Abstract: An open, volumetrically regulated patient fluid management system and method are disclosed. Fresh fluid is metered into a patient fluid exchange unit by a first metering device and spent fluid is drawn out by a pump. A back pressure regulator is provided across the pump to maintain its output pressure at a constant value. To the output of the pump are connected a second metering device and an open drain circuit. The second metering device meters out of the patient fluid exchange unit a predetermined quantity of spent fluid. The open drain circuit drains any fluid pumped by the pump, but not removed by the second metering device, to a drain open to atmospheric pressure. When the dialysis unit is deenergized, fluid in the dialyzer returns rapidly to atmospheric pressure by virtue of the open path through the open drain circuit, pump and back pressure regulator to the dialyzer.

Abstract: Hemodialysis ultrafiltration apparatus comprises a dialyzer. A closed circuit is provided for supplying fresh dialysate to and for removing spent dialysate from the dialyzer. Blood is supplied to and removed from the dialyzer. The closed circuit for supplying fresh dialysate and removing spent dialysate is apportioned into below mean dialyzer blood pressure and above atmospheric pressure sections, with the dialyzer being positioned in the below mean dialyzer blood pressure section. A mechanism is provided for controlling the pressure of fresh dialysate introduced into the below mean dialyzer blood pressure section to substantially match the pressure on the dialysate side of the dialyzer. A mechanism is provided for controlling the above atmospheric pressure portion of the spent dialysate circuit.

Abstract: Hemodialysis ultrafiltration apparatus comprises a dialyzer. A closed circuit is provided for supplying fresh dialysate to and for removing spent dialysate from the dialyzer. Blood is supplied to and removed from the dialyzer. The closed circuit for supplying fresh dialysate and removing spent dialysate is apportioned into below mean dialyzer blood pressure and above atmospheric pressure sections, with the dialyzer being positioned in the below mean dialyzer blood pressure section. A mechanism is provided for controlling the pressure of fresh dialysate introduced into the below mean dialyzer blood pressure section to substantially match the pressure on the dialysate side of the dialyzer. A mechanism is provided for controlling the above atmospheric pressure portion of the spent dialysate circuit.