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Biomedical subjects

M Lindheimer

Publications and source records attributed to M Lindheimer.

At least 19 recordsLinked to original sources
PubMed2004

Methodological and technical issues related to the diagnosis, screening, prevention, and treatment of pre-eclampsia and eclampsia.

In contrast with advances made in treating or eliminating many other serious disorders, severe morbidity and mortality associated with pre-eclampsia/eclampsia remain among the leading problems that threaten safe motherhood, particularly in developing countries. This article reviews technical issues related to diagnosis, screening, prevention, and treatment of pre-eclampsia and identifies corresponding needs. The authors stress the lack of standardized definitions of pre-eclampsia and eclampsia and discuss problems in blood-pressure measurements and assessment of urinary protein. They summarize the evidence for prevention strategies and screening tests for early detection. For treatment, magnesium sulfate has been proven effective, but not widely used. The authors outline priorities for narrowing the identified gaps and emphasize the need for coordinated efforts to reduce the morbidity and mortality due to pre-eclampsia/eclampsia. They conclude that the mystery of this disease must be resolved to achieve primary prevention of it.

Developing Countries↗
PubMed2001

A study of the adsorption of bile salts onto model lecithin membranes.

Bile salts play a central role in the promotion of cytotoxicity or cytoprotection. In this study, we examined the interaction of different bile salts with egg lecithin vesicles using 31P NMR spectroscopy. The effects of taurochenodeoxycholate (TCDC or 3alpha,7alpha,-dihydroxy-5beta-cholanoyl taurine, of tauroursodeoxycholate (TUDC) or 3alpha,7beta,-dihydroxy-5beta-cholanoyl taurine) and of taurobetamuricholate (TbetaMC or 3alpha,6beta,7beta,-trihydroxy-5beta-cholanoyl taurine), at various bile salt/lecithin ratios, were evaluated. From the percent 31P present in vesicles, the micellar capacity of bile salts to dissolve lecithin was determined. TCDC was incorporated into vesicles for bile salt/lecithin molar ratios lower than 0.62 while for TUDC and TbetaMC, the critical ratios were 0.94 and 1.1, respectively. The 31P chemical shift change was markedly larger with TCDC than that found with TUDC and TbetaMC. In order to specify the low interactions observed between hydrophilic bile salts and lecithin, we determined the intermixed micellar/vesicular bile salt concentrations (IMVC) of bile salt/lecithin solutions using rapid ultrafiltration-centrifugation for TUDC and lecithin solubility measurements for TUDC, TbetaMC and TCDC. The low IMVC obtained indicate that even hydrophilic bile salts were bound mostly to the mixed aggregates. In conclusion, the low disturbance in the arrangement of lecithin induced by TUDC and TbetaMC appears to be due to the interfacial location of these bile salts. TCDC (7alpha OH) penetrates more deeply in the membrane than the 7beta hydroxylated bile salts that may partly explain the distinct damaging effects of these bile salts.

Journal Article↗
PubMed2000

On the Behavior of Nonionic Surfactants at the N-Heptane/Silica Gel Interface: Influence of the Presence of Interfacial Water Inferred from Adsorption Isotherms and Calorimetric Data.

The behavior of two polydisperse nonionic surfactants, poly (oxyethylene) glycol alkylphenyl ether TX-35 and TX-100, at the prewetted silica gel/n-heptane and dried silica gel/n-heptane interfaces has been compared by the determination of the average adsorption isotherms of the polydisperse surfactants and of displacement enthalpies. From HPLC experiments, we could also separately quantify the adsorption of each ethyleneoxide (EO) fractions for silica gel from the polydisperse surfactant solution. The adsorption isotherms clearly indicate an incomplete preferential adsorption of the large (EO) chains over the small ones, as well on dried silica gel as on a prehydrated sample. This preferential adsorption and its driving force follow the solubility rules of the poly(oxyethylene) glycol alkylphenyl ether in an apolar solvent and support the idea of a solubility-limited adsorption: solubility in organic solvents of the smaller (EO) chains is much more significant than that of the longer ones and hence prevents adsorption of the smaller species. Consequently, it is observed that the presence of interfacial water decreases the affinity of TX-35 molecules for the hydrophilic silica surface due to the hydration of (EO) chains. In contrast, for TX-100 adsorption after the prewetting treatment the clearest trend is a drastic increase of the adsorption ascribed to the additional solubilization (and micellization) of the TX-100 molecules in the interfacial aqueous phase. The differential molar enthalpies of displacement show a change in the adsorption mechanism, depending on the presence of molecular water on the surface. In the initial part of the adsorption isotherm, a prevailing exothermic process is obtained with prehydrated silica and suggests that hydration of the polar heads of TX-35 and the solubilization of the TX-35 in interfacial water are occurring. For higher equilibrium concentrations, the enthalpies of displacement observed with the prehydrated adsorbent become slightly lower than those obtained with dry silica gel. It may be that this difference is due to the micellization phenomenon of the surfactant species with longer EO chains in interfacial water. These features emphasize the influence of interfacial water on the adsorption of EO fractions from organic solvent. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

