Abstract:
A syringe tip for generating nonlaminar spiral flow to flush indwelling vascular access devices, eliminating the need for start-stop flushing. The nonlaminar spiral flow is generated by spiral elements on the inner surface of the syringe tip.

Description:
This application is a division of U.S. patent application Ser. No. 09/939,381, filed Aug. 24, 2001, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to devices for flushing indwelling vascular catheters, and more particularly to syringe tips that create vortex or helical flow of flushing media to dislodge accumulated debris from the tip of the indwelling catheter. 
     2. Background of the Invention 
     Vascular indwelling catheters or vascular access devices are used to inject medication, withdraw blood, or monitor functions within the blood vessel such as blood pressure and heart rate. The operation of catheters is often compromised or completely prevented by the occurrence of thrombus formation. Thrombosis is the development of a blood clot within a vessel and/or a catheter. Immediately after a catheter or other vascular access device is inserted into a blood vessel, a coagulation cascade begins. Platelets and white blood cells attach to the catheter surfaces. As the platelets begin to aggregate, fibrin strands form to cover the foreign object. The types of thrombotic occlusions that occur in indwelling catheters are intraluminal thrombus, mural thrombus, fibrin tail or flap, and fibrin sheath or sleeve. 
     Intraluminal thrombi develop when blood enters the lumen of the catheter. Mural thrombi develop when the tip of the catheter causes injury to the inner vascular wall. A mural thrombus is formed when the fibrin from the vessel wall injury attaches to the fibrin building on the catheter surface. The adherence of fibrin, blood cells, and platelets to the end or tip of a catheter is called a fibrin tail or flap. As the tail or flap attached to the catheter sticks out into the blood stream, more cells and other blood products become deposited onto the tail. A persistent withdrawal occlusion is caused by the fibrin flap acting as a one-way valve, allowing the catheter to flush easily, but not allowing blood to be aspirated. A fibrin sheath or sleeve is formed from adherence of fibrin to the external surfaces of the catheter. The sleeve may cover the terminal tip of the catheter, and extend up the entire length of the catheter, also causing persistent withdrawal occlusion. 
     The purpose of flushing is to clean the accumulated residue from the internal lumen of the catheter or from the catheter tip. The common practice is to create a turbulent flow during flushing to promote a “scrubbing” effect in the lumen and at the tip of the catheter. Turbulent flow is usually provided by pulsative flushing. This technique utilizes a “start-stop” method that produces turbulence within the catheter lumen, reducing the potential for material to adhere to the catheter. 
     This “start-stop” turbulent positive pressure flushing is difficult to perform effectively and must be performed in narrowly prescribed ways. Notwithstanding training and practice, the turbulence generated is random and dependent upon the internal diameter of the catheter and rate of the flow of the flushing media, in addition to other factors, such as the time interval between starting and stopping. Furthermore, because the turbulence by this method is generally not uniform across the internal diameter of the catheter, turbulent forces upon opposing internal walls of the catheter may be unequal, producing a whip-like effect or oscillations at the catheter tip. If the catheter tip moves with force, it can cause damage to the inner lining of the blood vessel wall leading to increased thrombus formation. 
     The present invention overcomes these problems of the relatively unpredictable results of start-stop flushing by providing a syringe tip that produces uniform predictable nonlaminar flow. This flow is in the form of a controlled uniform helical spiral or vortex flow, which effectively scrubs the debris from the lumens and tips of indwelling vascular catheters and related devices, avoiding the necessity of using the relatively crude and uncontrolled method of pulsatile flushing. 
     SUMMARY OF THE INVENTION 
     The present invention is a syringe tip that produces a nonlaminar helical or spiral flow of liquid as the liquid is injected through the tip with a syringe. When the syringe tip is inserted into the proximal end of a catheter, the spiral flow is transmitted along the length of the catheter whereby the spiral flow can scrub or dislodge blood deposits from the catheter lumen and catheter tip. The spiral or helical flow is produced by spiral elements on and/or in the inner wall or in the lumen of the syringe tip. The spiral flow created by the syringe tip makes the syringe tip useful for flushing vascular catheters without having to use the less reliable method of high pressure start-stop flushing. 
     An advantage of the present invention is that it provides a syringe tip that creates nonlaminar spiral flow of catheter flushing media. 
