Abstract:
A specialized cannula and intraluminal cannula placement apparatus allow the insertion of an intraluminal cannula through a previously inserted standard I.V. catheter so that the intraluminal cannula extends beyond the end of a standard catheter. By using an intraluminal cannula of appropriate length, the intraluminal cannula may be used to bypass a flexure-caused obstruction in a vein during the administration of fluids in patients who are unable to cooperate with medical or veterinary procedures, most particularly with human infants, geriatric patients, and animals. Use of the specialized cannula and intraluminal cannula placement apparatus does not require removal of the previously placed I.V. catheter. The exterior diameter of the specialized cannula has a smaller diameter than the interior diameter of the previously placed standard I.V. catheter. A specially adapted seal seals the space between the inserted specialized cannula and a standard Luer hub of an I.V. catheter. In use, a health practitioner advances the specialized cannula through the standard I.V. catheter and into the vein with a pusher. When inserted, there is no extracorporeal extension to the hub of the standard I.V. catheter and the intraluminal cannula cannot be removed without simultaneous removal of the standard I.V catheter.

Description:
BACKGROUND 
     1. Field of the Invention 
     This invention relates to catheters placed in the veins or arteries of animals and humans for the continuous transmission of fluids. Often catheters become unusable due to blockage of the vein or artery distal to the tip of the inserted catheter. The present invention consists of a specialized cannula and associated intraluminal cannula placement apparatus for inserting the specialized cannula into and through the lumen (hollow center cavity) of a previously inserted standard I.V. catheter so that the tip of the specialized cannula extends substantially beyond the tip of the catheter to beyond a point of blockage. 
     2. Description of the Prior Art 
     In medical and veterinary practice it is common procedure to provide fluids and medications to patients through a catheter. The typical catheter used today has a female Luer fitting (standard I.V. catheter hub) on the proximal end to which fluid lines or medication introducing devices can be attached. The catheter is typically inserted into a vein in the hand, forearm, or forelimb in humans and in domestic cats, dogs, or other companion and domesticated animals. Often fluids are administered through the cephalic vein, a large superficial vein in the forelimb running from the hand or paw to the shoulder. The injection site is generally on the anterior surface of the limb, between the carpals and the elbow joint. However, depending on the circumstances, the catheter may be introduced in other areas. Puncturing of the skin for placement of the catheter is accomplished by a sharpened needle located inside the catheter that protrudes beyond the tip of the catheter. Even in skilled hands, the insertion of the catheter is not without some discomfort to the patient and can be traumatic especially in young and old human patients and in animals of any age. Since catheters are usually placed away from the first major limb joint, constriction of the vein or artery and obstructions to blood flow on the heart side of the catheter insertion point can occur if the joint is flexed and kept in a flexed position for any length of time. Continued flexion is more common in young and old human patients and in sedated animals that do not move around. Constriction may also occur due to other circumstances. When this occurs, prescribed fluid or medicant administration is interrupted. If occlusion of a vein persists, the catheter may become clotted and prevent further treatment. 
     When constriction seriously impedes the flow of fluid through the catheter, typical remedies are either to apply an external splint to restrict movement of the offending joint, to withdraw the catheter and replace it with another longer catheter more resistant to constriction/obstruction, or to withdraw the catheter and insert a new catheter above the point of constriction. The accompanying pain/discomfort of the replacement procedure, especially if locating the vein or artery proves difficult, makes an alternative procedure desirable. The specialized cannula and intraluminal cannula placement apparatus of the present invention alleviates the need for placement of a new catheter by providing a mechanism for the fluid tight insertion into and through the previously inserted catheter of a specialized cannula that is sufficiently long to bypass the point of constriction. The specialized cannula has an outside diameter that is smaller than the inside diameter of the standard I.V. catheter which allows the specialized cannula to be slidingly inserted through the catheter. For this reason, the specialized cannula is referred to as an intraluminal cannula. Despite the reduced diameter of the specialized cannula, sufficient flow of fluids for medical treatment can be maintained. As will be described in greater detail below, after insertion of the specialized cannula, the cannula placement assembly is detached and standard fluid lines or medication delivering devices can be fastened to the standard I.V. catheter hub as before. None of the prior art patents teaches the solution provided by the present invention. 
     In U.S. Pat. No. 7,156,836, Teo teaches a double cannula assembly that is used to overcome the problem of clotting within a cannula. In this invention, an outer cannula previously placed in a vein has inserted into it a smaller diameter inner cannula. The contacting surfaces between the outer surface of the inner cannula and the inner surface of the outer cannula provide a sliding tight fit which is sufficient to allow insertion of the inner cannula but tight enough to prevent blood or other fluids from seeping between the two surfaces. Since clots frequently form at the tip of the cannula, removing and inserting an inner cannula displaces the clot and reopens the passageway. When clotting occurs, the inner cannula is removed, leaving the outer cannula in place. If desired, a new inner cannula may then be inserted through the outer cannula. 
