbable adhesive can be applied continuously along the entire longitudinal length of the lumen tips  110  of the lumens  104  or selectively in an assortment of areas thereof. Preferably, the bioresorbable adhesive is applied such that the spots  2000  of adhesive facilitate the joining of the lumen tips  110  of the lumens  104  prior to insertion into a blood vessel and allow the distal extraction and return tips  110  of the lumens  104  to separate after insertion. The spots  2000  of bioresorbable adhesive can vary in number, size, and distance from one another in order to facilitate the joining and/or disjoining of the lumen tips  110  of the lumens  104 . 
         [0088]    In the embodiments described herein, the bioresorbable adhesive preferably dissolves after insertion into a blood vessel to provide separation of the lumen tips  110  of the lumens  104  in a time period ranging from one minute to one hour (but as long as several days or longer). This range can be controlled by using different compositions of the bioresorbable adhesive as well as by the amount of adhesive applied to join the lumen tips  110  of the lumens  104  together. 
         [0089]    In another embodiment with opposed distal fluid openings  112  (further described below), the bioresorbable adhesive can be water soluble such that the introduction of saline or similar type fluid will effectuate the separation of the lumen tips  110  of the lumens  104 . In this instance, the bioresorbable adhesive will not dissolve until a time after the introduction of the soluble solution into the lumens  104 . 
         [0090]      FIGS. 21-22  show cross-sections of the lumen tips  110  of the lumens  104  detailing alternate embodiments of the bioresorbable adhesive application.  FIGS. 21 and 22  show the bioresorbable adhesive  400  applied at a contact point  402  of the facing surfaces of the lumens  104 .  FIG. 21  shows one embodiment of an application of the bioresorbable adhesive  400  such that the adhesive  400 , as applied, joins non-contacting surfaces  2100 ,  2102  of the lumen tips  110  of the lumens  104 .  FIG. 22  shows a variation on the embodiment shown in  FIG. 21  where the bioresorbable adhesive  400  surrounds the lumen tips  110  of the lumens  104  forming a continuous cross-section of adhesive coating notwithstanding the lumen tips  110  of the lumens  104  extending therethrough. As stated above, the bioresorbable adhesive  400  need not be applied along the entire length of the lumen tips  110  of the lumens  104  but is preferably applied such that the adhesive  400  facilitates the joining of the distal extraction and return tip portions  110  of the blood extraction and blood return lumens  104  prior to insertion into a blood vessel and allows the lumen tips  110  of the lumens  104  to separate after insertion. Furthermore, the lumen tips  110  can have different coatings from one another and/or different from a coating on the catheter body  102 . 
         [0091]      FIG. 23  shows another embodiment where distal fluid openings (also called fluid passage holes)  112   a  are formed in the lumen tip  110   a  of the lumen  104   a . It should be understood from the drawings that in the embodiment shown, the distal fluid openings  112   a  can either be in addition to, or in place of, the pathway opening located at the distal end  116   a  of the lumen  104   a . Furthermore, the cut lumen  104   b  can have distal fluid openings  112   b  similar to those described here, whereby the fluid openings  112   b  would typically be included in the lumen tip segment  114  attached to the cut lumen tip  110   b  or subsequently formed in the lumen tip segment  114  after its attachment to the cut lumen tip  110   b.    
         [0092]    The distal fluid openings  112   a  can be any shape and size and can be located in a variety of places on the lumen  104   a .  FIG. 23  shows the distal fluid openings  112   a  located on facing (contacting) surface  2300  of the lumen tip  110   a  of the lumen  104   a . In this embodiment, the distal fluid openings  112   a  can be filled or covered with fluid activated bioresorbable adhesive and joined to the other lumen  104   b  along its facing surface  2302 . After insertion of the catheter body  102  into a blood vessel, saline or similar type fluid can be introduced into the lumen  104   a  at its proximal end  118  such that the fluid travels through the lumen  104   a  to the distal fluid openings  112   a  and dissolves the fluid activated bioresorbable adhesive thereby separating the lumen tips  110  along their longitudinal length to, e.g., facilitate hemodialysis. Bioresorbable adhesive can also be applied to the contact surfaces  2300 ,  2302  of each lumen  104  as previously described above in addition to the distal fluid openings  112   a  being filled or covered with fluid activated bioresorbable adhesive. 
         [0093]      FIGS. 1-7  and  11 - 23  illustrate double lumen configurations, but the split tip catheter devices and methods described herein can apply to any multi-lumen configuration. For example,  FIG. 24  shows an embodiment of a catheter body  2400  having three lumens  104   a ,  104   b ,  104   c , each having respective pathways  106   a ,  106   b ,  106   c . The catheter body  2400  can have any c 1 -c 1  cross-sectional configuration, and in this example is shown having the one in  FIG. 9 . One of the lumens  104   a  in this example has been split from the other lumens  104   b ,  104   c , and the lumen  104   a  been trimmed.  FIG. 25  shows the catheter body  2400  of  FIG. 24  where a second lumen  104   c  has been split from the other lumen  104   b  and trimmed. A lumen tip segment  2500  has been attached to the first trimmed lumen  104   a , and another lumen tip segment can be attached to the second trimmed lumen  104   c.    
         [0094]    The above embodiments describe a split distal end of a catheter, but in addition to or instead of splitting the distal end, the proximal end can also be formed in a split tip configuration in any way described above with respect to the distal end (e.g., in a double split-tip or “double-Y” configuration). Such a configuration can be useful in retrograde or reverse insertions where the catheter body is passed through a subcutaneous tunnel from venotomy site to the remote exit location. After tunneling the catheter, fluid couplings or other attachments can be disposed to the proximal end of the lumens.  FIG. 26  shows an embodiment of a catheter body  2600  having a split distal end  2602  and a split proximal end  2604 . A cuff  2606  can be attached to any location on the catheter body  2600  to enhance tissue ingrowth. The catheter can have any dimensions, but only as an example, the catheter body  2600  can have a length L 5  of about 38 cm, a length L 6  between a distal most end  2608  of the distal end  2602  and the cuff  2606  can be about 23 cm, and a length L 7  between the distal most end  2608  and a cut proximal end  2610  can be about 28 cm. 
         [0095]    Other embodiments are within the scope of the following claims. 
         [0096]    All publications, patent documents and other information sources identified in this application are hereby incorporated by reference.