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D K Stevenson

Publications and source records attributed to D K Stevenson.

At least 217 records · Page 12Linked to original sources
PubMed1989

Neonatal bilirubin production after preterm labor tocolysis with nifedipine.

We studied the in vivo total bilirubin production, as indexed by the carboxyhemoglobin level (HbCO), of infants whose mothers had ritodrine (RIT) tocolysis or underwent tocolysis with the calcium channel blocker, nifedipine (NIF). No difference in HbCO between the infant groups was detected: NIF 0.67 +/- 0.31% saturation and RIT 0.88 +/- 0.47% saturation. We conclude that NIF is unlikely to cause a clinically important increase in total bilirubin production when used at doses sufficient for tocolysis.

Bilirubin↗
PubMed1989

Interpreting the carboxyhaemoglobin concentration in fetal cord blood.

We calculated the fetal-to-maternal carboxyhaemoglobin concentration ratio in 19 mother-infant pairs at the time of term delivery. Mothers, who had a less than 10% drop in their carboxyhaemoglobin concentration during labour, had an average ratio of 1.40 +/- 0.19. For mothers whose carboxyhaemoglobin concentrations dropped by 10% or more during labour, the average fetal-to-maternal carboxyhaemoglobin concentration ratio was 1.83 +/- 0.48. There was a strong correlation (r = 0.82) between the percent change in maternal carboxyhaemoglobin concentration during labour and the fetal-to-maternal carboxyhaemoglobin concentration ratio at the time of delivery. We conclude that increased CO elimination during labour may be accompanied by rapid changes in the maternal carboxyhaemoglobin concentration, leading to a spuriously high fetal-to-maternal carboxyhemoglobin concentration ratio at the time of delivery.

Carbon Monoxide↗
PubMed1989

Stable individual differences in developmentally changing preterm infants: a replicated study.

In a longitudinal study with the Neurobehavioral Maturity Assessment (NB-MAP), developmental changes and stability of individual differences were assessed in 2 independent samples of preterm infants ranging from 32 weeks conceptional age to term. Individual stability of response was assessed using regression analysis with repeated measures on subjects. The large majority of the functions tested showed highly significant developmental gains with age and highly significant individual stability of performance across age. These findings replicated well across the 2 cohorts. The results are discussed in the light of the neurobiological stage of development of preterm infants during the last 8 weeks prior to term.

Humans↗
PubMed1988

Plasma prorenin and renin in childhood and adolescence.

We studied 108 subjects (age range, 4 to 76 years) to determine the effect of age on prorenin (inactive renin), active renin, and plasma renin activity in normal children, adolescents, and adults. Children and adolescents had lower prorenin concentrations and higher plasma renin activity and active renin concentrations than did adults. Prorenin concentrations were positively correlated with age over the range of 4 to 76 years, while plasma renin activity and active renin concentration were negatively correlated with age. Plasma prorenin and active renin concentrations from umbilical cord blood samples obtained from 11 newborns and arterial samples obtained from five infants were higher than those in samples obtained from children or adults.

Adolescent↗
PubMed1988

Grand multiparity: an obstetric or neonatal risk factor?

Grand multiparity has been considered to be a factor in maternal and neonatal morbidity. In addition, families with seven or more children have been associated with low socioeconomic status. To minimize the confounding effect of the socioeconomic status, the outcome of grand multiparity has been investigated in a mostly homogeneous, ultraorthodox Jewish community in Jerusalem, Israel. A total of 5916 deliveries in one community hospital (Bikur Cholim) were studied, of which 893 (13%) occurred in mothers who had given birth to seven or more infants. There was a significant decrease in the incidence of small for gestational age infants among the grand multiparous women (3.6% as opposed to 5.8% in the control population). This difference was independent of maternal age. Moreover, grand multiparous women gave birth to significantly more large for gestational age infants. No increase in obstetric complications or neonatal morbidity and mortality was found among the offspring of the grand multiparous mothers. Having taken socioeconomic status into account, we conclude that grand multiparity does not carry an increased risk of perinatal morbidity or mortality.

Delivery, Obstetric↗
PubMed1988

Heme oxygenase activity as measured by carbon monoxide production.

A method is described for the in vitro determination of heme oxygenase (HO) activity in animal tissue preparations through determination of carbon monoxide production. Tissue homogenates were centrifuged and the 13,000g supernatants were incubated in septum-sealed vials with methemalbumin in the presence and absence of NADPH at 37 degrees C for 15 min. The reaction was terminated by quick-freezing to -78 degrees C and the amount of carbon monoxide released into the headspace was determined by gas chromatography with a reduction gas detector. The CO produced through mediation of NADPH is used as a measure of HO activity and is expressed as nanomoles of CO produced per hour per milligram protein. The method permits analysis of as little as 2 microliter normal rat tissue homogenate representing 0.4 mg liver tissue (approx 40 micrograms total protein). The assay rate is 10-15 duplicate samples per hour with a precision of 3% for sample (4.47 +/- 0.13 SD nmol CO/h/mg protein) and 6% for blank reactions (0.59 +/- 0.10 nmol CO/h/mg protein) for 10 microliter liver supernatant. Various reaction parameters were studied. The method was used to compare HO activity in several tissue homogenates from normal rats and rats treated with COCl2.

Animals↗
PubMed1988

Refractory neonatal hypoxemia: diagnostic evaluation and pharmacologic management.

Hypoxemia refractory to oxygen administration and assisted ventilation is found in many clinical conditions and results from a variety of pathophysiologic disorders. Recent clinical and laboratory experience has demonstrated that the choice of therapy for an infant with refractory hypoxemia depends upon identification of the underlying etiologic and pathophysiologic conditions. The ideal therapies for many of these conditions have not yet been defined. We have provided, based on our experience, guidelines for selection of the most appropriate of the currently available therapies for many of these patients.

Blood Pressure↗
PubMed1988

Birth out of wedlock and the risk of intrauterine growth retardation.

Birth out of wedlock has been associated with maternal and neonatal problems, especially low birthweight, attributed mainly to the young maternal age of the unmarried mothers. We surveyed a cohort of 300 first-born infants delivered in Israel to unwed mothers, matched for parity, maternal age, and ethnic origin. No maternal complications were found among the unwed mothers. However, the incidence of intrauterine growth retardation among infants of the out of wedlock mothers was 53 of 293, compared with 20 of 297 among the control population (p less than 0.001). This difference in the incidence of intrauterine growth retardation may not be associated with young maternal age.

Adolescent↗
PubMed1988

Child-bearing after induced abortion: reassessment of risk.

We reviewed 1791 singleton pregnancies of women with a history of previous induced abortion and compared them with 14,857 pregnancies in mothers with no previous induced abortions. Therapeutic termination of pregnancy was associated with a statistically significant increase in the incidence of low birth weight infants and bleeding in the first trimester of pregnancy. When other variables were examined, no significant differences were found between the two groups, except for a significantly higher rate of stillbirths among women who had not had a prior induced abortion. There were no increases in major or minor congenital malformations.

Abortion, Therapeutic↗
PubMed1988

End-stage periventricular leukomalacia: MR evaluation.

A prospective study was performed to assess the capabilities of magnetic resonance (MR) imaging in evaluation of end-stage periventricular leukomalacia (PVL) in six children, aged 31-54 months, in whom PVL had been documented by neurologic ultrasonography during the neonatal period. Eight children of similar age (four premature infants and four full-term infants) with normal neurologic development served as controls. A characteristic triad of PVL abnormalities was seen on MR images: (a) abnormally increased periventricular white-matter signal intensity on the first and second echo images of a T2-weighted sequence (repetition time = 2,000-2,400 msec, echo times = 20 or 30 and 80 msec), most commonly observed in the trigone regions of the lateral ventricles bilaterally; (b) marked loss of periventricular white matter in these regions of abnormal signal intensity, predominantly in the periatrial regions; and (c) compensatory focal ventricular enlargement adjacent to regions of abnormal signal intensity. In patients with the classic periatrial distribution of PVL lesions, general correlation between the degree of neurologic impairment and the severity of MR abnormalities was demonstrated. MR imaging was useful in detecting subtle forms of PVL in cases in which neurologic damage was subclinical.