     In U.S. Pat. No. 3,633,579, Alley, teaches a device for placing an inner catheter within a cannula that has been previously inserted with a needle. A tapered locking ferrule coaxial with and surrounding the catheter is used to secure the catheter to the previously placed cannula. The ferrule is slid along the catheter until the distal end of the tapered ferrule enters a tapered proximal opening in the rear of the cannula. The ferrule is made of a softer material than that of the previously placed cannula, so that the ferrule may be wedged into the cannula taper, said wedging action causing the ferrule to constrict and grip the outer surface of the catheter thereby locking the catheter against axial movement relative to the cannula. The previously placed cannula does not have a standard I.V. catheter Luer lock at the rear end, and therefore, the previously placed cannula is incapable of attaching to the Luer lock of another cannula placement device. 
     In U.S. Pat. No. 3,515,137, Santomieri teaches a catheter unit using one cannula, which is placed using a leading needle and an inserter. The inserter is coaxial with the cannula, surrounds the cannula, and is made of a resiliently compressible material. Compressing the inserter grips the cannula and needle for insertion. After puncture and insertion, the grip on the inserter is loosened so that the needle may be withdrawn. The inserter can then be used to grip just the cannula to advance the cannula further into the vein. Repeatedly using the inserter to grip the cannula to advance it forward, and then loosening the cannula and sliding it towards the end of the cannula enables the user to advance the cannula as far as is desired into correct position within the body. 
     U.S. Pat. No. 4,235,232 by Spaven et al. teaches a hub device for use with catheter placement where the catheter is inserted through a dimple in the elastomeric material of the hub, which forms a seal around the catheter. 
     U.S. Pat. No. 4,613,329 by Bodicky teaches a catheter placement device with an elastomeric grommet with bore, through which the catheter is placed, said grommet permitting relatively low resistance to distal movement of the catheter and relatively high resistance to proximal movement of the catheter. 
     U.S. Pat. No. 4,068,659 by Moorehead and U.S. Pat. No. 4,068,660 by Beck teach a sterilizable disposable assembly for inserting a catheter into a vein wherein the catheter is located inside the needle and connected sheath during insertion. After insertion, pressure is applied to the skin above the insertion site to capture/hold the catheter in the vein while the needle is withdrawn. The trailing end of the catheter is pushed out of the sheath by the advancement of the leading edge of an inserter, which can be advanced by a handle protruding out of the sheath. The inserter has attached a stiffener, smaller in diameter and coaxial with the catheter, that extends substantially the length of the catheter. The stiffener is attached at the leading edge of the inserter and keeps the catheter from unduly flexing during insertion but is otherwise not attached to the catheter. The catheter placement assembly is discarded following placement of the catheter. 
     U.S. Pat. No. 4,205,675 by Vaillancourt teaches a catheter placement unit that is used with an introducer needle and introducer catheter. The catheter placement unit contains a connector with an internal bore and a male fitting for coupling to the catheter fitting to create a connection. 
     U.S. Pat. No. 4,634,433 by Osborne teaches a flexible sheath assembly for protecting the sterility of the exposed portion of a catheter, where the unexposed portion has been placed in a vein. When it is necessary to adjust the depth of insertion of the catheter, the flexible sheath assembly encasing the exposed portion of the catheter preserves the sterility of the catheter so that the depth of insertion can be adjusted without causing contamination. U.S. Pat. No. 4,767,409 by Brooks and U.S. Pat. No. 4,834,710 by Fleck similarly teach devices for protecting a catheter from contamination during and after placement in a vein. 
     U.S. Pat. No. 6,156,016 by Maginot teaches a catheter system comprising a guide catheter with guide lumen extending between a distal guide orifice and a proximal guide orifice. The catheter system also includes an original catheter within the guide lumen of the guide catheter. In addition, the system features a replacement catheter within the guide lumen of the guide catheter. 
     U.S. Patent Application Publication 2006/0116629 A1 by Tal et al. teaches a catheter insertion apparatus with a catheter featuring a first and second lumen. A first member moves within the first lumen to create a cavity, and a second member moves within the second lumen. Furthermore, the cavity created by the first member is designed for movement of the second member. 
     U.S. Patent Application Publication 2007/0100295 by Belley et al. teaches a device for use with catheter apparatus that features an internal seal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The preferred embodiments of the invention are illustrated in the drawings in which like reference numbers refer to like elements. 
