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Biomedical subjects

R K Creasy

Publications and source records attributed to R K Creasy.

At least 73 records · Page 4Linked to original sources
PubMed1980

Increased pressor activity in incubated plasma of pregnant rabbits.

A study to measure the pressor activity which is generated in incubated plasma of pregnant and nonpregnant rabbits was performed by means of a recently modified bioassay technique. It was found that plasma of normal pregnant rabbits generated significantly higher amounts of active pressor principle (APP) than those generated by plasma of nonpregnant rabbits. The possible relevance of these results to blood pressure regulation during normal and abnormal pregnancies is discussed.

Animals↗
PubMed1980

Oral ritodrine maintenance in the treatment of preterm labor.

Seventy patients with preterm labor and intact membranes were initially treated with ritodrine hydrochloride to delay preterm delivery. Tocolysis beyond 24 hours was achieved in 59 patients. Fifty-five of the 59 patients were then placed on either oral ritodrine or placebo as maintenance therapy in a randomized double-blind manner. If preterm labor recurred, the sequence of intramuscular and then oral treatment was repeated. The number of days gained after initiation of intramuscular treatment was similar in both groups (oral ritodrine = 34 days, oral placebo = 36 days). In those 55 patients receiving oral treatment, there was a smaller number of relapses requiring repeat intramuscular treatment in the oral ritodrine group (1.11 in the ritodrine patient vs. 2.71 in the placebo patient, p less than 0.05), and the mean interval between beginning oral treatment and the first relapse/delivery was 5.8 days in the oral placebo group and 25.9 in those receiving oral ritodrine (p less than 0.05). Cardiovascular side effects, notably maternal tachycardia and palpitations were frequent but well tolerated. The results suggest that oral ritodrine maintenance will decrease the incidence of recurrent preterm labor in patients who have had initial successful tocolysis.

Administration, Oral↗
PubMed1980

Increased heart rate response to parasympathetic and beta adrenergic blockade in growth-retarded fetal lambs.

To determine the influence of the autonomic nervous system on the circulation of normal and growth-retarded fetal lambs we measured the responses of heart rate and arterial blood pressure to parasympathetic (atropine 0.2 mg/kg) and beta-adrenergic (propranolol 1.0 mg/kg) blockade in the last quarter of gestation. The heart rate response to parasympathetic blockade increased with gestational age in both normal and growth-retarded fetuses but in the growth-retarded fetuses there was a significantly greater response to parasympathetic blockade than in control fetuses from 121 days' gestation to term. The heart rate response to beta-adrenergic blockade did not change with gestational age in normal fetuses. From 131 days' gestation to term the heart rate response to beta-adrenergic blockade in growth-retarded fetuses was significantly higher than in normal fetuses. The systemic arterial blood pressure responses to parasympathetic or beta-adrenergic blockade were similar in growth-retarded and normal fetuses. These results indicate an increased parasympathetic and beta-adrenergic influence on the heart of fetuses whose growth has been retarded. It may also suggest a more generalized increase in parasympathetic and sympathetic tone affecting other organs and systems in the growth-retarded fetal lambs.

Animals↗
PubMed1980

Fetal cardiovascular and metabolic responses to simulated diving in the Weddell seal.

Fetal responses to normobaric diving simulated by submersion of the maternal head for 20 min were studied in four conscious Weddell seals near term. Microspheres injected into the maternal aorta were distributed to the placenta and kidneys in the ratio of 0.4 in the control period and 19.3 during diving, suggesting minimal placental vasoconstriction. Fetal heart rate fell during diving from a mean control value of 90 to 34 beats/min after 4 min. The onset of fetal bradycardia was not consistently associated with changes in blood gas tensions. Diving was associated with a fall in fetal arterial O2 tension from 24 to 9 Torr, arterial CO2 tension rose from 47 to 85 Torr, and arterial pH fell from 7.35 to 7.24. Fetal-maternal gradients for CO2 and H+ transport remained constant, whereas the gradient for O2 transport fell from 47 Torr before diving to 14 Torr at the end of diving. Blood lactate concentrations increased three- to fourfold during diving and reached peak values 10-15 min after diving ended. The similarity of the fetal and maternal heart rate responses to diving is consistent with the presence of physiological oxygen-conserving reflexes akin to the adult's.

Animals↗
PubMed1980

Maternal and fetal metabolic responses to ritodrine in the sheep.

Ritodrine hydrochloride was infused intravenously for 60 minutes into pregnant ewes or for 29 minutes into fetal lambs, during the last third of gestation. The maternal and fetal acid-base balance and carbohydrate status was determined prior to, during, and after the ritodrine infusions. Ritodrine was also infused into pregnant sheep in labor until no further inhibition of uterine activity could be achieved. In these studies, acid-base balance was frequently assessed. The maternal or fetal infusion of ritodrine resulted in no major changes in maternal or fetal acid-base balance during the periods of study. Lactate and pyruvate concentrations in mother and fetus rose during the infusion. The lactate/pyruvate ratio remained stable, suggesting an increase in both aerobic and anaerobic glycolysis. Maternal glucose concentrations were significantly elevated after one hour of the ritodrine infusions to the ewes, but minimally elevated in the fetus. Fructose concentrations were unchanged. The possible role as fetal fuels of increased metabolic products of glycolysis caused by beta-adrenergic stimulation is discussed.

