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Biomedical subjects

S L Clark

Publications and source records attributed to S L Clark.

At least 19 recordsLinked to original sources
PubMed2000

Coumarin derivatives and breast-feeding.

Coumarin derivatives are the anticoagulants most widely used in the United States. These agents are relatively contraindicated during pregnancy, and the use of these drugs in breast-feeding women remains controversial. Much of the confusion regarding the passage of these agents into breast milk might stem from the fact that different agents possess significantly different chemical properties. A review of the chemical structure of different coumarin derivatives, as well as available clinical evidence, suggests that warfarin sodium is not excreted into breast milk, and can be safely given to women requiring therapeutic anticoagulation postpartum. For the rare patient who cannot tolerate warfarin sodium, the use of dicumarol, rather than anisindione, is preferred.

Anticoagulants↗
PubMed2000

Is vaginal birth after cesarean less expensive than repeat cesarean delivery?

OBJECTIVE: This study was undertaken to compare total medical costs of trial of labor after cesarean with those of elective repeat cesarean without labor, with both short- and long-term neonatal costs associated with such procedures taken into account. STUDY DESIGN: Costs associated with All Patient Refined diagnosis-related groups and Current Procedural Terminology for a large not-for-profit health care system were applied to an algorithm describing maternal and neonatal outcomes of trial of labor. Perinatal morbidity rates and cost estimates for long-term neurologic damage associated with uterine rupture were derived from published literature. RESULTS: If a 70% vaginal birth rate for women undergoing a trial of labor and delivery in a tertiary center with a mean uterine rupture to delivery time of 13 minutes is assumed, the net cost differential ranged from a saving of $149 to a loss of $217, depending on morbidity assumptions. For vaginal birth after cesarean success rates <70%, trial of labor in the presence of two previous scars, and institutional factors increasing the perinatal morbidity rate by just 4% with respect to that seen in tertiary centers, trial of labor resulted in a net financial loss to the health care system regardless of all other assumptions made. CONCLUSIONS: When costs as opposed to charges are considered and the cost of long-term care for neurologically injured infants is taken into account, trial of labor after previous cesarean is unlikely to be associated with a significant cost saving for the health care system. Recent government-mandated length-of-stay requirements are likely to make the economic benefit of vaginal birth after cesarean even less favorable. Factors other than cost must govern decisions regarding trial of labor or repeat cesarean.

Algorithms↗
PubMed1999

Migration of antigen-presenting B cells from peripheral to mucosal lymphoid tissues may induce intestinal antigen-specific IgA following parenteral immunization.

Parenterally administered immunizations have long been used to induce protection from mucosal pathogens such as Bordetella pertussis and influenza virus. We previously found that i.m. inoculation of mice with the intestinal pathogen, rotavirus, induced virus-specific Ab production by intestinal lymphocytes. We have now used adoptive transfer studies to identify the cell types responsible for the generation of virus-specific Ab production by gut-associated lymphoid tissue (GALT) after i.m. immunization. Three days after i.m. immunization with rotavirus, cells obtained from the draining peripheral lymph nodes of donor mice were transferred into naive recipient mice. We found that intestinal lymphocytes produced rotavirus-specific Igs (IgM, IgA, and IgG) 2 wk after transfer of either unfractionated cells, or unfractionated cells rendered incapable of cellular division by mitomycin C treatment. Additional studies demonstrated that rotavirus-specific IgA, but not IgG, was produced by intestinal lymphocytes after transfer of purified B cells. Ig allotype analysis revealed that rotavirus-specific IgA was produced by intestinal B cells of recipient origin, suggesting that migration of Ag-presenting B cells from peripheral lymphoid tissues to GALT may contribute to the generation of mucosal IgA responses after parenteral immunization. Strategies that promote Ag uptake and presentation by B cells may enhance mucosal IgA production following parenteral immunization.

Adoptive Transfer↗
PubMed1999

Maternal oxygen transport variables during the third trimester of normal pregnancy.

OBJECTIVE: The aim of this study was to measure and calculate oxygen transport variables in uncomplicated term pregnancies. STUDY DESIGN: Ten normotensive primiparous women between 36 and 38 weeks' gestation underwent pulmonary and radial arterial catheterization as part of a larger study. Seven women had studies repeated at approximately 12 weeks post partum. Measurements were made with patients in the left lateral recumbent position after a 30-minute stabilization period. Cardiac output was measured with the thermodilution technique. Blood samples were obtained simultaneously from the pulmonary and radial arteries and analyzed in duplicate for oxygen content with a blood gas analyzer. RESULTS: The oxygen contents of both arterial and mixed venous blood are significantly lower (P <.05) in the third trimester of pregnancy (15.96 and 11.97 mL/dL, respectively) than in the postpartum period (18.00 and 13.54 mL/dL). The fall in oxygen content during pregnancy prevents any significant increase in oxygen delivery in the third trimester (867. 59 mL/min) relative to the postpartum period (806.50 mL/min, P not significant). CONCLUSION: This is the first report of directly measured oxygen transport variables in healthy pregnant women.

