Device and technique for extracorporeal blood volume sequestration during hemodialysis

We developed a technique for a controlled and reversible volume perturbation of the cardiovascular system during hemodialysis. The capacitance of the extracorporeal circulation was modified by an expansion bag, using separate filling and draining lines connected to postpump and prepump sections of the arterial line segment, respectively. The connection to this bag was manually operated by three-way valves. The volume sequestered into the blood bag was continuously measured by a weighing scale. Filling and draining of the expansion bag was measured in eight patients in two subsequent routine dialysis treatments. Four volume shifts were done in each treatment. Filling and draining rates and times depended on extracorporeal blood flow as well as arterial and venous line pressures. Bag inflow and outflow volumes were 215.8 +/- 28.5 ml/min and 221.6 +/- 37.0 ml/min, respectively. The total volume transiently sequestered in the bag was 479.8 +/- 61.3 ml. The duration of the whole test was 4.5 +/- 0.8 minutes. During filling, residual dialyzer blood flow was transiently reduced to 58.5 +/- 21.6 ml/min and the filtration fraction reached 30 +/- 13%. There were no adverse events such as clotting in the blood bag or in the dialyzer. The method provides rapid, reversible, and safe volume shifts between the patient and the extracorporeal circulation with the potential to elicit a hemodynamic response for characterizing the patient during each dialysis treatment.