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Biomedical subjects

S L Clark

Publications and source records attributed to S L Clark.

At least 37 records · Page 2Linked to original sources
PubMed1996

Very advanced maternal age: pregnancy after age 45.

OBJECTIVE: Our purpose was to describe the maternal and fetal outcomes of pregnancies in women > or = 45 years old at delivery. STUDY DESIGN: A retrospective review of in-hospital deliveries after 20 weeks of gestation was performed in four Utah tertiary care hospitals for the 10-year period between 1985 and 1994. RESULTS: Seventy-nine cases were identified among 126,500 births, with an incidence of 0.63 per 1000 births. Maternal ages were 45 (n = 44), 46 (n = 21), and > or = 47 (n = 14) years. Three of the conceptions were assisted, including both twin gestations. Thirty-seven (46.8%) had obstetric complications during pregnancy; the most frequent complications were gestational diabetes (12.7%) and preeclampsia (10.1%). Median (range) gestational age at delivery was 39 (22.9 to 41.7) weeks; 12 (15.2%) deliveries occurred before 37 weeks. Eight (9.9%) karyotype abnormalities were diagnosed. The cesarean section rate was 31.7%; the most frequent indications were abnormal lie (n = 9), fetal distress (n = 5), and previous cesarean delivery (n = 5). There were no maternal deaths. Median (range) birth weight was 3466 (397 to 5085) gm; 14 (17.3%) were < 2500 gm and 16 (19.8%) were > 4000 gm. Twelve (14.8%) infants were admitted to the neonatal intensive care unit. The corrected perinatal mortality rate was 1.3% (1/78). CONCLUSIONS: In women > 45 years old at delivery maternal and fetal outcomes were generally good, but there was a high incidence of pregestational (chronic hypertension, hypothyroidism) and gestational (karyotype abnormalities, gestational diabetes, cesarean section, macrosomia) complications. This information may be helpful for counseling women between 45 and 50 years old who are considering pregnancy.

Apgar Score↗
PubMed1996

The relationship between oxygen saturation and pH in umbilical blood: implications for intrapartum fetal oxygen saturation monitoring.

OBJECTIVE: Our purpose was to evaluate the relationship between umbilical arterial blood oxygen saturation determined by hemoximetry (Sao2) and umbilical arterial blood pH and base excess determined by blood gas analysis to establish a "critical threshold" for fetal preductal arterial oxygen saturation determined by reflectance pulse oximetry (Spo2). STUDY DESIGN: Umbilical artery and vein blood specimens were obtained at delivery. Blood gas analysis and hemoximetry were performed. Polynomial regression analysis and receiver-operator characteristic curves were calculated for umbilical arterial blood Sao2 and theoretic preductal arterial blood Sao2 versus umbilical arterial blood pH and base excess. RESULTS: A total of 1101 paired umbilical artery and vein specimens were obtained. When the umbilical arterial blood Sao2 was > or = 30%, umbilical arterial blood pH was > or = 7.13 in 99.0% (388/392) of cases and < 7.13 in 1.0% (4/392) of cases. When umbilical arterial blood Sao2 was < 30%, umbilical arterial blood pH was > or = 7.13 in 91.4% (648/709) of cases and < 7.13 in 8.6% (61/709) of cases. CONCLUSIONS: From these analyses, it appears that an Spo2 cutoff value of 30% would be reasonable in clinical trials of intrapartum fetal pulse oximetry.

Acid-Base Imbalance↗
PubMed1996

Amniotic fluid index and perinatal morbidity.

Our purpose was: (1) to determine whether assessment of amniotic fluid index in high risk patients with a reactive nonstress test (NST) allowed improved recognition of the fetus at risk for perinatal morbidity than a reactive NST alone; and (2) to determine the optimal low amniotic fluid index (AFI) which should prompt clinical concern. The last NST performed within a week of delivery and amniotic fluid index were retro-spectively compared with various indices of perinatal morbidity. In fetuses with a reactive NST, decreasing AFI was directly correlated with a risk of 5-minute Apgar score of less than 7 and delivery for fetal distress. When various subgroupings of AFI were compared, 7 cm or greater appeared to have a better inverse correlation with the indices of morbidity than lower cut-off values. The addition of AFI assessment to the standard NST allows better prediction of perinatal morbidity than the NSTs alone. Seven centimeters appears to be a reasonable cut-off for clinical concern.

Amniotic Fluid↗
PubMed1995

Oxidized low-density lipoprotein decreases the expression of endothelial nitric oxide synthase.

