Margaret R. Ross

Sodium excretion in normal and hypertensive pregnancy: A prospective study

One hundred fifty-eight intravenous saline solution infusions (3 mmol Na per kilogram body weight) were performed in (1) normal primigravid women during the second and third trimesters and post partum, after 1 week of either a high, low, or ad libitum salt intake; (2) normotensive primigravid women during midpregnancy who later developed pregnancy-induced hypertension, and (3) seven proteinuric and seven nonproteinuric primigravid women with ad libitum salt intake who had established pregnancy-induced hypertension. Sodium excretion did not differ significantly between pregnancy and after pregnancy despite marked differences in plasma renin activity, aldosterone concentration, volume, and glomerular filtration rate. Sodium excretion after saline solution loading varied according to prestudy sodium intake and was reduced between the second and third trimesters, independent of dietary salt intake. Those destined to develop pregnancy-induced hypertension had sodium excretion similar to that of continuously normotensive subjects during the second trimester, but those with established proteinuric pregnancy-induced hypertension had the lowest plasma volume, plasma aldosterone concentration, and plasma renin activity and retained sodium to the same degree as salt-deplete women with normotension. These results demonstrate that the balance of sodium regulatory factors is similar between pregnancy and post partum, that prestudy salt intake and stage of gestation can alter the natriuretic response to saline solution loading, and that normal pregnant women retain more administered sodium in late pregnancy than in midpregnancy despite further increases in plasma volume and no alterations to blood pressure or glomerular filtration rate. Those with established proteinuric pregnancy-induced hypertension retain sodium avidly without stimulation of plasma renin activity or plasma aldosterone concentration, findings not apparent during midpregnancy in those who later developed this disorder.

Low-Dose Aspirin in High-Risk Pregnancy?

Objectives: To determine the value of low-dose aspirin (100 mg/day) therapy in high-risk pregnancies, and to assess improvement in maternal abnormalities in response to this therapy, we conducted a prospective, randomized, double-blind, placebo-controlled therapeutic study.Methods: One hundred and eight pregnant women with preexisting hypertension (n = 60) or renal disease (n = 28), or a history of early severe preeclampsia (n = 20) in a previous pregnancy, took either aspirin (n = 58) or placebo (n = 50) from 17 to 19 weeks amenorrhea till approximately 37 weeks amenorrhea. The main outcome measures were duration of pregnancy, birth weight, maximum antenatal blood pressure, and maximum antenatal serum uric acid level.Outcome: Median values for the maximum antenatal blood pressure were higher and for birth weight lower in placebo-treated than in aspirin-treated women. Noncompliance with treatment, as assessed by platelet aggregation studies, was high in both groups.Conclusion: There was a small but potent...

Progressive Resetting of Sodium-Renin-Aldosterone Relationships in Human Pregnancy

The responses of plasma renin activity (PRA), plasma aldosterone concentration (PAC), urine aldosterone excretion (UA) and plasma volume (PV) to dietary sodium manipulations were examined in 50 second and 40 third trimester primigravidae. PRA, PAC and UA fell significantly following one week on a high-salt (HS) diet and rose significantly following a low-salt (LS) diet at both stages. PRA values for pregnant subjects following intravenous saline loading at the completion of their HS diet were seven to eight-fold greater than for six non-pregnant subjects who had the same studies.The absolute values for PRA, PAC, UA and UNa. V, and the individual changes in each of these parameters following dietary manipulations were signficantly interrelated during both trimesters. The relationship between change in UNa.V (ΔNa) and change in PRA (ΔPA) was exponential., there was an increase in PRA independent of ΔNa during the second, but not the third trimester, and the sensitivity of ΔPA to ΔNa was greater in the third...

Diastolic Blood Pressure in Pregnancy: Phase Iv Or Phase V Korotkoff Sounds?