Risks of preeclampsia and adverse neonatal outcomes among women with pregestational diabetes mellitus. National Institute of Child Health and Human Development Network of Maternal-Fetal Medicine Units.

OBJECTIVES: This study was undertaken to determine the frequencies of preeclampsia and adverse neonatal outcomes among women with pregestational diabetes. STUDY DESIGN: This was a prospective observation of pregnancy outcomes among 462 women with pregestational diabetes mellitus (White classes B-F) and singleton pregnancies who were enrolled in a multicenter trial to compare low-dose aspirin with placebo for preeclampsia prevention. The main outcome measures were preeclampsia and neonatal outcomes. RESULTS: Among 462 women with pregestational diabetes, 92 (20%) had preeclampsia. Preeclampsia frequency rose significantly with increasing severity of diabetes according to White classification (class B, 11%; class C, 22%; class D, 21%; class R plus class F, 36%; P <.0001). Preeclampsia was also more common among women who had proteinuria at baseline (28% vs 18%; odds ratio, 1.75; 95% confidence interval, 1.02-3.01). Frequency of preterm delivery at <35 weeks' gestation rose greatly with increasing severity of diabetes (P =.0002). Women with proteinuria at baseline were significantly more likely to be delivered at <35 weeks' gestation (29% vs 13%; odds ratio, 2.6; 95% confidence interval, 1.5-4.6) and to have small-for-gestational-age infants (14% vs 3%; odds ratio, 5. 4; 95% confidence interval, 2.7-17.7), and they were less likely to have large-for-gestational-age infants (14% vs 40%; odds ratio, 0.2; 95% confidence interval, 0.1-0.5). CONCLUSION: Among women with pregestational diabetes mellitus, the frequency of preeclampsia rose with increasing severity of diabetes. Proteinuria early in pregnancy was associated with marked increases in adverse neonatal outcomes independent of preeclampsia development.

Aspirin↗
PubMed1999

Safety of labor epidural anesthesia for women with severe hypertensive disease. National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network.

OBJECTIVE: The aim of this study was to determine whether epidural anesthesia during labor increased the frequencies of cesarean delivery, pulmonary edema, and renal failure among women with severe hypertensive disease. STUDY DESIGN: We performed a secondary retrospective analysis of a subgroup population within a multicenter double-blind trial of low-dose aspirin therapy for women at high risk for development of preeclampsia. Subjects in whom severe hypertensive disease developed were selected. The primary outcomes were the overall frequencies of cesarean delivery among women with severe hypertensive disease who had labor with and without epidural anesthesia. Other maternal and neonatal outcomes were also compared between women who did and did not receive epidural anesthesia. RESULTS: Among the women with severe hypertensive disease (n = 444) 327 had labor. Among the women with severe disease who had labor there was no difference in either the overall cesarean delivery rate (32.1% vs 28.0%; P =.44) or the rate of cesarean delivery for fetal distress or failure to progress (27.8% vs 22.0%; P =.26) between women who did and did not receive epidural analgesia. Women with chronic hypertension were more likely to have a cesarean delivery overall if they received epidural anesthesia, but there was otherwise no difference in the frequencies of cesarean delivery for these indications between women with and without epidural anesthesia within each of the high-risk groups. Pulmonary edema was rare and acute renal failure did not develop in any women. CONCLUSION: Epidural anesthesia use did not increase the frequencies of cesarean delivery, pulmonary edema, and renal failure among women with severe hypertensive disease.