The atherogenic effects of low-density lipoprotein (LDL) may be mediated, in part, by its effect(s) on endothelial-derived nitric oxide (NO). To determine whether LDL can modulate NO production by changing NO synthase expression, we treated human saphenous vein endothelial cells with increasing concentrations of native or oxidized LDL (0-100 micrograms/ml) for various durations (0-72 h). Oxidized, but not native LDL caused a time-dependent decrease in steady-state NO synthase mRNA levels. This coincided with a maximal 56% decrease in NOS activity was determined by [3H]arginine to [3H]citrulline conversion. In the presence of actinomycin D, treatment with oxidized LDL reduced the half-life of NO synthase mRNA from 36 to 10 h. This decrease in NO synthase mRNA correlated with the degree of LDL oxidation and was attenuated by pretreatment with cycloheximide. Nuclear run-off studies showed a biphasic transcriptional pattern of NO synthase gene with an initial 25% decrease during the first 6 h followed by a maximal 2.2-fold increase over baseline during the subsequent 18 h. These results indicate that oxidized LDL regulates endothelial NOS expression through a combination of early transcriptional inhibition and post-transcriptional mRNA destabilization.

Amino Acid Oxidoreductases↗
PubMed1995

Amniotic fluid embolism: analysis of the national registry.

OBJECTIVE: We analyzed the clinical course and investigated possible pathophysiologic mechanisms of amniotic fluid embolism. STUDY DESIGN: We carried out a retrospective review of medical records. Forty-six charts were analyzed for 121 separate clinical variables. RESULTS: Amniotic fluid embolism occurred during labor in 70% of the women, after vaginal delivery in 11%, and during cesarean section after delivery of the infant in 19%. No correlation was seen with prolonged labor or oxytocin use. A significant relation was seen between amniotic fluid embolism and male fetal sex. Forty-one percent of patients gave a history of allergy or atopy. Maternal mortality was 61%, with neurologically intact survival seen in 15% of women. Of fetuses in utero at the time of the event, only 39% survived. Clinical and hemodynamic manifestations were similar to those manifest in anaphylaxis and septic shock. CONCLUSIONS: Intact maternal or fetal survival with amniotic fluid embolism is rare. The striking similarities between clinical and hemodynamic findings in amniotic fluid embolism and both anaphylaxis and septic shock suggest a common pathophysiologic mechanism for all these conditions. Thus the term amniotic fluid embolism appears to be a misnomer.

Adolescent↗
PubMed1995

Brachial plexus palsy involving the posterior shoulder at spontaneous vaginal delivery.

Brachial plexus injuries sustained at birth have most often been attributed to the maneuvers performed when attempting to relieve a shoulder dystocia or to deliver a breech vaginally. In the case now reported, the brachial plexus injury involved the posterior shoulder. As the delivery was spontaneous and without forceps or manual rotation, with delivery effected using only the McRobert's maneuver, it is hypothesized that maternal expulsive forces in conjunction with lodging of the posterior shoulder on the sacral promontory resulted in the injury.

Adult↗
PubMed1995

Regulation of G-protein alpha i2 subunit expression by oxidized low-density lipoprotein.

Oxidized low-density lipoprotein (LDL) inhibits signalling pathways mediated by pertussis toxin-sensitive guanine nucleotide-binding proteins (Gi proteins). To determine whether this inhibition is due to altered G protein alpha i subunit expression, mRNA and protein levels of alpha i isoforms were assessed in bovine aortic endothelial cells treated with oxidized LDL (0-100 micrograms/ml, 0-72 h). Oxidized LDL did not affect the expression of alpha i3, but did cause time- and concentration-dependent decrease in alpha i2 mRNA and protein resulting in a 3.2- and 3.5-fold reduction, respectively, after 72 h. This decrease in alpha i2 coincided with a 86% decrease in alpha i2 GTPase activity. Nuclear run-off studies did not show any significant effect of oxidized LDL on alpha i2 or alpha i3 transcription. In the presence of actinomycin D, oxidized LDL shortened the t1/2 of alpha i2 mRNA from 16 h to 8 h which was attenuated by cycloheximide. In addition, pulse-chase labelling with [35S]methionine revealed that oxidized LDL reduced the t1/2 of alpha i2 protein from 27 to 14 h. Our results indicate that oxidized LDL can modulate receptor-Gi coupling by downregulating the expression of alpha i2, but not alpha i3. The mechanism involves both mRNA destabilization and protein degradation.

Amino Acid Sequence↗
PubMed1995

Cardiac arrest during pregnancy.

Cardiac arrest occurs rarely in pregnancy. Nevertheless, the practicing obstetrician stands a likely chance of encountering this acute condition at least once over the course of a busy career. A basic understanding of maternal-fetal physiology and the acute management of cardiac arrest are of key importance. ECC is not significantly changed from that administered to the nonpregnant patient. Factors unique to pregnancy, however, such as lateral uterine displacement, effects of drugs on the mother and the fetus, and the issues of perimortem cesarean section should be understood by the consulting obstetrician. The critical period in management of these patients is within the first several minutes of the event. In many situations, the obstetrician may be the first to arrive and initiate therapy before the arrival of multidisciplinary assistance. Prompt initial management will give the mother and fetus the best chances for survival.