Acid-Base Equilibrium↗
PubMed1980

System for predicting spontaneous preterm birth.

The authors performed a prospective analysis of the value of a system for scoring the risk of preterm delivery (RPD). The RPD system predicts that approximately 10% of patients will have preterm labor and delivery. Although only one third of these patients deliver before term, they account for approximately two thirds of all preterm births. The discrimination of the RPD system is better for multigravid patients than for primigravid patients, and rescoring at 26 to 28 weeks' gestation improves the accuracy of prediction.

Female↗
PubMed1980

Prevention of preterm labor.

Ideally, prevention of preterm labor is preferable to efforts to inhibit the process once it has begun. However, before preventive treatment can be properly assessed, there is a need to delineate those patients that could benefit from therapy. Mathematical formulae based on epidemiology data are available to assist in prediction of preterm labor. Although their discriminatory powers are not yet at the level necessary for routine clinical usage, the systems can serve as a basis for attempts to improve the precision of prediction. If the predictive systems can be improved, we would then have a defined population on which preventive measures could be assessed. To date, there is no form of treatment that has been proven to prevent the onset of preterm labor.

Adult↗
PubMed1980

Diagnosis of preterm labor.

The obvious means by which one can make the diagnosis of preterm birth, namely preterm delivery, is not satisfactory if we are to optimize outcome of pregnancy. However, the indiscriminate use of drugs to inhibit questionable preterm labor is also not desirable. There is a pressing need for an improved method of diagnosis. If some biochemical means were available to diagnose preterm labor, the short-term use of tocolytic therapy (until the result of the testing procedure was known) would be indicated in questionable cases of preterm labor. Until such time that improved methods of diagnosis are available, it would seem preferable to err on the side of overdiagnosis, particularly in very early preterm labor where neonatal morbidity and mortality are excessively high.

Animals↗
PubMed1979

Antenatal prediction of graduated risk of hyaline membrane disease by amniotic fluid foam test for surfactant.

We measured amniotic fluid surfactant by the semiquantitative foam stability test within 24 hours before delivery of 410 infants, 64 of whom developed HMD diagnosed by standard criteria. When surfactant titers were ranked in eight categories, they predicted graded risks of HMD. On this basis we defined five "risk groups" with significantly different incidences of HMD (I = 0.5%; II = 10%; III = 25%; IV = 41%; V = 79%). Infants in Groups I and II were heavier and more mature than those in Groups III to V. However, among infants of equivalent GA or birth weight, the incidence of HMD still correlated significantly with the foam test results. Within each risk group the incidence of HMD was equal among infants delivered by vagina and by cesarean section, slightly greater among males than females, and inversely proportional to GA. In Group V the incidence of HMD was 100% among infants at less than 33 weeks' GA. We used this relationship to devise a system that improved prediction of HMD by combining the foam test results with GA.

Amniocentesis↗
PubMed1979

Cardiac and uterine hemodynamic responses to ritodrine hydrochloride administration in pregnant sheep.

The changes in the maternal circulation following administration of ritodrine hydrochloride were investigated in chronically prepared pregnant sheep. Low infusion rates of ritodrine (see text) elevated the maternal heart rate and cardiac output and decreased peripheral vascular resistance. Stroke work fell while minute work increased. The distribution of uterine blood flow did not change, as measured with microspheres. Simultaneously measured fetal cardiac output and umbilical blood flow were not altered. When ritodrine infusion rates (see text) were increased there was a slight but significant decrease in uterine perfusion pressure, and an increase in uterine vascular resistance with uterine blood flow decreasing. These changes were observed when the ewes were not in labor, and similar changes were again recovered with ewes in labor despite the simultaneous inhibition of uterine contractions. Selective beta blockade with practolol during ritodrine administration decreased the maternal tachycardia without affecting cardiac output, peripheral vascular resistance, or uterine vascular resistance.

Animals↗
PubMed1979

Identification of fetal growth retardation by ultrasonographic estimation of total intrauterine volume.

Recent literature has suggested that total intrauterine volume (TIUV) estimation is useful fir distinguishing normal from growth-retarded fetuses. One hundred seventy-nine measurements of TIUV were obtained from the ultrasonograms taken between 21 and 40 weeks of gestation in 140 patients who delivered average birthweight babies. We constructed a mean curve for TIUV with upper and lower 2.5 and 10% tolerance limits and later evaluated the TIUV's of 16 patients with growth-retarded fetuses. Nine of these fetuses had birthweights below the fifth percentile for gestational age, and in each of these pregnancies the TIUV ultimately fell below the lower 2.5% tolerance limit.

Birth Weight↗
PubMed1979

Regional blood flow during simulated diving in the conscious Weddell seal.

Changes in regional blood flow during simulated normobaric diving were studied in the conscious Antarctic Weddell seal (Leptonychotes weddelli) by injecting 25-microns radioactive microspheres into the left ventricle. Injections were performed before and 8--12 min after submersion of the head in iced seawater. Diving was associated with a fall in cardiac output from a mean control value of 39.8 +/- 10.2 to 5.6 +/- 3.4 l/min (mean +/- SD) and in heart rate from 52 +/- 15 to 15 +/- 4 beats/min. Blood flow to the splanchnic and peripheral vascular bed was reduced by more than 90%, cerebral blood flow was unchanged, right and left ventricular blood flow decreased by 85%, and adrenal blood flow decreased by 39%. The pulmonary fraction of the injected microsphere dose increased from 7.9 to 29.9% during diving. This may signify a large increase of peripheral arteriovenous shunting during the dive and/or increased bronchial artery blood flow. It is concluded that blood flow during diving is directed to organs and tissues according to their metabolic requirements.

Animals↗
PubMed1979

Plasma glucocorticoid and adrenocorticotropin concentrations measured serially in growth-retarded fetal lambs.

We studied the fetal pituitrary-adrenal axis in 9 growth retarded fetal lambs by serially measuring plasma glucocorticoids and ACTH concentrations from 115 to 140 days of gestation and adrenal blood flow at 138 days of gestation. At each gestational age period studied, plasma glucocorticoid and ACTH concentrations were similar in both growth retarded and control fetuses (Figs. 1, 2). However, ACTH concentration tended to be higher in the last 20 days of gestation in the growth retarded fetuses. This resulted in a significantly lower glucocorticoid/ACTH ratio between 121 to 130 days of gestation in the growth retarded fetal lambs as compared to the control fetuses (212 +/- 111 vs. 1042 +/- 257). The glucocorticoid/ACTH ratio in the growth retarded fetuses became similar to the ratio of the control fetuses at 131 to 140 days (445 +/- 145 vs. 554 +/- 182). Adrenal blood flow was significantly increased at term in the the growth retarded fetuses (535 +/- 87 vs. 302 +/- 40 ml/min/100g). These data indicate that the pattern of maturation of the fetal adrenal gland in the growth retarded fetal lamb is similar to that of the normal sized fetus. Because of the increased adrenal blood flow observed at 138 days of gestation, there is a suggestion of a decreased sensitivity to ACTH in these animals.

Adrenal Glands↗
PubMed1979

alpha-Melanocyte-stimulating hormone and adrenocorticotropin in the regulation of glucocorticoid secretion during the perinatal period in sheep.

To determine the role of other ACTH-like peptides in the regulation of glucocorticoid secretion in fetal sheep, we examined the responses of the adrenal gland of fetal and newborn sheep to comparable single doses of alpha MSH (75 micrograms) or ACTH (50 micrograms) during the last third of gestation and the first month of postnatal life. alpha MSH first increased the plasma glucocorticoid concentration at 121--130 days of gestation [from 16 +/- 1.5 to 36.9 +/- 9 (SE) ng/ml]; the response to alpha MSH persisted on days 131--140 of gestation and during the first month after birth. ACTH first increased the plasma glucocorticoid concentration at 131--140 days of gestation and increased it further in the first month after birth (from 18.9 +/- 3.6 to 97.0 +/- 10 ng/ml). The observations that the adrenal glands of fetuses and newborn lambs responded to alpha MSH at a dose comparable to that of ACTH and that the response to alpha MSH in the fetus preceded the response to ACTH may indicate that adrenal receptors mature during fetal development. These data also suggest that the regulation of the adrenal during fetal life may involve more than one tropic hormone.

Adrenocorticotropic Hormone↗
PubMed1979

Ultrasonography in the evaluation of intrauterine transfusion.

Numerous techniques have been described in the literature to aid the obstetrician in safely and easily performing an intrauterine transfusion. None, however, have addressed themselves to the question of whether the transfused cells actually enter the fetal peritoneal cavity. We have used gray-scale ultrasonography to evaluate this question in 4 patients who had undergone a total of 8 intrauterine transfusions. By scanning the fetal abdomen both before and after the transfusion, we were able to identify the transfused fluid within the fetal abdomen in all cases.

Abdomen↗
PubMed1978

Cardiac output and its distribution and organ blood flow in the fetal lamb during ritodrine administration.

The response of the fetal circulation to beta adrenergic stimulation with ritodrine hydrochloride has been investigated by long-term monitoring of the fetal lamb in utero. Ritodrine was infused intravenously either into the ewe or directly into the fetus, and cardiovascular and acid-base responses were measured. Fetal cardiac output and its distribution were measured with the use of radionuclide-labeled microspheres. The output of each ventricle also was measured by means of long-standing implanted electromagnetic flow transducers around the ascending aorta or pulmonary trunk during infusion of ritodrine at various rates into the fetus. Infusion of ritodrine (1.9 mcg. per kilogram per minute) into the ewe caused no change in fetal heart rate, blood pressure, cardiac output, or umbilical blood flow, but did cause an increase in fetal adrenal and myocardial blood flow. Ritodrine infused directly into the fetus produced a marked increase in fetal heart rate and a minimal change in cardiac output. There were no significant changes in fetal or maternal acid-base balance during the ritodrine infusions.

Acid-Base Equilibrium↗