Adult↗
PubMed1999

A modified definition for peripartum cardiomyopathy and prognosis based on echocardiography.

The diagnosis of peripartum cardiomyopathy is one of exclusion, made after careful search for an underlying cause. Research in this area is compromised by the reliance of some on clinical criteria alone without strict echocardiographic criteria. This article argues for uniform criteria that define peripartum cardiomyopathy, similar to the criteria for idiopathic dilated cardiomyopathy set forth by a National Heart, Lung, and Blood Institute-sponsored workshop and proposes that the new definition include heart failure within the last month of pregnancy or 5 months postpartum; absence of preexisting heart disease; no determinable etiology, the traditional definition; and strict echocardiographic criteria of left ventricular dysfunction: ejection fraction less than 45%, or M-mode fractional shortening less than 30%, or both, and end-diastolic dimension more than 2.7 cm/m2. Mortality from peripartum cardiomyopathy remains high, 25-50%, and a recent review related long-term prognosis to echocardiographic measures of left ventricular chamber dimension and function at diagnosis and recovery. We describe a modified pharmacologic echocardiographic stress test that might be useful in determining left ventricular contractile reserve in women believed to be recovered by routine echocardiographic studies. The test reproduces hemodynamic stress akin to pregnancy, and the data might be useful when counseling women on future childbearing. Women who respond with reduced cardiac reserve might be advised to avoid pregnancy.

Cardiomyopathies↗
PubMed1998

Maternal serum thromboxane B2 concentrations do not predict improved outcomes in high-risk pregnancies in a low-dose aspirin trial. The National Institute of Child Health and Human Development Network of Maternal-Fetal Medical Units.

OBJECTIVE: The aim of the study was too determine whether, in a low-dose aspirin trial in high-risk pregnancies, a decrease in maternal serum thromboxane B2 level predicted improved pregnancy outcomes. STUDY DESIGN: This multicenter, randomized, double-blind trial included 2539 women, 1010 of whom had sufficient serum samples at enrollment and at 24 to 28 weeks' gestation, 34 to 38 weeks' gestation, or both to assess longitudinal changes in thromboxane B2 level and their effects on pregnancy outcomes. Women were randomly assigned between 13 and 26 weeks' gestation to receive daily aspirin (60 mg) or placebo. RESULTS: Overall and in all subgroups women assigned to receive aspirin had markedly lower maternal thromboxane B2 concentration values than did those assigned to receive a placebo (P =.0001). Changes in thromboxane levels were not, however, correlated with adverse pregnancy outcomes. Women with >/=50% reduction in maternal serum thromboxane B2 concentrations from baseline had occurrences of preeclampsia (P =.922), preterm birth (P =.375), small for gestational age neonates (P =.938), and grade III or IV intraventricular hemorrhage (P = 1.000) similar to those of women who had <50% reduction. Similar results were found for women with thromboxane B2 level decreases of <15 versus >15 ng/mL and women with thromboxane B2 level decreases to <10 versus >/=10, <5 versus >/=5, and <1 versus >/=1 ng/mL. Maternal thromboxane B2 concentrations at enrollment were also not predictive of adverse outcomes. CONCLUSION: Neither maternal serum thromboxane B2 concentrations at enrollment nor their subsequent reduction were predictive of adverse pregnancy outcomes in a low-dose aspirin trial.

Aspirin↗
PubMed1998

Predictors of pre-eclampsia in women at high risk. National Institute of Child Health and Human Development Network of Maternal-Fetal Medicine Units.

OBJECTIVE: We assessed several variables as predictors for pre-eclampsia risk in a group of women at high risk. STUDY DESIGN: We studied 2503 women with either diabetes mellitus, chronic hypertension, multifetal gestation, or pre-eclampsia in a previous pregnancy who participated in a multicenter study comparing aspirin and placebo in preventing pre-eclampsia. We evaluated multiple variables for predicting pre-eclampsia risk with use of univariate and multivariable analysis. RESULTS: Parity and mean arterial pressure at randomization were most predictive of pre-eclampsia risk. The risk was 8% with a mean arterial pressure at enrollment of <75 mm Hg versus 27% with a mean arterial pressure >85 mm Hg (relative risk and 95% confidence interval 3.3 [2.4 to 4.4]). The risk of pre-eclampsia was 26% in nulliparous patients versus 17% in parous subjects (relative risk and 95% confidence interval 1.5 [1.3-1.8]). CONCLUSIONS: The finding that second-trimester mean arterial pressure affects pre-eclampsia risk suggests that the pathophysiologic process of preeclampsia is initiated before that time.

