in fig1 a catheter system 10 according to the invention is shown having a catheter body 12 with two internal lumens 14 a and 14 b . the catheter body 12 has a “ split - tip ” distal end 16 in which the body ( and lumens ) separate into two distal tip portions , 18 a and 18 b , which form a single - lumen distal blood removal extension tube and a single - lumen distal blood return extension tube , respectively . the split tips can , but need not have one or more side ports 20 a and 20 b , in fluid communication with one or the other of the lumens to facilitate blood removal and return , respectively , during hemodialysis . alternatively , or in conjunction with side ports , the distal ends can be open to provide fluid passageways for blood removal and return . the proximal end 22 of the catheter body can also be split into separate segments 22 a and 22 b and terminates with two access ports 28 a and 28 b , which can include couplings 34 a and 34 b , such luer - locks or the like , to couple the catheter to a hemodialysis machine in which blood is circulated and purified . proximal segments 22 a and 22 b thus provide a single - lumen proximal blood removal extension tube and a single - lumen proximal blood return extension tube , respectively . the overall system or kit of the invention can also include two intra - catheter stiffener elements 24 a and 24 b and two guidewires 26 a and 26 b ( shown within the respective lumens 14 a and 14 b ). the catheter body 12 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 durometers ). preferably , the intra - catheter stiffener elements 24 a and 24 b are composed of a stiffer form of polyethylene or other bio - compatible material . in addition to stiffening the assembly , the stiffener elements can also help to prevent kinking of the catheter during insertion . the catheter system 10 of fig1 provides for insertion of the distal end of the multi - lumen , split - tip , flexible catheter body 12 into a blood vessel using the intra - catheter stiffener elements and guidewires , as will be explained below . briefly , a distal portion of each guidewire is disposed at a desired position within the vessel . an intra - catheter stiffener element having a tapered tip to facilitate insertion into the vessel and to provide catheter stiffening is slidably disposed along the length of each catheter lumen until it extends beyond the distal tip of that catheter lumen . a proximal end of each guidewire is threaded through a distal end of a lumen extending along each of the intra - catheter stiffener elements . the catheter is then advanced over the guidewires and into the blood vessel . alternatively , the catheter can be advanced over the guidewires until the distal end is adjacent to the vessel , at which point the catheter and guidewires can be advanced together into the blood vessel . the guidewires and intra - catheter stiffener elements are then removed from the catheter . the methods and application kit described can be used for any split - tip catheter , and are particularly useful for insertion of subcutaneously tunneled hemodialysis catheters . a method of insertion according to the invention will next be described in connection with fig2 - 8 . the procedure involves not only inserting the catheter tips into a blood vessel but also forming a subcutaneous tunnel below a patient &# 39 ; s skin to secure the catheter in place and is sometimes described as antegrade or forward insertion . it will be appreciated , however , that the methods described herein can be used for inserting catheter tips into a blood vessel where tunneling is not necessary or desired . fig2 schematically shows an initial step of a method according to the invention in which a distal portion of a first guidewire 26 a is inserted in a vessel 4 of a patient 2 . the entry location 6 of the guidewire 26 a is referred to herein as the “ first location ” or the “ venotomy site .” this first location is typically a surgical incision that provides access to the desired blood vessel which typically includes the internal or external jugular , femoral or subclavian vein , and the vena cava , for example . in one preferred embodiment , the blood vessel chosen for catheter placement can be the right side internal jugular vein . in fig3 , a blood vessel sheath / dilator 30 is shown inserted over the first guidewire 26 a to dilate the vessel . the distal portion of a second guidewire 26 b is then inserted in the vessel 4 via the sheath / dilator 30 . with reference to fig4 , a subcutaneous tunnel 40 is formed ( before or after the insertion of guidewires 26 a and 26 b ) to anchor the catheter body in place and provide two remote ports for coupling the two lumens of the catheter to a dialysis machine . in fig4 , a catheter body 12 of an antegrade catheter has been disposed in a subcutaneous tunnel 40 between the first ( venous access ) location 6 and a second ( exit ) location 32 , such that the distal end of the instrument including the split tips 18 a and 18 b extend from the first location . prior to insertion , each of the lumens of catheter body 12 has been fitted with a hollow , tubular , intra - catheter stiffener element or liner , 24 a and 24 b , respectively . in fig5 , the first guidewire 26 a is threaded through a first lumen of the catheter assembly ( i . e ., through the lumen of intra - catheter stiffener element 24 a ). in fig6 , the second guidewire 26 b is threaded through the second lumen of the catheter assembly ( i . e ., through the lumen of intra - catheter stiffener element 24 b ). each of the guidewires is advanced through the catheter assembly to a point where two short loops of guidewire remain to facilitate placement in the vessel . as shown in fig7 , the catheter assembly is then advanced along the guidewires until the distal end 16 of the catheter is positioned at a desired position within the vessel . in a preferred embodiment , the catheter is advanced over the guidewires until the distal end is adjacent to the vessel , and then the catheter and the guidewires can be advanced together until the distal end of the catheter is positioned at a desired position within the vessel . the guidewires 26 a and 26 b can then be removed by withdrawing them via the proximal end 22 of the catheter body . likewise , the intra - catheter stiffener elements 24 a and 24 b can be removed ( either subsequent to the guidewires or at the same time ). advantageously , this method precludes using a vessel dilator larger than the catheter / stiffeners assembly for placement of the catheter within the vessel since the intra - catheter stiffener elements and the catheter itself provide vessel dilation . fig8 shows the catheter of fig7 with the