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Biomedical subjects

S Abbasi

Publications and source records attributed to S Abbasi.

At least 55 records · Page 3Linked to original sources
PubMed1990

Pulmonary mechanics and energetics of normal, non-ventilated low birthweight infants.

Pulmonary mechanics and energetics were determined in 33 healthy low birthweight infants (less than 1,500 g, 28-34 weeks gestation) who had never received ventilatory support. Tidal volume, dynamic pulmonary compliance, pulmonary resistance, pressure-volume relationships, and tidal flow-volume measurements were obtained by pneumotachography and the esophageal balloon technique. Standardized data collection and software data analysis by least mean squares technique yielded data at 0.5, 1, 2, and 4 weeks postnatally, as a function of gestational age (less than 30, 30-32, and greater than 32 weeks gestation). Relatively stable values were obtained for tidal volume and minute ventilation (normalized for body weight); these were associated with values of peak-to-peak esophageal pressure significantly (P less than 0.001) increasing from 4.4 +/- 0.3 SEM cmH2O at 0.5 weeks to 8.1 +/- 0.8 SEM cmH2O at 4 weeks of age. Dynamic pulmonary compliance ranged from 2.0 to 2.4 mL/cmH2O in the first 4 weeks of life. When normalized for weight, compliance decreased with age, which may suggest a slower pulmonary maturation as compared to increase of body weight. Mean pulmonary resistance decreased from 62.9 cmH2O/L/s at less than 30 weeks gestation to 32.5 cmH2O/L/s at greater than 32 weeks gestation, 0.5 weeks postnatally. Pulmonary resistance peaked at 2 weeks postnatally (P less than 0.05), at all gestational ages, then decreased. Changes in pulmonary mechanics resulted in increasing resistive work of breathing. Our findings suggest a postnatal retardation of pulmonary and airway growth, relative to gestation maturation. These data can provide an objective base of comparison for data in sick, low birthweight neonates.

Airway Resistance↗
PubMed1990

Surfactant protein-A in bronchoalveolar lavage fluid from neonates with RDS on conventional and high-frequency oscillatory ventilation.

Surfactant protein-A (SP-A) was measured in bronchoalveolar lavage (BAL) samples from ventilated neonates in order to study the concentration of SP-A with regard to: 1) high-frequency oscillatory ventilation (HFOV) vs. conventional mechanical ventilation (CMV); 2) the postnatal course and ontogeny of SP-A; and 3) the correlation with measurements of pulmonary function. Patients on HFOV had markedly lower BAL SP-A concentrations on days 1 and 2 compared to those on CMV, which may indicate influence of mode of ventilation on surfactant metabolism. The SP-A concentrations increased postnatally concurrent with resolution of acute respiratory distress syndrome. Finally, there were only weak correlations between BAL SP-A concentration and dynamic lung compliance and oxygen requirement.

Age Factors↗
PubMed1990

Retinopathy of prematurity: prevalence and treatment over a 20 year period at Pennsylvania Hospital.

This paper presents the results of a 20 year survey of ROP among less than or equal to 2000 g BW infants cared for at Pennsylvania Hospital. It relates changes in perinatal care and nutrition, survival rates, and serial serum E levels with incidence and severity of ROP. It includes our protocol for monitoring E nutrition so as to optimize its effectiveness at physiologic serum levels for prophylaxis for ROP. Also presented are the promising results of our experience with vitamin E at pharmacologic serum levels as a treatment for severe ROP (defined as in the Cryo ROP Trial). These indicate the need for a multicenter trial to assess the effect of pharmacologic Vitamin E therapy as an alternative or supplement to therapy of severe ROP with laser or cryo surgery.

Clinical Trials as Topic↗
PubMed1990

Safety and efficacy of long-term tocolysis with indomethacin.

Indomethacin was utilized in 24 pregnancies (31 exposed fetuses) in preterm labor who labored despite intravenous tocolysis. The mean gestational age at the start of indomethacin therapy was 25.1 weeks (+/- 4.4), mean duration of indomethacin therapy was 43.9 days (+/- 31.4), mean gestational age at delivery 33.1 weeks (+/- 3.7). Neonatal follow-up revealed the same incidence of complications in these indomethacin-exposed infants, when they were compared with all other infants born in the same time period and exposed to intravenous tocolytics only when matched for gestational age at delivery.

Apgar Score↗
PubMed1990

Maternal and fetal plasma vitamin E to total lipid ratio and fetal RBC antioxidant function during gestational development.