         FIG. 1  is a longitudinal cross-sectional view of the intraluminal cannula placement apparatus in its initial retracted position before coupling to a standard I.V. catheter. 
         FIG. 2A  shows a side view of the pusher.  FIG. 2B  shows a view of the pusher seen from above. 
         FIG. 3A  shows a long nose seal for use on the specialized cannula.  FIG. 3B  shows a short nose seal for use on the specialized cannula.  FIG. 3C  shows a cross sectional view of a short nose seal with a cannula mounted in the seal. 
         FIGS. 4A ,  4 B,  4 C,  4 D, and  4 E are perspective drawings of different embodiments of a protective sheath of the intraluminal cannula placement apparatus. 
         FIG. 5A  is a side view of a modified male Luer coupling.  FIG. 5B  is a cross sectional view of the modified male Luer coupling. 
         FIG. 6  is a perspective view of an exploded assembly of the intraluminal cannula placement apparatus showing a pusher, a stiffening rod, a seal, a specialized cannula, a sheath, and the modified locking male Luer adapter. 
         FIG. 7  is a longitudinally cross-sectional view of the modified locking male Luer coupling mounted at the distal end of the intraluminal cannula placement apparatus and engaging the locking ring of the female Luer fitting at the proximal end of an I.V. catheter. 
         FIG. 8  is a longitudinally cross-sectional view showing the modified locking male Luer coupling of the intraluminal cannula placement apparatus engaging the female locking ring of the female Luer fitting as shown in  FIG. 7 . Further, the pusher of the intraluminal cannula placement apparatus is shown advanced towards the distal end of the device pushing ahead of it the seal and cannula. The seal is shown just before it makes contact with the distal end of the interior lumen of the female Luer adapter. 
         FIG. 9  is similar to  FIG. 8  but shows the pusher sufficiently advanced to place the seal in engagement with the distal end of the interior lumen of the female Luer fitting on the standard I.V. catheter hub. 
         FIGS. 10A and 10B  show the placement of an intraluminal cannula in the foreleg of a dog. 
         FIG. 11  shows the placement of an intraluminal cannula in a human wrist. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Definitions 
     For clarity of description in this patent document, the following definitions apply: 
     “PROXIMAL” refers to a location on a device or a component that is closest to the practitioner when the device or component is used with a patient. 
     “DISTAL” refers to a location on a device or a component that is farthest from the practitioner when the device or component is used with a patient. 
     “PRACTITIONER” is generally inclusive of veterinarians, physicians, clinicians, surgeons, medical or veterinary technicians, nurses, lab technicians, and like personnel. 
     “PATIENT” includes both humans and animals that are undergoing medical procedures. 
     MODIFIED MALE LUER ADAPTER″ refers to a male Luer hub having the characteristics described in this patent document. 
     “STANDARD I.V. CATHETER HUB” refers to an industry standard female Luer lock hub attached to a semi-rigid I.V. tube, which may be of various gauges and length. 
     “CATHETER” shall mean a tube attached to a STANDARD I.V. CATHETER HUB that is introduced through the skin and into a vein or artery. This tube may also be referred to in the literature as a “cannula”, but in order to distinguish this tube from the intraluminal tube inserted by the device of the present invention, the term CATHETER will be used in this patent document. 
     “SPECIALIZED CANNULA” or “INTRALUMINAL CANNULA” shall both mean the tube with attached seal that is inserted by the intraluminal cannula placement apparatus of the present invention. A SPECIALIZED CANNULA is longer than a CATHETER and has an outside diameter smaller than the interior diameter of a CATHETER. 
     Description Of The Preferred Embodiments 
     The present invention provides for the insertion of a specialized cannula through a catheter, which has been previously inserted into a blood vessel, to overcome a constriction or obstruction (such as flexure of the limb). The specialized cannula is longer than the catheter and is sufficiently long to pass beyond the constriction or obstruction that is reducing the flow of blood in the blood vessel in which the catheter is inserted. The outside diameter of the specialized cannula is smaller than the inside diameter of the catheter so that the specialized cannula can be slidingly inserted. However, the inside diameter of the specialized cannula is large enough so that a medically sufficient amount of fluid may pass. Most importantly, the specialized cannula can be inserted without the need to remove the previously inserted catheter. Further, once installed, no part of the specialized cannula extends proximally beyond the end of the previously inserted female catheter hub. These and other features of the invention are described in the following written description and figures. 
