Medical fluid delivery sets and related systems and methods

A medical fluid pumping system, comprising:

• a medical fluid pumping machine comprising a drive mechanism;
• and
• a medical fluid delivery set comprising a syringe that can be operatively connected to the drive mechanism, the syringe comprising
• a medical fluid containment cylinder;
• and
• a plunger assembly that can be axially moved relative to the medical fluid containment cylinder, the plunger assembly comprising
• an inner plunger shaft comprising a seal that is slidably disposed within the medical fluid containment cylinder such that a substantially liquid-tight seal is maintained between the seal of the inner plunger shaft and an inner surface of the medical fluid containment cylinder as the plunger slides axially within the medical fluid containment cylinder, the seal of the shaft plunger and the medical fluid containment cylinder cooperating to at least partially define a fluid pump chamber, and
• an outer plunger shaft that at least partially surrounds the inner plunger shaft to form a space between an outer surface of the inner plunger shaft and an inner surface of the outer plunger shaft, the space being sized to receive a wall of the medical fluid containment cylinder therein,
• wherein, when the syringe of the medical fluid delivery set is operatively engaged with the drive mechanism, the drive mechanism can be operated to axially displace the plunger shaft assembly relative to the medical fluid containment cylinder to force fluid out of the fluid pump chamber and to draw fluid into the fluid pump chamber.