CHANGES IN HEMORHEOLOGY WITH FETAL INTRAVASCULAR TRANSFUSION

OBJECTIVE: Our aim was to determine the changes in fetal hemorheologic parameters caused by fetal intravascular transfusion for alloimmune a nemia. STUDY DESIGN: Fetal blood samples were collected before and aft er 95 fetal transfusions in 31 women. Fetal hematocrit, whole-blood vi scosity at a variety of shear rates, plasma viscosity, fetal fibrinoge n, and fetal plasma proteins were measured. RESULTS: Fetal whole-blood viscosity increased, sometimes massively, with transfusion. The rise in viscosity was principally dependent on the rise in hematocrit, with a linear rise in hematocrit producing a linear rise in the logarithm of whole-blood viscosity, but was also affected by the amount of adult plasma proteins present in the donor blood. CONCLUSIONS: Rises in fet al whole-blood viscosity during transfusion can be minimized by using donor blood that has been serum depleted to a high hematocrit (> 90%) and by restricting the end hematocrit to 50% to 55%.