Blood volume regulation in donors undergoing intermittent-flow plasmapheresis involving a high extracorporeal blood...

Intermittent-flow plasmapheresis (IFP) often involves a large extracorporeal blood volume (ECV) of donors during donation. Depending on equipment and donor characteristics, ECV can exceed 20 percent of a donor's blood volume (BV). It was the aim of this study to delineate mechanisms of BV regulation associated with these volume shifts.

Parameters of BV regulation were recorded in 60 donors (30 men, 30 women) undergoing IFP, who were randomly selected after stratification for sex and BV. Shock index (SI), stroke volume (SV), cardiac index (CI), and thoracic fluid content (TFC) were determined at the beginning of the procedure and when maximum ECV (ECV(max)) was reached with noninvasive techniques. In a control investigation, donors were kept in reclined position for the duration of an IFP session without actually donating.

SI increased significantly during IFP (+0.18; p < 0.0001). SV decreased significantly (-14.3 mL/stroke; p < 0.0001). CI did not decrease significantly (-0.07 L/min/m(2) body surface area; p = 0.33). Preservation of CI was due to a significant rise in heart rate (+13.4 beats/min; p < 0.0001). TFC decreased significantly during IFP (-0.77 kOmega(-1); p < 0.0001), indicating the development of an intravascular volume deficit. The changes of SI, heart rate, and TFC weakly correlated with ECV(max).

The hemodynamic response during IFP is consistent with a hypovolemic challenge of the donors and is sufficient to maintain cardiac function. ECV(max) during donation does not reliably predict the degree of hypovolemic stress, as long as it remains below 20 percent. This might warrant reevaluation of collection limits based on ECV(max).