Microcirculatory effects of normovolemic hemodilution in skeletal muscle.

The effect of successive normovolemic hemodilution was studied in the microcirculation of the skeletal muscle (tenuissimus) of the rabbit. Normovolemic hemodilution was obtained by the progressive equal replacement of blood with a 6% solution of dextran 70 (MW = 70,000). Systemic parameters (mean arterial pressure, heart rate, and systemic hematocrit) were monitored throughout the procedure to ensure that normovolemia was maintained, and that the animal did not have adverse responses to the procedure. Microcirculatory hemodynamics were characterized by the measurements of capillary red blood cell (RBC) flux, RBC velocity, capillary hematocrit (Hcap), and flowmotion (the effect of arteriolar vasomotion on capillary flow velocity). The same capillaries were chosen throughout a given experiment and the measurements in the hemodiluted states were normalized to the control value. The changes of RBC flux up to 50% hemodilution were not statistically significant and flux remained essentially constant. Capillary RBC velocity increased significantly, where it was 45% higher than control at 50% hemodilution. Hcap was maintained at the control level up to 25% hemodilution.