Techniques of Measuring Plasma Volume Changes in Pregnancy

Restricted plasma volume prior to and during pregnancy has been clinically linked to placental syndrome - that is to say, gestational maternal hypertensive sequellae on the one hand and fetal growth restriction on the other. Asmost of the plasma volume is localized at the venous side of the vascular system, when having a healthy heart, plasma volume largely reflexes venous reserve capacity to balance alterations in arterial needs. Plasma volume can be measured directly by bleeding, obviously not applicable to human research, or indirectly using dilution or indicator dilution techniques. The latter two techniques require first order kinetics. Moreover, the indicator must be traceable and measurable. Finally, when used in pregnancy, they must be safe for both mother and fetus. More novel bioelectrical impedance techniques claim to be able to estimate whole body extracellular fluid content. The reliability to assess plasma volume, as part of the extracellular volume, by bioimpedance, remains to be elucidated, but when consistent and precise, it has the potency to be highly applicable in daily care.