Measurement of rapidly and slowly circulating red cell volumes in hemorrhagic shock

¹ Department of Surgical Research, Michael Reese Hospital and Medical Center, Chicago, Illinois

Equilibration of injected Cr⁵¹-labeled red cells and Evan's blue dye (T-1824) in dogs occurred usually within 10 min in control conditions. Delayed equilibration of labeled red cells but not T-1824 was observed after hemorrhage and retransfusion of the withdrawn blood. Delayed equilibration of injected labeled red cells may be not only evidence for the presence of a slowly circulating red cell volume, but also may be used as a measurement of this volume. If a two-compartment system is assumed, then the initial volume of dilution of labeled red cells represents a relatively uniform mixing within a volume of rapidly circulating cells. The final volume of dilution of labeled red cells, beyond which no further dilution occurs, is assumed to represent total circulating red cell volume. The difference between these two volumes may represent a slowly circulating red cell volume. It is postulated that the so-called "sequestered" blood volume may, in part, be reflected in this slowly moving red cell volume. If so, the proposed approach under certain conditions may provide an index to its quantitation.