Abstract:
A hemodialysis and vascular access system which includes a catheter having an arteriovenous fistula utilizing an indwelling silastic venous end and an arterial end which is adapted to be anastomosed to an artery is described. The catheter includes a needle receiving s through which a needle is inserted to access fluid flow within the hemodialysis and vascular access system. The invention enables use of an “arterialized” indwelling venous catheter where blood flows from an artery through the hemodialysis and vascular access system and is returned to the venous system via an arrangement wherein the outflow opening is distinct and distant from the site where the catheter enters the vein. The site of blood return to the venous system is not directly fixed to the venous wall but is free floating within the venous system. This system provides a hemodialysis and venous access graft which has superior longevity and performance and is relatively easy to implant.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 08/835,316, filed on Apr. 7, 1997 now U.S. Pat. No. 6,102,884 which claims the benefit under 35 U.S.C. §119(e) of U.S. application Ser. No. 60/037,094, filed on Feb. 3, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     Currently, HD (hemodialysis) and vascular access for chemotherapy and plasmapheresis is achieved in one of several ways. Applicant&#39;s invention involves a new method and instrumentation for HD and vascular access designed to eliminate the problems of the prior methods and create a new, more durable, easier to use, vascular access system. 
     One prior art method involves a primary arteriovenous fistula. In this method, a native artery is sewn to a native vein creating a high flow system of blood in a vein which over time can be accessed with two hemodialysis needles attached to a dialysis machine. The problem with this method is that few patients are candidates secondary to anatomy and in others the veins or shunt fail to enlarge and mature properly even if the primary fistula remains patent. These arteriovenous fistulas also become aneursymol over time requiring revision. 
     Another method involves a subcutaneous prosthetic conduit (PTFE) in the shape of a tube which is sewn at either end to openings made in an artery and vein. This method causes recurrent stenosis at the venous outflow leading to thrombosis (i.e., graft closure) secondary to intimal hyperplasia at venous anastomosis. Thrombosis also occurs at needle puncture sites along the PTFE. 
     Another method involves a “tunneled” percutaneous dual lumen catheter which is inserted into a central vein. This causes recurrent thrombosis secondary to stasis of blood in the lumen (i.e., not a continuous flow system like an A-V fistula) and build up of fibrinous debris at the venous end. Further, the access end of the catheter protrudes through the skin making it cosmetically unappealing, cumbersome to live with, as well as more likely to become infected. 
     A further method involves the use of the Sorenson Catheter. This is a percutaneous (not tunneled) dual lumen catheter, placed into the central venous system, which is used to provide temporary access for the purposes of hemodialysis. These catheters are prone to kinking, clotting, infection, and poor flow rates. 
     A still further method of vascular access involves the “Port-a-cath”. This system of venous access, which utilizes a subcutaneous reservoir attached to a central venous catheter, is used for long term intervenous access for chemotherapy etc. (It is not intended for HD.) The ports are prone to clotting and must be continually flushed since they are a stagnant system. 
     Applicant&#39;s invention involves a vascular access system, known as the Squitieri Hemodialysis and Vascular Access System, which creates a continuous blood flow and which is easily accessed and resistant to clotting. These advantages provide ideal access for long term HD chemo or blood draws. An example, would be patients who are on coumadin which require weekly blood draws. This new system becomes less painful over time as the skin over the “needle access” site become less sensitive. The veins are spared repeated blood draws which results in vein thrombosis to such a degree that some patients “have no veins left” making routine blood draws impossible. 
     Among the more relevant prior art patents are U.S. Pat. Nos. 4,898,669, 4,822,341; 5,041,098; and, 4,790,826. None of the foregoing patents disclose a system having the features of this invention. U.S. Pat. No. 4,447,237 describes improvements in a valving slit which includes the provision of a flattened sleeve within an elastomeric body presenting opposed interior surfaces interengaged when the valving slit is in the closed condition and spaced apart when the valving slit is in the open condition. 
     SUMMARY OF THE INVENTION 
     A hemodialysis and vascular access system comprises a PTFE end which is sutured to an opening in an artery at one end and the other end is placed into a vein using any technique which avoids the need for an anastomosis between the silicone “venous” end of the catheter and the vein wall. The system comprises any material, synthetic or natural (i.e. vein) which can be sutured to the artery (i.e. preferably PTFE) at one end while the other end is composed of a material which is suitable for placement into a vein in such a way that the openings in the “venous” end of the system are away from the site where the graft enters the vein. The system may also be constructed of multiple layers of materials i.e. PTFE on the inside with silastic on the outside. The “Needle Receiving Site” may also be covered with PTFE to encourage self sealing and tissue in-growth. 
