Abstract:
An I.V. flush syringe assembly includes a barrel having an inside surface defining a chamber for retaining fluid, an open proximal end and a distal end with a passageway therethrough in fluid communication with the chamber. An elongate plunger having a proximal end, a distal end and a flexible stopper is slidably positioned in fluid-tight engagement with the inside surface of the barrel for drawing fluid into and out of the chamber by movement of the stopper relative to the barrel. The barrel includes anti-reflux structure for holding said stopper in a partially deflected position after fluid has been delivered from the chamber and the stopper is being force against the distal end of the chamber.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a divisional of pending U.S. application Ser. No. 10/530,817, filed Apr. 8, 2005, which is the National Phase entry of International Application No. PCT/US03/29918, filed Sep. 23, 2003, which claims priority from U.S. Provisional Application number 60/418,053, filed Oct. 11, 2002. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to syringe assemblies and particularly to syringe assemblies for use in I.V. flush procedures. 
         [0003]    An I.V. catheter is a commonly used therapeutic device. Many patients, in accordance with their therapy, have an I.V. catheter connected to a vein ready for use in various procedures or in fluid communication with an I.V. system for infusing liquids and medication. Many I.V. sets have I.V. ports which are in fluid communication with a catheter and allow access for the purpose of injecting medication into the patient, and for use in flushing techniques to maintain catheter integrity. Healthcare facilities have flushing protocols which depend on the amount of time the catheter will remain in the patient and the type of catheter being used. For example, a peripherally inserted central catheter (PICC) is a long flexible catheter, which is typically inserted into the central venous system (optimally with the tip terminating in the superior vena cava) via the superficial veins of the antecubital fossa. PICC lines are designed for use when intermediate or long-term therapy is prescribed. 
         [0004]    These catheter lines must be periodically flushed with saline flush solution and/or heparin lock flush solution depending on the protocol. Among other things, flushing saline solution removes blood from the catheter and heparin helps prevent the formation of future blood clots. The most common I.V. ports are covered by pierceable septums or pre-slit septums and are known in the art and sometimes referred to as “PRN” from the Latin pro re nata meaning “as the need arises”. The septum is preferably made of rubber or another elastomeric material which permits insertion of a sharp needle cannula in order to infuse fluids into or to withdraw fluids from the catheter. Upon withdrawal of the needle cannula the septum seals itself. Ports having pre-slit septums are used with blunt cannula. Typically, the blunt cannula is attached to a syringe and the syringe is moved to place a gentle pressure on the pre-slit septum which is forced open by the blunt cannula to establish fluid communication. Also, some I.V. sets have access valves which are responsive to the frusto-conically shaped tip of a syringe barrel for allowing fluid communication between the interior of the syringe and the catheter. 
         [0005]    Catheters are flushed using syringe assemblies filled with various fluids. In some cases, different fluids are injected sequentially in accordance with the protocol. For example, a saline solution followed by an anticoagulant such as heparin. The size of the syringe used to flush I.V. lines varies by various factors including the size and length of the catheter. Typically syringes of 1 ml, 3 ml, 5 ml and 10 ml volume are used. 
         [0006]    It is important in the flush procedure not to draw blood back into the catheter where it can clot and seal the catheter, commonly referred to as “reflux”. In order to prevent blood reflux into the catheter the user is encouraged to maintain a positive pressure in the line during the flush procedure. This may involve slowly withdrawing the syringe and cannula from the I.V. port while still applying pressure to the syringe plunger rod during the flush procedure. When using a syringe with an elastomeric stopper, the stopper is often compressed when it contacts the distal end of the syringe barrel at the completion of the flush procedure. When a user relieves the pressure to the plunger after the flush procedure is completed, the stopper will expand back to its normal size drawing liquid from the catheter into the syringe barrel. This is undesirable, since it can cause blood to enter the catheter at the catheter distal end (reflux). 
