Abstract:
An implantable access port in accordance with one embodiment of the invention comprises a hollow port casing having a first channel, a second channel and a third channel. A self-sealing insert may be disposed within the third channel. The implantable access port may further comprise a graft having a first branch, a second branch, and a third branch, the first branch extending from the first channel and adapted to be anastomosed to a vessel at a first location, the second branch extending from the second channel and adapted to be anastomosed to a vessel in a second location, the third branch extending at least partially into the third channel, wherein the third branch is disposed between the self-sealing insert and the hollow port casing. Methods for performing medical procedures associated with the implantable access port are also disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of Provisional Application No. 60/417,204, entitled IMPLANTABLE DIALYSIS ACCESS PORT, filed Oct. 9, 2002, the disclosure of which is hereby incorporated herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to access ports implantable into a mammal to gain access to veins and arteries thereof. Typically, such ports are implanted for use during hemodialysis. The access ports of the present invention may be utilized as an alternative to a typical arteriovenous (hereinafter “AV”) fistula, AV graft, or large central venous catheter used during modern kidney dialysis procedures. These ports are designed to raise the comfort level of a dialysis patient and to reduce the risk of access damage while also reducing the effort of the medical staff required to conduct the dialysis.  
           [0003]    Unfortunately, a significant number of individuals suffer from decreased kidney function. If the kidney function is depreciated enough, usually to approximately 10% of normal levels, an individual must either undergo kidney dialysis procedures or receive a kidney transplant. Dialysis procedures remove toxic substances, waste, and bodily fluids from the bloodstream when the kidneys are unable to do so. Presently, two types of dialysis are commonly utilized, peritoneal dialysis and hemodialysis.  
           [0004]    Peritoneal dialysis generally involves injecting special solutions into the abdomen of a patient through a port, or plastic tube. The special solution enters the abdomen and occupies the space around the abdominal organs known as the peritoneal cavity. Wastes, toxins, and excess bodily fluids mix with the special solution and are retained therein through osmosis. Once the special solution absorbs a sufficient amount of the wastes, toxins, and excess fluids, the combination may be drained out through the port. This process can either occur every four to six hours in a manual procedure, or continuously if used in conjunction with a cycler machine. While this procedure may usually be performed at home by the patient it will be appreciated that such a process creates a great burden on the patient, and typically interferes with normal life functioning.  
           [0005]    Hemodialysis is conducted by circulating blood through an external filtering machine. Typically, a patient will require hemodialysis three-times per week, with each session lasting approximately four hours.  
           [0006]    In hemodialysis, an “arterial” catheter removes blood from the body. The blood is then pumped across a semi-permeable membrane containing solutions to remove toxins, wastes, and excess bodily fluids. The cleansed blood is then returned to the body through a “venous” catheter. Other than in emergency situations, dialysis access is generally obtained through an AV fistula or AV graft. The same graft serves to both supply blood to the hemodialysis machine as well as return blood to the body. In this regard, two catheters are typically placed into the AV fistula or AV graft. The catheter closest to the heart typically serves as the “arterial” catheter, flowing blood from the body, and the downstream catheter typically serves as the “venous” catheter, returning blood to the body. Because the pressure gradient between the two needles is typically not great, the hemodialysis machine must include a pump to circulate the blood.  
           [0007]    Because, peripheral veins are typically too small in diameter to permit the required flow of 250 milliliters of blood per minute back into the body, AV fistulas are surgically created approximately six weeks before hemodialysis begins in order to artificially enlarge a vein. This is done by joining a vein to an artery in a localized area while the patient is under anesthesia. The increased blood from the artery causes the vein to enlarge and thicken, thus permitting larger flows through the vein then would otherwise be possible. After the six weeks that the fistula needs to heal, two dialysis needles may be placed within the enlarged and thickened vein. One needle permits blood to be removed for dialysis and the other permits cleansed blood to return to the enlarged and thickened vein.  
           [0008]    For individuals whose veins are not suitable for an AV fistula, an AV graft may be used. This procedure involves surgically grafting a portion of the patient&#39;s saphenous vein, a donor animal artery, or a synthetic conduit and using it to connect an artery to an existing vein. The grafted vein or prosthetic conduit may be double punctured to draw blood into the dialysis machine and return cleansed blood into the body.  
           [0009]    Neither AV fistulas nor AV grafts are ideal. The resulting increased blood through the veins may cause a neo-intimal hyperplasia which could occlude the veins and lead to access loss. Additionally, the direct flow of blood from an artery into the veins puts undue strain on the local vascular system in general, and the heart in particular. Finally, because blood is both withdrawn from and returned to the body in the same AV fistula, dialysis is typically inefficient because of the phenomenon of recirculation.  
