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Biomedical subjects

L S James

Publications and source records attributed to L S James.

At least 19 recordsLinked to original sources
PubMed1992

Long-term acid-base measurements in the fetal and maternal baboon.

OBJECTIVE: The purpose of the study was to examine the relationship between maternal and fetal acid-base indexes in the baboon. STUDY DESIGN: Eight animals maintained in a tether system were studied during the third trimester. Results were analyzed using analysis of variance. RESULTS: After recovery from surgery, pH in carotid artery blood of the fetus was 7.40 +/- 0.027 (mean +/- SD), PO2, 27.5 +/- 3.45 mm Hg; PCO2, 34.0 +/- 2.37 mm Hg; base deficit, 3.0 +/- 2.15 mEq/L; Hot, 33.4% +/- 2.69% and HbO2, 61.3% +/- 8.65%. The corresponding values in the mother were 7.48 +/- 0.035, 100.7 +/- 9.44 mm Hg, 26.4 +/- 2.95 mm Hg, 3.6 +/- 1.71 mEq/L, 32.6% +/- 4.0% and 97.9% +/- 1.28%, respectively. All indexes remained essentially the same until the onset of active labor, at which time the fetus became slightly acidotic and hypoxemic (pH less than 7.35, HbO2 less than 50%). CONCLUSION: The baboon fetus has slightly higher pH2 and lower PaCO2 than the human fetus and PaO2, base deficit, and maternal-fetal gradients across the placenta in these two primate species are comparable.

Acid-Base Equilibrium↗
PubMed1992

Hearing and neurodevelopmental outcome in survivors of persistent pulmonary hypertension of the newborn.

Thirty-four infants who had a diagnosis of severe persistent pulmonary hypertension of the newborn at birth (alveolar-arterial oxygen difference greater than 600) were treated without paralysis or hyperventilation to induce alkalosis. All survived. Twenty-seven of these 34 eligible infants (79%) underwent neurologic, intelligence, and audiologic testing between 10 months and 6 years of age. Children who were younger than 1 year of age at the initial hearing test were retested after they reached 2 years of age. The average IQ was within the normal range (mean = 96.23). None had sensorineural hearing loss. Severe neurologic abnormalities were seen in 4 children, 3 of whom had been severely asphyxiated at birth (determined by biochemical criteria). Mild neurologic abnormalities were observed in 5 children. Two infants had bronchopulmonary dysplasia because they required supplemental oxygen for 29 and 66 days, respectively, and had abnormal chest roentgenograms; 1 patient takes intermittent doses of albuterol (Ventolin) and neither currently requires supplemental oxygen. This study of 27 infants with severe persistent pulmonary hypertension of the newborn suggests that conservative management without induced alkalosis or respiratory paralysis is accompanied by no sensorineural hearing loss and a good neurologic outcome.

Apgar Score↗
PubMed1979

Human fetal oxygenation following paracervical block.

To test the hypothesis that fetal heart rate (FHR) changes following paracervical block may be secondary to fetal hypoxia, human fetal oxygenation was measured continuously using a transcutaneous electrode. Following the block, each fetus demonstrated a decline in oxygen tension (tcPO2) at 5 minutes, which reached its lowest value at a mean of 11.5 minutes and remained at this level for an average of 3 minutes. Following the block, FHR variability increased at 5.2 minutes. reaching its maximal level by a mean of 7.5 minutes. By 11 minutes, a decrease in FHR variability was noted, which lasted for approximately 17 minutes. Decreased variability was not uniformly associated with low tcPO2. On some occasions, fetal tcPO2 declined even in the absence of increased uterine activity, which was noted at times following the block. The severity of the tcPO2 decline appears related to the analgesic effectiveness of the block.

Anesthesia, Local↗
PubMed1979

Reduced uterine blood flow and fetal hypoxemia with acute maternal stress: experimental observation in the pregnant baboon.

The effects of maternal hyperexcitability on the fetus were studied in 17 baboons. In the period of agitation, induced by stressful stimulus such as exposure to bright light or by clamping of the toe, the mother exhibited an increase in arterial blood pressure and, in some instances, arrhythmia. These changes were accompanied by an increased uterine activity and reduced uterine blood flow, and resulted in a decrease in heart rate and arterial oxygenation in all fetuses. Fetal recovery was prompt after maternal agitation was terminated, either by removal of the stimulus or by sedation with pentobarbital or nitrous oxide. This sedation also prevented a decrease in uterine blood flow when stress was repeated.

Animals↗
PubMed1979

Relationship of fetal bradycardia to maternal administration of lidocaine in sheep.

The casual relationship between the use of lidocaine and fetal bradycardia and the effect of the drug on maternal and fetal hemodynamics were studied on 13 chronically instrumented pregnant sheep. Lidocaine was infused intravenously to the mother for 60 minutes during arterial lidocaine concentrations were maintained at 2 to 5 microgram per milliliter in the mother and at less than 2 microgram per milliliter in the fetus. A decrease in uterine blood flow and an increase in uterine vascular resistance and uterine activity occurred immediately following the administration of lidocaine to the ewe. These changes were followed by a transient fetal bradycardia in 12 out of 17 experiments, accompanied by a decrease in fetal PaO2 values. These phenomena were seen in the absence of such predisposing conditions as maternal hypotension and fetal acidosis. It would appear that the mechanism responsible for a transient fetal bradycardia following regional obstetric anesthesia, particularly paracervical block anesthesia, in the initially nonasphyxiated fetus may in part be related to a brief decrease in perfusion of intervillous spaces. The bradycardia can occur at low lidocaine concentrations in both the maternal and fetal blood in a range similar to that observed in clinical practice.

Anesthetics, Local↗
PubMed1979

Arginine vasopressin during gestation and parturition in sheep fetus.

The possible correlation between plasma arginine vasopressin (AVP) concentration and the processes leading to parturition was assessed in 11 chronically catheterized pregnant ewes. Samples of blood withdrawn intermittently during a 20-day period preceding labor and during parturition were analyzed for AVP by a specific radioimmunoassay, as well as for pH, PaCO2 and PaO2. Fetal AVP was 1.74 +/- 1.55 pg/ml and maternal AVP 1.47 +/- 0.74 pg/ml (mean +/- SD). No preparturient rise in fetal vasopressin was noted, but levels increased progressively during labor to reach peak levels in cord blood (range 7.5--8,000 pg/ml). There was no consistent rise in maternal vasopressin during the same interval. A relationship between prolonged antepartum intrauterine asphyxia and increases in fetal vasopressin was noted. It is concluded that the markedly elevated levels of vasopressin observed in cord blood are the result of intrapartum 'stress', but are not related to the initiation of parturition.

Animals↗
PubMed1979

Amniotic fluid microviscosity determined by fluorescence polarization: methodology and relation to gestational age.

The fluorescence polarization of 116 amniotic fluid specimens obtained from 22 isoimmunized pregnant women was determined. The degree of fluorescence polarization of amniotic fluid provides an index of microvisocity in lipid aggregates that is dependent on the lecithin-to-sphingomyelin ratio and the degree of saturation of fatty acid side chains. We confirmed the reproducibility of the measurement of amniotic fluid microviscosity (coefficient of variation, 2.0%). The measurements are not effected by bilirubin concentration of amniotic fluid dilution. The pattern of change of amniotic fluid microviscosity during gestation parallels the expected development of the surfactant system. Amniotic fluid microviscosity is high during early gestation and abruptly and sequentially decreases between the 28th and 36th week of gestation. Since the measurements are an accurate reflection of the biochemical properties of amniotic fluid lipids and parallel the development of the surfactant system, we conclude that amniotic fluid microviscosity may well serve as an indicator of the process of fetal lung maturation.

Amniotic Fluid↗
PubMed1978

Effects of endotoxin on the pregnant baboon and fetus.

Effects of E. coli endotoxin upon uterine activity and maternal and fetal condition were studied in four pregnant baboons and their fetuses. Uterine activity increased significantly following administration of endotoxin to the mother. Endotoxin also produced maternal circulatory collapse, severe acidosis, and profound fetal asphyxia resulting in death. Death also occurred in three of the four mothers within 24 hours without amelioration of their conditions.

Acidosis↗
PubMed1978

Renal response of fetal lamb to complete occlusion of umbilical cord.

The renal response of the fetal lamb to repeated complete occlusion of the umbilical cord was studied in nine chronically instrumented animals. Five episodes of occlusion of the umbilical cord, each lasting for two minutes, produced a twofold rise in fetal urine osmolality and sodium, chloride, and potassium concentrations. Output of urine and glomerular filtration rate remained essentially unchanged while free water clearance decreased from a control of +0.10 to -0.02 ml. per kilogram per minute at the end of the fifth episode. Electrolyte concentrations in urine remained elevated for at least two hours following the occlusions. In addition to changes in urine composition, there was a 50- to 200-fold increase in the fetal plasma concentration of vasopressin. These studies indicate that complete interruption of the umbilical circulation, even though of short duration, produces disturbances in fetal renal function that can lead to loss of electrolytes in the urine. They provide an explanation for the low sodium levels reported in asphyxiated newborn infants in renal failure.

Acid-Base Equilibrium↗
PubMed1978

Determination of fetal lung maturity by fluorescence polarization of amniotic fluid.

The degree of fluorescence polarization (P value) of 1,6-diphenyl-1,3,5-hexatriene has been shown to be an excellent indicator of the lecithin/sphingomyelin (L/S) ratio in laboratory prepared liposomal dispersions. In order to test the validity of this technique in amniotic fluid, the L/S ratio and P value of 161 amniotic fluid specimens were determined. In 127 the P value was less than or equal to 0.336 and the L/S ratio was greater than or equal to 2. In 26 the P value was greater than 0.336 and the L/S ratio was less than 2 (P less than 0.05). The amniotic fluid P value is affected by blood or meconium but not by surgical lubricants or bilirubin. We concluded that the degree of fluorescence polarization of amniotic fluid indicates fetal lung maturity as reliably as the L/S ratio. However, this method has important technical and practical advantages that make it more applicable for a clinical laboratory.

Amniotic Fluid↗
PubMed1978

Maternal ABO blood group type B: a risk factor in the developement of neonatal group B streptococcal disease.

In a prospective study of maternal genital colonization with group B streptococci (GBS) at the time of delivery, epidemiological data, including blood type (ABO group), were recorded for the 1,062 patients studied. Blood type B was found in a statistically significant higher proportion of patients colonized with GBS (28%) compared with the total population (16.4%) (P less than .005, X2 = 8.43). Women with blood type B were twice as likely to be colonized as those with types O or A. Hypotheses to explain this observation include the possibilities that GBS possess a B-like antigen, rendering parturients who lack anti-B antibody at increased risk for GBS colonization, or that GBS possess a receptor site for B surface antigens. One may speculate that a mutation toward an affinity for the human ABO blood group type B accounts for the advent of the group B Streptococcus as a significant perinatal pathogen.

ABO Blood-Group System↗
PubMed1977

Temperature gradient between fetus and mother as an index for assessing intrauterine fetal condition.

Temperature gradient between fetus and mother (deltaTF-M) was measured in 29 pregnant baboons. Thermocouples were implanted in the fetal esophagus and the maternal colon, and, in some instances, thermistor probes were also placed in the fetal esophagus, scalp, and shoulder muscle. Under steady-state conditions, the fetal temperature was found to be higher than that of the mother. Temperatures in the fetal esophagus, scalp, and shoulder were 0.47, 0.28, and 0.19 degrees C. respectively, higher than those in the maternal colon. There was an increase in deltaTF-M during acute fetal stress induced by asphyxia, secondary to occlusion of the umbilical cord, maternal aorta, or inferior vena cava, or to acutely increased uterine activity. This increase in deltaTF-M most likely reflects impairment of heat dissipation from the fetus to the maternal compartment. A decreased deltaTF-M was observed when the stress on the fetus was subacute and prolonged. This is probably the result of a diminution of heat production by the fetus as the metabolic rate is lowered during prolonged hypoxia. Ten to 30 minutes after the cessation of vital signs of the fetus, the deltaTF-M became zero.

Acute Disease↗
PubMed1977

High vasopressin concentrations in human umbilical cord blood--lack of correlation with stress.

Marked elevations in the vasopressin concentrations in human umbilical cord blood have been reported previously (4, 8). This could either be a part of generalized increase in the activity of fetal endocrine system at the time of birth, a phenomenon that has led to the concept of fetal participation in the onset of labor, or simply due to the stress of delivery. The present study is an attempt to examine the later possibility. Plasma vasopressin was determined by radioimmunoassay [9] in separately collected arterial and venous blood from the umbilical cords of 24 babies spontaneously delivered and 14 babies born after Caesarian Section in the absence of labor. Arterial acid-base determinations were done in each case. The Apgar Score was evaluated by one individual. In order to obtain a general idea of circulating concentration of this hormone in the neonatal period, vasopressin concentrations were determined in the systemic venous blood of 12 normal and 10 stressed babies. Vasopressin concentrations in the umbilical arterial blood of babies born after spontaneous delivery were remarkably high, as compared to all the other groups. Despite a wide range, between 5-2200 pg/ml, there was no correlation between the magnitude of vasopressin elevation and the severity of fetal asphyxia (Fig. 1). The present finding in part, confirms and expands previously observed increased vasopressin levels in the cord blood after spontaneous vaginal delivery. In addition, a lack of correlation between fetal asphyxia and the vasopressin levels suggests that these high levels may not be related to this form of stress.

Acid-Base Equilibrium↗
PubMed1977

Effects of terbutaline on the pregnant baboon and fetus.

The effects of terbutaline on the mother and fetus were evaluated in 8 near-term pregnant baboons. Significant suppression of postoperative spontaneous and oxytocin-augmented uterine activity was achieved with infusion rates of 0.36 and 0.56 microgram/kg/min, respectively. Maternal and fetal blood pressure and acid-base states as well as fetal heart rate were unaffected by the administration of terbutaline to the mother, but a mild maternal tachycardia was observed. Both maternal and fetal blood glucose increased during terbutaline infusion. Direct administration of terbutaline to the fetus did not alter the fetal cardiovascular or acid-base state. It is concluded that in the baboon, terbutaline is an effective tocolytic agent with minimal untoward effects on either mother or fetus.

Acid-Base Equilibrium↗
PubMed1976

Umbilical vein occlusion and transient acceleration of the fetal heart rate. Experimental observations in subhuman primates.

Transient acceleration of the fetal heart rate is commonly seen in the cardiotachometer tracing of the human fetus during labor. A likely cause appeared to be partial occlusion of the umbilical cord. On the basis of this hypothesis, fetal cardiovascular responses to partial occlusion of the umbilical cord or isolated intra-abdominal portion of umbilical vein were studied in near-term pregnant baboons and rhesus monkeys prior to and following sympathetic blockade with dibenzyline and propranolol. The responses were of two types. In the well-oxygenated fetus, partial occlusion resulted in transient acceleration of heart rate and a decrease in pulse pressure. This response was abolished with dibenzyline or propranolol. In the hypoxic fetus, partial occlusion resulted in either bradycardia and hypotension or hypotension with no alteration in heart rate. Thus, transient acceleration of the fetal heart rate can be explained on the basis of a sympathetic response to diminished venous return. It would appear to be an early sign of a potential cord complication. This response will not be seen if the fetus becomes asphyxiated and hypoxic.

Animals↗