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D K Stevenson

Publications and source records attributed to D K Stevenson.

338 records · Page 19Linked to original sources
PubMedDate not supplied

Tin-protoporphyrin inhibits carbon monoxide production in adult male Wistar rats with common bile duct ligation.

The excretion rate of CO (VeCO), an index of total bilirubin production, and the total plasma bilirubin level are significantly elevated by 72 h after ligation of the common bile duct in adult male Wistar rats. At 72 and 96 h, rats prepared in this manner were subcutaneously injected with 50 mumol/kg body weight of tin-protoporphyrin IX (TP) (n = 5) or saline (n = 6). At 120 h after surgery, the VeCO had fallen from the pretreatment level in the TP-treated animals by 22% (P less than 0.025) compared with no significant change in the saline-treated controls. The plasma total bilirubin level of the experimental animals had also declined by 32% (p less than 0.0005) compared with their pretreatment level. The hyperbilirubinemia of the saline-treated controls was not significantly modified. These results suggest that TP reduces bilirubin production and plasma total bilirubin levels in adult rats with surgically created obstructive jaundice.

Animals↗
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Comparison of bilirubin production in Japanese and Caucasian infants.

Bilirubin production, as indexed by serum carboxyhemoglobin (HbCOc), was studied in a group of normal term Japanese infants and Caucasian controls during the second to third day of life. Stringent entry criteria were employed in order to eliminate infants with hemolysis or other known causes of increased bilirubin production. The mean HbCOc of the Japanese infants (0.69 +/- 0.15% sat) was significantly higher than that of the Caucasian infant (0.58 +/- 0.17% sat). The serum total bilirubin was also significantly higher in Japanese infants (11.1 +/- 3.0 mg/dl versus 8.0 +/- 2.2 mg/dl). This difference may be attributable to environmental and/or genetic factors.

Asian People↗
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Relationship between breath and total body hydrogen excretion rates in neonates.

Our study examined the relationship of H2 excreted in breath to total body H2 excreted by neonates. We report simultaneously measured end-tidal H2 concentrations, plus breath H2 and total body H2 (breath H2 plus flatus H2) excretion rates in 10 neonates. End-tidal H2 concentrations varied from 2.4 to 192 ppm. Breath H2 excretion rates ranged from 0.20 to 6.5 and total body H2 excretion rates from 0.29 to 15.0 ml/h. The fractional breath H2 excretion in these infants was 48% (range 33-69%), compared with 21% reported in adults. The correlation coefficient for end-tidal derived H2 excretion and directly measured breath H2 excretion rates was 0.95 (p less than 0.001). We conclude that the proportion of total H2 excreted in the breath of neonates is increased compared with adults, suggesting that caution must be exercised when interpreting newborn breath H2 measurements and using adult norms.

Adult↗
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Effects of oral administration of tin and zinc protoporphyrin on neonatal and adult rat tissue heme oxygenase activity.

The purpose of this study was to investigate if oral metalloporphyrin treatment could suppress intestinal heme oxygenase (HO) activity and thus prevent HO-mediated heme degradation in this organ. Six hours after a single 40 mumol/kg oral dose of tin protoporphyrin (TP), zinc protoporphyrin (ZP), or heme to adult rats, no significant difference in the HO activity of the intestine was observed relative to control tissues. Moreover, the activity was not inhibited by in vitro exposure to 40 microM TP or ZP. Liver and spleen HO activity was also not significantly inhibited in vivo after oral administration of metalloporphyrins; however, in vitro exposure to TP or ZP decreased the HO activity of preparations from these organs significantly. Like adults, the intestinal HO activity of neonates was not inhibited effectively by oral administration of either metalloporphyrin. The results of subsequent in vitro exposure of control neonatal tissue preparations to ZP or TP was similar to those using adult tissue preparations. Even at 100 microM, only ZP seemed to have some in vitro inhibitory effect on the intestinal HO of suckling rats. We conclude that intestinal HO is less inhibitable by TP or ZP reaching the intestine via the stomach in concentrations at least 30-fold greater than those achieved after parenteral 40 mumol/kg doses, which cause significant hepatic and splenic HO inhibition. Intestinal absorption and enterohepatic circulation of heme, TP, and ZP do not seem to occur in amounts sufficient to consistently and significantly affect HO activity in liver or spleen.

