Abstract:
A single access dialysis needle system comprises a first cannula, a second cannula or sheath, and a barrier arranged on the outer surface of the first cannula. The distal end of the first cannula extends distal to the distal end of the second cannula or outer sheath, and the barrier is positioned between the respective distal ends. When the barrier is inflated or otherwise activated, it prevents or minimizes recirculation.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application is based upon co-pending U.S. provisional patent application Serial No. 60/354,467, filed Feb. 5, 2002, incorporated herein by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The invention relates to extracorporeal hemodialysis. More particularly, the invention related to a method and apparatus for dialyzing a patient&#39;s blood with a single venipuncture or cannulation.  
         BACKGROUND OF THE INVENTION  
         [0003]    Historically, kidney diseases have been of critical concern to human life. Many kinds of kidney diseases interfere with the function of the kidney such that the kidney ceases to remove waste and excess water from the blood. When the kidney is sufficiently impaired that large portions of the waste products and water are not removed from the blood, the life of the patient cannot be preserved unless a way is provided for artificially performing the function of the impaired kidney. Even today, the same general procedure is used for dialyzing patients&#39; blood that was used very early in the treatment of kidney disease.  
           [0004]    For example, the most commonly accepted practice for dialyzing a patient&#39;s blood extracorporeally requires the surgical creation of a subcutaneous, arterio-venous fistula. Thereafter, the subcutaneous venous system dilates secondary to the increase of blood flow derived from the artery to the vein through the fistula. Sufficient blood flow for dialysis is then obtainable by venipuncture with large bore needles. Normally, two hollow needles or cannulas are used to perform two venipunctures on the patient so that two blood-communication sites exist simultaneously in the patient. Conventionally, blood is withdrawn from one of the punctured blood vessels, forced through a hemodialyzer and thereafter forced into the other. The needles have to be substantially distant from one another to prevent recirculation of blood.  
           [0005]    The aforementioned procedure has been found to have serious disadvantages both to the patient and to the attending physicians, nurses, and technicians. The problems are particularly aggravated because most patients requiring extracorporeal hemodialysis must undergo treatment as frequently as three to four times per week. This means that if every venipuncture were completely successful, a patient would need to undergo from 6 to 8 venipunctures or cannulations each week.  
           [0006]    It is well-known that the duration and well-function of a fistula created by venipuncture is inversely related to the number of venipunctures. Tissue repeatedly subjected to the trauma of venipuncture is much more susceptible to thrombophlebitis, paravascular hemorrhage, clotting and infection. In fact, it is commonly found in patients who have experienced a number of venipunctures, that the tissues surrounding the most accessible veins develop large hematomas which obscure the veins, making successful venipuncture extremely difficult because of insufficient blood flow in the damaged blood vessels.  
           [0007]    Also contributing to the problem is the fact that once one successful venipuncture is made and blood is allowed to flow from the patient&#39;s body toward a hemodialyzer, the blood volume in the patient&#39;s body is reduced, making the second venipuncture very difficult. It has historically been found that while most skilled physicians or technicians are able to perform the first venipuncture with little difficulty, frequently a plurality of attempts is necessary before a second venipuncture can be performed on the same patient.  
           [0008]    In addition, while the pain and discomfort suffered by a hemodialysis patient is understandable, the multiple attempts at venipuncture often necessary to place the second needle result in increasing apprehension, and anxiety on the part of both the patient and the physician, nurse, or technician attending the patient further reduces the likelihood of successful venipuncture.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention, including a novel method and apparatus, reduces patient trauma and tissue damage by accommodating extracorporeal hemodialysis with a single venipuncture. Generally, once the venipuncture has been performed, blood is conducted away from the venipuncture site through one passageway in a double-lumen needle system. The blood is forced through the extracorporeal hemodialyzer and thereafter through the other passageway of the double-lumen needle system again to the venipuncture site. The current invention also reduces recirculation by preventing blood returned to a graft from being aspirated back into the hemodialyzer. A mechanical barrier, membrane, or other structure, such as a balloon, physically substantially separates blood that enters one needle from the blood exiting the other needle.  