Cardiopulmonary Resuscitation↗
PubMed1994

Intrapartum fetal pulse oximetry: the effects of maternal hyperoxia on fetal arterial oxygen saturation.

OBJECTIVE: Our purpose was to observe the effects of maternal oxygen administration on fetal arterial oxygen saturation in normal human fetuses during labor. STUDY DESIGN: Twenty healthy women with uncomplicated pregnancies were studied during active labor at term. Arterial oxygen saturation was measured by a noninvasive reflectance pulse oximeter designed for fetal application (Nellcor, Inc, Pleasanton, Calif.). The first group was studied during 20-minute intervals of inspired oxygen concentrations of 21%, 40%, and 100%. In a second group the effects of prolonged (45 minutes) supplemented 40% oxygen administration were evaluated. Differences between groups were analyzed by analysis of variance; significance was considered at p < 0.05. RESULTS: A significant increase in fetal arterial oxygen saturation (50% +/- 8% vs 64% +/- 6%, p < 0.0001) was detected in the group given 100% oxygen for 20 minutes but not in the groups that received 40% oxygen for 20 or 45 minutes. CONCLUSIONS: Prolonged maternal administration of 40% oxygen resulted in no significant demonstrable change in fetal arterial oxygen saturation determined by reflectance pulse oximetry in normal fetuses. Because the administration of oxygen by standard mask techniques rarely results in 40% inspired oxygen concentration, fetal benefits of such intrapartum maternal oxygen administration are questionable.

Adult↗
PubMed1994

Intrapartum fetal pulse oximetry: fetal oxygen saturation trends during labor and relation to delivery outcome.

OBJECTIVES: Our purpose was to study fetal arterial oxygen saturation trends by continuous pulse oximetry during labor in subjects with normal and abnormal delivery outcomes. STUDY DESIGN: Continuous fetal arterial oxygen saturation was measured during labor with a noninvasive reflectance pulse oximeter designed for fetal application. Averaged arterial oxygen saturation values were compared between stage 1 and stage 2 of labor, with stage 1 further subdivided into early (< or = 4 cm), middle (5 to 7 cm), and late (8 to 10 cm) phases. Delivery outcome was considered to be abnormal for any of the following conditions: gestational age < 37 weeks, maternal oxygen administration, delivery by cesarean section, 5-minute Apgar score < 7, umbilical artery pH < 7.10, birth weight < 2500 gm, or newborn intensive care unit admission. RESULTS: A total of 291 subjects were studied: 142 in Provo, 90 in Nijmegen and 59 in San Francisco. Subjects with delivery complications (n = 125) were evaluated separately from those with normal delivery outcomes (n = 160). Fetal arterial oxygen saturation was 58% +/- 10% (mean +/- SD) during the cumulative period of study for the normal-outcome group. A significant decrease (paired t test, p < 0.001) in fetal arterial oxygen saturation occurred from stage 1 (59% +/- 10%) to stage 2 (53% +/- 10%) labor. When stage 1 was subdivided into early (< or = 4 cm), middle (5 to 7 cm), and late (8 to 10 cm) phases, a gradual decreasing trend in fetal arterial oxygen saturation was observed: 62% +/- 9%, 60% +/- 11%, and 58% +/- 10%. CONCLUSIONS: With the use of reflectance pulse oximetry, a statistically significant decrease in fetal arterial oxygen saturation was observed during labor in women with normal and abnormal delivery outcomes.

Adult↗
PubMed1994

A comparison of cardiac index in normal term pregnancy using thoracic electrical bio-impedance and oxygen extraction (Fick) techniques.

OBJECTIVE: To correlate cardiac index in normal late third-trimester pregnancy using the thoracic electrical bio-impedance technique with that obtained from the oxygen extraction technique. METHODS: Eight carefully screened normal pregnant women underwent assessment of cardiac index using both the thoracic electrical bio-impedance technique and the oxygen extraction technique. Measurements were obtained in various positions. RESULTS: The correlation was good between the thoracic electrical bio-impedance and oxygen extraction techniques in the left lateral (r = 0.915) and right lateral (r = 0.863) positions, and the intercepts at the midpoints of the oxygen extraction data in these positions suggested good absolute correlation as well. Correlation between thoracic electrical bio-impedance and the Fick cardiac index was poor in all other positions. CONCLUSIONS: Thoracic electrical bio-impedance cardiac index assessment is influenced by maternal position and must be used with caution in clinical research protocols. This technique appears to be inappropriate for general clinical use during pregnancy.

Adult↗
PubMed1993

Acute hemodynamic and respiratory effects of amniotic fluid embolism in the pregnant goat model.

