Abnormalities of peripheral venous tone in women with pregnancy-induced hypertension

Forearm venous tone was measured in two groups of pregnant women: one group with pregnancy-induced hypertension and the other group with normal blood pressure. The women with pregnancy-induced hypertension were venoconstricted in the forearm (P less than 0.01) compared with the pregnant women with normal blood pressure. However, there was no difference in venous tone between the women with pregnancy-induced hypertension and non-pregnant women. There was an inverse correlation between mean arterial blood pressure and forearm venous tone (r = -0.581, P less than 0.001) for all the pregnant women studied. Further evaluation of peripheral venous tone may provide valuable information about the pathophysiology and treatment of women with pregnancy-induced hypertension.     

Changes in baroreceptor sensitivity for heart rate during normotensive pregnancy and the puerperium

Normal pregnancy is associated with marked changes in cardiovascular haemodynamics, which in part may be due to changes in autonomic control mechanisms. Baroreflex sensitivity for heart rate (BRS) was calculated in the supine and standing positions using power spectral analysis of pulse interval (PI) and systolic blood pressure (SBP) in 16 normotensive pregnant women and 10 normotensive non-pregnant controls. The pregnant women were studied on three occasions during their pregnancy (early, mid- and late gestation) and once during the puerperium. Supine total SBP variability increased between early and late pregnancy by 79% [95% confidence intervals (CI) 30%, 145%; P<0. 001], and supine high-frequency PI variability decreased by 75% (CI 51%, 88%; P<0.001). Supine BRS fell by 50% (P<0.001), with values returning to early-pregnancy levels in the puerperium, which were similar to those recorded in the control group. Standing SBP variability and BRS values were unchanged during pregnancy and post partum. The low/high frequency ratio of PI variability, taken as a surrogate measure of sympathovagal balance, increased by 137% (CI 42%, 296%; P<0.01) in the supine but not the standing position from early to late pregnancy. This was due to a decrease in high-frequency variability rather than to an increase in low-frequency variability, suggesting that these changes may have been due to vagal withdrawal rather than increased sympathetic activity. Normotensive pregnancy is associated with a marked decrease in supine BRS, although the exact mechanisms for these changes remain unclear. Further studies are required to define whether changes in BRS and sympathovagal tone in early pregnancy can be used to predict the onset of pregnancy-induced hypertension.     

Stimulation of active renin release in normal and hypertensive pregnancy

1. Active plasma renin concentration but not total renin concentration is reduced in women with pregnancy-induced hypertension compared with normotensive pregnant women. This study was conducted to determine whether women with pregnancy-induced hypertension are able to stimulate release of active renin. 2. Active plasma renin concentration was measured as the generation of angiotensin I at physiological pH in the presence of excess renin substrate, and total renin concentration was determined in the same way after trypsin activation. Inactive plasma renin concentration was calculated as the difference between total renin and active plasma renin concentrations. 3. Resting active plasma renin concentration was significantly greater in third-trimester primigravidae compared with normotensive non-pregnant women and active plasma renin and total renin concentrations rose significantly without a fall in inactive plasma renin concentration in both groups after 2 h ambulation, suggesting increased release of active plasma renin and not conversion of circulating inactive to active renin. These responses were blunted in women taking oral contraceptives. 4. Although the active plasma renin concentration was significantly reduced in third-trimester primigravidae with pregnancy-induced hypertension, total renin concentration was not significantly different compared with normotensive women of similar gestation and in both groups 30 min 60 degrees head-up tilt increased active but not inactive plasma renin concentration. 5. These studies show that in normal pregnancy active plasma renin concentration can be stimulated to a similar extent as in non-pregnant women, despite a higher resting level. This appears to be due to increased secretion of active plasma renin rather than conversion of circulating inactive to active renin.(ABSTRACT TRUNCATED AT 250 WORDS)     

Failure of impedance plethysmography to follow exercise-induced changes in limb blood flow

