PubMed Health⌕ Search

Biomedical subjects

R K Creasy

Publications and source records attributed to R K Creasy.

At least 19 recordsLinked to original sources
PubMed1995

Hormonal regulatory adjustments during voluntary diving in Weddell seals.

Subadult male Weddell seals were instrumented with microcomputer-based backpacks and were then monitored during voluntary diving and recovery periods in McMurdo Sound, Antarctica. Depth and duration of diving, swim speed, and dive pattern were routinely monitored. An indwelling venous catheter was used to collect plasma samples at various time periods before and following diving episodes, so that changes in plasma concentrations of hormones and of metabolites could be measured. Adrenergic and nitroxidergic regulatory effects were assessed indirectly by measuring concentration changes in catecholamine and cyclic guanosine monophosphate (cGMP), respectively. The studies found that (i), except for dives of less than several minutes, epinephrine and norepinephrine both increased as a function of diving duration, then rapidly decreased during recovery (with a half time of about 10 min), (ii) that the changes in catecholamine concentrations correlated with splenic contraction and an increase in circulating red blood cell mass (hematocrit), (iii) that the changes in catecholamines, especially [epinephrine], were inversely related to insulin/glucagon ratios, which mediated a postdiving hyperglycemia, and (iv) that in long dives (but not short ones) the changes in catecholamines correlated with increasing reliance on anaerobic metabolism, indicated by increased plasma lactate concentrations. These diving-catecholamine relationships during voluntary diving at sea were similar to those observed during enforced submergence (simulated diving) under controlled laboratory conditions. At the end of diving, even while catecholamine concentrations were still high, many of the above effects were rapidly reversed and the reversal appeared to correlate with accelerated nitric oxide production, indirectly indicated by increased plasma cGMP concentrations. Taken together, the data led to the hypothesis of important adrenergic regulation of the diving response in seals, with rapid reversal at the end of diving and during recovery being regulated by nitroxidergic mechanisms.

Animals↗
PubMed1994

Diurnal and gestational patterns of uterine activity in normal human pregnancy. The Uterine Activity in Pregnancy Working Group.

OBJECTIVES: To define the profile of 24-hour uterine activity in normal pregnancy and to correlate contraction frequency with physical activity and emotional stress diaries. METHODS: One hundred nine low-risk pregnant women who delivered at term recorded uterine contractions for 24 hours twice weekly from 20-40 weeks' gestation using an ambulatory monitor and kept a physical activity and emotional stress diary. Contractions per hour were calculated for each hour of the day and week of gestation, and related to physical activity and emotional stress. RESULTS: We analyzed 71,683 hours. No contractions were recorded in 73% of the hours, and fewer than four contractions per hour occurred in 96%. Significant inter-individual variability was noted. Contractions increased markedly with gestational age: The 95th percentile was 1.3 contractions per hour at 21-24 weeks, 2.9 at 28-32 weeks, and 4.9 at 38-40 weeks. A strong clustering of contractions occurred at night, which became pronounced after 24 weeks (night:day ratio 2:1 at 28-32 weeks). To adjust for the effects of gestational age and time of day, contractions per hour were converted to gestation- and hour-specific percentiles ("contraction percentiles"). Rest was associated with a fall in contraction percentile by 1.25, whereas coitus increased the contraction percentile by 5.52 (P < .05). No changes were noted with emotional stress. CONCLUSIONS: This study provides normative contraction data in uncomplicated pregnancy. A strong diurnal rhythm is present from 24 weeks onward, with 67% of contractions occurring at night. Contractions per hour increase with gestational age but rarely exceed three per hour before term. Rest and sexual activity have small but measurable effects on contraction frequency.

Activities of Daily Living↗
PubMed1992

Respiratory disease in very-low-birthweight infants after prenatal thyrotropin-releasing hormone and glucocorticoid. TRH Study Group.

Although prenatal glucocorticoid treatment reduces neonatal respiratory morbidity, respiratory distress syndrome and chronic lung disease (CLD) develop in many very-low-birthweight infants despite therapy. To investigate the effect of additional prenatal treatment with thyrotropin-releasing hormone (TRH), we did a multicentre, blinded, randomised trial. 404 women with threatened preterm delivery at less than 32 weeks' gestation received betamethasone plus TRH (4 doses of 400 micrograms 8-hourly) or betamethasone plus placebo. 103 infants who were fully treated and of less than 1500 g birthweight were evaluated during the neonatal period. TRH treatment (55 infants) did not affect the total incidence of respiratory distress syndrome (47% vs 58% in controls) or of severe respiratory distress syndrome (13% vs 25% in controls, p = 0.11). CLD (defined as requirement for supplemental oxygen at 28 days after birth) developed in significantly fewer TRH-treated infants (18% vs 44% of controls, p less than 0.01). The unadjusted relative risk of CLD with TRH therapy was 0.40 (95% CI 0.26-0.80, p less than 0.05), and this was not materially changed after adjustment for potentially modifying variables. There were significantly fewer adverse outcomes, defined as death or continuing oxygen requirement, in the TRH group than in the steroid-alone group both at 28 days and when infants reached 36 weeks' postconceptional age. The incidence of other complications of prematurity was similar in the two groups. Prenatal TRH reduces the incidence of chronic lung disease among betamethasone-treated infants.