Biological Transport↗
PubMed1999

Vibroacoustic and scalp stimulation.

Both VAS and scalp stimulation are useful in the evaluation of fetal compromise by decreasing the number of falsely abnormal FHR tests and limiting the number of unnecessary interventions, thus improving the efficiency of antepartum and intrapartum FHR monitoring. As is true for all types of fetal assessment using FHR monitoring, VAS and scalp stimulation have limitations, and a lack of response to these methodologies does not necessarily indicate fetal acidemia. When either VAS or scalp stimulation is employed, one must take into consideration their respective predictive values (see Table 1). Fetal VAS or scalp stimulation should be considered as one facet of comprehensive fetal evaluation. When these techniques are used in this manner, the clinician evaluating the fetus in the antepartum or intrapartum period may prevent unnecessary intervention and improve maternal and neonatal outcome.

Acoustic Stimulation↗
PubMed1998

Institutional influences on the primary cesarean section rate in Utah, 1992 to 1995.

OBJECTIVES: Our purpose was to evaluate institutional and organizational influences on cesarean section rates in Utah and to adjust such rates for differences in patient acuity. STUDY DESIGN: Data on cesarean section rates were derived from the Utah Hospital Discharge Database and adjusted for patient acuity by correcting raw cesarean rates for those patients undergoing cesarean section meeting regional gestational age transport criteria. RESULTS: When analyzed by means of 1-way analysis of variance, the following factors had a significant negative correlation (P < .05) with cesarean section rate: presence of a newborn intensive care unit and maternal-fetal medicine subspecialists, presence on the medical staff of obstetrician-gynecologist(s) as opposed to family physicians only, delivery volume >1500/y, urban location, and 24-hour in-house anesthesiology. When cesarean rates were corrected for acuity, facilities with maternal-fetal medicine specialists and a newborn intensive care unit had significantly lower rates (P < .001) and more uniform rates than otherwise similar institutions. CONCLUSIONS: More medically sophisticated physicians and institutions have lower cesarean rates when patient acuity is taken into account.

Cesarean Section↗
PubMed1998

Videoconferencing: practical advice on implementation.

Videoconferencing provides a useful tool for improving information flow, with clinical, educational and administrative uses being particularly relevant to rural and remote Australia. This paper describes the range of possible uses for computer-based videoconferencing and describes the authors' experience in delivering rural medical education in North Queensland via videoconference. Principles that ensure successful videoconferencing are outlined and are applicable to a variety of formats and uses. They include the need to keep it simple, the importance of thorough preparation, and ensuring that education drives technology, rather than the converse.

Education, Medical↗
PubMed1997

A prospective evaluation of fetal pericardial fluid in 506 second-trimester low-risk pregnancies.

OBJECTIVE: To measure fetal pericardial fluid in low-risk second-trimester pregnancies and to evaluate outcome for those with measurements greater than 2 mm. METHODS: Five hundred and six women were referred for sonography between 16 and 25 weeks' gestation for common obstetric indications (dating, fetal survey, and placental location) unrelated to an increased risk of anomalies. All cases were evaluated with two-dimensional and M-mode real-time ultrasonography with the use of a mechanical sector transducer. The maximum distance of the fetal hypoechoic cardiac rim was recorded. We reviewed maternal and infant charts for those with measurements greater than 2 mm. RESULTS: Median (range) maternal age was 25 (15-42) years. Median gravidity and parity were two (1-14) and one (0-11), respectively. Median estimated gestational age was 20.4 (16.3-24.9) weeks. Fetal pericardial fluid was seen in 360 of 506 (71%) fetuses. Of these 360 fetuses, the mean distance (+/- 2 standard deviation) of the fetal hypoechoic cardiac rim was 1.20 mm +/- 0.91 mm (95% confidence interval 1.15, 1.25). Among the 506 cases, the maximum measurement was 3 mm. Ten of the 506 (2%) cases had measurements greater than 2 mm. None of these ten fetuses had a cardiac structural abnormality or arrhythmia, and perinatal outcome was unremarkable. CONCLUSION: During second-trimester fetal ultrasonographic examination, visualization of pericardial fluid up to 2 mm in the fetus with current high-resolution technology is common and should not be regarded as pathologic.