1. The blood flow in the forearm and the calf of six healthy volunteers was measured at rest and after exercise by impedance plethysmography using pulsatile (QZp) and venous occlusion (QZocc) methods, and by venous occlusion strain gauge plethysmography (Qsg). 2. At rest, the impedance QZp method gave values slightly higher than those of Qsg. In the forearm, the ratio QZp to Qsg was 1.26 in the supine position and 1.97 in the upright sitting position. For the calf muscle, the ratios were 1.08 in the supine position and 1.23 in the upright position. 3. Immediately after exercise, Qsg increased from resting values of approximately 2-4 ml min-1 100 ml-1 to mean values of 16-25 ml min-1 100 ml-1 in upright and supine arm or leg exercise. In contrast, the QZp values after exercise increased to only 3.1-4.6 ml min-1 100 ml-1. QZocc likewise failed to show increases in flow except in the supine leg exercise, where flow increased to 8.7 ml min-1 100 ml-1. 4. In an additional subject, it was shown that electrode position had no significant effect on the QZp blood flow measurement after exercise. 5. The failure of QZp to accurately follow the change in Qsg with exercise was probably due in part to pulsatile venous outflow. In addition, changes in microvessel packed cell volume and shear rate may influence the observed QZp. It is concluded that impedance plethysmography is not valid for estimation of limb blood flow during reactive hyperaemia after exercise.     

Capillary permeability and extracellular fluid volumes in pregnancy-induced hypertension

1. Capillary permeability was determined by the disappearance rate of Evans Blue dye from plasma in healthy non-pregnant women, normal third-trimester primigravidae and primigravidae with pregnancy-induced hypertension. 2. Extracellular fluid volume was determined from the disappearance curves of injected mannitol in the same subjects and the plasma volume was measured by the Evans Blue dye dilution technique. 3. In normal pregnancy capillary permeability was not altered from that of non-pregnant subjects. Although extracellular fluid volume and plasma volume were increased in normal pregnant compared with non-pregnant women, the distribution of fluid between plasma volume and interstitial fluid volume was unaltered. 4. Women with established pregnancy-induced hypertension had a more rapid Evans Blue disappearance rate and a lower plasma volume than normal pregnant women, independent of the presence of proteinuria. Maternal plasma volume correlated positively and significantly with fetal birth weight in women with pregnancy-induced hypertension, emphasizing the important relationship between maternal plasma volume and fetal outcome. 5. The increased capillary permeability in women with pregnancy-induced hypertension was associated with a reduction in the plasma volume/interstitial fluid volume ratio but a normal extracellular fluid volume, suggesting that the reduced plasma volume did not result from sodium loss but rather from a redistribution of the total extracellular fluid volume. These changes did not differ significantly in subgroups with and without oedema.     

Serum digoxin-like substances in pregnancy-induced hypertension

1. Endogenous digoxin-like immunoreactivity (EDLI) was measured in the serum of 85 normotensive pregnant (NTP) women and 77 women with pregnancy-induced hypertension (PIH) by a radioimmunoassay (New England Nuclear). All women were in the third trimester. 2. EDLI, which was undetectable in serum from non-pregnant women, was present in NTP and PIH and was significantly higher in PIH. EDLI correlated with gestational age in NTP, but not in PIH. 3. Ouabain-sensitive Na+ transport was estimated in normal peripheral blood leucocytes after incubation with sera from 50 NTP and 42 PIH women. Significant inhibition of active Na+ transport occurred only with the serum of hypertensive patients without proteinuria. 4. EDLI did not correlate with the effect of the sera on active Na+ transport. The radioimmunoassay therefore provides a poor index of Na+ transport inhibitory activity in PIH.     

Platelet intracellular free calcium concentration in normotensive and hypertensive pregnancies in the human

1. Basal and stimulated platelet intracellular free calcium concentrations were measured in non-pregnant women and in third trimester patients who were either normotensive or who had pregnancy-induced hypertension or pre-eclampsia. There were 15 subjects in each group. 2. A trend for a reduction of the maximal response of platelet calcium levels to stimulation by 5-hydroxytryptamine was seen in pregnant groups compared with nonpregnant subjects, but this was significant only in pre-eclampsia. 3. No significant differences in basal or adenosine 5'-pyrophosphate-stimulated levels of platelet intracellular free calcium concentration were observed between the four groups. 4. These results illustrate that basal platelet calcium levels are unchanged in hypertension of pregnancy. Alterations in basal platelet calcium levels may not be involved in the platelet activation that is a feature of pre-eclampsia.     