Placental transfer of vitamin E was investigated from 19 to 35 weeks of gestation by analysis of fetal and maternal blood samples for total tocopherol, total lipids, and fetal red blood cell antioxidant reserves. Fifty-two fetal blood samples were obtained under ultrasonographic guide by percutaneous umbilical blood sampling. Thirteen were from fetuses with gestational age less than or equal to 22 weeks (x serum vitamin E = 0.4 +/- 0.14 mg/dl), 12 were from fetuses at 23-27 weeks gestation (x serum vitamin E = 0.4 +/- 0.21 mg/dl), and 27 were from fetuses with gestational age 28-38 weeks (x serum level = 0.37 +/- 0.18). Total lipid levels ranged from 140 to 216 mg/dl. Maternal plasma vitamin E concentrations correlated significantly with concurrent values in the fetus. There were no significant differences in serum vitamin E levels or vitamin E to total lipid ratio in samples from early, mid, or late gestation in either the mother or fetus. Red blood cell antioxidant reserve on samples from 18 fetuses were grossly abnormal by three different functional assays. On the basis of these data, placental transfer of vitamin E appears to be relatively constant through advancing gestation. Red blood cell antioxidant reserve is uniformly low.

Erythrocytes↗
PubMed1989

Effect of sustained pharmacologic vitamin E levels on incidence and severity of retinopathy of prematurity: a controlled clinical trial.

The incidence and severity of retinopathy of prematurity (ROP) as affected by vitamin E prophylaxis at pharmacologic serum levels (5 mg/dl) were evaluated in a double-masked clinical trial of infants with a birth weight less than or equal to 2000 gm or a gestational age less than or equal to 36 weeks. The infants were enrolled by age 5 days and randomly assigned to receive parenterally administered, and later orally administered, free alpha-tocopherol (vitamin E) or its placebo. Study medication was continued until retinal vascularization was complete or active ROP had subsided, except in infants with a diagnosis of severe disease, in whom vitamin E was substituted for study medication. Acute ROP data were collected on 755 infants. Logistic regression analysis, with control for immaturity, oxygen exposure, and other illness risk factors, showed a decrease in incidence of ROP in vitamin E-treated infants (p = 0.003, all infants; p = 0.035, infants weighing less than or equal to 1500 gm at birth). Among the 424 infants weighing less than or equal to 1500 gm at birth, the age at enrollment influenced treatment effect (age day 0 to 1, p = 0.006 (n = 288) vs age day 2 to 5, p greater than 0.1 (n = 136]. Overall, 77.6% of infants with ROP had mild disease. Moderate to severe ROP was confined to infants weighing greater than or equal to 1500 gm at birth (25 given placebo, 25 given vitamin E), with progression to severe disease in nine placebo-treated versus three vitamin E-treated infants (p = 0.048). The incidence of severe ROP per se was not significantly decreased (all birth weights, p = 0.086; less than or equal to 1500 gm birth weight, p = 0.080); the sample size was too small, however, to assess this end point adequately. An increased incidence of sepsis and late-onset necrotizing enterocolitis was found among vitamin E-treated infants weighing less than or equal to 1500 gm at birth who received study medication for greater than or equal to 8 days (p = 0.006). Because most ROP is mild in degree and regresses completely, the risk/benefit ratio of pharmacologic prophylaxis for ROP is unfavorable. Treatment of moderate and severe ROP with vitamin E above physiologic serum levels (greater than 3 mg/dl) appears promising and should be further investigated. The interpretation of cicatricial outcome was confounded by the small number of patients involved and by subsequent treatment of severe ROP in placebo-treated infants with vitamin E.

Age Factors↗
PubMed1988

Evaluation of neonatal pulmonary mechanics and energetics: a two factor least mean square analysis.

Pulmonary mechanics, using a two factor least mean square analysis technique, were determined in 22 preterm neonates with respiratory failure. The respiratory system is modelled as a linear mechanical system. Concurrent signals of airflow and transpulmonary pressure were utilized to calculate values of dynamic lung compliance and pulmonary resistances; these determinations were made over the entire tidal volume range. In addition, values of resistive work of breathing, pulmonary time constants, scalar records of sequential breaths, pressure-volume and flow-volume relationships were available for data review and interpretation. The mean +/- SEM value of tidal volume was 7.4 +/- 0.6 ml/kg; dynamic lung compliance was 0.44 +/- 0.04 ml/cmH2O/kg; and the pulmonary resistance of the whole breath was 106 +/- 9.1 cmH2O/liter/s. The resistive work of breathing (hysteresis) was 41.8 +/- 5.9 gm.cm/kg. In correlating the measured values of pressure and flow to those predicted by the model, the mean value of the correlation coefficient for the least mean square analysis for all 22 studies was 0.995 +/- 0.001; the standard error of estimate of the predicted pressure was less than 4.4% of the range of pressures measured. Thereby, the model was considered to be appropriate for the neonatal respiratory system. In addition to the traditional procedures of evaluating the respiratory status of a sick neonate, bedside analysis of pulmonary mechanics provide graphical information, and quantitative data which should be useful in day-to-day pulmonary management.

