Abstract:
A catheter system for locking a catheter to an implantable pump and for effectively flushing a catheter after implantation within a body. A locking component comprises an extension boot and catheter lock that together fluidly connect the catheter to the pump in a secure, safe and effective manner. A catheter component comprises a design having kink-resistant walls and a unique tip. A flushing component comprises a hub and stylet combination characterized by a hydrophilic coating on the stylet and a flush through hub to allow flushing of the stylet while inside the catheter.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a catheter system and more particularly to a catheter flushing and locking system for use with an implantable pump.  
       BACKGROUND OF THE INVENTION  
       [0002]     Use of implantable pumps for treating chronic pain conditions has become widely accepted practice when more conservative means of relieving pain have failed. Implantable pump technology can be divided into two primary categories, namely constant flow and programmable. Both technologies incorporate an indwelling catheter to establish a fluid path from a pump disposed subcutaneously to a desired anatomical site, including but not limited to, arterial or venous locations, the epidural space and the intrathecal space of the spine. Some of the reported complications with implanted pumps deal with the connection between the pump and the catheter, including leaks, disconnect and reduced flow. Other reported complications involve the catheter itself, which include but are not limited to, kinking, occlusion, disconnect, malposition, migration and reduced flow. Thus, the success of an implanted pump system is dependent in large part on a successful and dependable connection between the pump and the catheter as well as the design of the catheter and the introduction techniques utilized.  
         [0003]     Prior art implantable pumps employ relatively tedious and often complicated means for attaching the catheter to the pump, which also may promote problems for the entire pump and catheter system. For example, screw driven clamping connections are both complicated and unreliable as the required clamping action on the outer diameter of an unsupported catheter increases the risk of collapsing the inner lumen of the catheter. Stent based designs that do utilize internal support solve the problem of internal collapse, but require the additional step of attachment involving multiple sutures around the connection area. The suturing process, as well as the sutures themselves, can lead to broken or severed catheters at the suture site where the suture cuts through the catheter or surrounding support members. Also, variability in suture tying and force applied by the user leads to variability in attachment. Thus, a prior art approach to attaching the catheter to the pump has been to utilize a barbed stem connector. The pump is fit with a barbed or flared outer stem for the catheter to be placed therearound. The problem with these designs, which are common in subcutaneous access ports, is a connection that is relatively unsecured and potential damage to the catheter caused by the barbed section. Another related problem is that it is often difficult to ascertain whether a positive connection between the pump and catheter has been established. This can lead to catheter and/or pump damage as undue force is placed on the attachment system in order to get verification of the connection.  
         [0004]     In addition to these drawbacks of the prior art systems, one of the primary concerns to overcome in developing a successful and reliable attachment system is that the catheters are generally very small in diameter while the pumps to which they are connected are relatively large. Thus, it is often physically difficult to make the connection between the pump and the catheter.  
         [0005]     Accordingly, it is an object of the present invention, in a system involving an implantable pump and catheter, to provide a catheter system for use with implantable pumps and other known catheter-based systems that will maintain the effectiveness and longevity of the connection and system following implantation thereof.  
         [0006]     It is also an object of the present invention to provide a connection between the catheter and the pump which eliminates the need for suturing around the catheter, avoids potential collapse of the catheter or other attendant damage thereto.  
         [0007]     It is a further object of the present invention to provide a connection system for an implantable pump and catheter that overcomes the difficulty arising from the size difference between the catheter and pump.  
         [0008]     It is yet a further object of the present invention to provide a flexible interface between the catheter and pump body to facilitate attachment of the catheter and minimize strains on the connection.  
         [0009]     It is still a further object of the present invention to provide a connection system for an implantable pump and catheter, which is very easy and quick to implement.  
         [0010]     It is also an object of the present invention to provide a connection system for an implantable pump and catheter that confirms a secure connection.  
         [0011]     It is another object of the present invention to provide a connection system for an implantable pump and catheter that is reliable and long-lasting.  
         [0012]     It is yet another object of the present invention to provide a catheter with minimal contained dead space at the tip to minimize possible complications from static fluid in the system.  
         [0013]     It is still another object of the present invention to provide a stiffening stylet to facilitate positioning of the catheter that is easy to remove and minimizes bunching and displacement of the catheter tip during removal of the stylet.  