           [0010]    Recent dialysis advances involve the implanting of dialysis access ports beneath the skin. These ports generally contain a chamber plugged with a self-sealing material, such as rubberized silicone, with a synthetic catheter extending out from within the chamber. The port is placed under the skin and the catheter is surgically implanted into a vein. A second port is similarly implanted beneath the skin and its catheter is surgically implanted into another portion of the vein. One port may then be used to remove blood for dialysis while the other port is used to return the cleansed blood back to the body.  
           [0011]    Ports constructed in this manner tend to clot when not in use especially from the port from which blood is being drawn. Also, because both catheters are inserted into the same vein, portions of the cleansed blood that has been returned to the body may be recycled back into the dialysis machine, making the procedure inefficient. As such, improvements have been contemplated.  
           [0012]    One such improvement involves the implantation of a single port containing three recesses, each enclosed by self-sealing material. Two of the recesses are generally larger than the third. The larger two recesses include catheters extending from their reservoir to a vein within the body, typically the superior vena cava. The two larger recesses act in a substantially similar manner as the two separate ports previously described to remove blood for dialysis and replenish it to the body. The third recess includes two channels extending into the two larger recesses. An anti-clotting agent, such as heparin, may be deposited into the third recess where it is drawn off into the other two recesses. This helps to prevent the larger two recesses and associated catheters from clotting.  
           [0013]    Although these devices represent improvements over the previous dialysis techniques, there remains a need for further improvement.  
         SUMMARY OF THE INVENTION  
         [0014]    In accordance with one embodiment of the invention, there is disclosed an implantable access port comprising a hollow port casing having a first channel, a second channel and a third channel. A self-sealing insert may be disposed within the third channel. The implantable access port may further comprise a graft having a first branch, a second branch, and a third branch, the first branch extending from the first channel and adapted to be anastomosed to a first vessel at a first location, the second branch extending from the second channel and adapted to be anastomosed to a second vessel in a second location, the third branch extending at least partially into the third channel, wherein the third branch is disposed between the self-sealing insert and the hollow port casing.  
           [0015]    In another embodiment, an implantable access port may comprise a hollow arterial port casing having a first arterial channel, a second arterial channel and a third arterial channel. A self-sealing arterial insert may be disposed within the third arterial channel. The implantable access port may further comprise an arterial graft having a first arterial branch, a second arterial branch, and a third arterial branch, the first arterial branch extending from the first arterial channel and adapted to be anastomosed to an artery at a first arterial location, the second arterial branch extending from the second arterial channel and adapted to be anastomosed to an artery in a second arterial location, the third arterial branch extending at least partially into the third arterial channel, wherein the third arterial branch is disposed between the self-sealing arterial insert and the arterial hollow port casing. The implantable access port may further comprise a hollow venous port casing having a first venous channel and a second venous channel. A self-sealing venous insert may be disposed within the second venous channel. The implantable access port may further comprise a venous graft having a first venous graft end in fluid communication with the first venous channel and a second venous graft end adapted to be anastomosed to a vein. The arterial hollow port casing and the venous hollow port casing may be connected to each other.  
           [0016]    In accordance with one method of performing a medical procedure of the present invention, a first catheter may be inserted into a hollow arterial port casing implanted subcutaneously in a mammal such that blood flows continuously through portions of the hollow port casing and the first catheter is in fluid communication with the blood. The method may further comprise filtering the blood withdrawn from the first catheter and recycling the blood to a second catheter.  
           [0017]    In another embodiment of the present invention, an implantable access port may comprise a port casing having a graft with first and second ends extending therethrough and a channel extending from within the graft to an exterior surface of the port casing. A self-sealing insert may be disposed within the channel to seal against the flow of fluid. The first end of the graft may be adapted to be anastomosed to a vessel in a first location and the second end of the graft may be adapted to be anastomosed to the vessel in a second location.  
           [0018]    In yet another embodiment of the present invention, an implantable access port may comprise a port casing having a first channel extending therethrough and a second channel extending from the first channel to an exterior surface of the port casing. The implantable access port may further comprise a graft having a first end and a second end, the graft disposed within the first channel of the port casing such that the first end and the second end are exterior to the port casing. A self-sealing insert adapted to prevent fluid from passing may be disposed within the second channel. The first end and the second end of the graft may be adapted to be anastomosed to an artery such that blood will continuously flow through the port casing.  
           [0019]    In still another embodiment of the present invention, an implantable access port may comprise first and second port halves capable of being connected to each other and a port core adapted to be disposed between the first and second port halves when the first and second port halves are connected to each other. The first and second port halves each may comprise a first recess channel and a second recess channel, wherein the first recess channel of the first port half and the first recess channel of the second port half generally form a shaped opening when the first and second port halves are connected to each other and the second recess channel of the first port half and the second recess channel of the second port half generally form a chamber in which the port core is disposed when the first and second port halves are connected to each other. The port core may further comprise an upper section having an aperture filled with a self-sealing insert and a lower section having an aperture with a graft disposed therethrough, the graft may extend from within the shaped opening when the first and second port halves are connected to each other.  
