Blood volume changes in endotoxin shock.

Injection of E. coli endotoxin in dogs promotes hemodynamic changes in circulating blood volume and blood components. Adult mongrel dogs were given endotoxin and studied for 3 hours. Red-blood-cell (RBC) volume and whole-blood volume was measured using the Cr-51 RBC labeling method. Hematocrit and RBC counts were taken at various time periods. Whole-blood volume was not found to change significantly over the test period; however, plasma volume demonstrated a significant decrease by 60 minutes with a parallel increase in RBC volume. Hematocrit increased significantly by 60 minutes and continued its rise to a 30% increase at 3 hours. Circulating RBC counts demonstrated a 26% increase. RBC precursors such as reticulocytes and normoblasts were counted using standard microscopic methods and were observed to increase after injection of endotoxin. These data suggest that the increases in hemoconcentration after administration of endotoxin are caused not only by the loss of plasma from the circulation but also by release of RBCs from blood-forming organs.