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 conically shaped distal wall with an elongate tip extending distally therefrom, the elongate tip defining a passageway therethrough in fluid communication with the chamber; 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; characterized in that the stopper including a proximal end defining a cavity therein defining an inside surface, and a conically shaped distal end having a distal surface, a first discontinuity and a second discontinuity located distally from the first discontinuity; 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 that a distal tip on the distal end of the plunger contacts the inside surface of the stopper forcing part of 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. 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 conically shaped distal wall with an elongate tip extending distally therefrom, the elongate tip defining a passageway therethrough in fluid communication with the chamber; 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; characterized in that the stopper including a proximal end defining a cavity therein defining an inside surface, and a conically shaped distal end having a distal surface, a first discontinuity and a second discontinuity located distally from the first discontinuity; 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 that a distal tip on the distal end of the plunger contacts the inside surface of the stopper forcing part of 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.