           [0020]    In another method of implanting an implantable access port of the present invention, the method may comprise severing an artery such that the artery comprises a first end and a second end. Anastomosing a graft to the first end and the second end of the artery such that blood may flow continuously through the graft, wherein the graft is a component of a port core comprising an upper portion having an aperture extending into the graft, the aperture being partially filled with a self-sealing insert. The method may further comprise connecting a first port half and a second port half around the port core to form the complete implantable port. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with features, objects, and advantages thereof may best be understood by reference to the following detailed description when read with the accompanying drawings in which:  
         [0022]    [0022]FIG. 1 is a diagrammatic view of a hemodialysis system utilizing one embodiment of the implantable access port of the present invention;  
         [0023]    [0023]FIG. 1 a  is a partial blow-up view of the hemodialysis system utilizing one embodiment of the implantable access port of the present invention shown in FIG. 1;  
         [0024]    [0024]FIG. 2 is a perspective view of an implantable access port in accordance with one embodiment of the present invention shown attached to an artery and a vein;  
         [0025]    [0025]FIG. 3 is a cross-sectional view of the implantable access port of FIG. 2 taken along section lines A-A;  
         [0026]    [0026]FIG. 4 is a cross-sectional view of the implantable access port of FIG. 2 taken along section lines B-B;  
         [0027]    [0027]FIG. 5 is cross-sectional view of an implantable access port in accordance with another embodiment of the present invention;  
         [0028]    [0028]FIG. 6 is a perspective view of an implantable access port in accordance with yet another embodiment of the present invention shown in an unassembled position;  
         [0029]    [0029]FIG. 7 is a perspective view of the implantable access port of FIG. 6 shown in a partially assembled position;  
         [0030]    [0030]FIG. 8 is an exploded view of another embodiment of the implantable access port of the present invention; and,  
         [0031]    [0031]FIGS. 9 a - d  are perspective views depicting one method of installing an implantable access port constructed in accordance with another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0032]    In the following is described the embodiments of the implantable dialysis access port of the present invention. In describing the embodiments illustrated in the drawings, specific terminology will be used for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents that operate in a similar manner to accomplish a similar purpose.  
         [0033]    Referring to the figures, FIG. 1 depicts a diagrammatic view of a typical hemodialysis system utilizing one embodiment of the implantable dialysis access port  2  of the present invention. As shown in FIG. 1, the implantable dialysis port  2  may be implanted into the chest area  100  of the human body. The implantable dialysis port  2  may also be implanted into other areas of the body, so long as it is implanted in reasonable proximity to a medium sized artery, typically between 6 and 8 mm, for use with the implantable dialysis port  2 . As will be discussed, the implantable dialysis port preferably comprises an arterial port  4  and a venous port  6  connected to each other in a single structure. In other embodiments, the ports  4 ,  6  may be separate structures which may include features to permit their attachment to each other.  
         [0034]    As shown more particularly in FIG. 1 a , an arterial graft  12  generally extends through the arterial port  4  while a venous graft  18  extends from the venous port  6 . During the implantation process, the arterial graft  12  is preferably connected at each of its ends to the sidewall of an artery  26  while the end of the venous graft  18  is connected to a vein  34 . In other embodiments, the arterial graft  12  may be connected to the artery  26  by a pair of end-to-end anasomoses. Additionally, the venous graft  18  may take the form of a venous catheter which is inserted into the vein  34  such that it may enter the central venous system.  
         [0035]    As will be discussed in greater detail below, dialysis may be conducted by tapping the arterial port  4  with an arterial catheter  102  and the venous port with a venous catheter  104 . Each of the arterial and venous catheters  102 ,  104  are connected to a dialysis machine  106  comprising a pump  108  and a membrane  110 . Blood is permitted to flow from the artery  26  into the arterial port  4  and through the arterial catheter  102  into the membrane  110  of the dialysis machine  106  for cleansing. The pump  108  then drives the blood through the venous catheter  104  and the venous port  6  into the vein  34 . Other than the use of the implantable dialysis port of the present invention, this dialysis technique is similar to that presently utilized in the art. In addition, it will be appreciated that dialysis machines  106  may have pumps  108  in series prior to the membrane  110 , rather than after as previously discussed. Because of the pressure gradient between the arterial and venous systems inherent in a mammal, it may also be possible that no pump  108  is required as the patient&#39;s heart may be sufficient to circulate blood through the dialysis machine  106  as well as the patient&#39;s body.  