Adolescent↗
PubMed1997

Current status of the multicenter randomized clinical trial on fetal oxygen saturation monitoring in the United States.

Current clinical methods of intrapartum fetal assessment are sensitive but poorly specific in detecting fetal compromise during labor. These limitations have substantially contributed to the escalating cesarean section rate which occurred in the US during the last several decades. Experimental and clinical research efforts directed towards application of the oxygen saturation monitor (pulse oximeter) to intrapartum fetal assessment have produced encouraging results. If this new method of fetal assessment is to enter the clinical arena, safety and efficacy issues must first be properly evaluated via randomized clinical trials. The purpose of this report is to describe the design of a multicenter randomized clinical trial of intrapartum fetal oxygen saturation monitoring recently begun in the US. Specific aspects of the trial, including purpose, study design, sample size estimates, control and test groups, inclusion and exclusion criteria, fetal heart rate classification, definition of normal fetal arterial oxygen saturation (SpO2), clinical management protocol, and assessment of maternal-fetal outcomes will be addressed.

Female↗
PubMed1997

Monitoring wound healing by odour.

A pilot study using electronic aroma detection was performed over a six-month period to assess the aroma of chronic non-healing venous leg ulcers and the effect of appropriate antibiotic therapy on modification of the aroma. Deep infection with pathogenic organisms was found on biopsy culture in 13 out of 15 patients. Odour analysis was performed at weekly intervals on the ulcer dressings using an AromaScan instrument. Data points on the aroma maps moved from their pre-treatment presentation. Alterations in aroma data correlated well with the progress of the ulcers. Aroma analysis is shown to be a potential tool in monitoring the progress towards healing of chronic venous ulcers.

Aged↗
PubMed1996

Normal values for amniotic fluid index during uncomplicated twin pregnancy.

OBJECTIVE: To establish the gestational age trends of amniotic fluid index (AFI) in uncomplicated twin pregnancies. METHODS: Amniotic fluid index was measured in uncomplicated twin pregnancies seen between 1985 and 1993 and meeting the following criteria: 1) no maternal medical or obstetric complications, 2) normal growth of both twins by serial ultrasound, and 3) normal amniotic fluid volume by ultrasound. Amniotic fluid index was measured by adding the deepest vertical pockets in four quadrants, defined by the umbilicus and linea nigra. The relation between gestational age and AFI was evaluated using linear regression analysis. RESULTS: Two hundred eighty-two sets of twins were considered uncomplicated; 1101 AFI measurements were performed on these pregnancies between 25.5 and 40.5 weeks' gestation. Percentile values for AFI were determined according to gestational age. The regression equation relating the median AFI to gestational age was: AFI = 19.4 - 0.12 x gestational age (P = .03). The R2 value was 0.04. CONCLUSION: Gestational age trends in normative AFI measurements for twin pregnancies have been established. Their use will facilitate a more reproducible, quantitative diagnosis of oligohydramnios in twins, compared with subjective, qualitative approaches to amniotic fluid volume assessment.

Adult↗
PubMed1996

Third-trimester arterial blood gas and acid base values in normal pregnancy at moderate altitude.

OBJECTIVE: To report arterial blood gas and acid base values of normal nulliparous patients at moderate altitude for commonly used maternal positions. METHODS: Ten normotensive nulliparous women between 36 and 38 weeks' gestation volunteered to undergo radial and pulmonary artery cannulation as part of a larger study. Following instrumentation, baseline assessments were made in the left lateral recumbent position after a 30-minute stabilization period. Sequential measurements were then obtained in the left lateral, right lateral, supine, knee-chest, sitting, and standing positions. Blood samples were analyzed in duplicate for oxygen content on a blood gas analyzer. Statistical analysis was performed by analysis of variance of repeated measures with significance defined at P < or = .05. RESULTS: There was no significant difference in arterial blood gas or acid base values between any positions in this antepartum population of term healthy women. The composite mean values were as follows: pH 7.46, arterial carbon dioxide pressure (PaCO2) 26.6 mmHg, arterial oxygen pressure 88.3 mmHg, bicarbonate 18.2 mEq/L, saturated arterial hemoglobin level 0.96. CONCLUSION: Arterial blood gas and acid base values are not altered by maternal position in the late third trimester of pregnancy. The PaO2 in these women studied at moderate altitude was lower than previously reported for healthy pregnant women studied at sea level. Appropriate interpretation of arterial blood specimens of pregnant women should take into account both the pregnancy and altitude at which the women reside.