Adult↗
PubMed1997

Contractile reserve in patients with peripartum cardiomyopathy and recovered left ventricular function.

OBJECTIVES: Peripartum cardiomyopathy is a rare complication of pregnancy. Thirty percent of patients with this disorder are reported to recover baseline ventricular function within 6 months of delivery, but the ability of these ventricles to respond to hemodynamic stress is unknown. The aim of this investigation was to quantitatively assess the contractile reserve of patients with a history of peripartum cardiomyopathy and recovered left ventricular function. STUDY DESIGN: Baseline left ventricular contractility was assessed by use of the load and heart rate-independent relationship between end-systolic stress and rate-corrected velocity of fiber shortening. Data were acquired from "recovered" patients (10.5 +/- 11.6 months after delivery) and compared with data from matched nonpregnant controls with use of two-dimensionally targeted M-mode echocardiography and calibrated subclavian pulse tracings that were recorded over a wide range of afterloads (end-systolic stress) generated by methoxamine (1 mg/min) infusion. Contractile reserve was assessed by a dobutamine challenge (5 micrograms/kg/min) and quantified as the vertical deviation of the dobutamine end-systolic stress minus the corrected velocity of fiber shortening data point from the baseline contractility line. RESULTS: Patients with peripartum cardiomyopathy and matched controls had normal baseline heart rates, blood pressures, ventricular dimensions, and left ventricular function. Contractile reserve, however, was reduced in patients with recovered peripartum cardiomyopathy (0.30 +/- 0.12 vs 0.17 +/- 0.04 circ/sec, p < 0.03). CONCLUSIONS: Women with a history of peripartum cardiomyopathy who have regained normal resting left ventricular size and performance have decreased contractile reserve revealed by the use of a dobutamine challenge test. Ventricles of these women may respond suboptimally to hemodynamic stress in spite of evidence of recovery by routine echocardiographic evaluation.

Adrenergic beta-Agonists↗
PubMed1994

Nephrolithiasis in pregnancy.

Although the anatomical and physiological changes of normal pregnancy may predispose to kidney stone formation, it remains an uncommon occurrence. Correct diagnosis is often difficult. Ultrasonography has become the primary radiological diagnostic tool, with a limited excretory urogram only necessary in complicated cases. Nephrolithiasis during pregnancy occurs more frequently during the later stages of gestation, in multiparas, and without a difference in laterality. Conservative management with bed rest, hydration and analgesia can result in spontaneous passage of most stones in gravidas. Past experience of several groups suggests that cystoscopy and/or surgery can usually be done safely when absolutely necessary. Pre-existing stone disease can increase the incidence of maternal urinary tract infections by 10-20%. The most common obstetric complications of stones during gestation is premature labour induced by renal colic. Most drugs normally used to treat stone disease are contraindicated in gestation. Known inhibitors of stone formation are present in gestation and may partially explain why the incidence of stones is not increased in this hypercalciuric state.

Adult↗
PubMed1993

Peripartum heart failure associated with prolonged tocolytic therapy.

beta-Adrenergic receptor agonist tocolysis has been reported to cause noncardiogenic pulmonary edema. We report an association between chronic terbutaline therapy and cardiomyopathy in peripartum women. Among 15 gravidas who had peripartum heart failure, 4 had received prolonged terbutaline tocolysis. Although those four patients had completely normalized ventricular function, only 7 of the 11 others recovered. We suggest that gravidas receiving long-term beta-sympathomimetic tocolysis undergo close evaluation of cardiac function.

Cardiomyopathies↗
PubMed1991

Left ventricular mechanics in preeclampsia.