Endothelium-derived prostacyclin: effect of serum from women with normal and hypertensive pregnancy.

1. Pregnancy-induced hypertension (or pre-eclampsia) is characterized by vasoconstriction, platelet aggregation and altered capillary permeability, implying disordered endothelial function and/or structure. Serum from women with pregnancy-induced hypertension has been reported by others to be cytotoxic to endothelial cells in vitro. We hypothesized that such serum contains a factor that limits the ability of endothelial cells to produce and/or release prostacyclin. 2. Prostacyclin production by intact and damaged cultured human umbilical vein endothelial cells was measured after incubating these cells with serum from non-pregnant and normal pregnant women and women with pregnancy-induced hypertension. Confluent human umbilical vein endothelial cell monolayers (intact and damaged) were incubated with sera for 24 h at 37 degrees C followed by 1 h of incubation with added thrombin (stimulated production) or media (basal production). Supernatants were then collected for measurement of 6-keto-prostaglandin F1 alpha by radioimmunoassay. 3. Basal production of 6-keto-prostaglandin F1 alpha was greater in response to serum from non-pregnant women than to that from pregnant women. Within each group, sub-lethally damaged cells had a similar basal production of 6-keto-prostaglandin F1 alpha to that of intact cells. 4. Basal production of 6-keto-prostaglandin F1 alpha by intact or damaged cells incubated with sera from normal pregnant women and from women with pregnancy-induced hypertension was similar. 5. In all groups the addition of thrombin to intact endothelial cells increased 6-keto-prostaglandin F1 alpha production approximately 15-30-fold over basal levels, but only three- to five-fold in damaged endothelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hysteresis of the venous pressure-volume relationship in the forearm of borderline hypertensive subjects.

1. The forearm venous pressure-volume relationship was studied in 14 young men with borderline hypertension and in 16 control subjects of the same age and sex. Strain-gauge plethysmography was used to evaluate volume changes after slow increases and decreases in distention, in order to estimate the amplitude of the hysteresis curve. 2. Compared with normotensive control subjects, subjects with borderline hypertension had significantly higher values of blood pressure, heart rate and forearm blood flow. 3. Baseline forearm venous tone was slightly, but not significantly, increased in borderline hypertensive subjects (21.35 +/- 6.53 versus 18.75 +/- 5.95 mmHg ml-1 100 ml-1) and was significantly enhanced after a cold pressor test. The increase was no higher in the borderline hypertensive subjects than in the normotensive control subjects. 4. The area of the hysteresis curve was significantly decreased (7.58 +/- 3.58 versus 10.34 +/- 5.67 arbitrary units; P = 0.0092) as was the extent of isotonic relaxation (creep) (0.28 +/- 0.11 versus 0.39 +/- 0.22 ml/100 ml; P = 0.0098) in borderline hypertensive subjects compared with control subjects. Both parameters were unaffected by the cold pressor test. 5. The study suggests that the viscous component of the venous wall is altered in young patients with borderline hypertension, indicating intrinsic changes in vascular segments which are not exposed to increased intraluminal pressure.     

西安地区正常妊娠妇女孕早中晚期血常规检测指标参考区间的调查分析

目的建立西安地区妊娠女性孕早、中、晚期血液学相关参数的参考区间。方法选取空军军医大学第一附属医院2017年3月至2018年2月门诊妊娠女性1 197例,按照孕周分为孕早、中、晚期;选择同期体检健康的非孕育龄期女性300例作为健康人对照组;分别检测白细胞计数(WBC)、红细胞计数(RBC)、血红蛋白(Hb)、血细胞比容(Hct)、红细胞平均体积(MCV)、平均红细胞血红蛋白含量(MCH)、平均红细胞血红蛋白浓度(MCHC)、血小板(PLT)并进行统计分析,建立参考区间。结果妊娠女性在不同孕期RBC、Hb、HCT、MCV、MCH、MCHC的水平均低于健康人对照组,孕晚期下降达孕期最低水平(P0.05),不同孕期之间比较差异有统计学意义(P0.05)。妊娠女性WBC水平随孕周的增加逐渐升高,至孕晚期达最高水平,不同孕期之间WBC比较差异有统计学意义(P0.05)。妊娠女性PLT水平较健康人对照组降低,在孕晚期达最低水平(P0.05)。结论妊娠女性血液学相关参数不同于育龄期健康非孕女性,各临床实验室应建立女性妊娠各期血液学相关参数参考区间。     