Administration, Oral↗
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Limited value of nephelometry in monitoring the administration of intravenous fat in neonates.

To evaluate the usefulness of nephelometry in predicting hyperlipidemia in neonates receiving intravenous fat (IVF), 23 infants in our neonatal intensive care nursery had simultaneous measurements of the serum IVF level (as determined by nephelometry), triglyceride, cholesterol, and free fatty acid/albumin molar ratio. There was a positive correlation between the serum IVF level and triglycerides, but the IVF level did not reliably predict elevated triglycerides, cholesterol, or free fatty acid-albumin molar ratio. Thus, neonates receiving IVF emulsions cannot be monitored by nephelometry alone. Adequate monitoring requires measurement of specific lipid fractions.

Cholesterol↗
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Effect of phototherapy for neonatal jaundice on cognitive performance.

Phototherapy for neonatal hyperbilirubinemia was introduced to our medical center in March 1971. To assess the influence of phototherapy on subsequent cognitive outcome, we compared the intelligence test scores at 17 years of age of subjects born 4 months before and 10 months after the introduction of phototherapy. The intelligence quotient score (mean +/- SE) at 17 years for 84 subjects with severe neonatal hyperbilirubinemia was 108 +/- 2 for those treated by phototherapy and 107 +/- 2 for controls matched for gestational age and birth weight. The confounding effect on intelligence quotient scores of perinatal factors (bilirubin concentrations, gestational age, birth weight, Apgar score) and demographic characteristics (ethnic origin, socioeconomic status, paternal education) was taken into account in a multiple logistic regression analysis by using a General Linear Models procedure. Phototherapy was found to have no independent effect on intelligence quotient scores after adjustment for the effect of confounding factors. We conclude that for full-term newborn infants with neonatal hyperbilirubinemia, phototherapy had neither a beneficial nor an adverse effect on intellectual ability in late adolescence.

Adolescent↗
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Is fetal growth affected by cord entanglement?

Cord entanglement is a common occurrence during delivery. We examined the association of cord complications observed at delivery and birth weight. A retrospective survey of 12,241 births was performed, supplemented with a prospective study of an additional 456 deliveries. No adverse association was found in the retrospective data between cord coiled twice or more around the newborns' neck (8.3% of cases) and birth weight. Moreover, the incidence of cord around neck was significantly lower (p < 0.0006) in infants weighing less than 2000 gm at birth. A multiple regression analysis of the prospective data did not reveal any significant influence of cord complications on birth weight. We conclude that cord entanglement was not found to be a major cause of intrauterine disadvantage in pregnancies with a viable infant at term, as reflected by birth weight.

Adult↗
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Adverse perinatal outcome in the older primipara.

Delayed childbearing has become common and has raised the awareness of the possible risks for the mother and the newborn infant. The increased maternal and neonatal risks have been attributed largely to the lack of proper prenatal care. The aim of this study was to assess whether advanced maternal age is a significant risk factor in mothers who receive good prenatal care. We matched 161 cases 1:1 according to the following criteria: maternal and paternal ethnic origin, chronic diseases, marital status, and smoking during pregnancy. Our results show that the older women had babies with a significantly higher incidence of low birth weight (< 2500 gm, p = 0.001), prematurity (< 37 weeks, p = 0.02), intrauterine growth retardation (p = 0.001), abruptio placentae (p = 0.002), and cesarean section (p < 0.001). The average hospital stay for the babies of the older mothers was longer than that for babies of the younger mothers (8.4 vs 6.1 days, p = 0.003), and the incidence of hospitalization for more than 3 days in the neonatal intensive care unit was increased (10.3% vs 2.2%). Logistic regression did not support maternal age of 35 years and older as being the single significant risk factor for adverse neonatal and maternal outcome. We conclude that maternal age older than 35 years entails a higher risk for the mother and her newborn infant, even when good prenatal care is taken.

Adult↗
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Nitrovasodilator therapy for severe respiratory distress syndrome.