     The intraluminal cannula invention consists of two interrelated components. A specially adapted cannula is provided that may be placed within a previously inserted catheter and which has affixed to one end a seal that provides a fluid-tight secure connection to the previously inserted catheter. The specialized cannula is placed in the previously inserted catheter by the matching intraluminal cannula placement apparatus of the invention. 
     Referring now to  FIG. 1 , the overall construction of the invention can be seen. The specialized cannula and intraluminal cannula placement apparatus  100  of the present invention are shown in longitudinal cross section. A pusher tab  106  protrudes from within tubular protective sheath  118  through opening  120  in sheath  118 . Pusher tab  106  is attached to A substantially cylindrical pusher body  102  by connecting support  108 . The pusher body  102  has a hollow center  111  and a reduced diameter near its distal end  110  to provide clearance for seal  124  to flex. Located within tubular sheath  118 , pusher body  102  has an outside diameter slightly smaller that the interior diameter of tubular sheath  118  so that pusher body  102  may slide freely inside sheath  118 . The long axis A-A′ of pusher body  102  is substantially aligned with the long axis of sheath  118 . Pusher body  102  is shown in its initially retracted position near the proximal end  122  of sheath  118 . Flexible supporting rod  116  is attached to the distal end  112  of pusher body  102  centered on the long axis A-A′ of pusher body  102  and extends almost to the end of specialized cannula  128 . Flexible rod  116  adds rigidity to specialized cannula  128  during its insertion. However, rod  116  is shorter in length than specialized cannula  128  so that it cannot come into contact with a blood vessel wall when specialized cannula  128  is inserted. Rod  116  is also flexible so that it can flex to the contours of the blood vessel wall. A hole  126  in seal  124  provides for slidable engagement of seal  124  around rod  116 . Hole  126  has an interior diameter equal to or greater than the outside diameter of supporting rod  116 . To form the specialized cannula  128 , a flexible cannula  127  is secured to seal  124  within hole  126 . The interior diameter of specialized cannula  128  is greater than the outer diameter of rod  116  permitting the specialized cannula to slide over rod  116 . 
     At the distal end of the intraluminal cannula placement apparatus, tubular sheath  118  is secured within circular groove  132  formed by the extensions  134  and body  130  of modified male Luer coupling  129 . Tubular sheath  118  is seated at the distal end  136  of circular groove  132 . Modified male Luer coupling  129  has a body  130  from which extends tube extension  138 . The outer wall at the distal end  146  of tube extension  138  is tapered inwardly and has a reduced thickness from that of an unmodified male Luer coupling. Extensions  134 , body  130 , and tube extension  138  provide a hollow passageway  139  through modified male Luer coupling  129 . Modified male Luer coupling  129  also has a movable locking fastener  140  that slidable engages tube extension  138 . Locking fastener  140  is prevented from detaching from tube extension  138  by circular barb  142 . Spiral Luer lock fastening threads  144  are located on the interior surface of movable fastener  140 . 
     Further details of the construction of the various parts of the invention and their interrelationship can be seen in the following figures.  FIG. 2A  shows a side view and  FIG. 2B  shows a top view of pusher  102 . The smaller diameter  110  of distal end  206  of pusher body  102  is shown. As noted, the smaller diameter  110  of pusher  102  provides clearance for seal flange  304  to fold backwards towards the proximal end of  102  (as shown in  FIGS. 8 and 9 ). The forward edge  204  of support  108  is beveled to aid in separating the edges of a slot or serrated slot in tubular sheath  118  (not shown) that will be described below. The side  202  of tab  106  is ridged to aid in grasping. 
       FIGS. 3A ,  3 B, and  3 C show the construction details of seal  124 . The generally conical shape of seal  124  allows seal  124  to pass into lumen  704  of a female catheter hub adapter  702  and seat against the distal end  716  of the lumen  704  as shown in  FIG. 9 . Both configurations  124 A and  124 B of seal  124  have a substantially flat proximal surface  302  that is engaged by the distal end  206  of pusher  102 . Seals  124 A and  124 B depicted in  FIGS. 3A and 3B  differ in the length of the noses  310  and  312  to accommodate differences in the design of the “standard” I.V. catheter hub from different manufacturers. It has been determined through exacting measurement of the available standard Luer female catheter hubs that one or the other of the two seal designs/shapes  124 A or  124 B will fit all available female catheter hubs.  FIG. 3A  shows a long nose  310  seal  124 A while  FIG. 3B  shows a short nose  312  seal  124 B. The selection of a long nose or short nose seal is determined relative to the dimensions of the standard I.V. catheter hub selected by a practitioner. Other than the length of the nose, the seals are the same and are composed of a flexible material suitable for I.V. exposure. The distal end of the noses  310  and  312  are tapered at  314  to match the tapered wall  716  at the distal end of the lumen of female catheter hub  702 . The proximal end  302  of each seal  124 A and  124 B has a flexible flange  304  formed from an outer rim  308  and groove  306 . The diameter of the outer rim  308  is greater than the diameter of either nose  310  or  312  and of lumen  704  of the female catheter hub  702 . 