         [0007]    Therefore there is a need for simple, straight forward easy-to-manufacture syringe assemblies which reduce or eliminate reflux of blood into the catheter during and after the flushing procedure has occurred without changing flush protocols and procedures. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention is directed to a syringe having a compressible stopper. The stopper is held in position at the distal end of the barrel at the completion of the flush procedure. The stopper is held in a compressed form, by structure resisting its expansion. Since expansion of the stopper is substantially prevented at the completion of the flush procedure, reflux of blood into the catheter is minimized and/or eliminated. 
         [0009]    An I.V. flush syringe assembly includes a barrel having an inside surface defining a chamber for retaining fluid, an open proximal end and a distal end including a distal wall with an elongate tip extending distally therefrom having a passageway therethrough in fluid communication with the chamber. A plunger including an elongate body portion having a proximal end, a distal end with a flexible stopper slidably positioned in fluid-tight engagement with the inside surface of the barrel for drawing fluid into and driving fluid out of the chamber by movement of the stopper relative to the barrel. The elongate body portion of the plunger extends outwardly from the open proximal end of the barrel. The I.V. flush syringe includes anti-reflux means for holding the stopper in a partially deflected position when fluid has been delivered from the chamber and the stopper is in contact with the distal wall of the barrel. Such anti-reflux means provide structure on the stopper and/or barrel to hold the stopper in a partially deflected position to minimize or eliminate reflux by preventing the stopper from moving proximally and drawing blood into the catheter. 
         [0010]    The anti-reflux structure can include the stopper having an outwardly projecting rib and the inside surface of the barrel having a recess for receiving the rib when the stopper is in contact with and partially compressed against the distal wall of the barrel. The projection on the stopper may include one or more annular ribs and the recess in the barrel may include one or more annular grooves for accepting the ribs. 
         [0011]    The anti-reflux structure may also include a contact area on the inside surface of the barrel at the distal end of the barrel. The contact area has a higher coefficient of friction than the inside surface of the barrel which is outside of the contact area. The contact area is for engaging the stopper when the stopper is in contact and compressed against the distal wall of the barrel. The contact area may include a plurality of annular deformations. These deformations may be projections on the inside surface of the barrel. 
         [0012]    A method of flushing a catheter of the present invention comprises the steps of providing a syringe assembly including a barrel having an inside surface defining a chamber for retaining fluid, an open proximal end and a distal end including a distal wall with an elongate tip extending distally therefrom having a passageway therethrough in fluid communication with the chamber, a plunger including an elongate body portion having a proximal end, a distal end and a flexible stopper slidably positioned in fluid-tight engagement with the inside surface of the barrel for drawing fluid into and driving fluid out of the chamber by movement of the stopper relative to the barrel, the elongate body portion of the plunger extending outwardly from the open proximal end of the barrel, a quantity of flush solution in the chamber, and anti-reflux means for holding the stopper in a partially deflected position when the flush solution has been delivered from said chamber and the stopper is in contact with the distal wall. The method further includes providing a catheter having a proximal end, a distal end and a passageway therethrough and a housing having a hollow interior connected to the catheter and in fluid communication with the passageway, the housing having an access valve for allowing fluid communication with the hollow interior. The method further includes the additional steps of: placing the distal end of the catheter in a blood vessel; engaging the elongate tip of the barrel with the access valve so that the passageway of the syringe barrel is in fluid communication with the hollow interior of the housing; applying force to the plunger to move the stopper in a distal direction with respect to the barrel so that the flush solution in the chamber flows through the passageway into the hollow chamber of the housing and through the passageway of the catheter; and continue applying force to the plunger until the stopper contacts and presses against the distal wall of the barrel and is held in a partially deflected position by anti-reflux means. 
         [0013]    An alternate method includes the step of attaching a needle assembly to the elongate tip of the barrel. The needle assembly includes a cannula having a proximal end, a distal end and a lumen therethrough and a hub having an open proximal end containing a cavity and a distal end attached to the proximal end of the cannula so that the lumen is in fluid communication with the cavity. The attachment of the needle assembly to the barrel is through frictional engagement between the cavity in the hub and the elongate tip. This alternative method is used with a catheter having a proximal end, a distal end and a passageway therethrough and a housing having a hollow interior connected to the catheter and in fluid communication with the passageway of the catheter. The housing further includes a septum for allowing fluid communication with the hollow interior. Fluid communication is established by forcing the distal end of the cannula through the septum so that the lumen of the cannula is in fluid communication with the hollow interior of the housing. Also, the cannula may be permanently attached to the needle tip without the use of a hub. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a perspective view of a syringe assembly according to one embodiment of the invention. 
