Blood rheology in pre-eclampsia and intrauterine growth retardation: effects of blood pressure reduction with labetalol.
Blood viscosity ( Contraves L S 30) and its determinants were measured in 23 patients with mild/moderate pre-eclampsia, 10 patients with intrauterine growth retardation and 22 control subjects, matched for age and gestation. Both abnormal groups had a significantly increased blood viscosity at high shear rate (94 s-1) associated with increased haematocrit. Fibrinogen levels were also increased, but there were no significant differences between groups in plasma viscosity, low shear viscosity (0.94 s-1) or red cell deformability, measured by a low-shear washed cell system of filtration through 5-micron pore diameter Nuclepore filters. In the pre-eclamptic group, measurements were repeated after 1-2 weeks in nine patients treated with labetalol (a combined alpha and beta adrenergic blocker) and in 10 patients treated with bed rest. Labetalol reduced blood pressure but no change in rheology was seen in either group. Control of blood pressure by labetalol does not adversely affect rheology, in contrast to diuretics which are known to cause haemoconcentration and increased blood viscosity.