         [0036]    [0036]FIG. 2 depicts a perspective view of an implantable dialysis access port  2  as it is intended to be installed in the human body in accordance with the first embodiment of the present invention. As previously discussed, the implantable dialysis access port  2  preferably comprises an arterial port  4  and a venous port  6  connected to each other or formed together. The arterial port  4  includes an arterial port casing  8  having an opening  10  through its upper surface  11 . An arterial graft  12  extends through the arterial port casing  8 . The venous port  6  includes a venous port casing  14  having an opening  16  through its upper surface  17 . A venous graft  18  extends from the venous port casing  14 .  
         [0037]    The arterial graft  12  comprises a first end  20 , a second end  22  and midsection (not shown). The first end  20  and second end  22  are each exterior to the arterial port  4  while the midsection (not shown) is disposed within the arterial port casing  8  and in direct fluid communication with opening  10 . The first end  20  of the arterial graft  12  may be grafted to a medium-sized artery  26  within the human body. This graft is conducted in a surgical procedure and is typically an end to side anastomosis. Procedures of this type are well known in the art. Similarly, second end  22  of arterial graft  12  may be grafted to a second portion of artery  26 . This graft is also an end to side anastomosis.  
         [0038]    By grafting the arterial graft  12  to artery  26  in such a manner, a bypass of the artery through the arterial graft is created. Blood is therefore permitted to flow simultaneously through artery  26  and arterial graft  12 . The blood flowing through arterial graft  12  will also flow through arterial port casing  8  through the open midsection of arterial graft  12 . A self-sealing insert  28 , such as a rubberized silicone insert or the like, inserted within the opening  10  of arterial port casing  8  prevents this blood from flowing out through the opening  10  of arterial port casing  8 .  
         [0039]    When arterial port  4  is not being used for actual dialysis procedures, blood will continuously flow through arterial graft  12  in a parallel system to that of the blood flowing through artery  26 , and will then continue to flow throughout the remainder of the body. Because none of the blood within arterial graft  12  is permitted to remain stagnant, no clotting should occur.  
         [0040]    If preferred, the two grafts may also be conducted in end-to-end anastomosis. In either event, blood will be permitted to continuously flow through the arterial graft  12 , so as to help eliminate clotting therein.  
         [0041]    As previously stated, the implantable dialysis port  2  of the first embodiment also includes a venous port  6  connected to the arterial port  4 . Venous graft  18 , extending from venous port  6 , comprises a first end  30  and a second end  32 . The first end  30  is attached to the venous port casing  14  and is in direct fluid communication with opening  16 . The second end  32  is typically grafted to a vein  34  within the human body in an end to side anastomosis. Connection of the venous graft  18  may also be conducted by a large bore cannulation of a central vein, if so desired. In addition, the venous graft  18  may take the form of a venous catheter and may be inserted directly into a vein  34  so its end  32  may extend into the central venous system. Although continued reference may be made to venous grafts  18  throughout this text, it is to be understood that such references may also be interpreted as allowing for the use of venous catheters as well. Each of these types of connections are well known in the art.  
         [0042]    As with arterial port casing  8 , venous port casing  14  also contains a self-sealing insert  36  within its opening  16 . This self-sealing insert  36  prevents blood from flowing through opening  16  of venous port casing  14 . Once venous graft  18  is anastmosed to vein  34 , blood may freely flow from vein  34  through venous graft  18 . Because venous graft  18  is constructed in a “dead end” relationship with venous port  6 , blood may remain stagnant within the venous port  6  and venous graft  18  once the dialysis procedure is completed and the venous port  6  is sealed. It will be appreciated that the likelihood of blood being recycled back to vein  34  from first end  30  of venous graft  18  is inversely proportional to the length of the venous graft.  
         [0043]    It is well known in the art that stagnant blood may clot. To avoid the risk of clotting, the entire track from venous port  6  through venous graft  18  is preferably flushed with a saline solution. A pre-metered volume, approximately equal to the volume of the venous graft  18 , of heparin or other anti-clotting agent may then be injected into the venous graft. Thus, blood is completely displaced from the venous port  6 , opening  16  and venous graft  18  and is replaced with the anti-clotting agent. Upon start-up of the next dialysis procedure, the anti-clotting agent is permitted to flow from the body through the venous port  6  until fresh blood appears. The venous catheter  104  may then be connected to the dialysis machine  106  for initiation of the dialysis procedure. Similar procedures are well known in the medical industry. Because of the limited life-span of the self-sealing insert  36 , it is preferred that a single needle be utilized to withdraw the blood, flush the line, and fill the line with heparin.  
