Patent Publication Number: US-2022226613-A1

Title: Vascular access catheter with protectable inline needle and associated method of use thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. application Ser. No. 16/012,007, filed on Jun. 19, 2018, which is hereby incorporated by reference as if fully recited herein. 
    
    
     TECHNICAL FIELD 
     Exemplary embodiments described herein are directed to a vascular access catheter with an inline needle that is protectable by sliding displacement of the needle relative to the catheter, or vice versa. 
     BACKGROUND 
     Worldwide there are currently about 2 million patients with End Stage Renal disease (ESRD). There were about 660,000 such patients in the United States as of 2013 according to the United States Renal Data System (USRDS). Out of those 660,000 ESRD patients, about 465,000 patients were receiving hemodialysis treatment, which is the process of removing extra fluids and toxins from the body and maintaining normal electrolyte levels by passing the patient&#39;s blood through a dialysis filter and subsequently returning the blood to the patient. Hemodialysis is typically performed in 3-4 hour sessions, three times per week. 
     Because hemodialysis involves extracting blood from the patient and returning the filtered blood to the patient, hemodialysis obviously requires repeated access to the arteriovenous system of the patient. A fistula or graft is commonly created in order to provide an effective vascular access point. An arteriovenous (AV) fistula is a surgically created direct connection of an artery to a vein, which becomes a permanent (but surgically reversible structure after a sufficient healing period). An AV graft, while similar to an AV fistula, employs a plastic tube to connect and artery to a vein. In either case, once the fistula/graft is ready to use, the fistula/graft provides the arteriovenous access required to remove and return a patient&#39;s blood during hemodialysis treatment. The proper function of a fistula/graft is critically important for most hemodialysis patients. 
     One of the most important steps in the hemodialysis process is cannulation of the fistula/graft. Two needles are typically inserted into a fistula/graft for arteriovenous access. One of the needles is used to direct blood from the patient through a connected tube to the dialysis filter of the dialysis machine, while the other needle is used to direct filtered blood from the dialysis machine through a connected tube back to the patient. Required blood flow through the needles may be on the order of 250-550 ml/min. To achieve this blood flow, the needles used are usually of large diameter (e.g., between 17 and 14 gauge). 
     In operation of most currently used hemodialysis needles, the skin of a patient is pierced by the tip of the dialysis needle, and the needle is further inserted until the tip also pierces the fistula/graft. Once the needle is properly placed in the fistula/graft, it is normally secured in place by taping it to the associated limb of the patient. 
     As should be obvious, the tip of a hemodialysis needle is sharp. Use of a typical hemodialysis needle generally results in the sharp tip of the needle floating in the fistula/graft. Consequently, any needle migration or movement of the limb of the patient in which the fistula/graft has been created, can cause the needle tip to damage the fistula/graft, such as by causing a counter puncture of the fistula/graft wall. Such a puncture can result in infiltration where blood leaks outside of the fistula/graft. Studies have reported an annual infiltration rate of about 5.2% of all hemodialysis treatments, which is a significant problem. 
     Because blood is typically flowing through the hemodialysis needles at rate of 250-550 ml/min, a significant amount of blood can accumulate in surrounding tissues and form a hematoma as a result of a counter puncture and associated infiltration. An infiltration can be very painful, and often times requires that the fistula/graft be allowed to heal before further use. Thus, a patient may either have to miss dialysis treatment for a period of time, or a temporary dialysis catheter may need to be placed in a central vein of the patient in order to permit continued dialysis until the fistula/graft heals. It is also possible that an infiltration can lead to permanent loss of use of the damaged fistula/graft. 
     It can be understood from the foregoing description that there is a heretofore unmet need for an improved device and method for providing hemodialysis arteriovenous access without fistula/graft damage. A similar need exists for providing peripheral vessel access without damage. Exemplary vascular access catheter devices described herein satisfy this need. 
     SUMMARY 
     Exemplary vascular access catheter device embodiments described and shown herein are designed to provide hemodialysis arteriovenous access without fistula/graft damage, and may also be used to access peripheral vessels in non-dialysis patients. Generally speaking, exemplary vascular access catheter device embodiments include a catheter with an inline needle, where the sharp tip of the needle is protectable by the catheter during use to prevent fistula/graft or peripheral vessel damage due to, for example, limb movement or needle migration. Exemplary vascular access catheter device embodiments may also function to prevent needle stick injuries to persons performing hemodialysis or other procedures, and may allow for parking of the catheter before final engagement, which permits minor adjustments to the catheter and the needle to obtain optimum blood flow. 
     Certain combined hemodialysis needle and catheter devices are known. In one such known device, a needle protrudes from a catheter portion of the device and is used to pierce a patient&#39;s skin so as to facilitate insertion of the needle tip and a portion of an overlying catheter into the vasculature (e.g., fistula/graft) of the patient. Once placed in the patient&#39;s fistula/graft, the needle portion is subsequently withdrawn by retracting a plunger to leave only the catheter inserted. Retracting the needle pulls it out of the catheter and into a housing portion of the device so as to prevent needle injury to the fistula/graft during use. However, since the needle is withdrawn completely from the catheter and into housing, the catheter alone is responsible for conducting blood flow during hemodialysis treatment. Unfortunately, because the catheter is typically thin-walled plastic tubing, it is often weak, which may lead to kinking and possible partial collapse due to high blood flow rate, thereby impairing the hemodialysis procedure. 
     Exemplary vascular access catheter device embodiments described and shown herein are single use devices designed to produce vascular access (i.e., fistula/graft or peripheral vessel access), and to connect to a dialysis machine via elongate tubing in the case of a hemodialysis application. An exemplary vascular access catheter device includes an inline needle that is concentrically located within a slidable catheter portion while protruding slightly therefrom during certain times. The sharp tip of the needle may be used to pierce a patient&#39;s skin and fistula/graft or peripheral vessel, whereafter a catheter tip of the slidable catheter portion will follow the needle tip into the fistula/graft or peripheral vessel and the needle portion may subsequently be slidably retracted so that the needle tip is covered by the catheter during use of the device. The catheter position relative to the needle position may be secured to ensure that the needle tip remains within the catheter once the needle has been fully retracted. 
     The catheter of an exemplary vascular access catheter device is thus placed without removing the needle, thereby maintaining the catheter and needle in communication with the patient&#39;s blood without a break in the (e.g., dialysis) blood flow path. The needle tip is also protected by the catheter during use of the device, which prevents fistula/graft/peripheral vessel injury and infiltration in patients and needle stick injuries to health care workers and other users of the device. Further, since the needle still resides within a majority of the catheter, issues such as kinking and partial collapse of the catheter are avoided, thereby preserving blood flow. Unlike known combination needle and catheter devices, exemplary vascular access catheter device embodiments do not require any special training prior to use. 
     An exemplary vascular access catheter device may include a needle portion having a needle that extends from a needle hub, and a catheter portion that is supported on the needle portion and includes a catheter that extends from a catheter hub. The needle may extend concentrically within the catheter such that a sharp tip of the needle protrudes from an open end of the catheter when the catheter portion is in a retracted position/needle portion is in an extended position. The catheter portion is slidable relative to the needle portion, and vice versa, such that the catheter or needle may be linearly displaced to selectively expose or cover the needle tip. Some exemplary embodiments of a vascular access catheter device may also include a body portion that is supported on the needle portion. The body portion may include a gripping structure that facilitates handling and use of the device. In other embodiments, a gripping structure may be associated with the needle portion of the device. An exemplary gripping structure may be provided in the form of extending wings or in other forms that also facilitate removable attachment of the device to a patient during use. 
     In one exemplary vascular access catheter device, the position of the catheter portion relative to the needle portion of the device may be maintained by a retention mechanism in the form of a detent element on the catheter hub and an associated annular groove on the needle hub, or vice versa. 
     In another exemplary vascular access catheter device, the position of the catheter portion relative to the needle portion of the device may be maintained by a retention mechanism in the form of a bolt that extends from the needle hub through a detent groove in the catheter hub. 