           [0015]      FIG. 2  is a partially cross-sectioned side-elevational view of the syringe of  FIG. 1  with a needle assembly attached. 
           [0016]      FIG. 3  is an enlarged partial cross-sectional side elevation view of the distal end of the syringe assembly of  FIG. 2 . 
           [0017]      FIG. 4  is an enlarged partial cross-sectional side-elevational view of the distal end of the syringe assembly of  FIG. 2  with the stopper positioned in its distal-most position after flush solution has been delivered. 
           [0018]      FIG. 5  is a side-elevational view illustrating the syringe assembly in use with a catheter injection site. 
           [0019]      FIG. 6  is a perspective view of a syringe assembly according to another embodiment of the invention. 
           [0020]      FIG. 7  is a partially cross-sectioned side-elevational view of the syringe assembly of  FIG. 6 . 
           [0021]      FIG. 8  is an enlarged cross-sectional side elevation view of the distal end of the syringe assembly of  FIG. 7 . 
           [0022]      FIG. 9  is an enlarged cross-sectional side elevational view of the distal end of the syringe assembly of  FIG. 7  with the stopper positioned in its distalmost position after flush solution has been delivered. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]      FIGS. 1-4  show a syringe  20  according to the present invention generally comprising a barrel  22 , a plunger  24 . Barrel  22  has a generally elongate body including an open proximal end  28  having finger grips  29 , a distal end  30  and an inside surface  32  defining a fluid chamber  34 . Inside surface  32  includes a generally annular recess  35  towards distal end  30 . Distal end  30  further includes a tip  36  having a passageway  38  in fluid communication with the chamber  34 . The distal end of barrel  22  preferably, but does not necessarily include a locking luer type collar  40  concentrically surrounding tip  36 . The inside surface of the collar includes at least one thread  41 . A cannula  26  includes a proximal end  42 , a distal end  44  and a lumen  46  therethrough. The distal end may include a sharp tip or a blunt tip  48  as shown. The cannula may be connected directly to the tip of the syringe barrel to establish fluid communication between the lumen and the chamber. Also, the cannula may be part of a needle assembly  27  including a hub  37  having an open proximal end  39  containing a cavity  43  and a distal end  45  attached to the proximal end of the cannula so that the lumen of the cannula is in fluid communication with the cavity. The cavity of the hub can be removably frictionally engaged to the tip of the barrel as illustrated in  FIGS. 2-4 . 
         [0024]    Plunger  24  includes a proximal end  50  having a flange  51  and a distal end  52 . A flexible stopper  54  is disposed on the distal end of plunger  24 . 
         [0025]    Stopper  54  includes at least one annular rib and in this embodiment includes a proximal rib  56 , a middle rib  58  and a distal rib  60 . The stopper comprises any flexible resilient material suitable for providing sealing characteristics while under compression. For example, the stopper may be made of thermoplastic elastomers, natural rubber, synthetic rubber and the like. 
         [0026]    In operation, the syringe  20  is connected to a hypodermic needle assembly and filled with flush solution using known methods. The flush solution may be any solution intended for flushing. It is preferred that the flush solution be selected from the group consisting of saline flush solution and heparin lock flush solution. These solutions are known in the art and readily available. An example of a saline flush solution is 0.9% Sodium Chloride USP. An example of a heparin lock flush solution is 0.9% sodium Chloride with 100 USP units of Heparin Sodium per ml or 10 USP units of Heparin Sodium per ml. The syringe with needle assembly attached is used to pierce the pierceable septum or a blunt cannula may be inserted into a pre-split septum of a vial containing flush solution and the flush solution is drawn into the syringe barrel by pulling plunger rod flange  51  in the proximal direction while holding barrel  22 , to draw fluid through the needle cannula into the fluid chamber  34 . 
