Blood volume in pre-eclampsia: fantasy and reality.

A great deal has been stated recently about the importance of hypovolemia in pre-eclampsia and eclampsia from the point of view of pathogenesis and management. Some authors even believe that the so-called hypovolemia represents an etiologic factor and should be "corrected." In this paper, the hemodynamic factors that maintain the circulation in the normal nonpregnant and pregnant states are discussed. These factors are then used as a background for explaining the pathophysiologic abnormalities of the acute hypertensive disease of pregnancy. It is concluded that the slight decrease in blood volume observed in pre-eclampsia has no hemodynamic relevance; the blood volume is merely "fitting" a contracted vascular bed. The major abnormality resides in the constricted arteriolar system and not in the blood volume.