         [0014]     Further objects and advantages of the present invention will become apparent from the ensuing description and drawings.  
       BRIEF SUMMARY OF THE INVENTION  
       [0015]     In accordance with the present invention, a catheter system for locking a catheter to an implantable pump and for effectively flushing a catheter after implantation within a body is provided. A locking component comprises an extension boot and catheter lock that together fluidly connect the catheter to the pump in a secure, safe and effective manner. A catheter component comprises a design having kink-resistant walls and a unique tip. A flushing component comprises a hub and stylet combination characterized by a hydrophilic coating on the stylet and a flush through hub to allow flushing of the stylet while inside the catheter.  
         [0016]     What is claimed is a connection device for attaching a catheter to an implantable port or pump, wherein the catheter is in fluid communication with said port or pump, comprising a coupling device extending from said port or pump, comprising an arm portion and a stem, wherein the shape of the aim portion is substantially similar to an outer contour of said port or pump, and wherein the stem comprises a base portion and a tip portion and a locking device slideable along a length of the catheter, comprising varying diameter portions that communicate directly with diameters of the base portion and tip portion of the stem, wherein a locking connection is established therebetween.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]      FIG. 1  is a perspective view of an implantable pump with attached boot and stem according to the present invention.  
         [0018]      FIG. 2  is a side view of the boot and stem according to the present invention.  
         [0019]      FIG. 3  is an enlarged view of the stem in  FIG. 2 .  
         [0020]      FIG. 4  is a cross-sectional view of a stem according to the present invention.  
         [0021]      FIG. 5  is a cross-sectional view of a subassembly according to the present invention, including the stem of  FIG. 4 .  
         [0022]      FIG. 6  is a cross-sectional view of a boot according to the present invention, including the subassembly of  FIG. 5 .  
         [0023]      FIG. 7  is a longitudinal cross-sectional view of a catheter lock according to the present invention.  
         [0024]      FIG. 8  is an end view of the catheter lock in  FIG. 4 .  
         [0025]      FIG. 9  is a side view of a catheter and flushing hub of the present invention.  
         [0026]      FIG. 10  is a side view of a hub and stylet of the present invention.  
         [0027]      FIG. 11  is perspective view of the hub, stylet and catheter of  FIGS. 6 and 7 .  
         [0028]      FIG. 12  is a cross-sectional view of the hub and stylet of  FIG. 7 .  
         [0029]      FIG. 13  is a cut away view of a distal end of a catheter of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0030]     The following detailed description illustrates the invention by way of example, not by way of limitation of the principles of the invention. This description will clearly enable one skilled in the art to make and use the invention, and describes several embodiments, adaptations, variations, alternatives and uses of the invention, including what we presently believe is the best mode of carrying out the invention.  
         [0031]     The present invention is directed to a novel attachment device for securely connecting a catheter to a pump, which can be used in a variety of applications to optimize efficiency and effectiveness. The present invention is also directed to a unique catheter configuration, along with means for introduction and positioning thereof within the body, which offers several advantages over prior art catheters and introducing systems and can be used in various applications.  
         [0032]     One example of a suitable pump for use with the present invention can be seen in  FIG. 1  as implantable pump  10 . Implantable pump  10  could be any medical device that is implanted subcutaneously to deliver a steady stream of drugs or other fluids to the body. Generally, the implanted medical device will contain a septum through which an inner chamber to hold and dispense the drug or fluid can be accessed via a needle. The medical device will also have some type of mechanism to release the drug or fluid at predetermined intervals or in a steady stream at a given flow rate. This timed interval or flow rate can be regulated via mechanism within the medical device or outside of the body using other known means.  
         [0033]     Examples of implantable medical devices that would be suitable for use in conjunction with the present invention can be found in U.S. application Ser. No. 09/481,298, filed Jan. 11, 2000, entitled “Implantable refillable infusion device and septum replacement kit” and in U.S. Pat. Nos. 6,287,293, entitled “Method and apparatus for locating the injection point of an implanted medical device;” 6,213,973, entitled “Vascular access port with elongated septum;” 6,086,555, entitled “Dual reservoir vascular access port with: two-piece housing and compound septum;” 5,833,654, entitled “Longitudinally aligned dual reservoir access port;” 5,049,141, entitled “Programmable valve pump;” and 4,838,887, entitled “Programmable valve pump,” all of which are incorporated by reference herein.  
