Haemorheological changes in uraemic children in response to erythropoietin treatment.

The increased risk of hypertension during treatment of uraemic patients with recombinant human erythropoietin (rHuEpo) has been related to increased blood viscosity. We therefore studied rheological parameters determining whole blood viscosity in seven haemodialysed uraemic children and adolescents during treatment with rHuEpo (initial dose 75 IU/kg per week). Before treatment the patients were anaemic and had reduced red blood cell (RBC) deformability at low shear stress of 0.7 Pa in the rheoscope compared with six healthy control children (0.14 +/- 0.03 versus 0.19 +/- 0.02). The RBC membrane rigidity (i.e. membrane elastic shear modulus) determined in a flow channel was increased (2.04 +/- 0.26 versus 1.36 +/- 0.05 x 10(-5) N/m). After two weeks of rHuEpo, RBC deformability improved and RBC membrane rigidity decreased significantly. With increasing doses of rHuEpo the haematocrit rose steadily. After 14 weeks of therapy RBC deformability reached control values, and after 30 weeks RBC membrane rigidity became normal. RBC aggregation and plasma viscosity were similar in patients and controls and did not change significantly in response to rHuEpo. The early improvement of RBC deformability may lead to an increase in tissue oxygenation by facilitating microcirculatory blood flow.