intra - catheter stiffener elements and guidewires removed . the venous access incision is then closed and the catheter is secured subcutaneously ( e . g ., via an implanted cuff and / or sutures ). although the above detailed description has been presented in connection with an antegade insertion , it should be clear that the methods and systems of the present invention are equally useful in retrograde or reverse insertions ( where the catheter body is passed through the subcutaneous tunnel from venotomy site to the remote exit location ). thus , a method according to the invention for insertion of a retrograde catheter will next be described . an initial step for insertion of a retrograde catheter begins with placement of guidewires within the vessel as described above in connection with fig2 and 3 . fig9 illustrates a step of the method wherein the catheter body 12 has each of the lumens fitted with a hollow , tubular , intra - catheter stiffener element or liner , 24 a and 24 b , respectively . the intra - catheter stiffener elements can have a coupler at a proximal end that releasably couple to a mating coupler at a proximal end of the respective catheter lumen . guidewires 26 a and 26 b are threaded through the lumens of the catheter assembly as described above in fig5 and 6 . the catheter body is advanced along the guidewires until the distal end of the catheter in a desired location within the vessel . alternatively , the catheter body can be advanced along the guidewires until the distal end is adjacent to the vessel , and then the catheter and the guidewires can be advanced until the distal end is located at a desired position within the vessel . the guidewires and , optionally , the intra - catheter stiffener elements are then removed from the lumens . fig1 shows a step of the method wherein the catheter has been subcutaneously tunneled . a subcutaneous tunnel is formed between a second location 32 ( exit location ) and the first location 6 ( venotomy site ). couplers at the proximal end 22 of the catheter lumens are removed , or alternatively , severed therefrom to allow the proximal end of the catheter to be pulled through the tunnel 40 . in one embodiment , the proximal end of the catheter is pulled through subcutaneous tunnel from the first location until it extends from the second location . fig1 illustrates the catheter after tunneling with access ports 28 a and 28 b installed , or alternatively , replaced and ready to be coupled to a hemodialysis machine for blood purification . as noted above , it will be appreciated that the use of the intra - catheter stiffener elements provide sufficient stiffness so that the flexible split tips can be slid over the guidewires into the desired position with less effort and reduced likelihood of trauma . catheter kinking is mitigated during the insertion process , thus reducing complexity of catheter insertion . fig1 shows contents of a preferred embodiment of a kit 48 providing equipment to perform the above described methods . illustrated are two intra - catheter stiffener elements 50 a and 50 b , two guidewires 52 a and 52 b , a 6 - french sheath / dilator 54 and two vessel dilators of differing sizes 56 and 58 . it will be appreciated by one skilled in the art that other arrangements are contemplated , each having at least two intra - catheter stiffener elements . for example , in one embodiment , the insertion kit has a split - tip catheter and two intra - catheter stiffener elements . the kit is suitable for insertion of either antegrade or retrograde catheter configurations according to the illustrated methods described above . intra - catheter stiffener elements 50 a and 50 b are illustrated as 5 - french in size and of the same length . however , intra - catheter stiffener elements 50 need not be of the same size and length , but can be selected according to the size and length of the catheter to be inserted . further , intra - catheter stiffener elements need not have a round exterior shape , but rather , can have an external shape according to the size and shape of an interior of a catheter lumen , for example , oval shaped . in a preferred embodiment , each intra - catheter stiffener element has a tapered configuration along a distal portion to aid in dilating the catheter lumen , with a releasable coupler at a proximal end such as a luer - coupler at a proximal end . each has a hollow bore or lumen running along its length sized to slidably receive a guidewire as described above . each preferably has stiffness sufficient to prevent the catheter from kinking or otherwise distorting during the insertion procedure . it will be appreciated that the intra - catheter stiffener elements can be in kit form as separate from , or disposed within , the catheter lumens . guidewires 52 a and 52 b are illustrated as j - straight 0 . 038 ″ guidewires , however each can vary according to the application and catheter configuration . each can have a removable sheath to accommodate handling and facilitate placement within a desired location such as a vein . sheath / dilator 54 is illustrated as size 6 - french , however , other sizes may be used to puncture a wall of a vessel and accommodate one or more guidewires . dilators 56 and 58 are illustrated as size 14 - french and 16 - french , respectively , and are suitable for many catheter insertion procedures . in a preferred embodiment , a size 12 - french is provided in addition to or instead of one of the illustrated dilators . it will be appreciated , therefore , that the above methods and kits are useful for inserting hemodialysis catheters in a patient , and in general for multi - lumen split - tip catheters intended for other functions where body fluids are extracted and introduced . as such , the invention is not limited to those embodiments described above , but rather , is limited by the claims that follow .
methods and apparatus are disclosed for inserting flexible , multi - lumen catheters into blood vessels , and in particular , for inserting flexible , split - tip catheters into blood vessels . the invention accomplishes these objects by temporarily stiffening each catheter lumen and tip independently through use of intra - catheter stiffener elements disposed within the catheter lumens . this provides means for advancing the catheter / stiffeners assembly through a subcutaneous tunnel , and over a plurality of guidewires until a distal tip of the catheter is at a desired position within the vessel . the intra - catheter stiffener elements are sufficiently stiffening to allow advancing the catheter over guidewires , but sufficiently flexible to allow bending and looping of the catheter for proper placement within the vessel .