     During insertion of specialized cannula  128  (as will be described below), the flexible flange  304  folds back (towards its proximal end) to allow seal  124  to pass through the modified male Luer coupling  129  and into the standard female catheter hub  702 . Upon insertion of specialized cannula  128  into the standard female catheter hub  702 , flange  304  engages the side walls  706  of lumen  704  and, upon complete insertion, surface  314  of seal  124  engages the tapered walls  716  at the distal end of the internal lumen  704  of the standard female catheter hub  702 . Engagement of seal surface  314  with lumen surface  716  provides an initial fluid-tight seal. Further, flexible flange  304  expands against the side walls  706  of lumen  704  to create a fluid-tight seal that also permanently anchors seal  124  and specialized cannula  128  within the standard female catheter hub  702 . 
     As can be seen in the cross section of  FIG. 3C , seal  124  has a centrally located opening  126  starting with a flared opening  318  at the proximal surface  302 . Flared opening  318  extends distally along the longitudinal axis of seal  124  and reduces fluid flow friction maximizing fluid flow into cannula  127 . Flared opening  318  decreases in diameter to a diameter less than the outside diameter  324  of cannula  127 . Opening  320  through the distal portion of seal  124  is of substantially uniform diameter  322  and sized for the dimensions of the cannula  127  to be attached to the seal. Due to the differences in diameters of tapered opening  318  and cannula opening  320 , a stop is formed at  316  (as best send in  FIGS. 3A and 3B ) against which cannula  127  rests after insertion into hole  320 . Cannula  127  is permanently mounted in seal  124  against stop  316 . Cannula  127  can be held in place by compression of the seal material, or by means of appropriate cements, or formed by means of injection molding of the seal body  124  around cannula  127  by techniques known to those skilled in the art. The length of specialized cannula  128  is sufficient to extend beyond the site of possible flexural occlusion of a blood vessel when used in a clinical application. 
       FIGS. 4A-D  shows five embodiments of a protective sheath  118 . Sheath  118  shields cannula  128  and pusher  102  from contamination during handling and, in conjunction with modified male Luer coupling  129 , holds pusher  102  and cannula  128  in alignment with a standard I.V. catheter hub  702  during insertion. Further, the design of sheath  118  reduces the likelihood of blood or bodily fluid contamination of the patient or practitioner during use by containing fluids within sheath  118 . Sheath  118  is tubular and substantially cylindrical and is open at both ends. Various embodiments of protective sheath  118  are shown in  FIGS. 4A-4E . The internal diameter of sheath  118  is sized to slidingly engage the external diameter of pusher body  102 , to permit attachment of the protective sheath  118  to the modified male Luer coupling  129 , and to allow longitudinal passage of specialized cannula  128  through sheath  118  and through modified male Luer coupling  129 . The length of sheath  118  is adapted to the length of cannula  128  that is to be inserted. During storage, a cap (not shown) may be placed on the distal end of modified malel Luer coupling  129  so that the cannula does not protrude outside the intraluminal cannula placement apparatus before use and sterility is maintained. 
       FIGS. 4A-4E  show perspective views of the embodiments of sheath  118  with longitudinal guide tracks  414  and  416  traversing the wall of sheaths  118 . Pusher  102  is advanced manually along tracks  414  or  416 . In  FIGS. 4A-4D , tracks  414  and  416  do not extend fully to the proximal and distal ends of sheaths  118 . The proximal portion  122  of sheath  118  without a track prevents pusher  102  from exiting from the proximal end while the distal portion of sheath  118  without a track allows attachment of sheath  118  in slot  132  in modified male Luer coupling  129 . The internal and external diameters of sheath  118  are substantially uniform along its entire length. 
       FIG. 4A  shows an embodiment in which track  414  is a slit through the wall of sheath  118 . Sheath  118  is formed from a material that will allow the forward beveled edge  204  of pusher  102  to separate the wall material to permit advance of pusher  102  from the proximal to distal end of sheath  118  as far as slit  414  will allow. 
       FIG. 4B  shows a second embodiment of sheath  118 . This embodiment has a track that is a combination of a proximal slit  412  and a series of spaced perforations  416  along the longitudinal axis and through the wall of sheath  118 . The slit  412  additionally holds the pusher support  108  (and therefore pusher  102 ) at the proximal end  122  of sheath  118  prior to use. In use, the pusher  102  is manually moved distally within the protective sheath; the beveled edge  204  of support  108  cuts/separates the sheath  118  wall along the track of spaced perforations  416  during this action. 