Computer Simulation↗
PubMed1988

Sequential changes in pulmonary mechanics in the very low birth weight (less than or equal to 1000 grams) infant.

Pulmonary function tests were performed on 36 very low birth weight neonates (birth weight less than or equal to 1000 gm, gestational age less than or equal to 30 weeks, appropriate size for gestational age) from birth until 8 weeks of age. Tidal airflow was measured by means of a pneumotachygraph, and the transpulmonary pressure changes were determined by the esophageal balloon technique. Pulmonary mechanics and energetics were calculated by the least mean square analysis technique at 1/2, 1, 2, 4, 6, and 8 weeks of age. Compliance was lowest at 2 weeks and subsequently increased linearly (at approximately 0.1 ml/cm H2O/wk). When compliance was based on body weight, however, no change was noted with advancing age. Resistance was greatest at 2 weeks and subsequently decreased. The infants maintained a normal minute ventilation with a slightly increased resistive work of breathing. Despite our ability to wean 53% of the infants to room air by 8 weeks, none of them had pulmonary mechanics considered normal for term infants. Infants with and without bronchopulmonary dysplasia (BPD) had similar patterns of pulmonary development. At 8 weeks of age, the pulmonary mechanics in infants with BPD who had been weaned to room air were comparable to those in infants without BPD, an observation that calls into question the rationale for defining BPD at 4 weeks in this population. These data suggest that such pulmonary function profiles provide evidence of persistent lung parenchymal abnormalities.

Airway Resistance↗
PubMed1988

Prolonged fetal ritodrine exposure and immediate neonatal outcome.

Ritodrine hydrochloride was administered over a period of two years to a total of 200 women in premature labor. One hundred sixty-two (81 per cent) of the women carried pregnancy to 35 weeks or longer. To determine the effect of ritodrine on the neonates, the duration and amount of exposure, onset of exposure, and interval between cessation of exposure and delivery were correlated with gestational age, birth weight, Apgar scores, mortality, and the presence of hypoglycemia, hyperbilirubinemia, respiratory distress, and intrauterine growth retardation. Infants exposed for six weeks or more (long-term exposure) were significantly heavier than those exposed for shorter periods (short-term exposure), a difference that was possibly attributable to differences in gestational age at birth. Infants who were exposed as fetuses to ritodrine beginning at 30 weeks' or less gestation needed phototherapy more often than did infants whose fetal exposure began at after 30 weeks' gestation. Neither duration of exposure nor gestational age at birth was a significant factor in hyperbilirubinemia. Of infants delivered at or after 35 weeks' gestation, 32 (20 per cent) experienced early hypoglycemia; and 26 of these (81 per cent) were exposed up to the day of delivery. This outcome differed significantly from that of infants whose exposure stopped at least one week before delivery. In addition, respiratory distress syndrome was more common in those infants exposed up until delivery (34 of 36).(ABSTRACT TRUNCATED AT 250 WORDS)

Birth Weight↗
PubMed1988

Continuous skeletal muscle paralysis: effect on neonatal pulmonary mechanics.

Pancuronium bromide (Pavulon) is used to induce skeletal muscle paralysis in preterm infants, presumably for effective ventilatory support during acute respiratory failure. Twelve infants with respiratory failure were evaluated for sequential changes in pulmonary mechanics during continuous pancuronium administration (0.1 mg/kg every two to three hours) for more than 48 hours. The study weight of the neonates ranged from 980 to 2,950 g, and the postconceptional age ranged from 27 to 41 weeks. Pulmonary compliance, resistance, and resistive work of breathing were determined, using least mean square analysis technique, daily for three days and after discontinuation of pancuronium (even though there was no clinical improvement in ventilatory management). The dynamic pulmonary compliance decreased from 0.38 +/- 0.05 to 0.30 +/- 0.04 mL/cm H2O/kg (mean +/- SE) (P less than .05) and the total pulmonary resistance increased 51% from 115.6 +/- 21.3 to 174.9 +/- 27.3 cm H2O/L/s (P less than .005) during prolonged skeletal muscle paralysis. Upon discontinuation of pancuronium, the dynamic pulmonary compliance increased 43% to 0.43 +/- 0.4 mL/cm H2O/kg (P less than .05) and the total pulmonary resistance decreased by 41% (P less than .005). These data question the advisability of prolonged skeletal muscle paralysis in neonates and suggest the need for further detailed evaluation of the effects of prolonged paralysis on neonatal pulmonary mechanics.

Humans↗
PubMed1987

Energetics and mechanics of nutritive sucking in the preterm and term neonate.