Betamethasone↗
PubMed1992

Neonatal morbidity according to gestational age and birth weight from five tertiary care centers in the United States, 1983 through 1986.

OBJECTIVES: This study details the incidence, by gestational age and birth weight, of specific neonatal morbidities in singleton neonates without major congenital anomalies. STUDY DESIGN: Data were prospectively collected on all deliveries at five tertiary centers in the United States during the years 1983 through 1986. Pregnancies were meticulously dated and the gestational ages of the neonates at delivery were confirmed by Dubowitz score. RESULTS: The incidence of respiratory distress syndrome gradually decreases with increasing gestational age until 36 weeks. A marked decrease in the incidence of necrotizing enterocolitis, patent ductus arteriosus, intraventricular hemorrhage, and sepsis occurs after 32 completed weeks. The number of days of mechanical ventilation for respiratory distress syndrome and newborn stay in the tertiary care facility also were significantly reduced after 32 weeks. CONCLUSIONS: The incidence of both respiratory distress syndrome and patent ductus arteriosus is markedly decreased by both increasing gestational age and birth weight. The incidence of grade III and IV intraventricular hemorrhage, necrotizing enterocolitis, and sepsis virtually vanishes after 34 weeks. These data relating neonatal morbidities to gestational age are important to the obstetrician in the critical decision regarding the timing of delivery and to the parents, who can benefit from a realistic prediction of the neonatal course.

Academic Medical Centers↗
PubMed1992

Plasma thyroid hormones and prolactin in premature infants and their mothers after prenatal treatment with thyrotropin-releasing hormone.

We assayed TSH, triiodothyronine, free thyroxine, and prolactin (PRL) in plasma of women and infants participating in a trial of prenatal thyrotropin-releasing hormone (TRH) treatment for prevention of newborn lung disease. Women in labor at 26-34 wk of gestation received 400 micrograms of TRH i.v. every 8 h (one to four doses) plus 12 mg betamethasone (one or two doses); controls received saline plus betamethasone. Mean cord concentrations in control infants were TSH 9.7 mU/L, triiodothyronine 0.6 nmol/L (40.2 ng/dL), free thyroxine 14.4 pmol/L (1.13 ng/dL), and PRL 67.6 micrograms/L. TRH increased maternal plasma TSH by 100% at 2-4 h after treatment and decreased levels by 28-34% at 5-36 h. In cord blood of treated infants delivered at 2-6 h, TSH, triiodothyronine, and PRL were all increased about 2-fold versus control, and free thyroxine was increased 19%; the response was similar after one, two, three, or four doses of TRH. In treated infants delivered at 13-36 h, cord TSH and triiodothyronine levels were decreased 62 and 54%, respectively, and all thyroid hormones were lower after birth at 2 h of age versus control. We conclude that prenatal TRH administration increases thyroid hormones and PRL in preterm fetuses to levels similar to those normally occurring at term. Pituitary-thyroid function is transiently suppressed after treatment to a greater extent in fetus than mother, and infants born during the early phase of suppression do not have the normal postnatal surge in thyroid hormones.

Betamethasone↗
PubMed1991

Evaluation of phenazopyridine hydrochloride as a tool in the diagnosis of premature rupture of the membranes.

This is a prospective study to determine whether a maternal orally administered azo dye, phenazopyridine hydrochloride, would cross into amniotic fluid, and thus be of potential aid in the diagnosis of rupture of the membranes. Based on anecdotal experience, we hypothesized that this compound would cross the placenta and be excreted in the fetal urine, causing discoloration of the amniotic fluid. Ten patients with uncomplicated pregnancies undergoing elective amniocentesis for obstetric indications received an oral dose of 400 mg of phenazopyridine hydrochloride 4 hours prior to the procedure. Amniotic fluid was also available from five control patients who did not receive phenazopyridine hydrochloride. The typical orange-to-red discoloration of the urine was seen in all study patients, indicating ingestion of the dye. None of the ten patients had evidence of the azo dye in their amniotic fluid by visual inspection or by spectrophotometric absorbance. After the amniotic fluid samples were acidified, the presence of the azo dye was visually demonstrable, and spectrophotometry confirmed measurable concentrations (mean +/- SE: 13.08 +/- 0.72 micrograms/ml). We conclude that although phenazopyridine hydrochloride does cross the placenta into the fetal compartment, its presence causes a visual and spectrophotometric change in the color of amniotic fluid only when the normal basic pH of amniotic fluid is acidified.