         [0027]    Alternatively, the syringe may be filled with flush solution during the manufacturing of the syringe via a sterile filling method. Such prefilled syringes may be supplied with a tip cap, such as tip cap  23  releasably connected to tip  36  sealing passageway  38 . It is preferred that the tip cap is formed of material selected from the group of thermoplastic materials and elastomeric materials such as natural and synthetic rubber and thermoplastic elastomers. 
         [0028]    The syringe is now ready for use in flushing a catheter of an I.V. set. I.V. sets can be very complicated and may include multiple injection ports, a valve and/or other components. For the purpose of illustrating the present invention a simplified I.V. set  64  is illustrated in  FIG. 5 . I.V. set  64  comprises an I.V. site  65  which includes a housing  67  having a hollow interior  68  and a septum  69  at its proximal end. A catheter  70  having a conduit therethrough extends from the distal end of the housing. For this I.V. set, septum  69  is pre-slit for use with blunt cannula. The I.V. site may have a pierceable septum or a valve having structure for accepting the syringe barrel tip and being activated by the insertion of the tip to establish fluid communication with the catheter, such as the valve taught in U.S. Pat. No. 6,171,287. 
         [0029]    Blunt tip  48  of cannula  26  may be inserted through pre-split septum  69  of I.V. set  64 . Alternatively, a sharp tip of a needle cannula may be used to pierce a septum that it not pre-split, or the tip of the barrel may be engaged with a valve in the IV site. This establishes fluid communication between the interior  68  of the I.V. set and the chamber of the syringe barrel. The syringe barrel  22  is preferably held via finger grips  29 . Pressure is then applied to flange  51  of the plunger, for example by a thumb, in the distal direction. This moves the plunger  24  having the stopper  54  on its distal end, forcing the liquid such as flush solution  35  in the chamber  34  out of the chamber, through cannula  26  and into interior  68  of the I.V. set and then through catheter  70 . 
         [0030]    Referring to  FIG. 4 , the position of the plunger and stopper at the completion of the flush procedure is shown. As shown, the flange  51  does not contact the proximal end of the barrel at the completion of the flush procedure. Stopper  54  is now compressed. Distal rib  60  of the stopper is received within recess  35  of the barrel. Distal rib  60  fits within the recess  35  preferably via a friction fit or an interference fit. Thus, the stopper  54  is held in position at the distal end of the barrel  22 . This, in turn, holds the plunger  24  within the barrel. Therefore, reflux of liquid, including blood, into the catheter is prevented or minimized since the stopper is held in a compressed form and will not withdraw into the proximal direction. 
         [0031]    It is within the purview of the present invention to include additional recesses at the distal end of the barrel to receive the middle rib and the proximal rib. In such an embodiment, the recesses would be spaced apart in order to receive the ribs when the stopper is in a compressed form, typical at the end of the flush procedure. 
         [0032]      FIGS. 6-9  shown another embodiment of the invention where like elements are similarly numbered. In this embodiment of the invention, syringe assembly  120  includes plunger  24  and barrel  122 . A needle assembly  127  includes cannula  126  having a sharp distal end and hub  137  attached to distal end  130  of the barrel. Inside surface  132  of syringe barrel  122  includes a contact area  162 . The contact area may be, for example, one or more discontinuities, and/or a roughened portion of the inside surface. In operation, after the flush procedure has occurred, the stopper  54  is compressed at the distal end of the barrel within contact area  162  of the barrel. The contact area restrains the stopper from moving in the proximal direction. Therefore, stopper  54  is frictionally restrained by the contact area  162 , holding stopper  54  and plunger  24  within the barrel. The force required to overcome the friction between the stopper  54  and contact area  162  is more than the force required to overcome the friction between the stopper and the inside surface the barrel outside of the contact area. The force between the stopper and the contact area is sufficient to hold the stopper in a partially compressed state after the stopper contacts the distal end of the chamber. Thus, the stopper  54  is restrained from expanding out of its compressed form thereby preventing or minimizing reflux. 
         [0033]    Although the invention herein has been described with reference to particular embodiments it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention.