Low plasma volume coincides with sympathetic hyperactivity and reduced baroreflex sensitivity in formerly preeclamptic patients.

Background: Preeclampsia is associated with enhanced sympathetic activity as well as subnormal plasma volume. Meanwhile, in over 50% of these complicated pregnancies, the subnormal plasma volume has been found to persist for a prolonged period after pregnancy. The objective of this study is to test the hypothesis that in normotensive formerly-preeclamptic women, persistence of a subnormal plasma volume coincides with enhanced sympathetic activity and with it, an altered autonomic control of blood pressure.

Methods: Forty-eight formerly-preeclamptic women participated in this study. After measurement of their plasma volume by iodine 125-albumin indicator dilution, they were subdivided into a group with a normal plasma volume (plasma volume > 48 ml/kg lean body mass) and a group with a subnormal plasma volume (< or = 48 ml/kg lean body mass). We performed spectral analysis on their beat-to-beat blood pressure and heart rate recordings and compared both groups using non-parametric tests.

Results: Formerly-preeclamptic women with a subnormal plasma volume had a higher sympathetic activity (P = .001) and a lower baroreflex sensitivity (P = .04) than their counterparts with a normal plasma volume.

Conclusion: In normotensive formerly-preeclamptic women, a subnormal plasma volume coincides with a higher sympathetic activity in the blood pressure regulation and lower baroreflex sensitivity. Whether these alterations in the autonomic control mechanisms are a cause or effect of the subnormal plasma volume remains to be elucidated.