Presence of mechanical dyssynchrony in duchenne muscular dystrophy

Background

There are physiological reasons for the effects of positioning on hemodynamic variables and cardiac dimensions related to altered intra-abdominal and intra-thoracic pressures. This problem is especially evident in pregnant women due to the additional aorto-caval compression by the enlarged uterus. The purpose of this study was to investigate the effect of postural changes on cardiac dimensions and function during mid and late pregnancy using cardiovascular magnetic resonance (CMR).

Methods

Healthy non-pregnant women, pregnant women at 20^th week of gestation and at 32^nd week of gestation without history of cardiac disease were recruited to the study and underwent CMR in supine and left lateral positions. Cardiac hemodynamic parameters and dimensions were measured and compared between both positions.

Results

Five non-pregnant women, 6 healthy pregnant women at mid pregnancy and 8 healthy pregnant women at late pregnancy were enrolled in the study. In the group of non-pregnant women left ventricular (LV) cardiac output (CO) significantly decreased by 9% (p = 0.043) and right ventricular (RV) end-diastolic volume (EDV) significantly increased by 5% (p = 0.043) from the supine to the left lateral position. During mid pregnancy LV ejection fraction (EF), stroke volume (SV), left atrium lateral diameter and left atrial supero-inferior diameter increased significantly from the supine position to the left lateral position: 8%, 27%, 5% and 11%, respectively (p < 0.05). RV EDV, SV and right atrium supero-inferior diameter significantly increased from the supine to the left lateral position: 25%, 31% and 13% (p < 0.05), respectively. During late pregnancy a significant increment of LV EF, EDV, SV and CO was observed in the left lateral position: 11%, 21%, 35% and 24% (p < 0.05), respectively. Left atrial diameters were significantly larger in the left lateral position compared to the supine position (p < 0.05). RV CO was significantly increased in the left lateral position compared to the supine position (p < 0.05).

Conclusions

During pregnancy positional changes affect significantly cardiac hemodynamic parameters and dimensions. Pregnant women who need serial studies by CMR should be imaged in a consistent position. From as early as 20 weeks the left lateral position should be preferred on the supine position because it positively affects venous return, SV and CO.     

A cross-sectional study of basal platelet intracellular free calcium concentration in normotensive and hypertensive primigravid pregnancies

1. The intracellular free calcium concentration ([Ca2+]i) in washed human platelets was measured using the fluorescent indicator, fura-2, in a cross-sectional study of 36 normotensive, primigravid volunteers, 12 in each trimester of pregnancy and a further 12 at 6 weeks post partum. The results were compared with those obtained from 30 normal female volunteers not using oral contraception. 2. The mean basal [Ca2+]i in the platelets of the pregnant women in the first two trimesters (115.6 +/- 6.7 and 120.1 +/- 5.7 nmol/l, respectively) was not shown to differ significantly from that of normal non-pregnant volunteers (112.3 +/- 2.9 nmol/l). However, during the third trimester a significant increase in [Ca2+]i was noted (134.0 +/- 4.9 nmol/l; P less than 0.05), with a return to normal values in the post-partum period (108.2 +/- 6.1 nmol/l). 3. [Ca2+]i was also measured in the platelets of a group of 12 primigravid pregnant women in the third trimester whose pregnancies were complicated by gestational hypertension (pregnancy-induced hypertension and pre-eclampsia). A significant rise in basal [Ca2+]i was noted in the platelets of primigravidae whose pregnancies were complicated by pre-eclampsia (163.6 +/- 8.8 nmol/l) as compared with normotensive, third-trimester primigravidae (P less than 0.02). However, no correlation could be demonstrated between [Ca2+]i and systemic blood pressure.     