       FIG. 4C  shows a third embodiment of sheath  118  having a distal rolled flange  418  which is used to secure attachment of sheath  118  within slot  132  in modified male Luer coupling  129 . Opening  120  at the proximal end of track  414  will accommodate support  108  of pusher  102 . Opening  120  and a closed track  414  will restrain pusher  102  at the proximal end  122  of sheath  118  until use. In use, the user grasps tab  106  to advance pusher  102  distally within sheath  118 ; the beveled edge  204  of support  108  separates the sheath wall during this action. 
       FIG. 4D  shows a fourth embodiment of sheath  118  having a distal rolled flange  418  which is used to secure attachment of sheath  118  within slot  132  in modified male Luer coupling  129 . Opening  120  at the proximal end of track  416  will accommodate support  108  of pusher  102 . Track  416  is composed of spaced perforations. Opening  120  and a track  416  formed of spaced perforations will restrain pusher  102  at the proximal end  122  of sheath  118  until use. In use, the user will grasp tab  106  to advance pusher  102  distally within sheath  118 ; the beveled edge  204  of support  108  cuts the sheath wall along track  416  of spaced perforations during this action. 
     In a preferred embodiment shown in  FIG. 4E , slit  422  extends to the proximal end  122  of sheath  118 . Pusher  102  may then be easily inserted into sheath  118  at end  122 . After pusher  102  has been inserted, a cap  424  is placed over end  122  to both contain pusher  102  and to help seal sheath  118  against contamination. It will be appreciate that the more enclosed sheath  118  is, the less chance there is for contamination of the specialized cannula during insertion and less chance of patient blood leaking and getting on the patient or the practitioner. While those skilled in the art will recognize that there may be other variations of the sheath design not specifically discussed herein, all such variations that perform the same function as those described are considered within the teaching of this patent document. 
     Sheath  118  can be formed as a unitary item by continuous blow molding or injection molding, and materials such as polyethylene, polyolefin, or other copolymers, may be used. Sheath  118  alternatively may be assembled from more than one part formed separately. 
       FIG. 5  shows two views of one embodiment of modified male Luer coupling  129  with distal lock ring  140 .  FIG. 5A  is a schematic view of modified male Luer coupling  129 .  FIG. 5B  is a longitudinal cross-sectional view of the elements of modified male Luer coupling  129 . Modified male Luer coupling  129  serves to attach sheath  118  containing pusher body  102  and specialized cannula  128  to the standard female I.V. catheter hub  702 . Coupling  129  is referred to as “modified” since it has the following modifications from a standard male Luer adapter. First, coupling  129  has a circular groove  132  within outer wall  508  of its proximal end  510  into which the distal end of sheath  118  is secured. The slot  132  serves to position, stabilize, and protect the junction of the protective sheath  118  and the modified male Luer coupling  129 . A second feature of the modified male Luer coupling  129  is a set of protruding ribs  502  on the outer wall of its proximal portion  130  to assist the practitioner in grasping and aligning the intraluminal cannula placement apparatus  100  for proper connection to female Luer adapter. 
     A third feature of the modified male Luer coupling is the construction of tube extension  138 . The distal portion  506  of tube extension  138  has a standard industry taper at  146 . The taper at  146  has an initial standard Luer fitting outer diameter  504 , but a thinner than standard wall thickness  512 . The resulting modified male Luer coupling lumen diameter  514  is thus sufficiently enlarged to allow passage of specialized cannula  128  with seal  124  attached. The tapered distal portion  506  of the modified male Luer coupling  129  fits into the industry standard tapered female Luer hub  702  of the standard I.V. catheter. On the distal portion of modified male Luer coupling  129  there is a rotatable Luer locking fastener  140  that slidingly engages tube extension  138 . Proximal to the tapered end  506  of tube extension  138 , tube extension  138  has a circular raised barb  142  that prevents Luer locking fastener  140  from disengaging from the distal portion of modified male Luer coupling  129  after its placement during manufacture and during its clinical use. When modified male Luer coupling  129  is fastened with locking fastener  140  to female Luer adapter  702 , sheath  118 , pusher  102 , flexible rod  116 , and specialized cannula  128  are all aligned along a common central axis with female Luer adapter  702 . As noted above, a standard female Luer end cap (not shown) may be placed onto the distal end of intraluminal cannula placement apparatus  100  to maintain sterility of specialized cannula  128  and to prevent specialized cannula  128  from protruding beyond sheath  118  prematurely. 