         [0044]    As shown in FIG. 2, the flow of blood through the arterial port  4  will generally be in the direction of arrows A, away from the heart, while the flow of blood through venous port  6  will generally be in the direction of arrows B, toward the heart.  
         [0045]    [0045]FIG. 3 illustrates a cross section of the implantable dialysis access port  2  of FIG. 1, taken along section line A-A of FIG. 1. As can be seen, the arterial port  4  and venous port  6  of the implantable dialysis access port  2  may be constructed monolithically, so to form an integral unit. As will be described hereinafter, the arterial port  4  and the venous port  6  may also be constructed separately. If so constructed, they may remain separate when placed in the body, or may be adaptable such that they can be connected to form one unit.  
         [0046]    The arterial and venous port casings  8 ,  14  are generally constructed of a dense material such as plastic, stainless steel, or titanium, so as to be impenetrable by a needle. The material must also be compatible with implantation within the human body. The shape of the port casings  8 ,  14  must also be compatible with implantation into the human body. Accordingly, there preferably are no sharp edges.  
         [0047]    The arterial and venous grafts  12 ,  18  must also be constructed of biocompatible material. As well known in the industry, such grafts may be formed from expanded polytetrafluroethylene (PTFE), teflon or polyester.  
         [0048]    As may also be seen in FIG. 3, the opening  10  of arterial port casing  8  preferably comprises a plurality of indented regions  38 , or other surface irregularities, into which the self-sealing insert  28  may fit. The indented regions  38  assist to prevent the self-sealing insert  28  from being pulled from the arterial port casing  8  upon removal of a needle or being pushed into arterial graft  12  upon insertion of a needle, or otherwise becoming dislodged.  
         [0049]    Venous port casing  14  of venous port  6  is constructed in much the same manner as arterial port casing  8  of arterial port  4 . In this regard, port casing  6  may include a plurality of indented regions  40  for the purpose of securing self-sealing insert  36  there within.  
         [0050]    [0050]FIG. 4 depicts a more detailed cross sectional view of arterial port  4  in accordance with the first embodiment of the present invention taken along section line B-B of FIG. 1. In this view, it can be clearly seen that arterial graft  12  contains a branch portion  13  extending into opening  10  of arterial port casing  8 . The branch portion  13  of arterial graft  12  is either formed integrally with arterial graft  12  during the manufacturing process, or is grafted on in an end to side anastomosis prior to being installed into opening  10 . Preferably, the branch portion  13  extends beyond at least one of the indented regions  38 . When extending so, self-sealing membrane  28  will preferably provide sufficient pressure to secure branch portion  13  in place. Biocompatible adhesives may also be applied between the branch portion  13  of arterial graft  12  and the arterial port casing  8  to assist with securing of the branch portion  8  to the arterial port casing.  
         [0051]    Casing  17 , preferably formed of metal or other puncture resistant material, may also be included between the self-sealing insert  28  and the branch portion  13  of arterial graft  12 . The casing  17  may be provided to help prevent penetration, tearing, or other damage of the branch portion  13  of arterial graft  12  by the needle used during hemodialysis.  
         [0052]    Referring back to FIG. 3, the venous graft  18  may be connected to the venous port  6  in a different manner. In a preferred embodiment, venous port casing  14  includes a spout  52  having a diameter slightly smaller than that of venous graft  18 . Venous graft  18  is fitted over the entire spout  52  to form a shoulder area  54 . The shoulder area  54  is then held in place by a compression ring  56 , or other type of pressure fitting. The compression ring  56  may be a simple rubberized O-ring or may be a more elaborate fixture, such as a stainless steel clamp. Either way, the pressure fitting should be sufficient to prevent the ingress or egress of fluids past the connection. The fitting should also be of sufficient strength to completely secure the venous graft  18  to the spout  52 .  
         [0053]    Referring back to FIG. 4, it will be appreciated that portions of arterial port casing  8  fall below arterial graft  12  in this embodiment of the invention. One purpose of having arterial port casing  8  completely surround arterial graft  12  is to prevent a needle from piercing through the lower portion  15  of arterial graft  12  when the implantable dialysis port  2  is in use. The lower portion also prevents the arterial graft  12  from collapsing when a needle is inserted into the self-sealing membrane  28 . Preferably, any such needle will be calibrated so that it is not long enough to puncture the arterial graft  12 , but is long enough to enter the graft and come in contact with the blood flowing therein.  
         [0054]    As shown in FIG. 2, arterial port casing  8  and venous port casing  14  are each shown with securing members  44 . Each of these securing members  44  extend from the respective arterial or venous port casing  8 ,  14  and forms an aperture  46  there within. One purpose of the securing member  44  is to permit a surgeon to secure the implantable dialysis access port  2  within the body of the patient. Such securing may be conducted by suturing or stapling the securing member to tissue within the patient&#39;s body. Preferably, at least two such securing members are provided per arterial or venous port casings  8 ,  14 . This allows for a total of four tie-down points to secure the implantable dialysis port  2  in position, which is typically sufficient to prevent detachment.  
