The venous reservoir is omitted from an extracorporeal blood circuit system by substituting a blood reservoir in parallel with the arterial pump. The reservoir has an inlet connected to the outlet of the pump and an outlet connected to the inlet of the pump. At least three blood flow paths can be configured. A main path has the inlet and outlet of the reservoir blocked while pumped blood flows through the venous cannula, the oxygenator, and the arterial cannula. An accumulator path has the inlet to the oxygenator and the outlet of the reservoir blocked while blood flows through the venous cannula and the inlet to the reservoir. A discharge path has the inlet of the reservoir blocked while the outlet is open whereby blood from the reservoir flows into the oxygenator. In a fourth configuration, the ECC fluid can be recovered in the reservoir and hemoconcentrated for autologous transfusion.