Acid-Base Equilibrium↗
PubMed1996

The effects of maternal position and cardiac output on intrapulmonary shunt in normal third-trimester pregnancy.

OBJECTIVE: To assess the effect of pregnancy, maternal position, and cardiac output on intrapulmonary shunting (Qs/Qt) in normotensive nulliparous women near term. METHODS: Ten normotensive nulliparas between 36 and 38 weeks' gestation underwent pulmonary artery catheterization (via the subclavian route) and radial artery canalization. Baseline assessments were made with subjects in the left lateral recumbent position after a 30-minute stabilization period. Measurements were obtained sequentially in the left lateral, right lateral, supine, knee-chest, sitting, and standing positions. Each position change was followed by a 10-minute pre-measurement stabilization period. Cardiac output was measured via the thermodilution technique. Blood samples were obtained simultaneously from the pulmonary and radial arteries and analyzed in duplicate for oxygen content with a blood gas analyzer. Qs/Qt was calculated using the classic shunt equation. Statistical analysis was performed by analysis of variance of repeated measures of Qs/Qt and maternal position. The relationship of Qs/Qt to maternal cardiac output was evaluated by the correlation coefficient. Significance was defined as P < .05. RESULTS: Directly measured Qs/Qt averaged 15.3% in left lateral, 15.2% in right lateral, 13.9% in supine, 12.8% in knee-chest, 13.8% in sitting, and 13.0% in standing positions. There was no statistically significant correlation between Qs/Qt and cardiac output (R2 = 0.11, not significant). CONCLUSION: This is the first report of directly measured Qs/Qt in normal pregnant women in the third trimester. Qs/Qt values reported in pregnancy are higher than those reported in nonpregnant individuals.

Adult↗
PubMed1996

Intrapartum fetal pulse oximetry: past, present, and future.

Oxygen saturation monitoring (pulse oximetry) has markedly improved medical care in many fields, including anesthesiology, critical care, and newborn intensive care. In obstetrics, fetal heart rate monitoring remains the standard for intrapartum assessment of fetal well-being. Fetal heart rate monitoring is sensitive but nonspecific for detecting fetal compromise. Additional clinical information is needed to discern those fetuses not at risk for development of intrapartum acidosis to avoid unnecessary intervention. Fetal oxygen saturation monitoring is a new technique currently under development. This article reviews the evolution of intrapartum fetal oxygen saturation monitoring and proposes directions for future investigation.

Acidosis↗
PubMed1996

Prospective evaluation of the antenatal incidence and postnatal significance of the fetal echogenic cardiac focus: a case-control study.

OBJECTIVE: We evaluated the antenatal incidence and postnatal significance of echogenic cardiac foci observed during antenatal ultrasonography. STUDY DESIGN: During a 4-month period, all women undergoing dating ultrasonography between 16.0 and 24.9 weeks' gestation at one referral center were prospectively evaluated for an echogenic cardiac focus during an apical four-chamber view of the heart. Referrals for maternal or fetal complications were excluded. Postnatal echocardiography was performed for those identified with positive findings. Controls were selected from among normal subjects in the general group for comparison with the study group. RESULTS: Five hundred six consecutive fetuses were evaluated at a mean +/- SD gestational age of 20.6 +/- 1.6 weeks. There were 25 (4.9%) fetuses found to have echogenic cardiac focus (left ventricle = 19, right ventricle = 6). Echocardiography was performed between 0.3 and 20.1 weeks postdelivery. After birth, 12 echogenic left ventricle papillary muscles and three echogenic left ventricle chordae were identified; there were no postnatal right ventricle findings. There were no cases of intracardiac tumor or myocardial dysfunction; one neonate had minor structural malformations. There were no significant differences in maternal age, gravidity, parity, gestational age at ultrasonography, gestational age at delivery, or 5-minute Apgar scores. A significant difference was observed in birth weight between the control (n = 50) and study (n = 25) groups (3465 +/- 501 gm vs 3124 +/- 589 gm; p = 0.002). This difference persisted after correcting for gestational age, although all infants in both groups born after 37.0 weeks weighed > 2500 gm. CONCLUSIONS: The incidence of echogenic cardiac foci during routine midtrimester ultrasonography is 4.9%. As an isolated finding, the echogenic cardiac focus may be associated with a statistically significant but clinically insignificant decrease in birth weight. Because of these findings, we consider an isolated echogenic cardiac focus in a patient at low risk for cardiac abnormalities a variant of normal, which does not warrant follow-up clinical evaluation.

Case-Control Studies↗
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↗