         [0034]     The implantable pump  10  is shown in  FIG. 1  with an inventive boot  20  containing a stem  30  according to the present invention, which is shown in more detail in  FIGS. 2 and 3 . The boot  20  has an arm  24  that is curved to conform to the outside of the pump  10  so that the overall profile thereof is minimized to facilitate implantation and compatibility within the body. While the boot  20  is shown as curved to conform to the shape of the pump  10 , in an alternate embodiment a boot would take on any shape of the outer contour of a port or pump to realize the advantages mentioned above. The boot  20  attaches to the implantable pump  10  via connector tube  22 , which has a lumen  26  that fluidly connects the inner chambers of the implantable pump  10  (not shown) with the stem outlet  38 . Of course, the boot  20  can be adapted further to connect to various shapes and sizes of pumps other than implantable pump  10 . For instance, in the case of a conventional port with a straight stem, the boot  20  could be fashioned to replace the straight stem to reduce port profile, or in the case of a dual port system, the boot could likewise be fashioned to accommodate the shape of the housing to reduce the overall space occupied by the port or pump.  
         [0035]     Among the many advantages of the conformal shape of the boot are less tissue trauma and reduced force on the catheter and catheter interface with the port or pump (i.e. a stem). Also, in a preferred embodiment of the present invention, the boot is made of a flexible material (such as silicone or a compliant polymer) so that it can be pulled away from the port or pump to which it is attached. This is important because in many applications, the catheters are extremely small, meaning that a physician or medical technician can often find it very difficult to push the catheter onto a stem extending from the port or pump. By providing a flexible boot, the physician or medical technician can pull the boot away from the port or pump, thereby facilitating attachment of the catheter to the stem. After the catheter is sufficiently attached and the boot is released, it will snap back into place, conforming once again to the shape of the port or pump.  
         [0036]     In a preferred embodiment of the present invention, the stem  30  contains a base portion  32  and a tip portion  34  and is made of titanium. As shown in more detail in  FIG. 3 , the base portion  32  includes a forward portion  36  and an engaging lock portion  33 . The engaging lock portion  33  is shown as a larger diameter in a wing configuration near a connecting portion  35  that attaches to the arm  24  of the boot  20 . The engaging lock portion  33  is configured to communicate with the geometry of a locking mechanism (see  FIG. 4 ) to secure the catheter  120  to the boot  20 . Of course, the engaging lock portion  33  can take on various shapes and sizes and is not confined to the embodiment shown Indeed, other types of engaging devices could be employed that would certainly be within the scope of the present invention, including twist locks, spring locks, etc.  
         [0037]     The tip  34  is configured to receive the catheter  120  such that the lumen  122  of the catheter  120  fits over the tip  34  and is expanded by a tip end  39 . Depending on the size of the catheter  120 , the size of the tip  34  can vary, but generally, the diameter of a main body  37  of the tip  34  will be slightly larger than the lumen of the catheter so that a tight friction fit between the two is realized. In addition to the friction fit between the main body  37  of the tip  34  and the catheter  120 , tip end  39  has a conical shape with a base portion attached to the main body  37  to further ensure a tight fit between the catheter  120  and the tip  34 . The diameter of the base portion of the tip end  39  is larger than the diameter of the main body  37  to make disengagement difficult, but not so large that undue stress and resultant damage occurs to the catheter  120  as a result of compression to the wall thereof. The tip end  39  can also take on different forms other than the conical shape shown that will permit the catheter  120  to slide onto the stem  34 , while ensuring that sliding off of the stem is unlikely.  
         [0038]     In one embodiment of the present invention, a subassembly comprising a sleeve and a collar is attached onto a rear of the stem.  FIG. 4  shows a stem  230  prior to attachment of a subassembly. Stem  230  has a rear portion  240  with a barbed end  242  that extends from a base portion  232 . Stem  230  also contains a lumen therethrough, having three different sections. The first and largest diameter lumen section  222  is at barbed end  242 , which is connected to a second diameter lumen section  224  by transition region  223 , which in turn is connected to a third diameter lumen section  226  by transition region  225 . As is apparent from  FIG. 4 , the lumen sections decrease in diameter from the first to the third section. However, as should be appreciated, other possibilities exist which would be equally within the scope of the present invention (e.g., the sections increase in size, the sections remain constant in size, or the sections have varying diameters).  