Quantitative cardiovascular magnetic resonance in pregnant women: cross-sectional analysis of physiological parameters throughout pregnancy and the impact of the supine position

Background

There are physiological reasons for the effects of positioning on hemodynamic variables and cardiac dimensions related to altered intra-abdominal and intra-thoracic pressures. This problem is especially evident in pregnant women due to the additional aorto-caval compression by the enlarged uterus. The purpose of this study was to investigate the effect of postural changes on cardiac dimensions and function during mid and late pregnancy using cardiovascular magnetic resonance (CMR).

Methods

Healthy non-pregnant women, pregnant women at 20^th week of gestation and at 32^nd week of gestation without history of cardiac disease were recruited to the study and underwent CMR in supine and left lateral positions. Cardiac hemodynamic parameters and dimensions were measured and compared between both positions.

Results

Five non-pregnant women, 6 healthy pregnant women at mid pregnancy and 8 healthy pregnant women at late pregnancy were enrolled in the study. In the group of non-pregnant women left ventricular (LV) cardiac output (CO) significantly decreased by 9% (p = 0.043) and right ventricular (RV) end-diastolic volume (EDV) significantly increased by 5% (p = 0.043) from the supine to the left lateral position. During mid pregnancy LV ejection fraction (EF), stroke volume (SV), left atrium lateral diameter and left atrial supero-inferior diameter increased significantly from the supine position to the left lateral position: 8%, 27%, 5% and 11%, respectively (p < 0.05). RV EDV, SV and right atrium supero-inferior diameter significantly increased from the supine to the left lateral position: 25%, 31% and 13% (p < 0.05), respectively. During late pregnancy a significant increment of LV EF, EDV, SV and CO was observed in the left lateral position: 11%, 21%, 35% and 24% (p < 0.05), respectively. Left atrial diameters were significantly larger in the left lateral position compared to the supine position (p < 0.05). RV CO was significantly increased in the left lateral position compared to the supine position (p < 0.05).

Conclusions

During pregnancy positional changes affect significantly cardiac hemodynamic parameters and dimensions. Pregnant women who need serial studies by CMR should be imaged in a consistent position. From as early as 20 weeks the left lateral position should be preferred on the supine position because it positively affects venous return, SV and CO.     

脐血流监测对妊娠期高血压疾病孕妇妊娠结局的意义探讨

目的探讨妊娠期高血压患者胎儿脐动脉血流阻力指标对围产儿结局的影响。方法用粘度仪检测正常妊娠孕妇及妊娠期高血压孕妇血浆粘度(PV);用离心机检测红细胞压积(HCT)等;统计分析其妊娠中期(20~27周)及妊娠晚期(28~36周),并测定收缩期最大血流速度和舒张期血流速度的比值(S/D)和脉搏指数(PI)、阻力指数(RI)。探讨血液流变学各值与胎儿脐动脉血流指标相关性。结果妊娠高血压组妊娠中、晚期S/D、PI及RI值与正常妊娠组比较均有统计学差异。随着病情进展,中度、重度妊娠高血压组RI、PI值逐渐升高。妊娠期高血压病患者血液HCT、PV等值与胎儿脐动脉血流阻力指标各值呈正相关。结论 HCT、PV对妊娠期高血压病的发生、发展、严重程度及脐动脉血流阻力指标可能有重要影响。多项指标监测妊娠期高血压病患者血液流变学及胎儿脐动脉血流动力学,可提高预测妊娠期高血压症发生、发展及严重程度及其对围产儿预后影响的准确性。     

Abnormal vascular function and morphology in pre-eclampsia: a study of isolated resistance vessels

In order to obtain direct information about vascular changes associated with pre-eclampsia, the morphological and functional characteristics of isolated omental resistance vessels from 11 women with pre-eclampsia, 10 normotensive pregnant women and eight normotensive non-pregnant women were determined. In vessels from the women with pre-eclampsia, the ratio of media thickness to lumen diameter was increased, compared with that in vessels from the other two groups. The vessels from the women with pre-eclampsia had an increased responsiveness to angiotensin II and a decreased rate of relaxation, but only when compared with the vessels from the normotensive pregnant women. However, no difference in responsiveness to noradrenaline was found between any of the groups. The angiotensin II responsiveness of the vessels from the women with pre-eclampsia and from the non-pregnant women were similar, suggesting that pre-eclampsia is associated with an absence of the change in vascular function which normally occurs during pregnancy. The study provides direct evidence for an involvement of vascular abnormalities in the pathogenesis of pre-eclampsia.     