     A preferred embodiment comprises a combination of PTFE conduit sewn to an artery on one end of the system with the other end connected to a silastic-plastic catheter which can be percutaneously inserted into a vein via an introducer. The venous end may also be placed via open cut down. The seal around the system where it enters the vein may be “self sealing” when placed in percutaneous technique; it may be achieved with a purse string when done by open technique “cut down”; or, it may be sewn to the vein to create a seal with a “cuff” while the system continues downstream within the venous system to return the arterial blood away from the site of entry into the vein. The entire system can be positioned subcutaneously at the completion of insertion. This design is a significant improvement over existing methods because it avoids the most frequent complication of current HD access methods. By utilizing an indwelling venous end, one avoids creating a sewn anastomosis on a vein which is prone to stenosis secondary to neointimal hyperplasia. By having continuous flow through the silastic end of the catheter, thrombosis of these catheters can be avoided. Dialysis is made more efficient by decreasing recirculation of blood which accompanies the use of side by side dual lumen catheters inserted into a central vein. This invention not only benefits the patient but it also speeds dialysis thus saving time and money. 
     To summarize, the Squitieri Access System comprises a tube composed of PTFE and a silastic catheter. This tube is used to create an arteriovenous fistula. The PTFE end (arterial end) of the tube is sewn to an artery while the silastic catheter end is placed into the venous system by the Seldinger technique much like a standard central line. The entire system is subcutaneous at the completion of insertion. This system is a composite of the arterial end of a “gortex graft” joined to the venous end of a “permacath”. This system enjoys strengths of each type of access and at the same time avoids their weaknesses. 
     Accordingly, an object of this invention is to provide a new and improved vascular access system. 
     Another object of this invention is to provide a new and improved hemodialysis and vascular access system including an easily replaceable needle receiving site which has superior longevity and performance, is more easily implanted, more easily replaced, and is “user friendly” i.e. easily and safely accessed by a nurse or patient which is ideal for home hemodialysis. 
     A more specific object of this invention is to provide a new and improved Squitieri hemodialysis and vascular access system including a subcutaneous composite PTFE/Silastic arteriovenous fistula. 
     A further object of this invention is to provide a new and improved hemodialysis and vascular access system including a fistula utilizing an indwelling silastic end which is inserted percutaneously into the venous system and a PTFE arterial end which is anastomosed to an artery and including a unique needle receiving sites which are positioned anywhere between the ends and which have superior longevity and performance. 
     A further object of this invention is to provide a system constructed to preserve laminar flow within the system and at the venous outflow end to reduce turbulence and shear force in the vascular system to the degree possible. 
     A still further object of this invention is to provide a system wherein the arterial end (PTFE) may also be placed by percutaneous technique including one where blood entry holes are distant from the site where blood enters the veins. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects of this invention may be more clearly seen when viewed in conjunction with the accompanying drawings wherein: 
     FIG. 1 is a perspective view of the vascular access system comprising the invention; 
     FIG. 2 is a cross-sectional view of the needle access site taken along the line  2 — 2  of FIG. 1; 
     FIG. 3 is a cross-sectional view similar to FIG. 2 with a needle inserted into the access site; 
     FIG. 4 is a cross-sectional view of the coupling between the PTFE and the silicone venous end of the catheter; 
     FIG. 5 is a perspective view of an alternate embodiment of the invention with one port having a tube sewn to a vein; 
     FIG. 6 is a perspective view of the embodiment in FIG. 5 with a silastic tube floated down a vein; 
     FIG. 7 illustrates a ringed tube sewn to an artery and connected to a first access site which is joined to a second site by silastic tubing and includes an outflow through silastic tubing which is floated into the venous system; 
     FIG. 8 is similar to FIG. 7 but shows PTFE sewn to an artery and silastic tubing floated into a different portion of the venous system; 
     FIG. 9 depicts ringed PTFE tubing sewn to the subclavian artery and a dual access site coupled to the venous system at its other end; 
     FIG. 10 shows a multi-layered variation at the venous end of the system; 
     FIG. 11 discloses a quick coupler design utilized in conjunction with the system; 
     FIG. 12 is a unique port design utilized in conjunction with the system; 
     FIG. 13 shows holes where ports can be fixed in place while FIG. 13 a  and FIG. 13 b  show cross-sectional views which depict the internal construction of the invention with FIG. 13 b  illustrating multi-layered tubing; and, 
     FIG. 14 shows a variation of the system entry through vein wall (i.e. not percutaneous or purse string) wherein a cuff, sewn to vein as indwelling portion, is floated down stream. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings the Squitieri hemodialysis and vascular system, as shown in FIG. 1, comprises a PTFE/Dacron (or other synthetic or natural material) tube  10  of several centimeters in length which is attached at one end by means of a coupling to a needle access site or receiving site  20 . Adjustable band  18  regulates the blood flow through the access site  20 . The PTFE tube  10  is approximately 7 mm in diameter and transitions downward to an open end portion  19  approximately 4 mm in diameter. 