     In another exemplary vascular access catheter device, the position of the catheter portion relative to the needle portion of the device may be maintained by a retention mechanism in the form of a tab that extends from the needle hub through a detent groove in the catheter hub. 
     In another exemplary vascular access catheter device, the position of the catheter portion relative to the needle portion of the device may be maintained by a retention mechanism in the form of a pin or bolt that extends from the needle hub through a curved cam slot in the catheter hub. The cam slot may allow for parking of the catheter portion in an extended position before final engagement with a patient. adversarial 
     In another exemplary vascular access catheter device, the position of the catheter portion relative to the needle portion of the device may be maintained by a retention mechanism in the form of a retention slot in the catheter hub that engages a gripping element of the needle portion when the catheter portion is extended. The retention slot may be designed to lock the catheter hub to the gripping element such that the catheter portion cannot be again retracted once fully extended. 
     In another exemplary vascular access catheter device, at least one position of the needle portion of the device relative to the catheter portion of the device may be maintained by a locking mechanism in the form of at least one tab that extends from the catheter portion into at least one corresponding receiving slot in at least one gripping element associated with the needle portion. 
     An exemplary vascular access catheter device may include a seal between the needle and the catheter to prevent the leakage of blood from the device during use. 
     In at least one exemplary vascular access catheter device, at least a portion of the needle and catheter portion of the device may be enclosed within a safety cap when not in use. 
     The catheter hub and needle hub of an exemplary vascular access catheter device may be manufactured from a transparent or semi-transparent material to permit viewing of the flow of blood passing through the device during use. 
     Other aspects and features of the inventive concept will become apparent to those skilled in the art upon review of the following detailed description of exemplary embodiments along with the accompanying drawing figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following descriptions of the drawings and exemplary embodiments, like reference numerals across the several views refer to identical or equivalent features, and: 
         FIG. 1A  is a top perspective view of one exemplary embodiment of a catheter device according to the general inventive concept, with a catheter portion thereof in a retracted position that exposes a needle tip; 
         FIG. 1B  is a bottom perspective view of the catheter device of  FIG. 1A ; 
         FIG. 1C  is a side view of the catheter device of  FIG. 1A ; 
         FIG. 1D  is a cross-sectional view of the catheter device of  FIG. 1C ; 
         FIG. 2A  is a top perspective view of the catheter device of  FIG. 1A , with the catheter portion thereof in an extended position that covers the needle tip; 
         FIG. 2B  is a bottom perspective view of the catheter device of  FIG. 2A ; 
         FIG. 2C  is a side view of the catheter device of  FIG. 2A ; 
         FIG. 2D  is a cross-sectional view of the catheter device of  FIG. 2C ; 
         FIG. 3A  depicts the catheter device of  FIG. 10  with a protective cap; 
         FIG. 3B  depicts the catheter device of  FIG. 3A  with a section view of the protective cap; 
         FIGS. 4A-4B  are a top perspective view and a side view, respectively, of another exemplary embodiment of a catheter device according to the general inventive concept, with a catheter portion thereof in a retracted position that exposes a needle tip; 
         FIGS. 4C-4D  are a top perspective view and a side view, respectively, showing the catheter device of  FIGS. 4A-4B  with the catheter portion thereof in an extended position that covers the needle tip; 
         FIG. 5A  is a top perspective view of another exemplary embodiment of a catheter device according to the general inventive concept, with a catheter portion thereof in a retracted position that exposes a needle tip; 
         FIG. 5B  is an enlarged top plan and partial section view of a portion of the catheter device of  FIG. 5A ; 
         FIG. 5C  shows the catheter device of  FIG. 5A  with the catheter portion in an extended position that covers the needle tip; 
         FIG. 5D  is an enlarged top plan and partial section view of a portion of the catheter device of  FIG. 5C ; 
         FIG. 6A  is a top perspective view of another exemplary embodiment of a catheter device according to the general inventive concept, with a catheter portion thereof in a retracted position that exposes a needle tip; 
         FIG. 6B  shows the catheter device of  FIG. 6A  with the catheter portion in an extended position that covers the needle tip; 
         FIGS. 7A-7C  are side views of another exemplary embodiment of a catheter device according to the general inventive concept, wherein a catheter portion of the device is respectively shown in a fully retracted, partially extended and fully extended position; 
         FIGS. 8A-8B  depict a perspective view and a cross-sectional side view, respectively, of an exemplary catheter portion of an exemplary embodiment of a catheter device according to the general inventive concept; 
         FIGS. 8C-8D  depict various possible features of an insertion end of an exemplary catheter of an exemplary catheter portion such as that shown in  FIGS. 8A-8B ; 
         FIGS. 9A-9B  are various perspective views of a needle portion of another exemplary embodiment of a vascular access catheter device according to the general inventive concept; 
         FIGS. 10A-10C  are various perspective views of a catheter portion of an exemplary embodiment of a vascular access catheter device that also utilizes the needle portion of  FIGS. 9A-9B ; 
         FIG. 11A  is a perspective view of an exemplary embodiment of a vascular access catheter device comprising the needle portion of  FIGS. 9A-9B  assembled with the catheter portion of  FIGS. 10A-10C , and wherein the catheter portion of the device is respectively shown in a retracted position that exposes a needle tip of the needle portion; 
         FIG. 11B  is a top view of the catheter device shown in  FIG. 11A ; 
         FIG. 11C  is an enlarged cross-sectional side view of the catheter device shown in  FIG. 11A ; 
         FIG. 12A  is a perspective view of the exemplary catheter device of  FIG. 11A , with the catheter portion of the device residing in a partially extended position; 
         FIG. 12B  is a top view of the catheter device shown in  FIG. 12A , with a catheter of the device shown in partial transparency; 
         FIG. 12C  is an enlarged cross-sectional side view of the catheter device shown in  FIG. 12A ; 
         FIG. 13A  is a perspective view of the exemplary catheter device of  FIG. 11A , with the catheter portion of the device residing in a fully extended position; 
         FIG. 13B  is a top view of the catheter device shown in  FIG. 13A ; 
         FIG. 13C  is an enlarged cross-sectional side view of the catheter device shown in  FIG. 13A ; and 
         FIG. 14  depicts one exemplary embodiment of a vascular access catheter device assembly utilizing an exemplary embodiment of a vascular access catheter device as shown in  FIGS. 11A-13C . 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     One exemplary embodiment of a vascular access catheter device (e.g., arteriovenous catheter device)  5  is illustrated in  FIGS. 1A-2D . As may be observed, the device  5  includes a needle portion  25  on which is supported a body  10  and a catheter portion  55 . The body  10  includes a central mounting sleeve  15  and a pair of wing-like gripping portions  20  that extend substantially laterally outward from opposite sides of the central mounting sleeve. While the overall body  10  may be of various shapes, in this exemplary embodiment the gripping portions  20  of the body are shaped as shown to facilitate gripping and manipulation of the device  10  by a user and taping of the device to a limb of a patient after fistula/graft or peripheral vessel access. Similarly, the central mounting sleeve  15  is cylindrical and hollow in the exemplary embodiment so as to slide over a correspondingly-shaped hub of a needle portion (see below), the mounting sleeve may be of other shapes as needed to cooperate with a given needle hub. The body  10  may be constructed from various different materials, with plastic (e.g., fluoroplastic) being a particularly good material. 
     It also may be observed that the catheter device  5  includes a needle portion  25  and a catheter portion  55 . The needle portion  25  includes an elongate needle hub  30  having a proximal end  30   a  and a distal end  30   b . An axial bore  35  passes through the needle hub to provide, among other things, a pathway for blood flow during a hemodialysis or other vascular access procedure. Tubing (not shown) may be coupled to the proximal end  30   a  of the needle hub for connecting the catheter device  5  to a hemodialysis machine, as would be understood by one of skill in the art. 
