Abstract:
This invention provides a dialysis-access graft fistula having self-sealing ports for use in hemodialysis. The self-sealing ports can be repeatedly used for the cannulation required for the blood flows associated with hemodialysis. The ports self-seal after each puncture.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Applicant hereby claims priority based on Provisional Application No. 60/086,777 filed May 26, 1998, and entitled “Dialysis Graft With Self-Sealing Ports” which is incorporated herein by reference. 
    
    
     FIELD OF INVENTION 
     The present invention relates generally to the field of dialysis grafts, and more specifically to a dialysis graft having self-sealing ports for repeated cannulation. 
     BACKGROUND OF THE INVENTION 
     Hemodialysis is now a commonly practiced method of treating patients suffering from renal failure. Hemodialysis machines serve to remove life-threatening chemicals from the blood stream, when the kidneys can no longer effectively remove such chemicals. 
     In order to perform hemodialysis, access must be obtained to the blood flow system, and blood flows of 150 to 400 ml/minute are required. Blood from veins is inadequate to meet these flow requirements, and repeated puncture of a large artery is not feasible. 
     Accordingly, a medical procedure has been developed whereby a fistula is created by surgically anastamosing a superficial artery and a nearby vein. The fistula is a surgical connection of an artery to a vein. When such a connection is created, the blood flow through the blood vessels involved is increased since the flow resistant capillaries are bypassed. The pressure at the venous side of the fistula is also increased, causing the vein to enlarge its diameter and causing the walls of the vein to thicken. Once these changes have taken place, the transformed vein becomes a site with a suitably large diameter and blood flow to puncture with needles for the purpose of connecting the patient to a dialysis machine. 
     If a native vein is not available for the anastomosis because the patient&#39;s blood vessels are not suitable for the formation of a fistula or the patient&#39;s blood vessels are not healthy enough for a fistula to be created, an artificial vessel or vascular graft is used to bridge an artery and a nearby vein. The material of the graft is suitable for puncturing with needles to achieve the necessary access to the patient&#39;s blood system. 
     These type of grafts are often connected between the distal radial artery and the cephalic or basilic vein. Each end of the fistula is anastomosed in an end-to-side fashion to the respective artery or vein. The most commonly used material to form prosthetic vascular grafts is expanded polytetrafluoroethylene (PTFE). And cannulation of arteriovenous fistulas or graft fistulas with 14-16 gauge needles permits blood flow sufficient to carry out hemodialysis. 
     The grafts are implanted entirely below the skin to reduce the risk of infection and to provide better comfort to the patient between dialysis treatments. A hypodermic needle is used to cannulate the vessel through the skin. During cannulation of the graft fistulas, direct punctures of the graft walls are made with the needles. One puncture is made in the graft wall in the arterial side and one puncture is made in the venous side. Repeated punctures of the graft material promote rupture of the graft, pseudoaneurysms, and the development of organized thrombus within the lumen of the graft. Organized thrombus may be the cause of graft thrombosis and eventual graft failure. 
     Repeated, direct punctures of the graft wall also require compression for hemostasis following the dialysis session. Excessive compression during hemostasis may cause decreased flow within the graft and thrombosis. Also, there is very little subcutaneous tissue between the surface of the skin and the graft wall reducing the capacity of extra luminal coagulation of the blood within the surrounding tissue and therefore causing reduced hemostasis at the end of the procedure. 
     What is needed is a dialysis access graft fistula that better provides for repeated cannulation while reducing the occurrence of ruptures of the graft, pseudoaneurysms, and the development of organized thrombus; and that reduces the problems discussed above with hemostasis. 
     SUMMARY OF THE INVENTION 
     The present invention meets the above-described needs by providing a graft that is particularly suitable for repeated dialysis. The graft provides a fistula between an artery and a vein and comprises a series of septums on both the arterial as well as the venous side. The septums are made of a stretchable material so that after puncture and withdrawal of the needle, the septum seals by itself. This avoids repeated puncture of the graft wall thereby prolonging the life of the graft. The development of the dialysis graft with puncture septums is a significant improvement over existing technology and can improve utilization by facilitating puncture and maintenance while reducing the risk of common complications such as pseudoaneurysms and thrombosis. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is illustrated in the drawings in which like reference characters designate the same or similar parts throughout the figures of which: 
     FIG. 1 is a perspective view of the dialysis graft; 
     FIG. 2 is an enlarged side elevational view of the dialysis graft illustrating the positioning of the septums on the port chamber wall; and, 
     FIG. 3 is an enlarged side elevational view of an alternate embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention provides a dialysis graft with septums to provide improved access for dialysis, to reduce the uncertainty of puncture during the procedure, and furthermore, to protect the graft from damage caused by repeated punctures. In addition, this device will also eliminate the hemostasis factor discussed above. 
     As shown in FIG. 1, the dialysis graft  10  is anastomosed in end-to-side fashion between an artery  12  and a vein  14 . The dialysis graft is composed of one, two, or more segments of plastic or metal chambers  16  on the arterial side and on the venous side. Regular graft segments  18  are connected to the artery  12  and the vein  14  and in between the chambers  16 . 
     A lateral view of a port chamber  16  is shown in FIG.  2 . The port chamber  16  fits into the lumen  30  of a regular segment of the graft  18  by standard means. The port chamber  16  may be made of any suitable plastic material or metal. In the wall of the port chamber  16  are present a plurality of holes  17 . Each hole  17  forms septum  20 . Suitable materials for septums  20  include, but are not limited to, silicon and several other plastic polymers. Various materials for making septums  20  are well known to those skilled in the art. One port chamber  16  may contain several septums  20  distributed all around the port chamber  16 . Since the graft  10  is typically placed close to the skin  32 , the septums  20  are palpable underneath the skin for insertion of a needle  34 . The external surface of the septum  20  is made of a stretchable material that is suitable for repeated punctures. One of the most commonly available materials is made of silicon. The septums  20  can be covered internally with Teflon or some other clot-resistant material. 
     The needle  34  used for puncturing the septum should be a coreless needle, i.e., it should not cut the seal of the septum  20  but should open a hole that may tightly close after needle  34  withdrawal. One example of a suitable needle  34  for puncturing the septum  20  is a needle  34  with a beveled end. The beveled end will puncture the septum  20  but will not remove a core from the septum  20  material which is then able to self-seal after removal of the needle  34 . Each septum  20  should withstand several punctures and not suffer significant wear and tear. 
     A minimum of two septums  20  should be available on the arterial and venous side of graft  10  to allow healing of adjacent skin and to increase the number of allowable punctures. For example, for a patient requiring dialysis three times a week, a suitable dialysis graft  10  should have provision for 156 punctures per year. If there are two septums  20  on each side, each septum  20  will be punctured  78  times a year. A preferable dialysis graft  10  should be able to be used for several years. 
     In an alternate embodiment, in FIG. 3, a graft  100  is disposed through the inside of a tubular port chamber  16  of the present invention. Instead of connecting the graft  100  to opposite ends of the chamber  16 , the graft  100  extends completely through the inside of the port chamber  16 . 
     While the invention has been described in connection with certain preferred embodiments, it is not intended to limit the scope of the invention to the particular forms set forth, but, on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.