A method for priming at least a portion of the kit with previously-collected blood or blood product prior to flowing the patients whole blood into the inlet line of the kit, as part of a therapeutic procedure in which a selected blood component is separated from a patients whole blood, and replaced with a previously-collected blood component, the procedure utilizing a durable separation device comprising a programmable controller including a user interface and a single-use kit, the kit comprising an inlet line, a separation chamber, and a return pathway. The operator enters into the controller the hematocrit value of the previously-collected blood or blood product, then enters into the controller in response to a prompt by the controller a target hematocrit value for the previously-collected blood or blood product when residing in the kit. The operator then enters into the controller in response to a prompt by the controller an identification of the portion of the kit to be primed with the previously-collected blood or blood product. The identified portion of the kit is automatically primed with the previously-collected blood or blood product. The patient is then to be connected to the inlet line of the kit in response to a prompt from the controller after completion of the selected priming and the therapeutic procedure is commenced, including, but not limited to, tracking fluid balance and hematocrit of the patient, accounting only for the volume drawn from and to be returned to the patient.