         [0055]    [0055]FIG. 5 depicts a cross-sectional view of an arterial port casing  4 ′ formed independent of the venous port casing (not shown). This port casing  4 ′ is otherwise constructed similarly to the port casings previously discussed, complete with self-sealing insert  28 ′, indented regions  38 ′, branch portion  13 ′, casing  17 ′, and arterial graft  12 ′. As will be shown, arterial port casings  4 ′ of this type may be accompanied by separate venous port casings  6 ′.  
         [0056]    [0056]FIG. 6 depicts an implantable dialysis access port  2 ′ in accordance with a further embodiment of the present invention. Like the embodiment shown in FIG. 5, in this embodiment the arterial port  4 ′ and venous port  6 ′ are constructed as two separate elements. Each port  4 ′,  6 ′ includes a plurality of elongate protruding ribs  50  and a plurality of elongate receiving ribs  48 . Each of the protruding ribs  50  may flare outward from the respective port  4 ′,  6 ′ to form bulbous extending portions  52 . In the meantime, each of the receiving ribs  48  may extend inward of the port  4 ′,  6 ′ to form bulbous receiving portions  54  sized and shaped in registration with the bulbous extending portions  52 .  
         [0057]    Preferably, one port  4 ′,  6 ′ includes receiving ribs  48  and protruding ribs  50  alternating around its entire exterior surface while the other port  4 ′,  6 ′ includes such alternating ribs only along a single side, which preferably has a shape corresponding to that of the other element. For example, in the embodiment shown in FIG. 6, the arterial port casing  8 ′ of arterial port  4 ′ includes ribs  48 ,  50  around its entire exterior surface while venous port casing  14 ′ of venous port  6 ′ includes such alternating ribs  48 ,  50  only along a single side, which has an arcuate surface corresponding to the rounded surface of arterial port  4 .  
         [0058]    The receiving ribs  48  of venous port  6 ′ are in registration with the protruding ribs  50  of arterial port  4 ′ and the protruding ribs  50  of venous port  6 ′ are in registration with the receiving ribs  48  of arterial port  4 ′ to facilitate engagement of the two structures. If arterial port  4 ′ is provided with receiving ribs  48  and protruding ribs  50  around its entire exterior surface, it will be appreciated that venous port  6 ′ may then be engaged with arterial port  4 ′ in a number of axes of rotation. Such an arrangement is preferential as it permits a surgeon to strategically place the venous port  6 ′ in relation to the arterial port  4 ′ in accordance with the particularities of the individual into which the implantable dialysis access port  2 ′ is to be implanted.  
         [0059]    As shown in FIG. 7, in order to connect to arterial port  4 ′ to the venous port  6 ′, the two ports should be aligned such that the protruding ribs  50  of the venous port  6 ′ align with the receiving ribs  48  of arterial port  4 ′. Once aligned, the venous port  6 ′ may be slid relative to the arterial port  4 ′ to engage the two to each other. It will be appreciated that the bulbous protruding portion  52  will completely fill the bulbous receiving portion  54  of the respective receiving rib  48 .  
         [0060]    It is also a feature of this invention that the arterial port  4 ′ and the venous port  6 ′ may be implanted in different areas of the patient. For example, one port  4 ′,  6 ′ may be implanted in the left shoulder area while the other port  4 ′,  6 ′ is implanted in the right shoulder area. This will not alter the efficiency of dialysis. Rather, the ports  4 ′,  6 ′ may be implanted in this manner to achieve greater patient comfort. There is no requirement that the ports  4 ′,  6 ′ be in connected to each other, or even in proximity to each other.  
         [0061]    It will be appreciated that the ports  4 ′,  6 ′ shown in FIGS. 6 and 7 include an arterial graft (not shown) and a venous graft (not shown), respectively. Neither of these grafts has been shown in FIG. 6 and  7  for clarity. Notwithstanding, each may be provided in accordance with the techniques previously discussed with respect to the various other embodiments of the present invention.  
         [0062]    [0062]FIG. 8 depicts a perspective view of yet another embodiment of the present invention. In this embodiment, the arterial port  4 ″ is provided in three parts, a first arterial port half  200 , a second arterial port half  202 , and an arterial port core  204 .  
         [0063]    The first arterial port half  200  and the second arterial port half  202  may be combined to form a complete outer shell of the arterial port  4 ″. Each arterial port half  200 ,  202  comprises an arcuate portion  206  forming a shaped opening, such as a complete cylinder when combined. Each arterial port half  200 ,  202  also comprises a second arcuate portion  208  forming a chamber generally running perpendicular to the complete cylinder. The chamber and the complete cylinder are in fluid communication with each other, and overlap in portions of each.  