Short-term cortisol infusion in the brachial artery,with and without inhibiting 11 beta-hydroxysteroid dehydrogenase,does not alter forearm vascular resistance in normotensive and hypertensive subjects

BACKGROUND: Vascular tone is increased in primary hypertension, and glucocorticoids affect vascular tone. Local cortisol availability is modulated by activity of 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD). As this activity may be decreased in patients with primary hypertension, vascular sensitivity to cortisol may be increased in these patients. We studied the acute effect of cortisol on forearm vascular resistance (FVR) by infusing cortisol directly into the brachial artery, both with and without inhibition of 11 beta-HSD, in normotensive and hypertensive subjects. DESIGN: Twenty normotensive volunteers and 20 patients with primary hypertension participated in the study. After a 10-min infusion of vehicle (glucose 5%), cortisol was infused into the brachial artery in three stepwise increasing doses (3.5, 10.5 and 35 microg per 100 mL of forearm volume), each for 10 min. Next, the participants received placebo or 500 mg glycyrrhetinic acid (GA) orally, and 150 min later the same infusion schedule was repeated. Forearm vascular resistance was measured during the last 5 min of the infused vehicle and of each dose. Arterial and forearm venous plasma samples for measurement of cortisol and cortisone were taken at the end of the infusions of glucose 5% and the highest cortisol dose. RESULTS: In both normotensive and hypertensive subjects, neither the infusion of cortisol nor the administration of GA changed FVR. Also 2 h after the cortisol infusion there remained no change in FVR in both the normotensive and hypertensive groups who received placebo. Following the infusion of the highest cortisol dose, total plasma cortisone levels in the venous plasma were decreased compared with levels in the arterial plasma (36 +/- 3 and 49 +/- 4 nmol L-1, respectively, P < 0.05). The protein-bound venous cortisone was 37.1 +/- 4.8 nmol L-1 during the vehicle compared with 23.9 +/- 3.7 nmol L-1 during the cortisol infusion (P < 0.01), whereas the free cortisone level was not altered by the cortisol infusion. CONCLUSIONS: In both normotensive and hypertensive subjects, high-dose cortisol infusion both with and without 11 beta-HSD inhibition did not change FVR either immediately or after 2 h. We could not demonstrate in vivo 11 beta-HSD activity in the forearm vascular tissues. When binding of cortisone to CBG is changed, e.g. during cortisol infusion, arterio-venous changes in cortisone cannot reliably be used to assess (alterations in) local 11 beta-HSD activity.     

Usefulness of ambulatory blood pressure monitoring in pregnant women with type 1 diabetes.

OBJECTIVE: Pregnancy in type 1 diabetes is associated with an increased risk of developing pregnancy-induced hypertension (PIH). Ambulatory blood pressure monitoring (ABPM) has been used to screen for preeclampsia in nondiabetic pregnancy. To date, there are no data regarding ABPM during pregnancy in normotensive type 1 diabetic women. This study sought to establish blood pressure (BP) profiles for pregnant type 1 diabetic women using ABPM and determine whether the BP pattern can define a population at risk for developing PIH. RESEARCH DESIGN AND METHODS: ABPM was carried out for one 24-h period during each trimester--in the first trimester between weeks 7 and 12, in the second trimester between weeks 20 and 24, and in the third trimester between weeks 30 and 34--in 22 normotensive pregnant type 1 diabetic and 10 pregnant nondiabetic women. RESULTS: The incidence of PIH was fourfold greater in type 1 diabetic women than in control subjects. Diabetic women showed higher daily diastolic BP in the third trimester compared with nondiabetic pregnant women. Diabetic women who developed PIH in the third trimester showed significantly higher BP profiles throughout gestation than those who remained normotensive. Receiver operator characteristics curves for nighttime systolic BP showed the best predictive capacity for PIH, with a cutoff > 105 mmHg (85% sensitivity and 92% specificity). CONCLUSIONS: Our study confirms the early increase of BP in patients who will develop PIH and suggests that nighttime systolic BP >105 mmHg in the second trimester is a useful predictor of PIH. ABPM may be useful in screening for PIH in pregnant diabetic women.     

