BLOOD-VISCOSITY AND PERIPHERAL VASCULAR-RESISTANCE IN PATIENTS WITH UNTREATED ESSENTIAL-HYPERTENSION

objectives: The viscosity of blood is increased in patients with essen tial hypertension. The aim of the present study was to investigate the importance of the different variables of blood rheology to total peri pheral resistance, and to elucidate whether inappropriate regulation o f the formation of erythropoietin could be important. Design: Nineteen consecutive patients with untreated essential hypertension were exami ned and compared with a group of matched healthy volunteers. Methods: The haemorheologic variables were assessed by rotational viscometry an d the haemodynamic variables by bioimpedance cardiography. The serum c oncentrations of erythropoietin were determined by radioimmunoassay. R esults: The whole blood viscosity and peripheral resistance index were elevated in the hypertensive group. The two variables were positively correlated with each other (r = 0.68, P = 0.0015). The plasma viscosi ty and erythrocyte aggregation tendency were increased and the erythro cyte deformability, measured as fluidity, was decreased in the hyperte nsive patients. In the male subpopulation (n = 12) the aggregation ten dency was positively, and the deformability negatively, correlated wit h body mass index. The serum concentrations of erythropoietin were equ al in the two groups. Conclusions: The increased total peripheral resi stance in patients with essential hypertension may in part be explaine d by an increased blood viscosity, but the possibility of an opposite cause-effect relationship must also be taken into consideration. The h aemorheological abnormalities observed in the present patients cannot be explained by high serum levels of erythropoietin.