       FIG. 6  is an exploded view of the present invention  100  showing the interrelationships of its parts. Embodiments of the inventive device  100  may be supplied in different lengths since the desired length of specialized cannula  128 , sheath  118 , and flexible rod  116  can vary over a wide range. In most applications, the length is chosen so that the length of specialized cannula  128  (and necessarily the lengths of sheath  118  and flexible rod  116 ) is sufficient to pass a point of constriction or obstruction in a blood vessel once the specialized cannula is inserted. However, there may be applications where a practitioner wishes to insert a specialized cannula that does not extend past a constriction or obstruction and the present invention permits insertion of such a specialized cannula. In all cases, specialized cannula  128  is inserted through a female catheter hub  702  of a standard I.V. catheter that has been previously inserted into a blood vessel. In the preferred embodiment, pusher  102  is generally cylindrical in shape. However, it can be appreciated that pusher  102  may have any shape (i.e.; a cross section of cross, star, triangle, etc.) that serves to keep flexible rod  116  and specialized cannula  128  centered in sheath  118  and modified male Luer coupling  129 . In addition, sheath  118  may have any shaped cross-section along with an appropriately shaped pusher that is compatible with insertion into modified male Luer coupling  129 . 
     All components of the invention are made from sterilizable materials suitable for medial applications, preferably of polyurethane, silicone, or tetrafluoroethylene plastic such as PEBA (polyether block amide polymer, commercially available under the trade name PEBAX® (Autofina Chemicals, Inc., Philadelphia, Pa., USA), ISOPLAST® (engineering thermoplastic polyurethane) or other polyurethanes, nylon, or mixtures thereof suitable to the particular application. The chosen materials must be biocompatible and discourage the generation of a thrombus. The material of specialized cannula  128  may be made from a non-kinking material such as polyurethane. The choice of material from which to manufacture seal  124  is made with at least two properties in mind. Seal  124  has to be flexible enough to pass through modified male Luer coupling  129  and then return to its original shape. Seal  124  must also be firm enough to maintain essentially fluid-tight and secure seating in place at the distal end of the lumen of standard female I.V. catheter hub  702 . In the preferred embodiment, the seal is made of polyurethane. 
     The assembled specialized cannula and intraluminal cannula placement apparatus  100  is preferably packaged within a sterile outer container to maintain sterility of the device after manufacture, shipment, and storage before use. Kits containing the device  100  can further include other instrumentalities, devices, or materials normally associated with the use of an intravenous catheter, including but not limited to tubing, cleaning materials to establish aseptic conditions before insertion of the standard I.V. catheter and/or related components. 
     The method of use of the various elements of device  100  will now be described. Once a practitioner has observed a reduction in flow through a previously inserted standard I.V. catheter and has identified the cause of the reduction as a constriction or obstruction of the blood vessel, typically by flexion of a joint distal to the catheter and proximal to the heart, the practitioner can determine the length of specialized cannula  128  needed. The length needed is measured from the female catheter Luer lock hub  702  to a point past the constriction. An appropriately long intraluminal cannula placement apparatus and specialized cannula  100  is chosen. Under aseptic conditions, the practitioner removes any lines or devices secured to the female Luer lock hub  702  of the previously inserted catheter and engages the modified male Luer coupling  129  of intraluminal cannula placement apparatus  100  to female Luer lock hub  702 . As shown in  FIG. 7 , tapered extension  146  of modified male Luer coupling  129  slidingly engages the tapered side walls  706  of lumen  704  of female Luer lock hub  702 . The practitioner rotates locking fastener  140  of modified male Luer coupling  129  to engage circular locking tab  710  of female Luer lock hub  702  thereby rigidly coupling intraluminal cannula placement apparatus  100  to female Luer lock hub  702 . This coupling aligns apparatus  100  and the female Luer lock hub  702  along a common axis B-B′ which is coincident with axis A-A′ of apparatus  100  thereby aligning pusher  102 , flexible rod  116 , and specialized cannula  128  with the catheter  712  of the previously inserted female Luer lock hub  702 .  FIG. 7  shows the arrangement of the various elements after the practitioner has connected apparatus  100 . The intraluminal cannula placement apparatus  100  is usable with most all female Luer lock hubs  702 . Female Luer lock hubs  702  are manufactured to a standard specification such as the Terumo Surflo I.V. catheter 22G×1″ (Terumo Cardiovascular Systems Corporation, 6200 Jackson Road, Ann Arbor, Mich. 48103-9300, U.S.A.). Commercially available standard I.V. Luer lock catheter hubs are produced by various manufacturers including Abbott, Baxter, B. Braun, and Johnson &amp; Johnson. 
