Orthostatic stress response during the menstrual cycle is unaltered in formerly preeclamptic women with low plasma volume.

Contains fulltext : 51858.pdf (publisher's version ) (Closed access)Plasma volume (PV) varies with the menstrual cycle not only in healthy parous controls (CON) but also in formerly preeclamptic women with a subnormal PV (LPV). It is unknown whether formerly preeclamptic women with LPV are more susceptible to orthostatic stress than healthy controls. In this study, the authors compared autonomic responses to acute (standing from supine position) and gradual (menstrual cycle) orthostatic stress between LPV and CON. In 11 LPV (PV<or= 49 mL/kg lean body mass) and 7 CON, beat-to-beat blood pressure (BP) and heart rate (HR) were measured in supine position and after an orthostatic stress test, during the follicular phase (FP) and luteal phase (LP) of the menstrual cycle. Spectral analysis (fast Fourier transform) was performed on beat-to-beat signals to quantify the magnitude of the spontaneous BP and pulse interval (PI) fluctuations. The absolute powers within the low-frequency (0.04-0.15 Hz) and high-frequency (0.15-0.4 Hz) ranges of BP and PI were used as estimates for sympathetic and parasympathetic activity, respectively. Baroreflex sensitivity was calculated as the transfer function gain from low-frequency systolic BP to PI. Differences between groups, menstrual phase, and response to standing were compared by analysis of variance. Basal BP was comparable in both study groups. However, basal PI and spontaneous baroreflex sensitivity were lower in LPV than in CON. The autonomic responses to acute and gradual orthostatic stress were similar in the 2 groups, irrespective of the phase of the menstrual cycle. The cardiovascular response to acute and gradual orthostatic stress in both FP and LP is comparable in LPV and CON

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

Contains fulltext : 50660.pdf (publisher's version ) (Open Access)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

A subnormal plasma volume in formerly preeclamptic women is associated with a low venous capacitance.

Contains fulltext : 48810.pdf (publisher's version ) (Open Access)OBJECTIVE: Pregnancy induces a smaller rise in plasma volume in formerly preeclamptic women with a pre-existent subnormal plasma volume than in their counterparts with a normal plasma volume. These women also have a three times higher recurrence rate of pregnancy-induced hypertensive disorders. In this study we tested the hypothesis that a subnormal plasma volume in these women is related to a lower capacitance of their venous compartment. METHODS: In 31 nonpregnant formerly preeclamptic women with a subnormal plasma volume and eight parous controls, we infused intravenously 500 mL of a modified gelatin solution over 30 minutes. Before and after infusion we measured the circulating levels of alpha-atrial natriuretic peptide (alpha-ANP) and active plasma renin concentration (APRC). During volume loading, we recorded the change in heart rate, stroke volume, and cardiac output using pulse contour analysis. We measured the ratio of percent change in blood volume and percent change in cardiac output during volume loading as a marker for venous capacitance. RESULTS: During volume loading, patients differed from controls by a larger rise in alpha-ANP, pulse rate, and cardiac output, and by a lower estimated venous capacitance. The concomitant response of stroke volume and APRC did not differ appreciably between groups. CONCLUSION: Formerly preeclamptic women with a subnormal plasma volume differ from controls with a normal plasma volume by a reduced venous capacitance. These results support our hypothesis that, in these women, a subnormal plasma volume indicates the presence of a subnormal venous capacitance