Plasma adrenaline and noradrenaline during orthostasis in man: the importance of arterial sampling

Plasma adrenaline and noradrenaline were measured in arterial blood and in forearm venous blood during supine rest and after 30 min standing in normotensive, healthy 50-year-old men (n = 16). After 30 min standing, venous noradrenaline had increased from 1.61 +/- 0.11 to 4.22 +/- 0.30 nmol/l and arterial from 1.43 +/- 0.06 to 2.93 +/- 0.15 nmol/l. Orthostasis induced a seven-fold increment in the forearm arterial-venous difference of noradrenaline from -0.18 +/- 0.08 to -1.29 +/- 0.25 nmol/l (p less than 0.001). Orthostasis more than doubled the forearm arterial-venous difference of adrenaline from 0.15 +/- 0.03 to 0.31 +/- 0.05 nmol/l (p less than 0.001) since arterial adrenaline increased from 0.31 +/- 0.03 to 0.53 +/- 0.05 nmol/l and venous from 0.16 +/- 0.02 to 0.22 +/- 0.02 nmol/l. Arterial adrenaline correlated significantly with venous in the supine (r = 0.64, p less than 0.01) but not in the standing position (r = 0.34, NS). The results indicate that arterial concentrations of adrenaline are a much better indicator of sympatho-adrenal activity during orthostasis than peripheral venous concentrations. For noradrenaline, measurements of arterial concentrations during the orthostatic manoeuvre seem to provide information about the total noradrenergic sympathetic reactivity, while the corresponding measurements in peripheral venous blood represent the forearm locally.     

Plasma volume contraction: a significant factor in both pregnancy-associated hypertension (pre-eclampsia) and chronic hypertension in pregnancy

The role of plasma volume in hypertension in pregnancy (pre-eclampsia) was investigated. Significant volume expansion from non-pregnant levels (16.5 +/- 1.60 ml/cm height) was present throughout pregnancy in 189 normal women, reaching 23.1 +/- 1.21 ml/cm at 33-36 weeks amenorrhoea. In another 40 initially normotensive pregnant women who developed hypertension, similar early volume expansion was followed by significant volume contraction in the third trimester, before evaluation of blood pressure in 29 (20.6 +/- 1.26 ml/cm), after it in 11 (18.6 +/- 1.27 ml/cm). Equivalent volume contraction was present in another 44 women studied only after hypertension developed in the third trimester. Oedema had no value as a clinical sign. In another 30 women with chronic hypertension, blood pressure was inversely related to plasma volume (r = 0.822) and to fetal growth (r = -0.710), which was directly related to plasma volume (r = 0.701). Plasma volume depletion plays a significant role in hypertension in pregnancy.     

High plasma levels of a ouabain-like factor in normal pregnancy and in pre-eclampsia

Recent reports have described high levels of one or more substances which cross-react with digoxin antibodies in the serum of women with pre-eclampsia. We measured plasma ouabain-like activity and intraerythrocyte sodium and potassium concentrations, in addition to performing routine hypertensive laboratory tests, in 13 normotensive non-pregnant subjects, 15 normotensive pregnant women and 16 pre-eclamptic women (gestational age: 33-36 weeks). Plasma ouabain-like activity, measured as plasma-induced variations in ouabain binding to human erythrocytes, proved significantly higher in both groups of pregnant subjects as compared to normotensive non-pregnant women, and a significant difference was also found between pre-eclamptic and normotensive pregnant women, the former exhibiting higher plasma ouabain-like activity. No differences in intracellular sodium and potassium levels were detected among the three groups studied. Though there is reason to believe that the high plasma levels found both in normal and hypertensive pregnancy may depend on placental production, we are not in a position to define with any degree of certainty what the mechanism or mechanisms are that regulate ouabain-like factor production.