Effects of neonatal polycythemia and hemodilution on capillary perfusion

The effects of neonatal polycythemia on nutritive capillary perfusion were investigated by a television microscopy technique. The capillary blood flow velocity in skin was measured in 12 neonates with polycythemia before and after treatment with hemodilution, and in 13 healthy control infants. The capillary blood flow velocity in the patients was 0.11 (0.02 to 0.34) mm/sec and in the healthy control infants 0.30 (0.17 to 0.44) mm/sec (p less than 0.01, median and range values). In relation to the absolute hematocrit change after treatment range, -20% to 0%), the capillary blood flow velocity increased nonlinearly (range, +733% to -14%; r = -0.98; p less than 0.001). The postnatal age was found to contribute significantly to the variation in results--the neonates with polycythemia studied during the first day of life had a very slow skin capillary circulation and responded to treatment with a more pronounced increase in capillary blood flow velocity than did the older patients. This in vivo model for capillary perfusion indicates that an insufficient microcirculation may be involved in the pathophysiology responsible for the morbidity associated with neonatal polycythemia.