Improved gas exchange in infants with severe respiratory distress syndrome has been reported in association with infusion of nitroprusside and during inhalation of nitric oxide. To evaluate the association between nitrovasodilator therapy and clinical improvement in premature neonates with severe respiratory distress syndrome, we reviewed the courses of 22 infants with severe respiratory distress syndrome who were treated with sodium nitroprusside for at least 24 hours. These infants had birth weights of 2049 +/- 828 gm (range 720 to 3430 gm), gestational ages of 32.5 +/- 3.5 weeks (range 25 to 38 weeks), high ventilator settings before treatment (FIO2 of 100%, peak inspiratory pressures of 37.8 +/- 6.1 cm H2O [range 30 to 50 cm H2O], and mean airway pressures of 18.0 +/- 3.3 cm H2O [range 12.3 to 26 cm H2O]), and low pretreatment PaO2 of 49.3 +/- 9.4 mm Hg (range 27 to 69 mm Hg). Baseline oxygenation indexes were 39.4 +/- 12.1 (range 18.6 to 66.7). Nitroprusside infusion was temporally associated with increased PaO2, decreased PaCO2, and reduced oxygenation index. Potentially beneficial changes were inconsistent in infants with pulmonary interstitial emphysema and were greatest in infants treated with end-expiratory pressures of at least 4 cm H2O. These observations provide a basis for the hypothesis that nitrovasodilator therapy produces improvement in gas exchange in premature infants with severe respiratory distress syndrome.

Humans↗
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Prenatal ritodrine administration and the incidence of respiratory distress syndrome in premature infants.

UNLABELLED: Prenatal exposure to ritodrine may be associated with a lower incidence of RDS in premature infants, independent of its effect on prolongation of pregnancy. OBJECTIVE: The purpose of this study was to assess the neonatal respiratory outcome of premature infants according to whether their mothers were treated prenatally with ritodrine. STUDY DESIGN: A retrospective review was done of all 247 infants born at 34 weeks of gestation or less in our hospital during a 6-year period. A multivariate logistic regression was used to adjust for possible confounding variables. RESULTS: Among the ritodrine-exposed infants respiratory distress syndrome developed in 9.5% (4/42) compared with 28% (57/205) in the unexposed group (p < 0.012; adjusted odds ratio 4.88, 95% confidence interval 1.27 to 18.70). The gestational age and birth weight were similar in the two groups. The incidence of transient tachypnea of the newborn and other neonatal complications was not statistically different between the two groups. CONCLUSION: Ritodrine was associated with a significantly lower incidence of respiratory distress syndrome in premature infants, independent of the effect of ritodrine on prolongation of pregnancy.

Female↗
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Supplemental oxygen may decrease progression of prethreshold disease to threshold retinopathy of prematurity.

The optimum level of oxygen saturation for infants with prethreshold retinopathy of prematurity (ROP) is unknown. We reviewed our conversion rate from prethreshold to threshold ROP between 1985 and 1993 during which time target levels of oxygen saturation rose in a stepwise fashion. A retrospective study of 153 infants with prethreshold ROP was performed at Stanford University between 1985 and 1993 that showed that target minimum oxygen saturation rose from 92% (1985-1987) to 95% (1988) to 96% (1989) to 99% (1990-1993). In addition, we looked at 26 infants between 1994 and 1996 who were excluded from the STOP-ROP study and who were not receiving supplemental oxygen in an effort to maintain equipoise for that study. Infant characteristics were tabulated, and rates of progression from prethreshold to threshold ROP were calculated. Rates of progression to threshold varied little between 1985 and 1989 (average 37%), but dropped to 7% for the period between 1990 and 1993. From 1994 through 1996 the rate of progression to threshold disease rose again, to 38%. Moderate supplemental oxygen (target saturation 99% with PO2 no higher than 100 mm Hg) was associated with regression of prethreshold ROP, without appearing to arrest retinal vascular maturation.

Birth Weight↗
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Favism by proxy in nursing glucose-6-phosphate dehydrogenase-deficient neonates.

Two nursing neonates deficient in glucose-6-phosphate dehydrogenase developed severe hyperbilirubinemia despite phototherapy. Mothers of both the infants had recently eaten fava beans. The hemolytic triggers found in fava beans may have been absorbed by the mothers and excreted in their breast milk. Carboxyhemoglobin determination performed on one of the infants reflected ongoing hemolysis.

Breast Feeding↗