     A needle  40  of the needle portion  25  has a proximal end  40   a  thereof inserted sufficiently far into the bore  35  in the distal end  30   b  of the needle hub  30  to securely retain the needle. The proximal end  40   a  of the needle  40  may be retained in the needle hub  30  by a press fit or a similar interaction between the components. Alternatively, or in conjunction with such other techniques, an adhesive or other affixation mechanism may be used to further secure the needle  40  in the needle hub  30 . A distal, free end  40   b , of the needle is provided with a sharp point  45  for the purpose of piercing the skin of a patient and subsequently accessing the patient&#39;s fistula/graft or peripheral vessel. The specific needle gauge, needle construction, etc., may vary in keeping with accepted practices understood in the art. 
     The inside diameter of the central mounting sleeve  15  of the body  10  is dimensioned to pass over a portion of the needle hub  30 . As shown, the needle hub  30  may include a protruding collar  50  or similar element that is designed and located to abut a distal face of the central mounting sleeve  15  and to thereby act as a stop for the body  10  when the body is properly installed on the needle hub  30 . The collar may also act as a rear (retraction) stop for the catheter portion  55 , as is described in more detail below. 
     The central mounting sleeve  15  of the body  10  may be retained on the needle hub  30  of the needle portion  25  by any of the same techniques mentioned above relative to securing the needle  40  in the bore  35  of the needle hub. Other techniques known to those of skill in the art may also be employed. Threaded engagement of the central mounting sleeve  15  and the needle hub  30  is also possible. 
     As shown particularly clearly in the section view of  FIG. 1D , the collar  50  is located such that some length of the needle hub  30  extends distally therefrom. As is described below, this distally-extending portion of the needle hub  30  of this exemplary catheter device  5  is designed to retain and act as a guide for sliding movement of the catheter portion  55  of the device. 
     In similar fashion to the needle portion  25 , the catheter portion  55  includes a catheter hub  60  with proximal and distal ends  60   a ,  60   b . The size and shape of the catheter hub  60  is selected so that the catheter hub will cooperate with the needle hub  30 . More specifically, the catheter hub  60  is of substantially cylindrical shape, and includes a first central bore  70  at the proximal end  60   a  that is dimensioned to permit the catheter hub to slide over the portion of the needle hub  30  that extends distally of the collar  50 . This arrangement allows the catheter portion  55  of the catheter device  5  to be supported on the needle portion  25  and to slide linearly relative to the needle hub  30  (and the body  10 ). A second central bore  75  extends inward from the distal end  60   b  of the catheter hub  60  and opens into the proximally-located needle hub receiving bore  70 . 
     The catheter portion  55  further includes a hollow catheter  80  that extends longitudinally outward from the distal end  60   b  of the catheter hub  60 . In this exemplary embodiment, the catheter  80  has an open proximal end  80   a  that is inserted sufficiently far into the second bore  75  in the catheter hub  60  to securely retain the catheter. The proximal end  80   a  of the catheter  80  may be retained in the catheter hub  60  by any of the needle retention techniques mentioned above or by any other acceptable technique known to one of skill in the art. In other embodiments, the catheter  80  may be an integrally molded part of the catheter hub  60 . A distal, free open end  80   b , of the catheter  80  may be tapered and/or may include any other features that may facilitate entry of the free end of the catheter into the fistula/graft or peripheral vessel of the patient subsequent to initial access by the needle  40  and/or may facilitate blood flow during a hemodialysis or other vascular access procedure. 
     The inside diameter of the catheter is preferably similar in dimension to the outside diameter of the needle  40  so as to produce a close tolerance but sliding fit between the catheter  80  and the needle  40  when the catheter hub  60  is installed over the needle hub  30 . Nonetheless, a seal  115  may be placed at or near the entry point of the second bore  75  into the first bore  70  to prevent possible blood leakage between the needle  40  and the catheter  80  during use of the catheter device  5 . As with the needle  40 , the specific construction of the catheter  80  may otherwise vary in keeping with accepted practices understood in the art. For example, the catheter may be constructed from a fluoroplastic material. 
     From the foregoing description and corresponding  FIGS. 1A-2D , it should be understood that when the body  10  and catheter portion  55  are properly assembled to the needle portion  25 , as explained above, the needle hub  30  is substantially concentrically located within the catheter hub  60 , the needle  40  is substantially concentrically located within the catheter  80 , and the catheter hub  60  and attached catheter  80  are together linearly slidable relative to the needle hub  30  and the attached needle  40 . As shown in the drawing figures, a gripping element  85  or similar feature may be provided on the catheter hub  60  to facilitate sliding of the catheter portion  55  by a user of the device  5 . 
       FIGS. 1A-1D  show the catheter portion  55  in a retracted position, which results in the needle tip  45  and perhaps some additional length of the needle  40  protruding from the open distal end  80   b  of the catheter. This is the proper position in which the catheter portion  55  should reside during initial piercing of the patient&#39;s skin and accessing of the underlying fistula/graft or peripheral vessel using the needle  40  of the device  5 . 
     With the tip of the needle  40  and the catheter  80  residing in the patient&#39;s fistula/graft or peripheral vessel, the catheter portion  55  may then be placed in an extended position (see  FIGS. 2A-2D ) by sliding the catheter portion linearly and in a distal direction along the needle hub  30  such that the sharp tip  45  of the needle becomes covered by the distal end  80   b  of the catheter  80 . A distal catheter hub hard stop or a similar mechanism (see below) may be used to ensure proper linear positioning and possibly position retention of the catheter portion. With the needle  40  and the catheter  80  properly located in the fistula/graft or peripheral vessel of the patient, the catheter device  5  may be secured against movement, such as but not limited to by taping the gripping portions  20  of the body  10  to the limb of the patient. 
     As should be readily obvious to one of skill in the art, placing the catheter  80  of the exemplary catheter device  5  into the fistula/graft or peripheral vessel and over the needle tip  45  as described above serves to prevent the needle tip from damaging the fistula/graft or peripheral vessel and also, therefore, prevents infiltration and related hematoma problems. And unlike known devices, the needle  40  of the exemplary device  5  remains largely within the catheter  80  during a hemodialysis or other vascular access procedure, thereby substantially eliminating any chance that the catheter may collapse, kink, etc., and interfere with blood flow or cause damage on its own. 
     As described above, the catheter portion  55  has a retracted position where the catheter  80  is kept from interfering with use of the needle to initially access the fistula/graft or peripheral vessel of a patient. Likewise, the catheter portion  55  also has an extended position where the open distal end  80   b  of the catheter  80  will extend at least equal with if not beyond the tip  45  of the needle and into the fistula/graft or peripheral vessel currently accessed by the needle. Consequently, it is preferable to provide a mechanism by which it can be ensured that the catheter portion  55  is properly in the retracted position or the extended position, and by which either position can be maintained once selected. 
     In the case of the exemplary catheter device  5  of  FIGS. 1A-2D , position retention is provided by a detent mechanism formed through interaction of certain elements of the catheter hub and the needle hub. This relationship may be reversed in other embodiments. 
     Referring to the sectional views of  FIGS. 1D and 2D , it may be more specifically understood that abutting contact between the proximal end  60   a  of the catheter hub  60  and the distal side of the collar  50  of the needle hub  30  will act as a hard stop that can be used to set the proper retracted position of the catheter portion  55 . It may also be observed that the exemplary catheter hub  60  of the exemplary catheter device  5  includes an inwardly-directed annular projection  90  at its proximal end  60   a . The annular projection  90  may have a hook shape as shown, but other shapes are also possible. As explained further below, the annular projection  90  essentially acts as the lever element of the detent mechanism. 
     It may also be observed in  FIGS. 1A and 2D  that the needle hub  30  of the exemplary needle portion  25  is provided with an annular groove  95  near the distal end  30   b  thereof. The annular groove  95  essentially acts as the pawl element of the detent mechanism. As shown in  FIG. 2D , when the catheter portion  55  is placed in the extended position, the annular projection  90  of the catheter hub  60  becomes releasably engaged with the annular groove  95  in the needle hub  30 , thereby limiting the amount of possible linear movement and setting and retaining the extended position of the catheter portion  55 , absent an overcoming displacement force provided by the user. Optionally, a second annular groove (not shown) may be similarly placed in the needle hub  30  in the area of the collar  50  to engage with the annular projection  90  of the catheter hub  60  and to releasably retain the catheter portion  55  in its retracted position absent an overcoming displacement force provided by the user. 
