The relation between venous reserve capacity and low plasma volume

Prepregnant low plasma volume (LPV) is associated with subsequent gestational hypertensive disease. It is unknown to what extent an LPV affects the venous reserve capacity (VRC). We tested the hypothesis that LPV reduces the VRC, as indicated by presyncope or altered cardiovascular changes in response to head-up tilt.

In 52 nonpregnant women with a history of preeclampsia or recurrent miscarriage, the authors assessed plasma volume, stroke volume, and cardiac output and determined blood pressure, heart rate, and autonomic responses to stepwise inflicted head-up tilt.

12 participants had LPV, which related to presyncope when compared with subjects with normal plasma volume (NPV). Women with LPV without presyncope demonstrated a circulatory response comparable to NPV women at the expense of consistently higher heart rate.

LPV decreases the capacity to cope with head-up tilt without affecting the response pattern, suggesting reduced VRC.