Increased systemic vascular resistance and contracted blood volume are characteristic findings in preeclampsia. These alterations in cardiovascular hemodynamics can adversely affect ejection phase indices of left ventricular performance making it difficult to separate abnormalities resulting from changes in load from those caused by depressed myocardial contractility. To address this issue the contractility-sensitive, load-independent relationship between left ventricular end-systolic wall stress and rate-corrected velocity of fiber shortening was assessed in 10 nulliparous patients with preeclampsia. Comparisons were made with data obtained from 10 age-matched normotensive women with uncomplicated pregnancies (control subjects). Studies were performed by means of two-dimensionally targeted M-mode echocardiography and calibrated carotid pulse tracings during early labor, 1 day after delivery, and 4 weeks after delivery. During early labor and 1 day after delivery, patients with preeclampsia had elevated blood pressure and increased total systemic resistance. These parameters returned to normal by 4 weeks after delivery. Before delivery and 24 hours after delivery, the patients with preeclampsia had lower overall left ventricular performance (as measured by cardiac output and rate-corrected velocity of fiber shortening) and higher left ventricular afterload (as measured by left ventricular end-systolic wall stress) when compared with control subjects. These differences were no longer present 4 weeks after delivery. Despite the time-related intergroup differences in hemodynamics, left ventricular contractility was similar between normotensive and preeclamptic subjects at all stages of the study. Thus when load is eliminated as a confounding variable, the decrements in overall left ventricular performance measured in patients with preeclampsia reflect a mechanically appropriate response to increased afterload rather than an abnormality in the ventricular contractile state.

Adult↗
PubMed1987

Reduced glomerular filtration rate and hypercalciuria in primary struvite nephrolithiasis.

Struvite nephrolithiasis is caused by infection with bacteria that possess the enzyme urease, and convert urea to ammonia that raises urine pH and crystallizes with magnesium and trivalent phosphate ion. Of the 75 of our 1431 stone patients with struvite stones 52 were women. Struvite stones occurred almost exclusively in women; a minority of women and most men had mixed stones of struvite and calcium oxalate. Increased serum creatinine levels and reduced creatinine clearance were common in patients with struvite stones, not in those with mixed stones; both were rare in calcium stone disease. Men and women with mixed struvite, calcium oxalate stones were hypercalciuric, but women with struvite stones were not. Patients with mixed stones usually had initial symptoms of stone passage, and were less likely to need surgery, including nephrectomy, or to form contralateral stones. Patients with struvite stones usually presented with infection or no symptom, not passage. We conclude that struvite stones occur in two forms. The struvite stone is a disease of women, presumably occurring de novo from infection. The mixed stones occur in both sexes, presumably from secondary infection in hypercalciuric patients who begin with calcium-oxalate stone disease.

Blood Pressure↗
PubMed1987

In vitro activity of nicotinamide adenine dinucleotide- and nicotinamide adenine dinucleotide phosphate-linked 15-hydroxyprostaglandin dehydrogenases in placentas from normotensive and preeclamptic/eclamptic pregnancies.

Concentrations of prostaglandins E2 and I2 may be decreased in preeclamptic and eclamptic pregnancies. Because these prostaglandins produce vasodilation and inhibit platelet aggregation it has been suggested that a reduction in their biosynthesis might play an important role in the pathogenesis of the hypertension and coagulation abnormalities associated with preeclampsia. Placental tissue is an extremely rich source of several enzymes that catalyze the catabolism of prostaglandins. The present study was initiated to determine whether one of these catabolic enzymes might be increased in preeclamptic/eclamptic pregnancies. The activities of the NAD- and the NADP-linked 15-hydroxyprostaglandin dehydrogenases were measured in 16 preeclamptics (mean diastolic pressure, 108 +/- 13 mmHg) and compared with 16 normotensive controls matched for age (20.8 +/- 5.43 vs. 20.6 +/- 5.16) and gestational week of delivery (34.6 +/- 5.40 vs. 35.0 +/- 5.06). These results indicate that the activity of the placental NAD-linked 15-hydroxyprostaglandin dehydrogenase is elevated in preeclampsia (40.1 +/- 31.3 vs. 14.9 +/- 8.30 mU/g tissue, P less than 0.01). If this increase were also expressed in vivo, its effect on prostaglandin metabolism could be mistaken for impaired prostacyclin biosynthesis unless both the 6-keto- and 6,15-diketo-metabolites of prostacyclin were measured.

Adolescent↗