     Another advantage of the present invention is that it can be used to dislodge blood-derived deposits from the catheter lumen and/or catheter tip. 
     Another advantage of the present invention is that it produces effective flushing of vascular catheters without producing a random turbulent flow, thereby avoiding oscillations at the catheter tip which can damage the inner wall of a blood vessel. 
     Another advantage of the present invention is that the syringe tip can be permanently or removably attached to a syringe. 
     Another advantage of the present invention is that it requires no special training or practice for use in flushing vascular catheters. 
     Another advantage of the present invention is that it is simple and inexpensive to construct. 
     Another advantage of the present invention is it&#39;s dual function: flushing vascular catheters and use in all other nonvascular syringe applications. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a typical syringe used for flushing catheters but having the syringe tip of the present invention, illustrating the helical or spiral elements on the inner surface of the syringe tip. 
     FIG. 2 shows a typical catheter inserted into a vein with a removable syringe tip inserted into the proximal end of the catheter. 
     FIG. 3 illustrates the creation of helical or spiral flows of fluid as it is injected through the syringe tip of the present invention. 
     FIGS. 4 a  and  4   b  show a catheter with blood-derived deposits at the distal tip and how flushing media is flushed through the syringe tip of the present invention and flows in a controlled spiral or helical fashion down the length of the catheter to dislodge the blood-derived deposits. 
     FIGS. 5 a  and  5   b  show enlarged frontal and side views of the syringe tip of the present invention illustrating the spiral or helical protruding elements on the inner surface of the syringe tip. FIG. 5 c  shows a view of the internal lumen of the syringe tip from the distal end. 
     FIGS. 6 a  and  6   b  show views of syringe tips with two or three protruding spiral elements on the inner surface. 
     FIGS. 7 a,    7   b,  and  7   c  show views of syringe tips with one, two, or three helical or spiral depressions on the inner surface. 
     FIGS. 8 a,    8   b,    8   c,  and  8   d  show views of syringe tips with a star shaped bore, a twisting bisection luminal inclusion, a twisting triform luminal inclusion, and a quadraform luminal inclusion. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     While the following description details the preferred embodiments of the present invention, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced in various ways. 
     FIG. 1 shows a typical syringe  10  known in the art, which can be used for flushing. The syringe has a cylindrical barrel  11  having a distal end  12  and a proximal end  13 . The syringe has a plunger  14  with a piston head  15  which forces liquid out of distal end  12 . Many syringes of this type have luer fittings  16  which contain syringe tip  17 . Syringe tip  17  of the present invention is shown in an enlarged view to illustrate the spiral elements  65  on inner surface  62 . The syringe tip  17  of the present invention has a circular inner bore defined by inner surface  62  and an outer surface  63 . The syringe tip of the present invention can be constructed as a permanent tip of a syringe or can be constructed as an adaptor to fit over the standard tip of a syringe. 
     FIG. 2 shows a typical vascular catheter  30  known in the art inserted in an arm vein  31 . The catheter has a proximal end  32  for insertion of a syringe tip  17  and a distal end or tip  33 , which resides in the lumen of the blood vessel. Syringe tip  17  is shown in this figure as an adapter which can fit over a standard syringe tip, i.e., removably attachable to a syringe tip. 
     FIG. 3 shows flushing liquid  40  being injected out of syringe tip  17  in a spiral  41  fashion. In this figure, syringe tip  17  is shown as part of the syringe barrel  11  at distal end  12  within luer fitting  16 , i.e. permanently attached. 
     FIG. 4 a  shows syringe tip  17  of the present invention inserted into the proximal end  32  of catheter  30 . At distal end  33  of catheter  30  is shown blood-derived debris  50 , which typically forms, by thrombosis at catheter tips and associated lumens after insertion into the lumen of a blood vessel. Syringe tip  17  is shown in the adapter configuration. Lip  51  of adapter  17  is constructed to fit tightly and removably over a standard syringe tip or any other device for infusing fluid such as needles, catheters, tubes, and the like. Although lip  51  is depicted as a simple annular fitting, it may be constructed in many other configurations including luer-lock fittings, needle-like fittings, and the like. 