Energetics and mechanics of sucking in preterm and term neonates were determined by simultaneous records of intraoral pressure, flow, volume, and work of individual sucks. Nine term infants (mean postconceptional age: 38.6 +/- 0.7 SD weeks; mean postnatal age: 18.4 +/- 6.1 SD days) and nine preterm infants (mean postconceptional age: 35.2 +/- 0.7 SD weeks; mean postnatal age: 21.9 +/- 5.4 SD days) were studied under identical feeding conditions. Preterm infants generated significantly lower peak pressure (mean values of 48.5 cm H2O compared with 65.5 cm H2O in term infants; P less than 0.01), and the volume ingested per such was generally less than or equal to 0.5 mL. Term infants demonstrated a higher frequency of sucking, a well-defined suck-pause pattern, and a higher minute consumption of formula. Energy and caloric expenditure estimations revealed significantly lower work performed by preterm infants for isovolumic feeds (1190 g/cm/dL in preterm infants compared with 2030 g.cm/dL formula ingested in term infants; P less than 0.01). Furthermore, work performed by term infants was disproportionately higher for volumes greater than or equal to 0.5 mL ingested. This study indicates that preterm infants expend less energy than term infants to suck the same volume of feed and also describes an objective technique to evaluate nutritive sucking during growth and development.

Biomechanical Phenomena↗
PubMed1986

Staphylococcus epidermidis-associated enterocolitis.

Nineteen infants (mean +/- SD gestational age 30 +/- 2 weeks, birth weight 1.28 +/- 0.53 kg) with Staphylococcus epidermidis bacteremia were found on retrospective chart review to have had signs and symptoms of acute enterocolitis. This S. epidermidis-associated enterocolitis constituted 37% of the 51 cases of enterocolitis and 23% of the 81 cases of S. epidermidis sepsis during the study period. S. epidermidis-associated enterocolitis was relatively mild compared with other forms of enterocolitis. Although abdominal radiographs showed markedly abnormal bowel gas patterns with distended bowel loops and bowel wall edema, only one infant had pneumatosis intestinalis and none had portal venous or free intraperitoneal gas. Only three infants had neutropenia, and five had thrombocytopenia. None of these infants required surgical intervention. Although bloody stools often persisted for weeks, none of the neonates had prolonged feeding intolerance or development of a stricture. We conclude that S. epidermidis infection is commonly associated with a mild form of enterocolitis in the neonate and that this association should be considered when selecting antibiotics for therapy.

Enterocolitis↗
PubMed1986

Neonatal pulmonary manifestations due to prolonged amniotic leak.

Neonatal pulmonary manifestations of prolonged (2-8 weeks) amniotic fluid leak (PAL) were evaluated in 22 neonates. The severity of respiratory insufficiency was evaluated by a profile scoring system based on arterial blood gases, ventilatory support, and evidence of "fetal compression". The spectrum included acute respiratory failure with pulmonary hypoplasia (3), pulmonary hemorrhage (2), severe bronchopulmonary dysplasia (3), subacute lung disease (5), and transient respiratory disease (2). Seven neonates were completely asymptomatic. Clinical manifestations were correlated to age of onset and duration of PAL. The onset of PAL in the asymptomatic babies had occurred after 32 weeks gestation (mean +/- SEM, 33.5 +/- 1.1 wk; duration was 4.4 +/- 1.1 wk). In symptomatic neonates the onset of PAL was 24.0 +/- 1.0 weeks; duration being 6.0 +/- 0.6 weeks. When PAL occurred before 22 weeks and the duration of leak was longer than 6 weeks, the pulmonary profile score was less than 3 and associated with severe respiratory sequelae. These manifestations culminated in neonatal demise despite aggressive conventional ventilatory techniques. Onset of PAL between 23 and 28 weeks gestation and continuing longer than 8 weeks also was associated with a similar outcome. Duration of PAL between 2 and 7 weeks in this group was associated with less severe pulmonary manifestations and higher scores. Pulmonary morbidity was significantly correlated to the initial profile score (P less than .05) and was influenced by the prenatal reduction in thoracic volume.

Amniotic Fluid↗
PubMed1986

Improved survival and short-term outcome of inborn "micropremies".

Survival and significant chronic morbidity were determined by retrospective chart review for 107 inborn "micropremies." "Micropremies" are defined as appropriate-for-gestational age neonates of less than 1,001 grams and less than or equal to 28 weeks gestation. The overall survival rate for "micropremies" was 64 percent, ranging from 20 percent at 24 weeks to 83 percent at 27 weeks gestation. Race and sex are important determinants of survival in these infants. The incidence of severe, chronic morbidity in "micropremies" is relatively low. The acceptable outcome for "micropremies" supports aggressive perinatal management for fetuses as low as 24 to 25 weeks gestation. However, it is important for physicians to use current statistics from their own institutions when counseling parents and making management decisions.

Humans↗