OBJECTIVE: Our purpose was to determine the acute-phase central hemodynamic and respiratory effects of raw, filtered, filtered and boiled, and meconium-containing amniotic fluid. STUDY DESIGN: Pregnant goats (Capra hircus) in the last one third of pregnancy were given freshly collected autologous amniotic fluid in a volume of 2.5 ml/kg of body weight. Observations were then made at 10, 30, 60, 120, and 180 minutes after amniotic fluid embolism. Pulmonary artery catheters and femoral artery lung water catheters were placed for specimen and data collection. RESULTS: Marked pressor responses were observed in both the pulmonary and systemic circulations with all amniotic fluid infusions. The pressor response was similar with raw, filtered, and filtered and boiled amniotic fluid. The pressor response seen with amniotic fluid containing meconium was significantly greater than that seen with the other forms. No significant effects were observed on cardiac or respiratory function except in the meconium group, where transient left ventricular dysfunction was accompanied by an acute increase in extravascular lung water and dysoxia. CONCLUSIONS: The Capra hircus model is appropriate for the further study of amniotic fluid embolism. The acute pressor effects are transient and involve both the systemic and pulmonary circulations. Left ventricular dysfunction and dysoxia were observed only with embolism of amniotic fluid containing meconium.

Amniotic Fluid↗
PubMed1993

Asthma in pregnancy. National Asthma Education Program Working Group on Asthma and Pregnancy. National Institutes of Health, National Heart, Lung and Blood Institute.

This manuscript is a summary of a comprehensive report dealing with asthma and pregnancy issued by the working group on Asthma and Pregnancy, National Institutes of Health (NIH), National Heart, Lung, and Blood Institute. The report was developed by a panel of obstetricians, pharmacologists, internists, allergists, and pulmonologists, who met over an 18-month period under the auspices of the NIH. Undertreatment of pregnant asthmatics, partially because of unfounded fears of adverse pharmacologic effects on the developing fetus, remains the major problem in the management of asthma during pregnancy in the United States. The four key components of asthma management during pregnancy are: 1) objective assessment of maternal lung function and fetal well-being, 2) avoidance or control of environmental precipitating factors, 3) pharmacologic therapy, and 4) patient education.

Asthma↗
PubMed1993

Severe pulmonary hypertension in pregnancy following successful repair of ventricular septal defect in childhood.

BACKGROUND: Because of advances in surgical repair, an increasing number of women born with structural cardiac disease now live to reproductive age. Patients treated successfully in childhood are followed for varying periods of time, then may be lost to follow-up or told that no follow-up is necessary because their condition is stable. However, the hemodynamic changes that accompany pregnancy may result in cardiovascular decompensation, even after years of apparently good health. CASES: We have recently cared for two women who had undergone repair of congenital heart disease in childhood. Although they thought that their repair was complete and they had been asymptomatic until the pregnancy, both presented with symptoms and signs of severe pulmonary hypertension, subsequently confirmed on cardiac catheterization. One patient elected to terminate her pregnancy, and the other died in the immediate puerperium. CONCLUSION: Despite normal physical function and an absence of abnormal physical findings, a thorough cardiac evaluation including echocardiography should be considered for pregnant patients with a history of repaired congenital heart disease, especially if the original defect is known to lead to pulmonary hypertension.

Adult↗
PubMed1993

Preliminary experience with intrapartum fetal pulse oximetry in humans.

Electronic fetal heart rate (FHR) monitoring is commonly used to assess fetal well-being during labor. Nonreassuring patterns in many cases are associated with normal fetal acid-base condition, leading to unnecessary operative intervention. Fetal pulse oximetry has several potential advantages over FHR monitoring because it assesses not only pulse, but also arterial oxygen saturation and tissue perfusion. We describe our preliminary experience with the Nellcor N-400 Fetal Oxygen Saturation Monitor and FS-10 Oxisensor in 73 subjects during active labor at term. The mean (+/- standard deviation) duration of monitoring was 161.4 +/- 106.0 minutes, with sensor contact achieved 67.3 +/- 22.5% of the time during labor. Data were successfully recorded in all patients, with a reliable signal obtained 50.1 +/- 21.6% of the time during labor. The mean fetal oxygen saturation was 57.9 +/- 10.0%. The potential for research and clinical applications appears promising with further sensor and monitor development.

Adult↗
PubMed1992

Successful pregnancy outcomes after amniotic fluid embolism.

Two patients who survived cardiorespiratory arrest occurring in association with amniotic fluid embolism syndrome were seen during the subsequent pregnancy. Both had uneventful pregnancies and delivered at term without complications. These are the only case reports of pregnancy after amniotic fluid embolism, and they support a model of amniotic fluid embolism involving chemically abnormal amniotic fluid rather than an unusual sensitivity to normal amniotic fluid.

Adult↗