     FIG. 4 b  shows flushing liquid  40  being injected out of syringe tip  17  through catheter  30  and out through catheter tip  33 . Blood-derived debris  50  is shown as dislodged by the spiral or helical flow  41  of flushing liquid  40 . Syringe tip  17  is shown as an integral permanent part of luer fitting  16  at the distal end  12  of syringe  11 . With the syringe tip of the present invention it is possible to flush the catheter effectively with a single uninterrupted injection of flushing fluid and the start-stop procedure is not required. 
     FIG. 5 a  shows a perspective view from distal end  61  of syringe tip  17 . Syringe tip  17  has a proximal end  60  which will fit onto distal end  12  of a syringe, either permanently or reversibly by methods known in the art. Syringe tip  17  has a distal end  61  through which flushing fluid  40  is ejected. Syringe tip  17  has an inner surface  62 , an outer surface  63 , and a circular lumen  64 . Outer surface  63  may be of any suitable shape; preferably circular, such that syringe tip  17  is shaped like a cylinder. The inner surface  62  of syringe tip  17  has a spiral or helical element  65  which begins at a point that is flush with proximal end  60  and ends at a point that is flush with distal end  61 . This spiral element  65  twists 360E as it courses evenly and smoothly from the proximal end  60  to the distal end  61 . As flushing fluid  40  is pushed through distal end  61 , flushing fluid  40  is forced into a rotating, spiral, or helical flow  41 . FIG. 5 a  shows a single spiral element  65 , which protrudes from inner surface  62  into lumen  64  of syringe tip  17 . 
     FIG. 5 b  shows a side view of syringe tip  17 , illustrating how spiral element  65  twists 360E as it courses evenly and smoothly from proximal end  60  to distal end  61 . FIG. 5 c  shows a view of the internal lumen  64  of syringe tip  17  from distal end  61 . 
     FIGS. 6 a  and  6   b  show views of syringe tip  17  with two ( 65   a, b ) or three ( 65   c, d, e ) spiral elements  65  on the inner surface  62 . These spiral elements also protrude from inner surface  62  into lumen  64 . Spiral elements  65  on inner surface  62  may also be indentations into inner surface  62 . Spiral elements that are indentations are depicted in FIGS. 7 a,    7   b,  and  7   c  where FIG. 7 a  shows a single spiral element  65 , FIG. 7 b  shows two spiral elements,  65   a  and  65   b,  and FIG. 7 c  shows three spiral elements,  65   c,    65   d,  and  65   e.    
     In the examples shown in FIGS. 5 a - 7   b  the spiral elements  65  that are protrusions from the inner surface  62  into lumen  64  or indentations into inner surface  62  or a combination thereof, can be round, square, triangular, or a combination thereof, or any other suitable shape. The spiral elements may form less or more than a complete 360E turn. For example, the spirals may make only a one eighth (45E) turn or several complete turns. 
     FIGS. 8 a,    8   b,    8   c  and  8   d  show alternate embodiments of the present invention. FIG. 8 a  shows syringe tip  17  wherein lumen  64  is in the shape of a five-point star which, twists or spirals from proximal end  60  to distal end  61 . FIG. 8 b  shows syringe tip  17  with a bisection luminal inclusion  70  having a 45E twist from proximal end  60  to distal end  61 . Luminal bisection  70  may also have a central discharge tube  71 . FIG. 8 c  shows syringe tip  17  with a triform luminal  80  inclusion with a 45E degree twist from proximal end  60  to distal end  61 . Triform luminal inclusion may also have central discharge tube  71 . FIG. 8 d  show syringe tip  17  with a quadriform luminal inclusion  90  with a 45E twist and center discharge tube  71 . These inclusions may also make one or more complete turns. 
     The foregoing description has been limited to specific embodiments of this invention. It will be apparent, however, that variations and modifications may be made by those skilled in the art to the disclosed embodiments of the invention, with the attainment of some or all of its advantages and without departing from the spirit and scope of the present invention. For example, the syringe tip of the present invention may be used in a variety of lengths and diameters and with other flushing devices besides syringes. The syringe tip may be made of plastic, metal, or glass. The syringe tip may be used to flush any type of indwelling tube. The syringe tip may have any external shape as desired. 
     It will be understood that various changes in the details, materials, and arrangements of the parts which have been described and illustrated above in order to explain the nature of this invention may be made by those skilled in the art without departing from the principle and scope of the invention as recited in the following claims.