         [0039]      FIG. 5  illustrates subassembly  250  in cross-section, including the stem  230 , a sleeve  260  and a collar  270 . In this embodiment, the sleeve  260  is made of silicone or like material, while the collar  270  is made of stainless steel. Certainly, however, other materials are possible and would be equally within the scope of the present invention. The sleeve  260  has a length  262 , which in one embodiment is in the range of approximately 0.5 in to 1.0 in. Of course, a length shorter than 0.5 in and longer than 1.0 in would also be within the scope of the present invention. The subassembly is constructed by sliding the sleeve  260  over the rear portion  240  of the stem  230  until a proximal end of the sleeve  260  abuts a flange  234  of the base portion  232 . The collar  270  is then crimped into place around the sleeve  260  between the barb  242  and the flange  234  to secure the sleeve  260  to the stem  230 . The length of the collar  270  in this embodiment should be long enough to tightly secure the sleeve  260  to the stem  230  to prevent relative movement, but short enough to lie in its crimped state between the barb  242  and the flange  234 . It should be appreciated, however, that the length of the collar  270  can vary depending on the application and materials involved. It should also be appreciated that sleeve  260  could be secured to stem  230  in other ways, such as through the use of adhesives, etc.  
         [0040]     Referring to  FIG. 6 , a boot  280  is illustrated in cross-section, including the subassembly  250 . In this embodiment, the subassembly  250  is overmolded to form the boot  280 , using a molding process as is well-known and understood in the art (although other means of forming a boot around subassembly  250  are also possible). While certainly many different materials are possible for the boot  280 , in this embodiment, the boot  280  is made of silicone. It is important to note that by utilizing a silicone or like material, a silicone to silicone bond is formed along a majority of the overmolded segment, providing a superior mechanical bond in which stem  230  is secured within boot  280 . Such a construction prevents the possibility of delamination of the stem  230  from the boot  280  and leaks associated therewith.  
         [0041]     Referring now to  FIGS. 7 and 8 , a catheter lock  40  is shown.  FIG. 7  illustrates a longitudinal cross-sectional view of the catheter lock  40 , which in the preferred embodiment is made of a hard shell construction (for example, polyacetal resin, polycarbonate or polysulfones) to positively fit over the catheter  120  to secure in place and provide an audible and tactile lock and to provide added security against inadvertent needle sticks.  FIG. 8  shows an end view of the catheter lock  40  from the locking end thereof, which is the end that engages with the base portion  32  of the stem  30 . Not shown in either view is an optional radiopaque feature, which can be a metal ring, ink or other material on the distal end of the catheter lock  40 , providing easy visualization under x-ray or fluoroscopy to verify lock engagement and position. Of course, a radiopaque section could be added to many different portions of the catheter lock  40  for accomplishing the same objective. The catheter lock of the present invention provides an easy, one-step connection mechanism to secure a catheter to an extension of a port or pump, eliminating the need for cumbersome suturing, which may cause damage to the catheter and/or the connection. While a preferred embodiment of the catheter lock is described herein, it should be appreciated that many configurations are possible that would certainly be within the scope of the present invention.  
         [0042]     Referring again to  FIGS. 7 and 8 , the catheter lock  40  has five distinct diameter portions each having a particular function with respect to the locking of the catheter  120  to the stem  30 . A middle portion  42  of the catheter lock  40  contains the smallest diameter d 1 , which is sized slightly larger than the outside diameter of the catheter  120  so that the catheter lock  40  can slide freely along the length thereof. A distal portion  44  of the catheter lock  40  has a slightly larger diameter d 2  to allow the catheter  120  to move freely after the catheter lock  40  is secured to the boot  20 . The front portion of the catheter lock has three diameter portions  46 ,  48  and  49 , having respective diameters d 3  d 4  and d 5 , designed to mate with the base portion  32  of the stem  30 , and thereby providing a secondary tactile locking mechanism as will be explained in more detail below. Also positioned in the front portion of the catheter lock  40  are slits  50  positioned on opposite sides thereof to facilitate the movement of the diameter portion  49  of the catheter lock  40  over the engaging portion  33  of the stem  30  and the subsequent locking action therebetween.  