           [0010]    In another embodiment of the invention, an access needle system comprises a cannula, a sheath around the cannula to form an annular space, and a hemostasis valve surrounding at least the proximal end of the cannula and being in fluid communication with the annular space. The sheath has one or more lateral ports or openings, and hoses in fluid communication with the proximal end of the cannula and the hemostasis valve or the annular space extend to a blood hemodialyzer. Preferably there will be a barrier to block or partially obstruct fluid flow. The barrier may comprise an inflatable balloon membrane, or other mechanical structure. Optionally a second sheath may partly surround the first sheath and uncover the one or more ports in the inner sheath when the outer sheath is moved proximally. Alternatively, the outer sheath may have one or more lateral pores that may align with one or more lateral pores of the first sheath when the second sheath is slid along the first sheath.  
         OBJECTS OF THE INVENTION  
         [0011]    It is a primary object of the present invention to provide an improved method of extracorporeal hemodialysis using a single venipuncture for each treatment.  
           [0012]    It is another object of the present invention to provide an improved apparatus facilitating extracorporeal hemodialysis with a single venipuncture.  
           [0013]    It is yet a further object of the present invention to provide a single access dialysis needle having two lumens and a barrier wherein extracorporeal homodialysis can be performed using a single venipuncture.  
           [0014]    These and other objects and features of the present invention will become more fully apparent from the description below. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is a partly cross-sectional schematic view of an embodiment of the system of the invention for dialyzing a patient&#39;s blood using a single venipuncture;  
         [0016]    [0016]FIG. 1A is a partly cross-sectional schematic view of a variation of the embodiment shown in FIG. 1 where the two cannulae are coaxial;  
         [0017]    [0017]FIG. 2 is a schematic illustration of a portion of the system shown in FIG. 1 in position in a patient&#39;s dialysis conduit;  
         [0018]    [0018]FIG. 3 is a cross-sectional view of another embodiment of the system of the invention where at least one sheath is arranged circumferentially around a cannula; and  
         [0019]    [0019]FIGS. 4 and 5 are each an oblique view of the embodiment shown in FIG. 3. 
     
    
     DETAILED DESCRIPTION OF INVENTION  
       [0020]    The invention can perhaps be better understood from the drawings. In FIG. 1 a dialysis needle system  2  comprises a first cannula  4  with an annular balloon  6  and a second cannula  8 . Balloon  6  is in fluid communication with an inflation lumen  12  and an inflator  14 . Balloon  6  is deployed after insertion of the cannula and positioning within a dialysis fistula. The proximal end  16  of first cannula  4  and the proximal end  18  of second cannula  8  are separated or otherwise configured so that each of proximal ends  16  and  18  can be attached to hoses  20 ,  22  attached to a hemodialyzer (not shown). First cannula  4  and second cannula  8  are shown in FIG. 1 to be essentially parallel. It should be noted that it is within the scope of the invention that first cannula  4  and second cannula  8  can be coaxial to one another. For example, as shown in FIG. 1A, second cannula  8   a  circumferentially surrounds first cannula  4   a . Balloon  6   a  is in fluid communication with an inflation lumen  12   a  and an inflator  14   a . Balloon  6   a  is deployed after insertion of the needle system and positioning within a dialysis fistula. The proximal end  16   a  of first cannula  4   a  and the proximal end  18   a  of second cannula  8   a  are separated or otherwise configured so that each of proximal ends  16   a  and  18   a  can be attached to hoses  20   a ,  22   a  attached to a hemodialyzer (not shown).  
         [0021]    Needle system  2  is shown in FIG. 2 in position in a patient&#39;s dialysis conduit or vessel  26 . Annular balloon  6  is inflated to cause blood flow in dialysis conduit  26  to go in the direction of arrows  28  into a lumen  30  of second cannula  8 . Blood flows into hose  22 , to a hemodialyzer (not shown), through hose  20 , and then into a lumen  32  of first cannula  4 . Annular balloon  8  functions to stop the flow of blood and separate the blood streams into and out of dialysis needle system  2 , thereby preventing recirculation of blood. It is within the scope of the invention that blood could also flow in the opposite direction, that is, in the directions opposite to the arrows shown in FIG. 2.  
         [0022]    In the embodiment of the invention shown in FIG. 3, a first or inner sheath  38  is circumferentially arranged around a cannular or needle  40  to form annular space  42 , and optionally a second or outer sheath  44  is circumferentially and slidably arranged around inner sheath  38 . The distal portion  52  of inner sheath  38  is sealingly attached to dilating member  50 , which surrounds the distal portion  53  of cannula  40 .  
         [0023]    Adjacent to dilating member  50  is an annular support member  54  through which cannula  40  extends. Support member  54  is affixed to or integral with dilating member  50  and provides support for sheath distal portion  52 .  
         [0024]    Inner sheath  38  preferably has an expandable section  56  having longitudinal cut or score lines  57 , for example, from at least about 4 to about 20, or more, such cut or score lines and optionally a latitudinal score line  58 . When sheath  38  is pushed or slid distally, section  56  forms a barrier structure  59  in the radial direction, as shown in FIG. 5. If outer sheath  44  is used, it is slid proximally to expose barrier section  56  and at least one opening  60 . Alternatively, an opening  60  in inner sheath  38  could become aligned with an opening  62  in outer sheath  44  when sheath  44  is moved in the proximal direction.  
         [0025]    It is within the scope of the invention that the embodiment of the invention shown in FIGS.  3  to  5  may have a barrier element other than the structure described above. For example, this embodiment may have an inflatable balloon with an inflation lumen and an inflator, as described for needle system  2 . Other barrier structure known now or to be developed would be similarly operable.  
         [0026]    The proximal end  68  of cannula  40  is in fluid communication with a stationery shaft  70 , which is connected to a flexible hose (not shown) which preferably has a threaded luer connector  74  at its proximal end. A hemostasis valve  76  slidably encompasses the distal end  78  of stationary shaft  70  and the proximal portion  80  of inner sheath  38 . Also, hemostasis valve  76  is in fluid communication with a port  82 , which is connected to a flexible hose (not shown) which preferably has a luer connector  86  at its proximal end. Preferably hemostasis valve  76  has at least one sealing ring  88 , such as an O-ring or a rubber membrane, on or in the surface adjacent shaft  70 . Preferably valve  76  is affixed to the proximal portion  80  of inner sheath  38 . Both luer connectors  74 ,  86  are intended to connect to a hemodialysis machine (not shown).  
         [0027]    [0027]FIGS. 4 and 5 are each an oblique view of the embodiment of the invention depicted in FIG. 3. In FIG. 4 outer sheath  44  is in its initial position relative to inner sheath  38 , where port  60  in inner sheath  38  and barrier structure section  56  are covered.  
         [0028]    If outer sheath  44  is used, it is moved longitudinally in the proximal direction, for example, by gripping the outer surface of outer sheath  44 , and then port  60  in sheath  38  and barrier section  56  are uncovered. Hemostasis valve  76  and the proximal  80  of inner sheath  38  are displaced in the distal direction to cause distal section  56  to expand radially to form barrier structure  59 . Blood flow is represented by arrows  108 ,  110 ,  112 , and  114 .  
         [0029]    The device of the invention comprises conventional physiologically acceptable materials, especially those that can be sterilized, as would be appreciated by those skilled in the art. Typically the components described herein will be made from rigid or slightly flexible polymers and/or co-polymers, several as polypropylene, polyethylene, polystyrene, polybutylene, and co-polymers thereof. Sealing ring  88  would preferably be comprised of a suitable flexible polymer, rubber or elastomer.  
         [0030]    The outer surface of the device should be configured or designed to minimize friction or interference with movement or body surfaces or tissue. The outer surfaces of the device according to the invention should be as smooth as possible. For example, the distal surface  92  of hemostasus valve  76  can be rounded as in FIG. 3 or tapered as shown in FIGS. 4 and 5.  
         [0031]    The invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive and the scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.