A medical pump apparatus including an internally sterile pumping chamber having a flexible diaphragm forming a wall portion and a drive rod extending through the diaphragm in a rotating vane disposed within the pumping chamber. A motor rotates a revolving hook which engages the drive rod to drive the vane within the pumping unit. The pumping chamber is isolated from the motor by the fluidtight attachment of the drive rod through the flexible diaphragm. Fluid is pumped into the inlet of pumping chamber through the hollow shaft of the vane and out through a fluid conduit of the vane, subsequently out the outlet of the pumping chamber.