Amniotic Fluid↗
PubMed1991

Lifestyle influences on prematurity.

It is apparent from this review that the lifestyle of an individual gravida can potentially lead to a premature delivery. Some of these adverse behavioral characteristics may be dealt with by education and motivation, and some with actual medical treatment. However, there also appears to be significant need for public policy reorientation if we are to make a significant impact on the problem of preterm delivery.

Employment↗
PubMed1990

Early signs and symptoms of preterm labor.

Patient and staff education concerning the subtle signs and symptoms that precede a clinical diagnosis of preterm labor have not been well established. Therefore we interviewed 100 patients for the presence or absence of various symptoms and signs during the 7 days preceding diagnosis of preterm labor. An additional 100 patients without preterm labor matched for gestation were chosen at random as control subjects. A history of increased uterine contractions, menstrual cramps, constant backache, constant pelvic pressure, increased amount and consistency and color change of vaginal discharge, and increased frequency of urination were present with a statistically significant higher frequency in patients with preterm labor compared with controls. Twenty-nine percent of patients did not report any uterine contractions and only half described them as painful. Fewer than 50% of the women reported contractions as frequently as every 10 minutes or more.

Adult↗
PubMed1990

Preterm labor.

Explore the source record for details and available documents.

Adrenal Cortex Hormones↗
PubMed1990

Prevention of preterm birth: clinical opinion.

Spontaneous preterm delivery continues to be the most significant problem facing clinicians as we enter the 1990s. Prevention of preterm labor still awaits needed improvements in prediction. At present, most preterm birth prevention programs are based upon the early recognition of preterm labor followed by prompt tocolysis. Programs based upon patient education and support, daily contact by trained nurses, intermittent cervical assessment, and daily sampling of uterine activity have been associated with a decrease in preterm birth. The exact contribution of each component to reduce preterm birth remains to be defined and, at present, a combination of the components is still suggested.

Female↗
PubMed1989

Routine umbilical cord blood gas determinations?

Between 1986 and 1988, 1924 term nulliparous patients with spontaneous onset of labor were studied to assess the importance of obtaining umbilical cord blood gas levels on all deliveries. The umbilical cord arterial and venous pH values (expressed as mean +/- 2 SD) were 7.24 +/- 0.14 (n = 1694) and 7.32 +/- 0.12 (n = 1820), respectively. The incidence of newborn depression (1- or 5-minute Apgar score less than 7) was 14.1%; of these depressed newborns, the incidence of normal umbilical cord arterial pH values (greater than or equal to -2 SD) was 77.8%. Of the vigorous newborns, there was a 2.1% incidence of umbilical cord arterial blood acidemia. Umbilical cord arterial blood acidemia in vigorous newborns was not highly predictive of specific morbidity in the immediate newborn period. Regression analysis demonstrated the umbilical cord arterial pH to correlate best with the Apgar scores when compared with all other arterial or venous blood gas measurements. We reached the following conclusions: (1) that obtaining cord arterial pH values in vigorous newborns should be considered since the values will provide objective documentation or normal fetal acid base balance in 98% of infants. (2) Only a cord arterial pH determination is recommended since it reflects fetal or newborn status more accurately than all other measurements. Additional measurements increase the likelihood of abnormal results and do not contribute to neonatal management. (3) An umbilical cord blood pH value is extremely useful in ruling out the diagnosis of birth asphyxia in the depressed newborn.

Acid-Base Equilibrium↗
PubMed1989

The effect of magnesium sulfate tocolysis on the fetal biophysical profile.

The biophysical profile has proved to be a valuable tool for the assessment of fetal well-being, independent of gestational age. Magnesium sulfate is commonly used as a tocolytic agent, yet relatively little is known about its effects on the biophysical activities of the fetus. To investigate the effects of magnesium sulfate on the biophysical profile, we performed serial studies on patients who received tocolytic therapy with this agent because of preterm labor. A total of 16 women with 22 fetuses at 26 to 34 weeks' gestation in spontaneous preterm labor were studied. An initial biophysical profile was performed at the time of admission, and a second examination was performed when maternal serum magnesium levels reached 6 to 8 mg/dl. On admission all fetuses had reactive nonstress test results and 21 of 22 (95%) demonstrated sustained fetal breathing movements. With magnesium sulfate tocolysis, 50% of fetuses had nonreactive nonstress test results, and only 4 of 22 (18%) demonstrated sustained fetal breathing movements. Fetal tone, gross body movements, and amniotic fluid volume were found to be unaffected by magnesium sulfate tocolysis.