         [0043]     The advantage of the catheter boot and locking system as described herein is the ease of connection in combination with the difficult disengagement of the catheter after assembly is complete (will not disengage at clinical loads/extensions). With reference to  FIGS. 3 and 7 , a catheter connection in a preferred embodiment will be described. After the catheter  120  has been established within the body, for example having an end established in the spine as described above, and is tunneled or otherwise delivered to the location of the pump or port, the catheter connection thereto takes place. As mentioned, the catheter lock  40  is configured to slide freely along the catheter  120  and therefore can be threaded onto the end of the catheter  120  quite easily just prior to connection to the boot  20 .  
         [0044]     The lumen  122  of the catheter  120  is first slid onto the tip portion  34  of the stem  30  until the catheter  120  is midway along the section  37 . The catheter lock  40  is then slid onto the stem  30  and pressed in a direction toward the boot  20  until an audible clicking sound is heard and a positive connection is felt The slits  50  enable the catheter lock  40  to flex outward slightly when pressed over the engaging portion  33  to facilitate the connection. After connection has been established between the catheter lock  40  and the stem  30 , the forward portion  36 , having a diameter substantially equal to d 3  is within portion  46  and the engaging portion  33 , having its largest diameter substantially equal to d 4  is within portion  48 . Because portion  49  has a diameter d 5  slightly smaller than that of the largest diameter of the engaging portion  33 , once a connection has been established, the catheter lock cannot be pulled off of the stem  30 . Portion  42 , having diameter d 1 , is superimposed over the catheter on section  37  of the stem  30 , preventing movement of the catheter within the lock due to the compression applied thereon and providing a primary obstacle for removal of the catheter  120  from the stem  30 . In addition, this arrangement acts to seal the connection against fluid leakages between the various interfaces. Portion  49  with diameter d 5  provides a secondary obstacle by preventing movement of the catheter lock in a direction away from the boot  
         [0045]     The inventive catheter lock can be used in conjunction with various pumps and ports as mentioned, as well as with a host of different catheters and catheter systems. Examples of intended uses for the catheter system described herein is to deliver pain medicating drug(s) to a patient at locations in the body including the intrathecal space, the epidural space, arterial and venous areas and directly into tissue. A preferred embodiment of the catheter system of the present invention can be seen in  FIGS. 9-13 .  
         [0046]     Referring to  FIG. 9 , a catheter system  110  has a flushing hub  140  for flushing a catheter  120  during placement thereof in a patient&#39;s body, including a main hub body  154 . At a proximal end of the flushing hub  140 , an opening  158  provides access to an inner lumen  152  (see  FIG. 12 ). At a distal end of the flushing hub  140 , a cannula  156  extends therefrom and is in communication with the inner lumen  152 . The cannula  156  surrounds a stylet  160 , which can be seen in phantom within the catheter  120 , and which is attached to the main hub body  154 . The relation between the stylet  160  and the cannula  156  and main hub body  154  can be better seen in  FIGS. 10 and 11 .  
         [0047]      FIG. 11  shows the flushing hub  140  and stylet  160  along the length of the catheter  120 . The flushing hub  140  allows catheter flushing without removal of the stylet  160  as well as the withdrawal of bodily fluid to confirm catheter location. The stylet  160  provides internal rigidity to the catheter  120  and allows for maneuverability via torque transmission down the stylet  160  from the proximal end of the catheter system  100  to facilitate precise placement of the tip. In the preferred embodiment, the stylet  160  is coated with a hydrophillic coating for ease of removal from the catheter  120 . The coating reduces catheter bunching that can compromise the physical properties of the catheter  120  by leading to destructive forces on the catheter  120 . The coating further reduces traction internal to the catheter  120  during stylet withdrawal and reduces the potential of tip and/or catheter malposition.  