Encephalomalacia↗
PubMed1988

Effect of bupivacaine hydrochloride on bilirubin production in neonatal rats.

The rate of bilirubin production was studied in 12-hour-old rats exposed to bupivacaine HCl by subcutaneous injection. The bilirubin production was estimated by measuring the excretion rate of carbon monoxide (VeCO) using an open flow-through system. No significant difference was found between the VeCO of bupivacaine HCl-treated and control animals, or between the levels of bilirubin in the pooled blood of treated (0.92 +/- 0.32 SE mg/dl) and control (1.0 +/- 0.28 SE mg/dl) animals. These negative findings support the clinical studies which have not demonstrated an association between epidural anesthesia with bupivacaine HCl and neonatal jaundice.

Animals↗
PubMed1988

In vitro carbon monoxide production by the small intestine of suckling and adult Wistar rats: effect of parenteral tin-protoporphyrin.

Single subcutaneous doses (25 mumol/kg body weight) of tin-protoporphyrin (TP), a potent competitive inhibitor or heme oxygenase (HO), were administered to both suckling and adult Wistar rats. The effect of TP on the carbon monoxide excretion rate (VeCO), an index of total bilirubin formation, and on in vitro carbon monoxide (CO) production by the small intestine were evaluated. Whereas the VeCO of the adult group was decreased (p less than 0.0005) after TP, that of the suckling rat was unchanged. Gradients of CO production along the small intestine were observed in sucklings as well as adults; however, these gradients were in opposite directions. Intestinal CO production was greatest in the adult duodenum, decreasing distally; conversely, the CO production was greatest in the suckling ileum, decreasing proximally. No significant difference in CO production between control and TP-treated adult intestinal mucosa was observed. In sucklings, a significant reduction of intestinal CO production in the TP-treated rats was detected in the duodenum only (p less than 0.05). The results suggest that suckling rats differ from adults in terms of the capacity to produce CO and the direction of the gradient of CO production along the intestine. We conclude that (1) TP may not substantially decrease the in vivo production of CO by the small intestine at a dose which inhibits hepatic and splenic heme oxygenase, and (2) because after a heme load, heme is excreted into the intestine after TP administration, heme-degrading, CO-producing processes in the intestine may contribute to an animal's VeCO under such conditions.

Aging↗
PubMed1988

Lack of inhibition of intestinal heme oxygenase by antibiotics and tin-protoporphyrin.

We assessed the in vivo and in vitro effects of antibiotics and tin-protoporphyrin (TP) on intestinal heme oxygenase (HO) activity using a gas chromatographic assay. This method measures the carbon monoxide produced from heme in the presence of NADPH. After in vivo administration of kanamycin (10 mg/kg body weight), ampicillin (200 mg/kg body weight) or neomycin (60 mg/kg body weight) with or without TP (65 mumol/kg body weight) to suckling rats, no significant difference in HO activity along the small intestine was observed. In vitro exposure of adult rat intestinal preparations to the antibiotics showed no significant decrease in HO activity between control and experimental tissue preparations. A concentration-dependent stimulatory effect of neomycin was observed. Subcutaneous administration of TP (25 mumol/kg body weight) to adult male Wistar rats revealed no significant inhibition of the intestine. However, in vitro addition of TP (12.5 microM) to the control tissue preparations of adult Wistar rats revealed highly significant inhibition in liver and spleen when compared to the unexposed control tissues. In contrast, when TP was added to control intestinal preparations no inhibition was observed. These findings suggest that suckling rat intestinal heme oxygenase is not inhibited by in vivo treatment with high concentrations of kanamycin, ampicillin, or neomycin. Furthermore, these antibiotics are not in vitro inhibitors of adult rat intestinal HO. Finally, adult rat intestinal HO is not inhibited either in vivo or in vitro by a concentration of TP that significantly inhibits liver and spleen activity.

Animals↗