Effects of hemodilution on skin microcirculation.

Red blood cell (RBC) velocity, capillary hematocrit (Hctcap), RBC flux, and arteriolar diameter were studied in the subcutaneous connective tissue of the Syrian hamster skinfold window preparation during successive normovolemic hemodilutions with 6% solutions of Dextran 70. The experiments were carried out in the unanesthetized animal. Heart rate (HR), mean systemic arterial pressure (Psys), and systemic hematocrit (Hctsys) were monitored throughout the procedure to ensure that normovolemia was maintained and hemodilution caused no adverse effects. The changes of RBC flux in the hemodiluted state, up to 50% hemodilution (Hctsys = 25% +/- 4), were not statistically significant when compared with control (t test, P less than 0.5). At this Hctsys, capillary RBC velocity increased by 60% and Hctcap decreased by 30%. Both of these changes were statistically significant relative to control. The arteriolar diameter did not change significantly during the reduction of Hctsys. The animals were studied during subsequent days to determine the chronic effects of hemodilution. Hctsys increased by approximately 12% per day after the experiment, and the systemic parameters returned to the prehemodiluted state in direct proportion to the reestablishment of the Hctsys.