Blood rheology and hypertension in hemodialysis patients treated with erythropoietin

Fifteen hemodialysis patients suffering from stable anemia were treated with recombinant human erythropoietin (r-HuEPO). Within 16 weeks, hematocrit values increased from 23.7 +/- 1.2 to 35.7 +/- 0.2%. Simultaneously, mean predialytic blood pressure rose significantly from 131/79 to 139/85 mm Hg. Three out of 15 patients developed frank hypertension and had to be put on antihypertensive therapy. When the hematocrit was lowered again from 36.3 +/- 1.8 to 30.5 +/- 1.2% in these 3 patients, blood pressure was attenuated and the antihypertensive medication could be reduced or abolished. With rising hematocrit values, whole blood viscosity increased at both low (+42%) and high shear rates (+33%) without reaching the values seen in healthy subjects. By contrast, plasma viscosity was already elevated in hemodialysis patients prior to r-HuEPO treatment and showed only a slight, but insignificant increase during r-HuEPO treatment. Since whole blood viscosity is one factor that determines vascular resistance, it is conceivable that the development of hypertension during correction of the renal anemia is, at least partly, due to an increment of blood viscosity.