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A positive displacement flush syringe includes a barrel having a chamber for retaining fluid and an elongate tip extending distally therefrom having a passageway therethrough in fluid communication with the chamber. A plunger having a stopper which is slidably positioned in said chamber for driving

A positive displacement flush syringe includes a barrel having a chamber for retaining fluid and an elongate tip extending distally therefrom having a passageway therethrough in fluid communication with the chamber. A plunger having a stopper which is slidably positioned in said chamber for driving fluid out of the chamber by movement of the stopper relative to the barrel is provided. Further, structure is provided to move fluid distally in the passageway after fluid has been delivered from the chamber and the stopper is in contact with the distal wall of the chamber.

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1. An I.V. flush syringe assembly comprising: a barrel including a cylindrical side wall 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, the elongate tip defining a passa

1. An I.V. flush syringe assembly comprising: a barrel including a cylindrical side wall 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, the elongate tip defining a passageway therethrough in fluid communication with the chamber; anda plunger including an elongate body portion extending outwardly from the open proximal end of the barrel, a proximal end, a distal end having a discontinuity and a spring disposed at the distal end;a resilient 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;wherein the stopper includes a distal end having a distal surface including a distally directed projection shaped to fit in the chamber of the barrel, a first discontinuity and a second discontinuity located distally from the first discontinuity and a proximal end defining a cavity therein;wherein the distal end of the plunger is connected to the stopper by a complementary detent structure defining a first detent position wherein the plunger discontinuity engages the first discontinuity and a second detent position wherein the plunger discontinuity engages the second discontinuity;wherein the detent structure is configured so that a distally directed force applied to the plunger after fluid has been delivered from the chamber causes the spring to compress and the plunger to move distally with respect to the stopper from the first detent position to the second detent position so a distal tip on the distal end of the plunger contacts the inside surface of the stopper forcing the distally directed projection on the distal end of the stopper into the passageway of the elongate tip to move fluid distally in the passageway after fluid has been delivered from the chamber and the stopper is in contact with the distal wall. 2. The syringe assembly of claim 1 wherein the inside surface of the stopper includes a proximally directed protuberance configured to contact the distal tip of the plunger when the plunger and the stopper are engaged in the second detent position. 3. The syringe assembly of claim 1 wherein the stopper includes a conically shaped distal surface and the inside surface of the barrel at the distal wall being conically shaped wherein the total included angle of the inside surface of the barrel at the distal wall is greater than the total included angle of the stopper distal surface. 4. The syringe assembly of claim 1 wherein the discontinuity on the distal end of the plunger includes a raised projection. 5. The syringe assembly of claim 4 wherein the raised projection is an annular ring. 6. The syringe assembly of claim 5 wherein the first discontinuity is a recess for containing the raised projection on the distal end of the plunger. 7. The syringe assembly of claim 6 wherein the recess is annularly shaped. 8. The syringe assembly of claim 1 including flush solution in the chamber. 9. The syringe assembly of claim 8 further including a tip cap releasably connected to the tip of the syringe barrel for sealing the passageway. 10. The syringe assembly of claim 9 wherein the flush solution is selected from the group consisting of saline flush solution and heparin lock flush solution. 11. The syringe assembly of claim 1 wherein the stopper is made of material selected from the list consisting of thermoplastic elastomers, natural rubber, synthetic rubber, thermoplastic materials and combinations thereof. 12. The syringe assembly of claim 1 further comprising a needle assembly including 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 needle assembly being removably attached to the tip of the barrel through engagement of the tip to the cavity so that the lumen is in fluid communication with the chamber. 13. An I.V. flush syringe assembly comprising: a barrel including a cylindrical side wall with 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, the elongate tip defining a passageway therethrough in fluid communication with the chamber;wherein the distal wall of the barrel defines a total included angle A;a plunger including an elongate body portion extending outwardly from the open proximal end of the barrel, a proximal end, a distal end having a discontinuity, a distal tip and a spring positioned between the distal tip and the distal end;a resilient stopper operably engaged to the plunger and 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;wherein the stopper includes a distal end having a distal surface including a distally directed projection shaped to fit in the chamber of the barrel, a first discontinuity and a second discontinuity located distally from the first discontinuity and a proximal end defining a cavity therein;wherein the distal end of the stopper defines a total included angle B;wherein the distal end of the plunger is connected to the stopper by a complementary detent structure defining a first detent position in which the plunger discontinuity engages the first discontinuity and a second detent position in which the plunger discontinuity engages the second discontinuity;wherein the detent structure is configured so that a distally directed force applied to the plunger after fluid has been delivered from the chamber causes the spring to compress and the plunger to move distally with respect to the stopper from the first detent position to the second detent position so a distal tip on the distal end of the plunger contacts the inside surface of the stopper forcing the distally directed projection on the distal end of the stopper into the passageway of the elongate tip to move fluid distally in the passageway after fluid has been delivered from the chamber and the stopper is in contact with the distal wall; andwherein the total included angle A is greater than the total included angle B. 14. The syringe assembly of claim 13 wherein the inside surface of the stopper includes a proximally directed protuberance configured to contact the distal tip of the plunger when the plunger and the stopper are engaged in the second detent position. 15. The syringe assembly of claim 14 wherein the discontinuity on the distal end of the plunger includes a raised projection formed by an annular ring. 16. The syringe assembly of claim 15 wherein the first discontinuity is a recess for containing the raised projection on the distal end of the plunger. 17. The syringe assembly of claim 16 wherein the recess is annularly shaped. 18. The syringe assembly of claim 17 including flush solution in the chamber. 19. The syringe assembly of claim 18 wherein the flush solution is selected from the group consisting of saline flush solution and heparin lock flush solution. 20. The syringe assembly of claim 19 further comprising a needle assembly including 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 needle assembly being removably attached to the tip of the barrel through engagement of the tip to the cavity so that the lumen is in fluid communication with the chamber.