Patent Publication Number: US-2005143687-A1

Title: Blood treatment catheter and method

Description:
REFERENCE TO RELATED APPLICATIONS  
      This application is a continuation-in-part of pending application Ser. No. 10/116,299 filed Apr. 4, 2002 entitled: Blood Treatment Catheter And Method, the entire disclosure of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION  
      This invention relates in general to blood treatment catheters and more particularly to a design for use in hemo-dialysis in which blood clot build-up within the catheter between uses of the catheter is minimized.  
      The hemo-dialysis catheter is maintained in the patient between dialysis sessions. In order to avoid blood clot within the catheter, a charge of heparinized saline is placed in the catheter to displace the blood and prevent blood clot. This state is called heparin lock.  
      In a typical catheter having a central aspirating lumen and an annular infusion lumen, the openings near the distal end of the infusion lumen are staggered axially. Accordingly, when the heparinized saline is charged into the annular infusion lumen, one of two things occur that negates the function of the heparinized saline and tends to allow a blood clot to form.  
      In one situation, the heparinized saline exits from the proximal most port thereby failing to displace the blood distal of that exit port.  
      In another situation, the heparinized saline may be inserted with sufficient flow speed to displace all of the blood in the annular catheter. However, the patient&#39;s blood gradually circulates through the openings in the annular lumen, displacing the heparinized saline allowing a blood clot to develop over the zone between proximal and distal openings.  
      The heparinized saline is locked into the lumens and this state is often referred to as heparin lock. The blood clot at the distal zone prevents the heparin lock from performing its anti-clotting function at that zone.  
      Accordingly, it is an object of this invention to provide a catheter design that maximizes the effect of the heparin lock.  
      Accordingly, it is a further purpose of this invention to provide the above purpose in a design which provides a relatively smooth surface to facilitate ease of insertion of the catheter into the patient.  
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       FIG. 1  is a schematic illustration of the positioning of the hemo-dialysis catheter  10  of this invention through the jugular vein. In  FIG. 1 , the catheter is inserted into the patient at point A and into the vein at point B.  
       FIG. 2  is an elevation view of an embodiment of the catheter of this invention in which an annular lumen provides infusion and a central lumen provides aspiration. Infusion ports  22  are at the distal end of the infusion lumen. An aspiration port  36  is at the distal end of the aspiration lumen.  
       FIG. 3  is an elevation view of the zone around the distal infusion port of a first embodiment of the  FIG. 2  catheter showing a plurality of arcuate circumferential ports  22   a;  all of which intersect a single radial plane.  
       FIG. 4  is a partial longitudinal sectional view along the  FIG. 3  catheter portion.  
       FIG. 5  is a cross-sectional view along the plane  5 - 5  of  FIG. 3 .  
       FIG. 6  is a longitudinal sectional view of a second embodiment of the  FIG. 2  catheter in which the infusion port arrangement  22  is a circumferential port  22   b  interrupted by four radial ribs  34  (see  FIG. 8 ) that support the distal end of the annular infusion tube.  
       FIG. 7  is a longitudinal sectional view through the ribs  34  of the  FIG. 6  catheter.  
       FIG. 8  is a cross-sectional view along the plane  8 - 8  of  FIG. 7  showing the four chamber section of the circumferential infusion lumen immediately adjacent to the infusion port  22   b.    
       FIG. 9  is an elevational view of a third embodiment showing a set of triangular infusion ports.  
       FIG. 10  is a cross-sectional view along the plane  10 - 10  of the  FIG. 9  catheter. 
    
    
     DEFINITIONS  
      Infusion and Aspirating Port and Ports  
      The embodiments shown in  FIGS. 3, 6 , and  9  contain a plurality of infusion exit ports. A design can be provided in which there is a single circumferential exit port with upstream supports for the annular lumen. The essential feature is that the port or ports all lie along one plane that is substantially perpendicular to the axis of the catheter.  
      Accordingly, it should be understood that, as applied to either infusion or aspiration lumens, the terms “port” or “ports” or “port arrangement” in the specification and claims are used to include a single port and/or a set of ports.  
     BRIEF DESCRIPTION  
      In brief, the catheter disclosed has both aspiration and infusion lumens. In the embodiments shown, at a distal zone, the tube carrying the aspiration lumen extends distally of the end of the tube defining the infusion lumen. At its distal end, the infusion lumen is substantially annular, extending around the aspiration tube and has one or more infusion ports that provide emission of fluid all within a single plane.  
      All of the infusion ports are deployed along a single plane that is substantially perpendicular to the axis of the catheter. This infusion exit port arrangement serves to avoid blood clot during heparin lock in the annular infusion tube.  
      All of the infusion ports face radially outward to minimize having the port wall edges snag tissue and impede insertion into the catheter.  
     BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       FIGS. 1 and 2  illustrate the overall design of the catheter  10  embodying the invention.  
      In particular, a standard infusion tube  12  and aspiration tube  14  are combined at a juncture  16  to provide a single tube  18  distal of the juncture  16 . The tube  18  contains infusion and aspiration lumens. The tube  18  is inserted into a patient at point A and passed into the jugular vein  20  at point B to be positioned at a desired location; often in the right atrium.  
      As can be seen in the embodiments shown in  FIG. 3  through  10 , the infusion lumen  24  is a circumferential lumen around the aspiration lumen  26  in the zone that is immediately proximal of the infusion exit port arrangement  22 . A tubular wall  28  defines the aspiration lumen  26 . The infusion lumen  24  is defined by tubular wall  28  as an inner wall and an outer wall  30 . The port  22  arrangement is in the outer wall  30 . The outer wall  30  terminates or merges into the wall  28  at the built-up zone  32 .  
       FIGS. 3 through 5  illustrate a first embodiment of this invention in which the infusion port set  22  is constituted by four circumferential ports  22   a  separated by small outer wall sections  30   a.  The port arrangement  22  is at the distal end of the annular infusion lumen  24 . The four ports  22 a are along a single plane which is substantially perpendicular to the axis of the annular infusion lumen  24 . The ports  22   a  face radially outward and thus the central axis of each port  22   a  is substantially perpendicular to the axis of the annular infusion lumen  24 .  
      The small outer wall sections  30   a  merge into the wall  28  at the built-up zone  32 . Thus small segments  30   a  of the outer wall  30  extend through the infusion port zone  22  and define the ports  22   a.  The approximate dimensions in one embodiment of the openings  22   a  are 135 mils by 20 mils (0.135 inches by 0.020 inches) and the segments  30   b  are 25 mils wide.  
       FIGS. 6 through 8  illustrate a second embodiment of this invention in which the exit port arrangement  22  are four circumferential ports  22   b  spaced apart by radial webs  34 .  
      Over a portion of the exit port arrangement  22   b,  a web design shown in  FIG. 8 , is employed at the exit ports  22   b.  This web design assures that the ports  22   b  are maintained open and prevents the wall  30  from collapsing onto the wall  28 . This web design involves four thin webs  34  which extend proximally from the ports  22   b  for about three millimeters in the embodiment shown.  
      The web  34  supports are not required in the design shown in  FIGS. 3-5 . In that design, the outer wall  30  extends past the ports  22   a  to merge into the wall of the aspiration lumen and thus does not require extra support.  
      It should be understood that the design of this invention includes an embodiment in which the webs  34  extend the length of the catheter from junction  16  to infusion exit ports  22 . Such a design is not presently preferred because it provides a stiffer catheter with a lower flow rate than do the designs disclosed herein.  
       FIGS. 9 and 10  show a third embodiment in which the ports set  22  are a set of triangular ports  22   c  nested next to each other. The ten wall segment  30   b  provides a sturdy structural support for the distal end of the outer wall  30  while maximizing the cross-sectional area and flow rate of each port.  
      The design of this invention avoids blood clot development during heparin lock. When the catheter is implanted in a dialysis patient and is not in use, it becomes important to avoid blood clotting in the catheter. This is done by injecting a predetermined amount of heparinized saline into the catheter while the catheter is resident in the patient&#39;s body to essentially fill up the interior of the catheter with heparinized saline. The heparinized saline is held or locked into the lumens between dialysis treatment. This is called heparin lock.  
      In the prior art designs employing co-axial lumens, the outer annular lumen normally has a plurality of openings near the distal end axially displaced from one another. The heparinized saline fills up to the proximal most opening and then exits from that opening and thus fails to fill the space distal of that proximal most opening. A blood clot may form in that space, blocking the openings. Alternatively, if the heparinized saline does completely occupy the catheter lumen, the portion distal of the most proximal hole will gradually be replaced by the patient&#39;s blood and end up creating the blood clot that blocks the catheter openings. Clot formation leads to reduced flow rates and may require intervention to clear the catheter.  
      By having all the openings of the annular lumen aligned in a single plane perpendicular to the axis of the lumen, the blood clot problem that blocks certain of the ports is avoided. In each of the embodiments shown, the infusion port set  22  are the only infusion ports from the annular lumen  24 .  
      Indeed, whether the annular lumen is used for infusion or for aspiration, this co-planar alignment of openings avoids this blood clot limitation on the heparin lock function. Although the embodiments disclosed show that the annular lumen is the infusion lumen, it should be understood that the invention has equal value where the annular lumen is an aspiration lumen.  
      It is important that these co-planar openings face radially outward rather than face partially forward. The radially outward facing opening structure serves two purposes. First it minimizes recirculation of filtered blood from the infusion opening to the aspiration opening. Second, it assures a smoother surface to facilitate insertion of the catheter.  
      In summary, to provide the above advantages, the geometry of the openings have two important characteristics. A first is that the surface of the openings are substantially parallel to the axis of the catheter. The second is that the openings are all on a common plane near the end of the annular lumen; which common plane is substantially perpendicular to the axis of the catheter.  
      While the foregoing description and drawings represent the presently preferred embodiments of the invention, it should be understood that those skilled in the art will be able to make changes and modifications to those embodiments without departing from the teachings of the invention and the scope of the claims.