Objective: To determine the magnitude of Phase IV-V diastolic blood pressure differences in human pregnancy.Methods: Blood pressure was measured by a standardized technique, using a Hawkesley random zero sphygmomanometer, in 221 pregnant women. Measurements were made in the second and third trimesters of pregnancy. The study included a number of women with chronic hypertension and a number with preeclampsia.Main Outcome Measures: Magnitude of Phase IV-V differences in normal and hypertensive pregnant women.Results: As expected, values for Phase V diastolic blood pressure were lower than for those for Phase IV, both in the second and in the third trimesters of pregnancy. In the third trimester, the median difference between Phase IV and V Korotkoff sounds was 5 mm Hg in normals, 7 mm Hg in chronic hypertensives, and 5 mm Hg in women with preeclampsia.Conclusion: These differences are within the error of the measurements as made in clinical practice. The smallest differences were found in women with preecla...

Comparison of simultaneous renal clearances of true endogenous creatinine and subcutaneously administered lothalamate in man

125I-iothalamate and true endogenous creatinine clearances, measured over two short collections periods of 1 and 2 h, were compared simultaneously in 70 patients with a variety of renal diseases and a wide range of renal function. Reproducibility of the iothalamate clearance was 18.5% and that of the creatinine clearance 12.2%. The slope of the regression was not significantly different from 1 (95% confidence interval, CI, 0.964-1.155) for the whole group, nor in any subgroup chosen. The intercept at 12.6 ml/min (CI = 5.0-20.2) indicates that there is some creatinine secretion, but this was constant at all levels of GFR. It is concluded that although the clearance of true creatinine obtained during short collection periods consistently overestimates GFR by a constant proportion, it is a reproducible and accurate measure of GFR suitable for use in the clinical setting.

Renin Activation in Normal and Hypertensive Human Pregnancy

Severe pregnancy-associated hypertension (P-AH, preeclampsia) is characterised by lowered plasma renin activity and plasma renin concentration, despite concomitant plasma volume contraction. Measurement of total (active + trypsin activatable) and active renin concentrations in peripheral blood of 13 women with P-AH revealed low active levels, but total renin concentrations (193 ± 61 ng/ml A1) which were not significantly different from those of 20 normotensive pregnant women (174 ± 54 ng/ml A1). Women with more severe P-AH as assessed by the presence of proteinuria (± 500 mg per day) had the lowest levels of active renin concentration (3.9 ± 1.3 ng/ml A1, vs 10 ± 4.5 in the normals, p < 0.01). This may represent failure of secretion of active renin or failure of activation of inactive renin.

Alterations in erythrocyte Na+,K+-cotransport in normal and hypertensive human pregnancy.

Many physiological variables known or thought to affect erythrocyte Na+,K+-cotransport are altered in pregnancy. The interrelationships of Na+,K+-cotransport and pregnancy were therefore examined. Values were elevated by more than 30% in both second and third trimesters with a return towards non-pregnant levels in the postpartum period. Although pregnancy was also associated with elevated plasma cholesterol, renin activity and aldosterone, there was no significant relationship within the pregnant group between Na+,K+-cotransport and any of these factors. No change could be demonstrated in Na+,K+-cotransport values after 7 days of either high (greater than 250 mmol/day) or low (less than 50 mmol/day) sodium intake and values for those who developed pregnancy-associated hypertension (PAH, pre-eclampsia) were not significantly different from those in continuously normotensive women in either the second or the third trimesters of pregnancy.

24-HOUR URINARY CREATININE EXCRETION IS NOT ALTERED IN HUMAN PREGNANCY

Objective: To assess whether creatinine excretion alters in human pregnancy.Methods: Longitudinal study of 24-h urinary excretion of creatinine during human pregnancy.Main Outcome Measures: Relative creatinine excretion as pregnancy advanced.Results: Twenty-four-hour creatinine excretion remained relatively constant as pregnancy advanced.Conclusions: Creatinine excretion can be used with confidence during pregnancy for estimation of completeness of collection in examination of 24-h excretion of other metabolites.We have shown that 24-h creatinine excretion is relatively constant during human pregnancy. Creatinine excretion can therefore be used with confidence during pregnancy for estimation of completeness of collection in examination of 24-h excretion of other metabolites.