     Subsequent to coupling, the practitioner grasps pusher tab  106  that protrudes from sheath  118  and advances pusher  102  longitudinally along the length of sheath  118  towards female Luer lock hub  702 . As pusher  102  is advanced, the distal end  112  of pusher  102  engages the proximal surface  302  of seal  124  and advances seal  124 , flexible rod  116 , and specialized cannula  128  towards and into female Luer lock hub  702 . Simultaneously, the beveled edge  204  of support  108  follows and separates an opening in guide track  414  or  416  in sheath  118 . As pusher  102  is advanced, the alignment along a common central axis insures that flexible rod  116  and specialized cannula  128  enter catheter  712  attached to the female Luer lock hub  702 . Specialized cannula  128  is kept from kinking or otherwise distorting as it enters catheter  712  by flexible rod  116 . In this manner, the distal end of specialized cannula  128  is advanced longitudinally within sheath  118 , through modified male Luer coupling  129 , into female Luer lock hub  702 , through catheter  712 , and into the blood vessel until seal  124  engages the wall  716  at the distal end of the interior lumen  704  of female Luer lock hub  702 .  FIG. 8  shows specialized cannula  128  inserted into catheter  712  immediately before the distal end  314  of seal  124  engages the walls  716  at the distal end of the interior lumen  704  of female Luer lock hub  702 . The flange  304  of seal  124  is shown bent proximally in sealing engagement with the interior walls  706  of Luer lock hub  702 . 
       FIG. 9  shows the distal end  314  of seal  124  fully seated against the wall  716  at the distal end of the interior lumen  704  of female Luer lock hub  702 . By engaging the interior walls  706  of lumen  704  of Luer lock hub  702 , flange  304  of seal  124  securely holds specialized cannula  128  in place so that specialized cannula  128  cannot be removed without removing catheter  712  (and attached female Luer lock hub  702 ). This means that any blood clots or fibrin that might accumulate between specialized cannula  128  and catheter  712  will not be stripped off by just removal of specialized cannula  128  to enter the patients blood steam to cause complications. 
     Once seal  124  is securely in place, flexible rod  116  is withdrawn from female Luer lock hub  702  by reversing the direction of pusher  102 , and the intraluminal cannula placement apparatus is disconnected from female Luer lock hub  702  by unscrewing locking fastener  140  of modified male Luer coupling  129 . Female Luer lock hub  702  may then be reattached to I.V. supply lines. A major advantage of the use of this invention is that insertion of seal  124  and specialized cannula  128  adds no extracorporeal components to female Luer lock hub  702  that would lengthen the exposed female Luer lock hub  702  or otherwise hinder the normal attachment of fluid lines or other delivery devices to female Luer lock hub  702 . The intraluminal cannula placement apparatus is discarded after the specialized cannula is in place. 
       FIGS. 10A and 10B  show the use of an intraluminal cannula  128  in a veterinary setting after it has been placed in the foreleg  800  of a dog.  FIG. 10B  is an enlargement of foreleg  800  shown in  FIG. 10A . A standard catheter  712  with Luer hub  702  had been inserted just distal to the radial carpal joint  802 . The dog&#39;s elbow joint is flexed at  804  and may cause obstruction of blood vessel  806 . Intraluminal cannula  128  has been positioned through and beyond the point of flexion  804  to provide for the continuous flow of fluids in the previously placed I.V. catheter. The previously inserted female Luer lock hub  702  remains attached to the previously placed catheter  712  within the blood vessel  806 . A practitioner determines the length of intraluminal cannula  128  needed to pass beyond the point of obstruction. As noted above, the required length is measured from the female catheter Luer lock hub  702  to a point past the point of obstruction  804 . The specialized cannula and intraluminal cannula placement apparatus  100  of the present invention can be scaled to provide intraluminal cannulas of the appropriate length. 
       FIG. 11  shows the intraluminal cannula  128  as it may be used for a human. A previously placed catheter  712  with Luer lock hub  702  is shown placed in the back of a human hand  900 . The standard catheter  712  is inserted in blood vessel  904 . Wrist  902  is shown bent in a manner that normally obstructs the flow of fluids from IV tubing  906  through catheter  712 . Intraluminal cannula  128  has been inserted through catheter  712  and passed beyond the point of obstruction at wrist  902 . 
     From the proceeding description of the construction of the cannula placement apparatus and specialized cannula, those skilled in the art will appreciate that variations of construction may be employed without departing from the teachings of the present disclosure, and any such varied embodiments are considered within the scope of this disclosure and the claims appended hereto.