     The access site  20  includes an in line aperture  16 , see FIG. 2, having a silicone tube  41  connected thereto at one end leading to a long flexible plastic/silastic/silicone tube  12  with transverse holes  13  along its free end. The number of holes  13  may vary within predetermined limits to achieve optimum results. The end  36  may be beveled for ease of insertion. This tubular arrangement functions as a subcutaneous connection between the arterial and venous systems. It may also be modified to allow part of the system to exit through the skin  14  (FIG. 3) to provide access to the blood circulation without placing needles  15  (FIG. 3) through the skin  14  into the fistula (usually at the PTFE end). 
     Along the length of the catheter specially constructed needle access sites  20  (FIGS. 1,  7 ,  8 , and  10 ) are located to receive specially designed needles  15  into the system to gain access to the blood stream which flows through aperture  16 . This method avoids perigraft bleeding which leads to thrombosis either by compression of the graft by hematoma or by manual pressure applied to the graft in an attempt to control the bleeding. 
     The needle access areas  20  which are designed to receive needles  15  etc. to allow access to the system are in line conduits with self-sealing material  25  which is here shown as a silicone member  25  which can be located beneath the skin surface. The silicone member  25  comprises an oval configuration exposed within the frame  26  for ease of puncture. The system may be accessed immediately after insertion without having to wait for the graft to incorporate into the tissues as is the case with the current methods of subcutaneous fistulas. These access areas  20  will protect the graft since they are uniformly and easily utilized requiring little training or experience. The “needle receiving” sites  20  are designed in such a way to preserve laminar flow as far as possible (i.e. not a reservoir arrangement). Needle receiver sites  20  may be connected to a system via “quick couple”  45  for easy exchangability, see FIG.  11 . 
     FIGS. 2 and 3 disclose a needle access site  20  wherein a silicone member  25  is mounted within a plastic or metal frame  26 . A protruding portion  27  of member  25  extends upwardly through the aperture  31  while a flange portion  28  extends outwardly on both sides of the portion  27  to be gripped by teeth  29  on the internal surface of frame  26  and member  32 . The frame  26  includes an in-line aperture or passage  16  through the needle access site  20  for blood flow. The blood flow is accessed by inserting needles  15  through the silicone member  25  which is preferably oval in shape. The teeth  29  seal the arterial pressure. The passage  16  of the needle receiving site  20  is tubular in shape. 
     The open end portion  19  of the PTFE tube  10  is sewn to an opening in an artery  30 , see FIGS. 5,  6 ,  7 ,  8  and  9 , while the flexible plastic tube  24  of the system having been inserted percutaneously lies in the venous system in such a way that the openings  13  in the silastic tube  12  are downstream from the site where the flexible plastic tube  24  enters the vein  40  (see FIGS.  5  and  6 ). The venous end may be inserted via “cutdown”. The purpose of the system is to allow communication between an artery  30  and a vein  40  in such a way that the system may be accessed by either puncturing the PTFE segment or by entering the specialized “needle receiving” site  20 . This allows blood to flow from the system to a hemodialysis (HD) machine (not shown) and then return into the venous outflow portion at a more distal (venous end) location allowing the blood to return from the HD machine (not shown) back into the patient. 
     FIG. 4 discloses, as an alternative, a “glued” connection between PTFE tubing  60  and silicone tubing  61  wherein the PTFE tubing  60  is inserted into an enlarged portion of silicone tubing  61  wherein the longitudinally extending portion includes a raised section  63  which locks a raised section  64  of PTFE tubing  61  within the silicone tubing  61 . 
     In this invention, the materials used may vary as specified herein. The system may be constructed of one or more specific materials. The arteries and veins used may also vary. Material may also be covered with thrombus resistant coatings (heparin, etc.) or biologic tissue. The system may in specific cases be “ringed” for support. 
     The same concept of using an arterialized venous access catheter may be applied to the use of long term indwelling catheters used to give chemotherapy etc., making the current ports obsolete as these new access systems will have a decreased thrombosis rate and they will no longer need to be flushed as continuous blood flow through the system makes thrombus formation unlikely. This will definitely cut down on costs since it will decrease nursing requirements in out patient settings, etc. 