         [0048]     The catheter  120  is closely fitted over the cannula  156  to provide a continuous pathway from the inner lumen  152  of the flushing hub  140  into the lumen  122  of the catheter  120 , thereby allowing for the flushing of fluid from the cannula  156  through the lumen of the catheter  120  around the stylet  160  to wet the stylet surface before exiting from the holes  126  at the distal end of the catheter  120  (see  FIG. 13 ).  
         [0049]      FIG. 12  shows a cross-sectional view of the flushing hub  140 . From this view, the inner lumen  152  of the main hub body  154  can be seen, with opening  158  at the proximal end thereof. In this particular embodiment, the stylet  160  is shown affixed to the body  154  and extends through the inner lumen  152 , leaving a channel  153  on either side of the stylet  160  for fluid flow. Of course, the stylet  160  could be affixed in other locations not directly within the center of the inner lumen  152  of the main hub body  154 . Also, the inner lumen  152  could be differently configured, depending on the features desired in a given catheter system.  
         [0050]     Turning now to  FIG. 13 , a cut-away view of a distal end of the catheter  120  is shown In the preferred embodiment, catheter  120  has a lumen  122  and walls  124  made of high durometer silicone for kink resistance and its beneficial properties with regard to biocompatibility and biodurability, though other materials are certainly possible that would similarly afford the advantages of the preferred material, such as polyethylene and polyurethane. The walls  124  in the preferred embodiment are relatively thick to further the goal of kink resistance, together comprising approximately half of the external diameter of the catheter (ie., if the catheter  120  had an outside diameter of nominally 0.055 inches, each wall  124  in cross-section would have a thickness of at least 0.014 inches). At the distal end of the catheter  120 , a tip  130  is rounded in the form of a bullet and made of a highly radiopaque material to provide a dual advantage of a geometry that is less traumatic to bodily tissues and anatomical structures and an enhanced visibility, which facilitates location determination during and after introduction to the patient&#39;s body. The radiopaque material utilized for the tip  130  in a preferred embodiment is a combination of cured liquid silicone and tungsten powder in approximately 50% by weight of each component.  
         [0051]     In the walls  124  of the catheter  120 , a set of side holes  126  are provided to allow passage of fluid to and from the lumen  122 . The side holes are drilled perpendicular to the surface thereof to limit surface area anomolies that may result in tissue trauma and/or catheter damage upon placement. A catheter segment  128  between the tip  130  and a side hole  126  is filled with similar material as the tip  130  to form plug  132 . This feature, combined with the closed-ended geometry of the catheter  120  eliminates dead space that can host proteinaceous material and the like, which, if present within a catheter lumen, can propogate into an occlusion thereof.  
         [0052]     As mentioned, one application of the present invention is for use along with an implantable pump to deliver medication to the intrathecal space in a patient&#39;s spine. An indwelling catheter, such as catheter  120 , is utilized to establish a fluid path from a subcutaneous pump through the dura membrane. The procedure generally consists first of embedding the catheter in the spine (5 to 10 cm). A drop of the spinal fluid is then allowed to form at the proximal end of the catheter  120  to confirm catheter location, after which the catheter is clamped. A tunnel is formed from the spine to the area of the abdomen, where the pump will be implanted, and the catheter is pulled through and cut to length. The catheter is then attached to the pump as described above through the use of an inventive boot and catheter lock. The pump is placed in a previously created pocket in the area of the abdomen and the pocket is closed. Implantation of the described system is relatively quick and easy and provides for prolonged delivery of drugs or medication to the spine.  
         [0053]     The present invention has been described above in terms of a presently preferred embodiment so that an understanding of the present invention can be conveyed However, there are many alternative arrangements for a catheter system not specifically described herein but with which the present invention is applicable. For example, there are many different applications and configurations for a catheter locking system that would be within the scope of the present invention and similarly, there are many applications for a catheter and flushing system other than those specifically described. Although specific features have been given, the catheter system for locking a catheter to an implantable pump and for effectively flushing a catheter after implantation within a body of the present invention would equally be embodied by other configurations not specifically recited herein. The scope of the present invention should therefore not be limited by the embodiments illustrated, but rather it should be understood that the present invention has wide applicability with respect to catheter systems generally. All modifications, variations, or equivalent elements and implementations that are within the scope of the appended claims should therefore be considered within the scope of the invention.