         [0064]    The arterial port core  204  comprises a graft  210  extending through a cylindrical lower casing  212 . The graft  210  may be secured to the cylindrical lower casing  212  with a biocompatible adhesive or mechanically. Mounted upon the cylindrical lower casing  212 , or formed integrally therewith, may be a cone-shaped upper section  214 . The cone-shaped upper section may be filled with a self-sealing insert  216 , supported therein by surface irregularities or biocompatible adhesives, as in other embodiments of the present invention.  
         [0065]    In other embodiments of the invention, one half of arterial port core  204  may include a venous port coupled to its exterior surface, or may otherwise be adapted to accept a venous port being coupled to its exterior surface.  
         [0066]    As shown in FIGS. 9 a  through  9   d , the arterial port  4 ″ may be implanted into the body of a mammal. To achieve such implantation, an artery, such as artery  26  shown in FIG. 9 a , may be severed in two to form a first artery end  218  and a second artery end  220 , as shown in FIG. 9 b . Preferably, the artery  26  is at least a medium sized artery of approximately 6 to 8 mm in diameter. As shown in FIG. 9 c , the graft  210  of the arterial port core  204  may be anastamosed to the first artery end  218  and the second artery end  220  such that it is interposed therebetween to permit blood to flow from the first artery end  218  to the graft  210  and then through the second artery end  220 , or vice-versa. Because the entire port is not installed in this step, the gap in the artery may be as little as approximately 2 cm, rather than the approximately 6 cm that would be required if the entire port were implanted at this time. The first arterial port half  200  and the second arterial port half  202  may then be placed around the combination such that the arcuate portions  206  surround the graft  210  and the second arcuate portions  208  surround the cylindrical lower casing  212  and the cone-shaped upper section  214 . As shown in FIG. 9 d , the fist arterial port half  200  may then be snapped together with the second arterial port half  202  to form the complete arterial port  4 ″.  
         [0067]    It will be appreciated that methods of connecting the two port halves  200 ,  202  to each other are well known in the industry and include snap closures, as well as other mechanical fixation methods such as nuts and bolts, screws, biocompatible adhesives, and the like. If mechanical devices are utilized, they may be coated after installation with a biologic glue or silicone to prevent tissue growth. It will be appreciated that once complete, the arterial port  4 ″ may be used in the same manner and for the same procedures as described with regard to other aspects of the present invention, including hemodialysis through puncturing of the semi-permeable membrane  216 .  
         [0068]    The arterial port  4 ″ is preferably of a sufficient length to completely cover and protect the anastomosis between the graft and the artery at each location.  
         [0069]    As previously discussed, implantation techniques suitable for implanting the implantable dialysis access ports  2  in accordance with certain embodiments of the present invention are well known in the medical arts. The implantable dialysis access port  2  is typically implanted subcutaneously in the shoulder area below the clavicle, although it may also be implanted elsewhere in the body. It is placed such that the self-sealing insert  28  of arterial port  4  and self-sealing insert  36  of venous port  6  face outward from the chest, just below the surface of the skin. Preferably, these ports  4 ,  6  are located at slightly different elevations, as shown in FIG. 1, or are constructed of different geometries, such as shown in FIGS. 6 and 7 where the arterial port  4 ′ includes a domed head  56  and the venous port includes a flat upper surface  58 . The purpose of providing a distinction between the two ports  4 ,  6  is so that a dialysis technician, or other medical personnel, may identify each port  4 ,  6  during the dialysis procedure by applying slight pressure to the skin with her fingers to discern the elevation and/or shape. As previously discussed, the arterial port  4  should be hooked up to the input of the dialysis machine and the venous port  6  hooked up to the output to take advantage of the pumping power of the patient&#39;s heart.  
         [0070]    Referring back to the embodiment shown in FIG. 2, after implantation of the ports  4 ,  6 , the first end  20  and second end  22  of arterial graft  12  may be grafted to artery  26 . Techniques for such end to side grafts are well known in the industry and may be employed. It will also be appreciated that end-to-end anastomosis may also be utilized. Once the grafts are in place, blood will be permitted to flow through arterial graft  12  which is in direct fluid communication with opening  10 . However, blood is prevented from escaping from arterial port casing  8  by the placement of self-sealing insert  28 . Similarly, venous graft  18  may be grafted upon vein  34  to permit blood to flow from vein  34  through venous graft  18  which is in direct fluid communication with opening  16 . Blood is prevented from flowing past arterial port casing  8  by virtue of the placement of self-sealing insert  36 . Once the arterial graft  12  and venous graft  18  are in place, the implantable dialysis access port may be sutured or stapled into its final placement utilizing securing members  44 , as previously discussed. The patient&#39;s skin may then be sutured and the patient permitted to heal.  