     In alternate embodiments shown in FIGS. 5 and 6, the system comprises an arterial reservoir structure or port  50  with needle accessible top portions  51   a  and  51   b , each of which a preferably-constructed of silicone. The arterial reservoir structure  50  is connected to an outlet tube  53  of PTFE (gortex-ringed), which is sewn to an artery  30  at its other end. The venous outlet tube portion  57  is constructed in a similar way but it is either sewn to a vein  40  via gortex ringed portion  52  or is placed percutaneously into the central circulation via an indwelling venous (silicon) catheter  42  as shown in FIG.  6 . There is no continuous flow through this version of the system since the ports are not connected. Flow is established when the system is attached to an HD machine with a needle  15  in the arterial port  51   a  to deliver blood to the HD machine and a second needle  15  is placed in the venous port  51   b  to the vein  40  to deliver blood to the patient. The ports  51   a ,  51   b  will remain flushed with heparin when not in use to avoid clotting when accessed through the skin  14  with needles  15 . The ports  51   a ,  51   b  will also provide high flow access to both the arterial and venous systems. FIG. 6 shows two separate ports  51   a  and  51   b  with the outlet tube  53  sewn to an artery  30  and the indwelling venous catheter  42  floated down a vein  40 . 
     FIG. 7 illustrates, in an anatomical drawing, an outlet tube  53  of PTFE (ringed gortex) sewn to an artery  30  at  62  and coupled at its other end  62   a  to the needle access site  20 . The site  20 , see FIGS. 1-3, is joined by silastic tubing  68  to a second access site  20   a  which has an outlet silastic tube  65 . The outlet tube  65  includes a plurality of perforations  66  at its outlet end which is positioned in the venous system  67  through vein  40 . Either site  20  or  20   a  can be used for needle access. 
     FIG. 8 depicts an embodiment similar to that of FIG. 7 except that the coupling between the artery  30  and the first needle access site  20  is PTFE tube  69 . The entry to the venous system  67  is via vein  40  which has silastic tubing  65  floated therein. A PTFE tube portion  69   a  joins parts  20  and  20   a.    
     FIG. 9 illustrates a dual needle access site  80  which is coupled via outlet tube  53  of PTFE (gortex-ringed) to the subclavian artery  30  and floated into the venous system  67  via silastic tubing  65 . The dual site  80  provides additional access through  25   a ,  25   b  in approximately the same area with tubing (not shown) extending through the dual site needle access site  80 . 
     FIG. 10 depicts a variation of the invention at the venous end wherein the outlet of the port  20  comprises PTFE tubing  91  located within a silastic catheter  92 . This design is appropriate if thrombosis is a problem in the outlet silastic portion of the shunt. 
     FIG. 11 discloses a quick coupler  45  joining the PTFE outlet tube  53  (gortex-ringed) to the port  46  in the needle access site  20 . A plastic or metal member  47  includes a portion  48  which engages the cylindrical PTFE tubing  10 , an intermediate portion  49  extending perpendicularly outward and an end portion  43  tapered outwardly at an angle and including an inward projection  44 . The projecting portion  44  of the member  47  engages a slot  54  in the port  46  firmly fixing the cylindrical PTFE tubing  10  therebetween. Portion  48  is made of flexible material to allow a gentle curve in tubing as it exits/enters port. 
     FIG. 12 is an exploded view of a new port embodiment wherein the port  71  comprises a frame  72  having an inlet coupling  73  and an outlet coupling  74 . The plastic or metal frame  72  includes a recessed reservoir  76  and end walls  78   a  and  78   b . An upper member  85  having a top or upper member  85   a , a recess  83  and downwardly projecting sides  87   a  and  87   b  fits within walls  77   a  and  77   b . The upper member  85  includes an oval silicone access site  90 . The member  45  rapidly couples the PTFE tubing  10  to site  71  with tubing  88  which fits over the inlet coupling  73  and the outlet coupling  74  with recessed portions  75   a  and  75   b  which engage tubing  88  (only one of which is shown) and have couplers  45  (only one of which is shown) which slide over the tubing  88  to engage the inlet and outlet couplings  73  and  74 . 
     A housing  86  includes a top portion  86   a  and a side portion  86   b . The top portion  86   a  includes an aperture which surrounds and provides a means for accessing the oval silicone access site  90 . This embodiment provides a quick assembly for a needle access site  71 . 