Adult↗
PubMed1989

Evaluation of a risk-scoring system for prediction of preterm labor.

A scoring system was used prospectively to screen 7329 patients for risk of preterm labor over a 6-year period. When 15.8% of patients (1156 of 7329) were scored as high risk, sensitivity was 42.4% (multiparas, 55.2%, nulliparas, 29.8%) and positive predictive value was 22.8%. The incidence of preterm labor increased with increasing risk score; gestational age at delivery was negatively correlated with risk score. Analysis of individual factors revealed that more than half were not of predictive value in the population under investigation. A simplification of the system, defining 12 of the factors as major (high risk) and six as minor (2 or more indicates high risk) yielded a high risk group of 14.1%, sensitivity of 41.0%, and positive predictive value of 24.6%. Thus, although risk scoring does predict a substantial proportion of patients with preterm labor, its sensitivity is less than ideal. No advantage was gained with a larger and more complex system. Planning for preterm birth prevention programs should include recognition of the limitations of risk scoring, consideration of simplified systems, and investigation of additional biochemical or biophysical screening methods.

Female↗
PubMed1988

Maternal brain death during pregnancy. Medical and ethical issues.

We present in detail a case of a 27-year-old primigravida who was maintained in a brain-dead state for nine weeks. An apparently normal and healthy male infant weighing 1440 g was delivered. The newborn did well and was found to be growing and developing normally at 18 months of age. Although the technical aspects of prolonged life support are demanding and the economic costs are very high (+217,784), there are ample ethical arguments justifying the separation of brain death and somatic death and the maintenance of the brain-dead mother so that her unborn fetus can develop and mature.

Adult↗
PubMed1988

Intramuscular versus intravenous ritodrine hydrochloride for preterm labor management.

A prospective, interinstitutional comparative trial was undertaken to examine the efficacy, safety, and pharmacodynamics of different administration routes of ritodrine hydrochloride for the management of preterm labor. Forty-five subjects between 20 and 36 weeks' gestation received either intravenous (n = 24) or intramuscular (n = 21) therapy. Successful tocolysis occurred in 14 of 21 (67%) patients in the group treated intramuscularly and in 16 of 24 (67%) patients in the group treated intravenously. A greater mean dose (8.6 versus 3.3 mg/hour) and a higher mean serum concentration (38.9 versus 24.7 micrograms/ml) were needed to achieve successful tocolysis in the intravenous group as compared with the intramuscular group. Patients who did not respond to tocolytic therapy in both groups had levels of ritodrine in the blood either equivalent to or greater than those of subjects who were successfully treated. Analysis of ritodrine levels in the successfully treated intramuscular group demonstrated significant differences in blood levels depending on muscle group used. These differences can be at least partially attributed to higher mean doses administered to patients receiving vastus lateralis injections as compared with those receiving gluteal muscle injections. The results suggest that intramuscular administration of ritodrine is an efficacious and safe route of drug delivery. Additional studies are needed to better define dose-response curves for the intramuscular administration of ritodrine hydrochloride.

Buttocks↗
PubMed1988

Prevention of preterm birth.

Prevention of prematurity is the principal goal of all obstetric care. Although conquest of preterm births may yet be a distant goal that will require substantial improvements in understanding the pathophysiology of PTD, interim progress is possible. Increased attention to prematurity prevention as the focus of prenatal care can have an impact now, without introducing unproven or hazardous techniques or medication. Reproductive health care aimed at the prevention and elimination of social, demographic, and medical correlates of prematurity can yield results if obstetricians take the lead in educating both patients and society at large about the hazards of prematurity. Progress is more likely if a global strategy is used in all pregnancies as reported by Papiernik et al., Meis et al., and Herron et al. These studies have similar messages of hope and caution: All reported benefit in decreasing the frequency of preterm births, all required substantial and widespread patient and provider education, and all required a sustained effort before any effect was noted. Main et al. showed that these programs are not likely to produce a quick turnaround in PTD rates in all populations; progress will be slow. Reports of limited success or even failure should not result in abandonment of the goal, but rather in renewed and imaginative efforts toward it.

Bed Rest↗