         [0071]    As best shown in FIG. 4, self-sealing insert  28 , conforms to the internal shape of the port casing within which it is placed, in this case arterial port casing  8 . The self-sealing insert,  28  is typically formed from rubberized silicone. Other materials may also be used, so long as the material is sufficiently elastic so as to seal against the back pressure of the blood when the implantable dialysis port  2  is not being used for dialysis, so long as it is compatible with placement inside the human body, and so long as it will self-seal upon removal of a needle, among other required qualities. Preferably, the self-sealing insert  28  will be able to remain self-sealing through a lengthy lifespan and numerous needle punctures.  
         [0072]    Dialysis on a patient who has the implantable dialysis access port  2  previously installed is intended to be relatively simple and nearly pain free. On the patient&#39;s scheduled dialysis day, either the patient or a technician locates the implantable dialysis access port  2  just below the surface of the patient&#39;s skin. Because the arterial port  4  and venous port  6  are on different elevations, are shaped differently or are at different locations in the body, they can be distinguished from one another easily. Once they are located and distinguished, the patient or technician must pierce the patient&#39;s skin and self-sealing membrane  28  of the arterial port  4  with a needle and arterial catheter assembly  102  to permit uncleansed blood from the body to flow into the dialysis machine  106 . Similarly, the patient or technician must pierce the patient&#39;s skin and the self-sealing membrane  36  of the venous port  6  with a needle and venous catheter assembly  104  to enable cleansed blood from the dialysis machine  106  to be returned to the body. Such piercing may initially be conducted with the aid of a local anesthetic to alleviate any pain the patient may endure. However, after several iterations of the process, a desensitized callous should form which may then be pierced such that no local anesthesia will be required upon subsequent punctures.  
         [0073]    It will be appreciated that the needle used for this technical procedure is preferably a side port non-coring type needle. This type of needle allows blood to either enter or exit the needle from the side of the needle, but will not cause extensive damage to the self-sealing insert  28 , such as would be caused by a coring type needle.  
         [0074]    Following the dialysis procedure, the arterial catheter  102  transferring blood from the body to the dialysis machine  106  may be removed. The venous catheter  204  transferring blood from the dialysis machine  106  to the body may be separated from the needle puncturing the self-sealing insert  36  of the venous port  6 . The venous port  6  may then be flushed with a saline solution. Finally, a metered amount of anti-clotting agent, such as heparin, may be injected. The heparin injected should be sufficient to displace all of the blood from within the venous port  6  and venous graft  18 . The heparin should be sufficient to prevent clotting of blood within these areas between dialysis sessions.  
         [0075]    Typically, each of the elements of the implantable dialysis port  2  will last for the lifetime of the patient. Thus, the implantable dialysis port  2  may remain in a single implanted location. Nevertheless, if one element fails, it will typically be one of the grafts  12 ,  18 . Even if a graft  12 ,  18  fails, the implantable dialysis port  2  may remain in the same location after the graft is surgically repaired, using conventional methods known in the medical arts.  
         [0076]    As stated, the invention provides an arterial port  4  in direct fluid communication with an artery  26  and a venous port  6  in direct fluid communication with a vein  34 . This permits the invention to be very efficient, as blood is drawn off and returned to different systems within the body. In addition, it permits use of dialysis machines with less powerful pumps, as much of the energy required to pump the blood is provided by the heart. In fact, for some individuals, a pump will not be required as the natural pressure gradient between the arterial and venous systems may be sufficient to drive the blood through the complete system. Because an external pump may not be required, the heart may not be subjected to an increased pressure output.  
         [0077]    Additionally, because blood from the venous and arterial systems is used there is no risk of ischemia due to esteal syndrome, as with methods of the prior art. There is also no risk of destruction of the local venous system.  
         [0078]    In addition to use of the self-sealing inserts such as self-sealing insert  28 , it will be appreciated that various mechanical valves may also be utilized. Such valves should serve the purpose of preventing unwanted blood flow from within the port  4 ,  6 , while permitting selective entry of a catheter device for blood input or output. Such valves should also be provided with self-sealing abilities.  
         [0079]    It will also be appreciated that a single implantable dialysis port, configured with a “pass through” type graft such as arterial access port  4 , may have uses other than for dialysis. Such uses include situations where patients require frequent vascular injections or infusions of therapeutic fluids. Other uses include situations where a patient may require constant monitoring of blood gases or frequent drawing of blood, such as patients relying on in-home cardiac support systems. In such cases, the single port may be implanted and utilized to assist with the procedures.  
         [0080]    Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.