     FIG. 13 shows a typical dual port system showing holes  55  where ports  20  can be fixed in place, while FIG. 13 a  and FIG. 13 b  show cross-sectional views which depict the internal construction of the invention with FIG. 13 b  illustrating multi-layered tubing. 
     FIG. 14 discloses a cuff  56  which is made of PTFE and sewn to a vein. No physiological/functional venues anastomosis is created as blood is returned at the end of the system distant from the cuff. The silastic end  12  may still be lined with PTFE. 
     The Squitieri Hemodialysis/Vascular Access System avoids creation of a venous anastomosis, a revolutionary advancement, i.e. there is no site for neointimal hyperplasia at a venous anastomosis which accounts for the vast majority of PTFE arteriovenous graft failures (60-80%). This is accomplished by returning the blood into a larger vein via an indwelling venous catheter  42 . The site of blood return to the venous system is not fixed to the vein wall where neointimal hyperplasia occurs with the standard PTFE bridge graft. This feature represents a tremendous advantage over the present grafts. 
     As a further advantage, the system is not stagnant and prone to thrombosis, i.e. constant flow through the new system avoids the problem of clotting inherent in indwelling dual lumen venous catheters which remain stagnant when not in use. It also avoids need to flush catheters with heplock thereby reducing nursing costs to maintain the catheter. 
     The Squitieri system avoids externalization of components which are prone to infection. Since dual lumen catheters exit the skin  14 , they frequently lead to sepsis requiring catheter removal despite subcutaneous tunneling. This new access is entirely subcutaneous. 
     Very importantly the system proposed herein, avoids problems with the aspiration of blood from the venous system and “positional” placement through continuous flow. A frequent problem with dual lumen catheters is their inability to draw blood from the venous system due to clot and fibrinous debris ball-valving at the tip of a catheter. This new system receives blood directly from arterial inflow which ensures high flow rates needed for shorter, more efficient dialysis runs. It also avoids the frequent problem of the catheter tip “sucking” on the vein wall inhibiting flow to the dialysis machine and rendering the access ineffective. 
     The system avoids recirculation seen with dual lumen catheters resulting in more efficient and more cost effective dialysis. 
     The system avoids the need for temporary access with incorporation of “Needle Access Sites”  20 . A-V fistulas and gortex grafts must “mature” for several weeks before use. This creates a huge strain on the patient as well as the doctor to achieve temporary access while waiting to use the permanent access. Temporary access is very prone to infection, malfunction and vein destruction. By placing sites  20  designed to receive needles  15  along the new access, the system may be used the day it is inserted. 
     The system avoids PTFE needle site damage with the incorporation of “Needle Access Sites”  20 . Needle access directly into PTFE is presently uncontrolled and user dependent. Often, PTFE is lacerated by access needles. While this system may be accessed via the PTFE segment, the needle receiving sites are the preferred method. This leads to excessive bleeding which requires excessive pressure to halt the bleeding causing thrombosis of the graft. “Needle Access Sites”  20  on the Squitieri access system allow safe, quick, and easy entry into the system and avoid the complications inherent in placing needles directly into PTFE. It also avoids perigraft bleeding which will compress and thrombose the graft. By eliminating the long time needed to compress bleeding at the needle site, the system shortens dialysis runs. 
     The Squitieri system permits an easier, faster insertion technique. Only one anastomosis the arterial end and a percutaneous placement of the venous end is required. A modification allows the system to be sutured to the vein wall while the system tubing is floated down stream from this site where the system enters the vein  40 . This saves operating room time at thousands of dollars per hour. The technique is easier with faster replacement. It avoids difficult and time consuming revision of venous anastomosis required to repair venous outflow occluded by neointimal hyperplasia. If the system malfunctions, the silastic catheter end  65  slips out easily and the arterial end of the outlet tube  53  is thrombectomized. New access sewn to the thrombectomized end of the outlet tube  53  of PTFE at the arterial end and the silastic venous end is replaced percutaneously via Seldinger technique or “open technique”. 
     The end result of the above advantages translates into superior patency rates and a decreased complication rate with this new system. Patients are spared the repeated painful hospitalizations for failed access as well as the emotional trauma associated with this difficult condition. The physicians are spared the dilemma of how to best treat these patients. This system will have a large impact on the current practice of vascular access in areas such as hemodialysis; plasmapheresis; chemotherapy; hyperalimentation; and chronic blood draws. 
     While the invention has been explained by a detailed description of certain specific embodiments, it is understood that various modifications and substitutions can be made in any of them within the scope of the appended claims which are intended also to include equivalents of such embodiments.