A flush syringe assembly comprising: a barrel including a 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 a tip extending distally therefrom having a passageway therethrough in fluid communication with said chamber; and an elongate plunger rod disposed within the barrel, the plunger rod comprising a distal portion and a proximal portion, the plunger rod further comprising a distal end including a stopper having a distal face and a proximal end; characterized by one or more pulsing elements disposed on the plunger rod and the inside surface of the barrel that provide increased mechanical interference between the plunger rod and barrel, the one or more pulsing elements being rotatable to create pulsatile movement or continuous and unimpeded movement of the plunger rod within the barrel, the one or more pulsing elements include at least one extension disposed on the outside surface of the plunger rod, the extension extending radially outwardly toward the inside surface of the barrel; and at least one protrusion disposed on the inside surface of the barrel the protrusion extending radially inwardly toward the outside surface of the plunger rod, the at least one extension cooperating with the at least one protrusion to increase the interference between the plunger rod and the barrel to require an increased mechanical force to be applied to advance the plunger rod distally into the barrel from the open proximal end of the barrel to the distal wall of the barrel, the plunger rod is rotatable within the barrel to create pulsatile movement or to create continuous and unimpeded movement of the plunger rod within the barrel, and, in use, movement of the plunger rod in the distal direction creates an interference with the barrel and alignment of the at least one extension and the at least one protrusion results in variations in the interference between the plunger rod and barrel that requires an increase in mechanical force applied to the plunger rod in the distal or proximal direction to overcome the interference. a barrel including a 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 a tip extending distally therefrom having a passageway therethrough in fluid communication with said chamber; and an elongate plunger rod disposed within the barrel, the plunger rod comprising a distal portion and a proximal portion, the plunger rod further comprising a distal end including a stopper having a distal face and a proximal end; one or more pulsing elements disposed on the plunger rod and the inside surface of the barrel that provide increased mechanical interference between the plunger rod and barrel, the one or more pulsing elements being rotatable to create pulsatile movement or continuous and unimpeded movement of the plunger rod within the barrel, the one or more pulsing elements include at least one extension disposed on the outside surface of the plunger rod, the extension extending radially outwardly toward the inside surface of the barrel; and at least one protrusion disposed on the inside surface of the barrel the protrusion extending radially inwardly toward the outside surface of the plunger rod, the at least one extension cooperating with the at least one protrusion to increase the interference between the plunger rod and the barrel to require an increased mechanical force to be applied to advance the plunger rod distally into the barrel from the open proximal end of the barrel to the distal wall of the barrel, the plunger rod is rotatable within the barrel to create pulsatile movement or to create continuous and unimpeded movement of the plunger rod within the barrel, and, in use, movement of the plunger rod in the distal direction creates an interference with the barrel and alignment of the at least one extension and the at least one protrusion results in variations in the interference between the plunger rod and barrel that requires an increase in mechanical force applied to the plunger rod in the distal or proximal direction to overcome the interference.