     To guard against inadvertent contact with the sharp tip  45  of the needle  40 , a protective device may be associated with the needle. As illustrated in  FIGS. 3A-3B , a cap  100  having an open proximal end  100   a  and a closed distal end  100   b  may be provided in this exemplary catheter device embodiment to enclose the needle  40  and catheter and to protect users from accidental needle sticks. When such a cap is provided, the cap may vary in shape and size. Such a cap may also be removably retained on the catheter device in different ways. In this example, the open end of the cap is provided with an inwardly-projecting retention ridge  105  that is located and configured to engage a corresponding annular cap retention groove  110  (see e.g.,  FIG. 10 ) provided in the catheter hub  60  near the distal end  60   b  thereof. Engagement of the retention ridge  105  with the cap retention groove  110  removably secures the cap  100  to the catheter hub  60 . 
     Other cap retention techniques may be employed with other catheter device embodiments. Other exemplary catheter device embodiments may or may not include a cap. 
     Other exemplary catheter device embodiments also may utilize catheter portion position retaining mechanisms that differ from the particular detent mechanism shown in  FIGS. 1D and 2D  and described above. One exemplary embodiment of such an alternative position retention mechanism is depicted in  FIGS. 4A-4D . 
     The exemplary arteriovenous catheter device  200  depicted in  FIGS. 4A-4D  again includes a body  205  and a catheter portion  225  that are supported on a needle portion  210 . The design and interrelationship of each of the needle portion  205  and the catheter portion  225  is generally as described above, as is the basic concept of using the device  200  in a hemodialysis operation. Thus, the needle portion  210  again includes a needle hub  215  and a needle  220 . Likewise, the catheter portion  225  again includes a catheter hub  230  and a catheter  235 . 
     In the case of the exemplary arteriovenous catheter device  200  shown in  FIGS. 4A-4D , the catheter portion retention mechanism employs a bolt element  240  having a shaft portion  245  that extends from the needle hub  215  through a detent groove  250  in the catheter hub  230  to limit movement and retain the position of the catheter portion  225  of the device relative to the needle portion  210  of the device. The shaft  245  of the bolt element  240  may include an enlarged end portion  255  to ensure the bolt element shaft  245  and the detent groove  250  in the catheter hub  230  remain engaged. 
     As shown most clearly in  FIG. 4B , the detent groove  250  may be configured such that the shaft  245  of the bolt element  240  is in contact with the closed end of the detent groove  250  when the catheter portion  225  is in a retracted position. Referring also to  FIG. 4D , it can be further observed that the detent groove  250  may include one or more detent notches  260  that are releasably engageable with the shaft  245  of the bolt element  240  when the catheter portion  225  is in an extended position. The interaction between the detent notches  260  and the shaft  245  of the bolt element  240  serves to retain the catheter portion  225  in the extended position unless an overcoming displacement force is provided by the user. 
     Another exemplary embodiment of an alternative catheter portion position retention mechanism is depicted in  FIGS. 5A-5D . The exemplary arteriovenous catheter device  300  depicted in  FIGS. 5A-5D  again includes a body  305  and a catheter portion  325  that are supported on a needle portion  310 . The design and interrelationship of each of the needle portion  305  and the catheter portion  325  is generally as described above, as is the basic concept of using the device  300  in a hemodialysis operation. Thus, the needle portion  310  again includes a needle hub  315  and a needle  320 . Likewise, the catheter portion  325  again includes a catheter hub  330  and a catheter  335 . 
     In the case of the exemplary arteriovenous catheter device  300  shown in  FIGS. 5A-5D , the catheter portion retention mechanism employs a tab  340  that extends from the catheter hub  325  into a detent groove  345  in the needle hub  315  to limit movement and retain the position of the catheter portion  325  of the device relative to the needle portion  310  of the device. The tab  340  may be provided, for example, in the form of a pin. 
     As shown most clearly in  FIG. 5B , the detent groove  345  may be configured such that the tab  340  is in contact with the closed end of the detent groove  345  when the catheter portion  325  is in a retracted position. Referring to  FIG. 5D , it can also be observed that the detent groove  345  may include one or more detent notches  350  that are releasably engageable with the tab  340  when the catheter portion  325  is in an extended position. The interaction between the detent notches  350  and the tab  340  serves to retain the catheter portion  325  in the extended position unless an overcoming displacement force is provided by the user. 
     Another exemplary embodiment of an alternative catheter portion position retention mechanism is depicted in  FIGS. 6A-6B . The exemplary arteriovenous catheter device  400  depicted in  FIGS. 6A-6B  again includes a body  405  and a catheter portion  425  that are supported on a needle portion  410 . The design and interrelationship of each of the needle portion  410  and the catheter portion  425  is generally as described above, as is the basic concept of using the device  400  in a hemodialysis operation. Thus, the needle portion  410  again includes a needle hub  415  and a needle  420 . Likewise, the catheter portion  425  again includes a catheter hub  430  and a catheter  435 . 
     In the case of the exemplary arteriovenous catheter device  400  shown in  FIGS. 6A-6B , the catheter portion retention mechanism employs a pin  440  that extends from the needle hub  415  through a curved cam slot  445  in the catheter hub  430  to limit movement and retain the position of the catheter portion  425  of the device relative to the needle portion  410  of the device. The cam slot  445  may be configured so as to wrap at least partially around the circumference of the catheter hub  430 . As such, a linear displacement of the catheter hub  430  along the needle hub  415  will also produce a rotation of the catheter portion. During use of this exemplary arteriovenous catheter device  400 , the cam slot  445  allows for parking of the catheter portion  425  in an extended position before final engagement, which permits minor adjustments to the catheter  435  and the needle  420  to obtain optimum blood flow. 
     Another exemplary embodiment of a vascular access catheter device  500  is illustrated in  FIGS. 7A-7C . As may be observed, the device  500  includes a needle portion  505  and a catheter portion  540 . The needle portion  505  includes an elongate needle hub  510  having a proximal end  510   a  and a distal end  510   b . A hollow interior of the needle hub provides a pathway for blood flow during a hemodialysis procedure or when the device is otherwise used to access peripheral vessels. Tubing  515  may be coupled to the proximal end  510   a  of the needle hub  510  for connecting the catheter device  500  to a hemodialysis machine or to another device, as would be understood by one of skill in the art. 
     A needle  520  of the needle portion  505  has a proximal end (not visible) thereof that may be inserted sufficiently far into the bore at the distal end  510   b  of the needle hub  510  to securely retain the needle therein. The proximal end of the needle  520  may be retained in the needle hub  510  by a press fit or a similar interaction between the components. Alternatively, or in conjunction with such other techniques, an adhesive or other affixation mechanism may be used to further secure the needle  520  in the needle hub  510 . A distal, free end  520   b , of the needle is provided with a sharp point  525  for the purpose of piercing the skin of a patient and subsequently accessing a fistula/graft or peripheral vessel. The specific needle gauge, needle construction, etc., may vary in keeping with accepted practices understood in the art. 
     The needle portion  505  in this exemplary embodiment further includes a pair of wing-like gripping elements  530  that extend substantially laterally outward from opposite sides of the needle hub  510 . While the gripping elements  530  may be of various shapes, in this exemplary embodiment the gripping elements  530  of the body are shaped as shown to facilitate gripping and manipulation of the device  500  by a user and taping of the device to a limb of a patient after fistula/graft or peripheral vessel access. 
     As previously described, the exemplary catheter device  500  also includes a catheter portion  540  that is supported on the needle portion  505  and includes a catheter hub  545  with proximal and distal ends  545   a ,  545   b . The size and shape of the catheter hub  545  is selected so that the catheter hub will cooperate with the needle hub  510 . More specifically, the catheter hub  545  is of substantially cylindrical shape, and includes a first central (needle hub-receiving) bore  550  at the proximal end  545   a  that renders the needle hub substantially hollow and is dimensioned to permit the catheter hub to slide over the needle hub  510 . This arrangement allows the catheter portion  540  of the catheter device  500  to be supported on the needle portion  505  and for the catheter hub  540  and the needle hub  510  to slide linearly relative to one another as illustrated in  FIGS. 7A-7C . A smaller diameter second central bore  555  (see also  FIG. 8B ) extends inward from the distal end  545   b  of the catheter hub  545  and opens into the needle hub receiving bore  550  to allow passage of the needle  520  through the distal end of the catheter hub  545 . 
     The catheter hub  545  of this exemplary catheter device  500  further includes a pair of diametrically opposed gripping element relief slots  560 , through which the gripping elements  530  of the needle portion  505  may protrude when the catheter portion  540  is properly installed over the needle portion  505 . If an exemplary catheter device embodiment utilizes only a single gripping element  530 , the catheter hub  545  may, but is not required to, include only one corresponding gripping element relief slot  560 . 
     The catheter portion  540  further includes a hollow catheter  565  that extends longitudinally outward from the distal end  545   b  of the catheter hub  545  and includes open proximal and distal ends. In some embodiments, the proximal end (not visible) of the catheter  565  may be inserted sufficiently far into the second central bore  555  in the catheter hub  545  to securely retain the catheter therein. In such an embodiment, the proximal end of the catheter  565  may be retained in the catheter hub  545  by any of the needle retention techniques mentioned above or by any other acceptable technique known to one of skill in the art. In other embodiments, the catheter  565  may be an integrally molded part of the catheter hub  545 . A distal, free open end  565   b , of the catheter  565  may be tapered and/or may include any other features that may facilitate entry of the free end of the catheter into the fistula/graft or peripheral vessel of the patient subsequent to initial access by the needle  520  and/or may facilitate blood flow during a hemodialysis or other vascular access procedure. 
     The inside diameter of the catheter  565  is preferably similar in dimension to the outside diameter of the needle  520  so as to produce a close tolerance sliding fit between the catheter  565  and the needle  520  when the catheter hub  545  is installed over the needle hub  510 . Nonetheless, a seal  590  (see  FIG. 8B ) may be placed at or near the entry point of the second bore  555  into the first bore  550  to prevent possible blood leakage between the needle  520  and the catheter  565  during use of the catheter device  500 . As with the needle  520 , the specific construction of the catheter  565  may otherwise vary in keeping with accepted practices understood in the art. For example, the catheter  565  may be constructed from a fluoroplastic material. 
     From the foregoing description and corresponding  FIGS. 7A-7C , it should be understood that when the catheter portion  540  is properly assembled to the needle portion  505 , as explained above, a portion of the needle hub  510  is substantially concentrically located within the catheter hub  545 , a portion of the needle  520  is substantially concentrically located within the catheter  565 , and the catheter hub  545  and attached catheter  565  are together linearly slidable relative to the needle hub  510  and the attached needle  520 . As shown in the drawing figures, a grip  570  or similar feature may be provided on the catheter hub  545  to facilitate sliding of the catheter portion  540  by a user of the device  500 . 
       FIG. 7A  shows a position where the needle portion  505  is fully extended relative to the catheter portion  540  (or the catheter portion is fully retracted relative to the needle portion), which results in the needle tip  525  and perhaps some additional length of the needle  520  protruding from the open distal end  565   b  of the catheter. This is the proper positioning of the needle portion  505  and the catheter portion  540  for initial piercing of the patient&#39;s skin and accessing of the underlying fistula/graft or peripheral vessel using the needle  520  of the catheter device  500 . 
     After the tip of the needle  520  has been inserted into the patient&#39;s fistula/graft or peripheral vessel, the catheter portion  540  may be moved toward an extended position (see  FIGS. 7A-7C ) by sliding the catheter portion linearly and in a proximal-to-distal direction along the needle hub  510  such that the sharp tip  525  of the needle  520  becomes covered by the distal end  565   b  of the catheter  565  and a portion of both the needle and the catheter temporarily reside in the fistula/graft or peripheral vessel. The grip  570  on the catheter hub  545  may be used to facilitate linear movement of the catheter portion  540 . 
     Once blood flash is seen in the catheter  565 , the needle portion  505  may be slid slightly in a proximal or distal direction to move the needle  520  relative to the catheter  565  and to resultantly achieve optimum blood flow and position. The needle portion  505  may then be “parked” in this position, but the positional relationship of the catheter  565  and needle  520  may also be further adjusted if needed to maintain an optimized blood flow. Once the final desired position of the catheter  565  and optimized blood flow is achieved, the needle portion  505  is retracted (such as by using the gripping elements  530 ) relative to the catheter portion  540  until travel of the needle portion is halted by a hard stop and the needle portion reaches an irreversible position (as explained below). With the catheter  565  properly located in the fistula/graft or peripheral vessel of the patient and the needle portion  505  placed in the irreversible retracted position, the catheter device  500  may be secured to the limb of the patient using tape or another technique known in the art. 
     As should be readily obvious to one of skill in the art, placing the catheter  565  of the exemplary catheter device  500  into the fistula/graft or peripheral vessel and over the needle tip  525  as described above serves to prevent the needle tip from damaging the fistula/graft or peripheral vessel and also, therefore, prevents infiltration and related hematoma problems. And unlike known devices, the needle  520  of the exemplary catheter device  500  remains partially within the catheter  565  during a hemodialysis or other vascular procedure, thereby substantially eliminating any chance that the catheter may collapse, kink, etc., and interfere with blood flow or cause damage on its own. 
     As described above, the catheter portion  540  has a retracted position where the catheter  565  is kept from interfering with use of the needle  520  to initially access the fistula/graft or peripheral vessel of a patient. Likewise, the needle portion  505  has an extended position that corresponds to the retracted position of the catheter portion  540  and a retracted position where the needle  520  is drawn into the catheter  565  and out of the fistula/graft or peripheral vessel once the catheter is inserted therein and blood flow has been optimized. Consequently, in addition to securing the overall catheter device  500  to the patient, it is also preferable to provide mechanisms by which it can be ensured that the position of the catheter portion  540  relative to the position of the needle portion  505  will be maintained after the needle  520  has been fully retracted. 
     As may be understood from  FIG. 7A , contact between the distal end  510   b  of the needle hub  510  and the interior wall of the distal end of the catheter hub  545 , and/or contact between a leading edge of the gripping elements  530  and a distal terminus of the gripping element relief slots  560  may act as a hard stop and set the fully extended position of the needle portion  505  and the fully retracted position of the catheter portion  540 . 
     Referring to  FIGS. 7B-7C , it may be observed that in the case of the exemplary catheter device  500 , a needle portion retraction hard stop and needle portion retracted position retention functionality are both provided via interaction of certain elements of the catheter hub  545  and the needle hub  510 . More specifically, the proximal end of at least one of the gripping element relief slots  560  in the catheter hub  545  leads into a needle portion retention mechanism having a retention slot  575  that extends further toward the proximal end  545   a  of the catheter hub. 
     The needle portion retention mechanism also includes a retention tab  580 —which may be an integral portion of the catheter hub  545 . The retention tab  580  protrudes into the retention slot  575  near a distal end thereof. The retention tab  580  may be shaped to facilitate passage of the corresponding needle portion gripping element  530 —which also comprises an element of the needle portion retention mechanism—when the needle portion is moved in a distal-to-proximal direction relative to the catheter portion  540  toward its fully retracted position, but to prevent passage of the gripping element upon a subsequent attempt to thereafter move the needle portion in a proximal-to-distal direction back toward its extended position. For example, and as shown, the retention tab  580  may have a distal (leading) edge that slopes toward the proximal end  545   a  of the catheter hub  545 , but a proximal (trailing) edge that is substantially parallel to the proximal end of the catheter hub (i.e., substantially transverse to the central axis of the device  500 ). Other retention tab trailing edge shapes may also be possible, as long as the trailing edge of the retention tab  580  is operative to engage the leading edge of the gripping element  530  and to prohibit an extending motion of the needle portion  505  once the needle portion has reached its fully retracted position. 
     The retention tab  580  may be aligned with a recess  585  or similar contour in the retention slot  575  to facilitate passage of the gripping element  530  past the retention tab  580  during an extending movement of the catheter portion  540 . Passage of the gripping element  530  past the retention tab  580  during an extending movement of the catheter portion  540  may be instead or further facilitated by some controlled degree of flexibility of the retention tab  580  and/or the gripping element  530 . For example, it will be common for a user to bend the gripping elements  530  when displacing the needle portion  505  during insertion or retraction of the needle  520  and to return the gripping elements to a substantially flat position before taping the catheter device  500  to a limb of a patient. Such a bending of the gripping elements  530  may also assist in passage of the gripping elements past the retention tab  580  of the retention mechanism during retraction of the needle portion  505 . 
     As may be best observed in  FIG. 7C , the position of the retention tab  580  and the size and shape of the portion of the retention slot  575  that resides proximally of the retention tab is such to accommodate a corresponding portion of the gripping element  530 . More particularly, said portion of the retention slot  575  is preferably of like shape and only slightly larger than the corresponding portion of the gripping element  530  so as to trap the corresponding portion of the gripping element  530  between the trailing edge of the retention tab  580  and a proximal terminus of the retention slot  575 , and to minimize or prohibit any further linear movement of the catheter portion  540  relative to the needle portion  505 . Abutting contact between the proximal terminus of the retention slot  575  and a proximal edge of the gripping element  530  also functions as a hard stop for the fully retracted position of the needle portion  505 . Likewise, the size and shape of the portion of the retention slot  575  that resides proximally of the retention tab also substantially prevents any rotation of the catheter portion  540  relative to the needle portion  505  when the needle portion is in a fully retracted position. 
     For further reference and clarity, a perspective view and a cross-sectional side view of the exemplary catheter portion  540  of the exemplary catheter device  500  of  FIGS. 7A-7C  is shown in  FIGS. 8A and 8B , respectively. As previously stated, the dimensions of a given catheter device according to the inventive concept may vary as needed. However, in the exemplary embodiment of the device  500  of  FIGS. 7A-7C , the length of the catheter hub  540  may be about 38 mm; the outside diameter of the catheter hub may be about 5.6 mm; the inside diameter (bore  550 ) of the catheter hub may be about 4 mm (for a wall thickness of about 0.8 mm); the length of the gripping element relief slot(s)  560  in the catheter hub may be about 17 mm; the length of the catheter  565  may be about 17 mm; the inside diameter of the catheter may be about 1.9 mm; and the catheter may have a wall thickness of about 0.25 mm. 
     As further illustrated in  FIGS. 8C-8D , the catheter  565  may have a tapered distal end  565   b  to facilitate insertion into the hole in a patient&#39;s skin and fistula/graft or peripheral vessel created by the leading end of the needle  520 . A plurality of orifices  575  may also be distributed about the distal end  565   b  of the catheter  565  to optimize blood flow into the catheter. For example, four diametrically opposed smooth orifices  575  may be present and each orifice may have a diameter of about 0.7 mm. 
     The material(s) used to produce the exemplary device  500  may also vary. For example, parts of the device  500  other than the needle  520  may be comprised of one or more thermoplastic polymers. In this regard, it has been found that manufacturing the catheter hub  545  from a polycarbonate, polyethylene or polypropylene material provides good results, as does manufacturing the catheter from polyethylene, polypropylene or flouroethylenepropylene (FEP). The needle  520  may be comprised of an acceptable metallic material or of any other material that is currently known to be acceptable or hereafter becomes acceptable in the art. 
     Another exemplary embodiment of a vascular access catheter device  600  is illustrated in  FIGS. 9A-14 . As may be best observed in  FIGS. 9A-9B and 10A-10C , the device  600  includes a needle portion  605  having an elongate, hollow, needle hub  610  from which extends a needle  615 , and a catheter portion  700  having a hollow body  705  with a projecting and hollow catheter hub  710 . A catheter  715  extends forward from the catheter hub  710 . 
     As may be better observed in  FIGS. 11A-13C , the needle portion  605  and the catheter portion  700  are assembled to one another such that the needle hub  610  of the needle portion  605  is located within the body  705  of the catheter portion, and the needle  615  of the needle portion extends through the catheter hub  705  and into/through the catheter  715  of the catheter portion. The needle portion  605  and the catheter portion  700  are designed and assembled so as to be slidable relative to one another, which allows the needle  615  to be extended and retracted relative to the catheter  715  during use of the device  600 , as is described in more detail below. The combination of the hollow catheter  715 , the hollow needle  615  and the cooperating hollow interior of the needle hub  610  provides a pathway for blood flow during a hemodialysis procedure or when the device  600  is otherwise used to access peripheral vessels. 
     Further details regarding the exemplary needle portion  605  of the device  600  may be observed by referring to  FIGS. 9A-9B  and the cross-sectional views of  FIGS. 11C, 12C and 13C . As shown therein, the exemplary needle hub  610  is generally elongate and includes a through-bore that imparts a substantially hollow construction to the needle hub. The needle hub  610  is dimensioned to fit within a hollow receiving cavity  750  in the body  705  of the catheter portion  700 . The bore through the needle hub  610  forms a pathway for blood flow when the device  600  is in use. 
     The needle  615  of the needle portion  605  has a proximal end  615   a  thereof that is inserted into the bore in the needle hub  610  at a distal end  610   b  thereof. An internal diameter dimension of the bore in the needle hub  610  and an outside diameter dimension of the proximal end of the needle  615  may be selected so that the proximal end of the needle is securely retained in the needle hub such as by a press fit or a similar interaction between the components. In other embodiments, retention of the needle in the needle hub may be accomplished with adhesive, or by any other technique understood by those of skill in the art. Other techniques for coupling the needle to the needle hub may also be used, the only limitation being that the needle and needle hub move together in a sliding fashion relative to the catheter portion of a given device. 
     A distal, free end, of the needle  615  is provided with a sharp point  615   b  for the purpose of piercing the skin of a patient and subsequently accessing the patient&#39;s fistula/graft or a peripheral vessel. The specific needle gauge, needle construction, etc., may vary in keeping with accepted practices understood in the art. 
     In this exemplary embodiment of the device  600 , a gripping and actuating component  650  is coupled to the needle hub  610 , and moves with the needle hub relative to the catheter portion  700  of the device. As described in more detail below, the gripping and actuating component  650  helps to facilitate movement of the needle portion  605  during use of the device  600 . 
     The exemplary gripping and actuating component  650  used herein includes a pair of wing-like gripping portions  655  that extend in opposite and substantially transverse directions from a central connecting element  660 . While the gripping portions  655  of the gripping and actuating component  650  are provided with the illustrated wing-like shape to facilitate gripping and manipulation of the device  600  by a user, as well as taping of the device to a limb of a patient after fistula/graft or peripheral vessel access, the gripping portions of alternative embodiments may employ other shapes. 
     The central connecting element  660  of the gripping and actuating component  650  is a substantially cylindrical component having an axial through-bore of a diameter that can receive the needle hub  610 . More particularly, the outside diameter of at least a portion of the needle hub  610  and the diameter of the through-bore in the central connecting element  660  are preferably selected to produce a tight fit that is sufficient to retain the central connecting element on the needle hub in the course of ordinary use of the device  600 . In other embodiments, however, retention of the central connecting element  660  on the needle hub  610  may instead be accomplished with adhesive, by plastic welding, or by any other technique understood by those of skill in the art. In still other exemplary embodiments, the needle hub  605  and the gripping and actuating component  650  may be one unitary structure instead of separate components. For example, the needle hub  605  and the gripping and actuating component  650  may be a singular molded component, with the gripping elements extending in transverse opposite directions from a central area thereof. 
     In this exemplary embodiment of the device  600 , a hard stop  665  may be located on the exterior of the needle hub  610  to help properly locate the central connecting element  660  of the gripping and actuating component  650 . The exemplary hard stop  665  is comprised of a shoulder that extends outward from the outer surface of the needle hub  610 . The outer diameter of the hard stop (shoulder)  665  may be, but is not required to be, the same as the outer diameter of the central connecting element  660  of the gripping and actuating component  650 . When present in other embodiments, the hard stop may be a tab or another element that does not encircle the needle hub, but against which the central connecting element of the gripping and actuating component may nonetheless abut. 
     A needle portion position locking slot  680   a ,  680   b  (only slot  680   a  visible in  FIGS. 9A-9B ) is also present in each of the wing-like gripping portions  655  of this exemplary gripping and actuating component  650 , the purpose of which is described in more detail below. A single one of such slots may be present on a gripping portion of other exemplary device embodiments. 
     The wing-like gripping portions  655  of the gripping and actuating component  650  are preferably bendable to facilitate grasping and manipulating of the device  600  during use. For example, and without limitation, each of the wing-like gripping portions  655  may preferably be bent at least upward (relative to the orientation of the device during normal use) and also toward each other. In this example, the wing-like gripping portions  655  are sufficiently bendable such that the outward, upper faces  670   a ,  670   b  thereof may be placed into abutting contact and held between the thumb and index (or other) finger(s) of a user during, for example, the process of inserting the needle  615  of the device  600  into a patient. 
     One of a cooperating pair of releasable engagement features  675   a ,  675   b  may be located in each of the wing-like gripping portions  655  to aid in alignment and possible temporary retention of a bent and abutting position of the wing-like gripping portions. In this exemplary embodiment, the releasable engagement features are provided in the form of a protruding tab  675   a  and a corresponding receiving slot  675   b , but when present in other embodiments, such engagement features may take any functional form that would be understood by one of skill in the art. 
     Further features of the catheter portion  700  of the device  600  may be observed by particular reference to  FIGS. 10A-10C . As shown, the catheter portion  700  of the device  600  includes a body  705  of generally elongate and substantially hollow construction. The substantially open interior of the body  705  is dimensioned so as to permit uninterrupted sliding movement of the needle hub  610 . 
     A distal end  705   b  of the body  705  forms a catheter hub  710  that extends axially in a proximal-to distal direction and which, in this exemplary embodiment, includes a distal end of reduced diameter and a tapered portion that connects the distal end to the body. A hollow catheter  715 , having an open distal end  715   b  and a proximal end  715   a  (see, e.g.,  FIG. 11C ) designed for retention within the catheter hub  710 , extends axially from the distal end of the catheter hub in a proximal-to distal direction. 
     The proximal end  715   a  of the catheter  715  may be retained in the catheter hub  710  by any of the needle retention techniques mentioned above or by any other acceptable technique known to one of skill in the art. In other embodiments, the catheter  715  may be an integrally molded part of the catheter hub  710 . The free, distal end  715   b  of the catheter  715  may be tapered and/or may include any other features that may facilitate entry of the distal end of the catheter into the fistula/graft or peripheral vessel of a patient subsequent to initial access by the needle  615 , and/or may facilitate blood flow during a hemodialysis or other vascular access procedure. Along with the needle  615 , the specific construction of the catheter  715  may vary in keeping with accepted practices understood in the art. For example, the catheter  715  may be constructed from a fluoroplastic material. 
     The exemplary body  705  of this exemplary device  600  embodiment also includes a grip  720  or similar feature that extends from the body to facilitate sliding or retention of the catheter portion  700  by a user of the device. A pair of needle portion position locking tabs  740  are also present on opposite sides of the body  705 , the purpose of which is described in more detail below. A single one of such tabs may be present on the body of other exemplary device embodiments. 
     This exemplary embodiment of the body  705  further includes an opening that is provided to accommodate the wing-like gripping portions  655  of the gripping and actuating component  650  associated with the needle portion  605 , and sliding movement thereof, when the needle portion and the associated gripping and actuating component are assembled to the catheter portion  700 . In this exemplary embodiment, the opening is comprised of a pair of slots  725  (see  FIGS. 10B-10C ) that pass through opposite walls of the body  705 . The body  705  may further include a hard stop(s)  730  that sets the limit of travel of the needle portion  605  toward the proximal end of the body  705 . 
     The slot  725  resides above a bottom section, or gripping and actuating component support wall  735  of the body  705 . The gripping and actuating component support wall  735  of the body  705  helps to retain and guide the gripping and actuating component  650  of the needle portion  605  during use of the device  600 . In this exemplary embodiment of the device, the gripping and actuating component support wall  735  is an independent (separate) element that is coupled to and retained on the body  705 . In other embodiments, the gripping and actuating component support wall may be an integral (e.g., molded) portion of the body as long as the needle portion  605  can be properly assembled to the catheter portion  700 . 
     Reference to the assembled device views of  FIGS. 11A-13C , and particularly to the cross-sectional views of  FIGS. 11C, 12C and 13C , reveals a more thorough understanding of the construction and operation of the exemplary vascular access catheter device  600 . 
       FIGS. 11A-11C  illustrate the exemplary device  600  with the needle portion  605  in a fully extended position relative to the catheter portion  700 , which results in the needle tip  615   b  and perhaps some additional length of the needle  615  protruding from the open distal end of the catheter  715 . This is the proper position in which the catheter portion  700  should reside during initial piercing of a patient&#39;s skin and accessing of the underlying fistula/graft or peripheral vessel using the needle  615  of the device  600 . 
     Referring now specifically to  FIG. 11C , it may be observed that the catheter  715  is installed into the body  705 , with the proximal end of the catheter secured within the bore of the catheter hub  710 . Likewise, the needle portion  605 , with the gripping and actuating component  650  coupled thereto, is installed in the catheter portion  700  with the needle hub  610  of the needle portion arranged in the open interior of the body  705  and the needle  615  extending through the catheter  715 . This assembled arrangement of the needle portion  605  and the catheter portion  700  allows for slidable movement of the needle portion relative to the catheter portion, and vice versa. The limit of slidable (extending) movement of the needle portion  605  toward the distal end of the catheter portion  700  in this exemplary device embodiment, occurs at the point of contact between forward edges of the gripping portions  655  of the gripping and actuating component  650  and a rear face of a lower wall  755  of the body  705  that resides rearward of the catheter hub  710 . As should be apparent, a different hard stop(s) to extending movement of the needle portion  605  may instead be provided. 
     The inside diameter of the catheter  715  is preferably similar in dimension to the outside diameter of the needle  615 , so as to produce a close-tolerance but sliding fit between the catheter and the needle after the needle portion  605  and the catheter portion  700  of the device  600  are assembled to one another. Nonetheless, a seal  800 , such as without limitation, an O-ring, may be placed at or near the meeting point of the bore in the catheter hub  710  and the open interior of the of the catheter portion body  705  to prevent possible blood leakage between the needle  615  and the catheter  715  during use of the device  600 . 
     From the foregoing description and a review of corresponding  FIGS. 11A-11C , it should be understood that when the needle portion and the catheter portion  700  are properly assembled, as explained above, the needle  615  is substantially concentrically located within the catheter  715 , and the body  705  and attached catheter  715  are together linearly slidable relative to the needle hub  610  and the attached needle  615 , and vice versa. For example, the body  705  and attached catheter  715  may be slidably displaced relative to the needle hub  610  and needle  615  by maintaining the position of the needle portion  605  using the gripping and actuating component  650  and using the grip  720  on the body  705  to slide the catheter portion  700  relative to the needle portion. Likewise, the needle hub  610  and needle  615  may be slidably displaced relative to the body  705  and attached catheter  715  by maintaining the position of the body and using the gripping and actuating component  650  to slide the needle portion  605  relative to the catheter portion  700 . 
     As mentioned above, the position of the device  600  illustrated in  FIGS. 11A-11C , with the needle  615  protruding from the distal end of the catheter  715 , is the position of the device to be used to initially pierce a patient&#39;s fistula/graft or peripheral vessel with the needle tip  615   b . It should also be understood that when the device is used in this position as described, the distal end of the catheter  715  will follow the needle  615  into the fistula/graft or peripheral vessel. 
     Once the needle  615  and a sufficient length of the catheter  715  have been initially placed in the fistula/graft or peripheral vessel, the needle portion  600  may be moved to an intermediate position relative to the catheter portion, as shown in  FIGS. 12A-12C , or may be moved directly to a final position relative to the catheter portion, as shown in  FIGS. 13A-13C . 
     As illustrated in  FIGS. 12A-12C , once blood flash is seen in a length of blood transfer tubing that is normally attached to the proximal end  610   a  of the needle hub  610  (see, e.g., tubing  810  in  FIG. 14 ), it may be desirable in some cases to partially retract the needle portion  605  in a distal-to-proximal direction relative to the catheter portion  700  to resultantly achieve optimum blood flow and position. This partially retracted position of the needle portion  605  relative to the catheter portion  700  is referred to generally herein as a “parked” position. The positional relationship of the catheter  715  and the needle  615  may also be further adjusted if needed to maintain an optimized blood flow. 
     As indicted in  FIGS. 13A-13C , either subsequent to “parking” the needle portion  605 , or directly after initial insertion of the needle  615  and catheter if acceptable blood flow is achieved without employing a “parking” step, the needle portion is fully retracted relative to the catheter portion  700 . Full retraction of the needle portion  605  occurs in this exemplary embodiment at the point of contact between rear faces/edges of the gripping portions  655  of the gripping and actuating component  650  and forward faces/edges of the hard stops  730  on the body  705  of the catheter portion  700 . The needle portion  605  cannot be moved any farther toward the proximal end of the body  705  during normal use of the assembled device  600 . The fully retracted position of the needle portion  605  may be indicated by an audible click or other sound. 
     In the fully retracted position, a returning (i.e., proximal-to-distal) movement of the needle portion  605  toward the previously described “parked” position ( FIGS. 12A-12C ) or extended position ( FIGS. 11A-11C ) is preferably prevented by means of a needle portion locking mechanism. The needle portion locking mechanism is comprised of and operates via engaging interaction of the needle portion position locking tabs  740  on the body  705  of the catheter portion  700  and the needle portion position locking slots  680   a ,  680   b  on the gripping portions  655  of the gripping and actuating component  650 . Particularly, and as best illustrated in  FIG. 13C , when the needle portion  605  is placed in the fully retracted position, the needle portion position locking tabs  740  on the body  705  enter the needle portion position locking slots  680   a ,  680   b  on the gripping portions  655  of the gripping and actuating component  650 . Entry of the locking tabs  740  into the locking slots  680   a ,  680   b  may produce the audible locked position-indicating click or other sound mentioned above. 
     In this embodiment of the device  600 , sliding movement of the needle portion  605  relative to the catheter portion  700  (or vice versa) is no longer possible after the needle portion position locking tabs  740  on the body  705  become engaged with the needle portion position locking slots  680   a ,  680   b  on the gripping portions  655 . Rather, the needle portion locking mechanism causes the device  600  to become permanently locked in the fully retracted position which, because the needle tip is covered by the catheter, prevents possible needle stick injuries to health care workers or other users upon removal of the device from the patient and subsequent disposal of the device. 
     While the exemplary embodiment of the device  600  described and shown herein includes a needle portion locking mechanism that causes the device  600  to become permanently locked in the fully retracted position, it should be apparent to one of skill in the art that it is also possible, if desired, to provide an exemplary vascular access catheter device with a releasable needle portion locking mechanism. For example, an exemplary device may be provided with needle portion position locking tabs and cooperating needle portion position locking slots whose engagement is sufficient to generally prevent unintended movement of the needle portion toward its extended position during normal use, while nonetheless allowing for deliberate disengagement of the needle portion locking mechanism via a user-applied sliding force of abnormally high magnitude on the needle portion or the catheter portion of the device. 
     With the needle portion  605  and needle  615  of the exemplary device  600  locked in the fully retracted position and the catheter  715  properly located in the fistula/graft or peripheral vessel of the patient, the catheter device  600  may be secured to the limb of the patient using tape or another technique known in the art. 
     As should be readily obvious to one of skill in the art, placing the catheter  715  of the exemplary catheter device  600  into a fistula/graft or a peripheral vessel and over the needle tip  615   b  as described above serves to prevent the needle tip from damaging the fistula/graft or peripheral vessel and also, therefore, prevents infiltration and related hematoma problems. And unlike known devices, the needle  615  of the exemplary catheter device  600  remains largely within the catheter  715  during a hemodialysis or other vascular procedure, thereby substantially eliminating any chance that the catheter may collapse, kink, etc., and interfere with blood flow or cause damage on its own. 
     As described above, therefore, the needle portion  605  has an extended position where the needle tip  615   b  extends beyond the catheter  715  and the catheter is thereby kept from interfering with initial use of the needle  615  to access the fistula/graft or peripheral vessel of a patient. Likewise, the needle portion  605  has a retracted position where the needle  615  is drawn into the catheter  715  and out of the fistula/graft or peripheral vessel while the catheter itself remains inserted therein, which prevents the needle/needle tip from causing damage to the fistula/graft or peripheral vessel. Consequently, in addition to securing the overall catheter device  600  to the patient, it is also preferable to provide a mechanism, such as the exemplary needle portion locking mechanism described above, whereby it can be ensured that the position of the needle portion  605  relative to the position of the catheter portion  700  will be maintained after the needle  615  has been fully retracted. 
     To guard against inadvertent contact with the sharp tip  615   b  of the needle  615  when the needle is in an extended position, a protective device, such as but not limited to a cap may be associated with the needle. When a cap is used, the cap may be the same as or similar to the cap shown in  FIGS. 3A-3B . Any of the cap retention techniques mentioned herein may be employed in such an embodiment. 
     One exemplary embodiment of a vascular access catheter device assembly  805  utilizing the exemplary vascular access catheter device  600  described above, is illustrated in  FIG. 14 . As shown, a length of blood transfer tubing  810  is connected at one end to the proximal end  610   a  of the needle hub  605 . The proximal end  610   a  of the needle hub  605  may have a barbed profile or may otherwise be adapted to facilitate connection of such tubing. A stopper element  815  is located at the opposite end of the tubing  810 , and in between the exemplary vascular access catheter device  600  and the stopper element resides a clamp  820 . The exemplary assembly  805  is provided for purposes of illustration, not limitation, and one of skill in the art would understand that there are numerous possible variations of a vascular access catheter device assembly employing the exemplary vascular access catheter device  600 . 
     Various exemplary vascular access catheter device embodiments have been described and shown herein for purposes of illustration. Other variations are also possible. For example, and without limitation, the catheter hub and needle hub of an exemplary vascular access catheter device, may be manufactured from a transparent or semi-transparent material to permit viewing of the flow of blood passing through the device during use. 
     As used herein, the term “distal” is intended to refer to the end of the catheter device where the needle normally resides, and the term “proximal” is intended to refer to the end of the catheter device where fluid transport tubing is normally connected. 
     As used herein, the terms “axial” or “axially” are intended to refer to a direction that is parallel to the length-wise axis of the element/component to which the term is being applied. 
     As used herein, the term “central axis” is intended to refer to the symmetrical axis of a component or the device, and the term “central bore” is intended to refer to a bore that is symmetrical about the central axis. 
     As used herein “first” and “second” are intended only to differentiate between two elements or components for purposes of description, and not to indicate an order, a preference, or superiority or inferiority, of any kind. 
     As used herein, the term “irreversible” is intended to mean not able to be reversed under normal operation or when subjected to normal operating forces, and does not necessarily require that reversal is impossible under other conditions. 
     As used herein, the term “prohibit” is intended to mean prevent or make impossible under normal operation or when subjected to normal operating forces, and does not necessarily require that prohibition is impossible under other conditions. 
     While certain embodiments of the inventive concept are described in detail above, the scope of the inventive concept is not considered limited by such disclosure, and modifications are possible without departing from the spirit of the inventive concept as evidenced by the following claims: