One-year follow-up of 89 infants with birth weights of 500 to 749 grams and respiratory distress syndrome randomized to two rescue doses of synthetic surfactant or air placebo. Canadian Exosurf Neonatal Study Group. Canadian Exosurf Neonatal Follow-Up Group

Surfactant-replacement therapy for respiratory distress in the preterm and term neonate

Respiratory failure secondary to surfactant deficiency is a major cause of morbidity and mortality in preterm infants. Surfactant therapy substantially reduces mortality and respiratory morbidity for this population. Secondary surfactant deficiency also contributes to acute respiratory morbidity in late-preterm and term neonates with meconium aspiration syndrome, pneumonia/sepsis, and perhaps pulmonary hemorrhage; surfactant replacement may be beneficial for these infants. This statement summarizes indications, administration, formulations, and outcomes for surfactant-replacement therapy. The impact of antenatal steroids and continuous positive airway pressure on outcomes and surfactant use in preterm infants is reviewed. Because respiratory insufficiency may be a component of multiorgan dysfunction, preterm and term infants receiving surfactant-replacement therapy should be managed in facilities with technical and clinical expertise to administer surfactant and provide multisystem support.

Surfactant therapy for respiratory distress syndrome in premature neonates: a comparative review

Exogenous surfactant therapy has been part of the routine care of preterm neonates with respiratory distress syndrome (RDS) since the beginning of the 1990s. Discoveries that led to its development as a therapeutic agent span the whole of the 20th century but it was not until 1980 that the first successful use of exogenous surfactant therapy in a human population was reported. Since then, randomized controlled studies demonstrated that surfactant therapy was not only well tolerated but that it significantly reduced both neonatal mortality and pulmonary air leaks; importantly, those surviving neonates were not at greater risk of subsequent neurological impairment. Surfactants may be of animal or synthetic origin. Both types of surfactants have been extensively studied in animal models and in clinical trials to determine the optimum timing, dose size and frequency, route and method of administration. The advantages of one type of surfactant over another are discussed in relation to biophysical properties, animal studies and results of randomized trials in neonatal populations. Animal-derived exogenous surfactants are the treatment of choice at the present time with relatively few adverse effects related largely to changes in oxygenation and heart rate during surfactant administration. The optimum dose of surfactant is usually 100 mg/kg. The use of surfactant with high frequency oscillation and continuous positive pressure modes of respiratory support presents different problems compared with its use with conventional ventilation. The different components of surfactant have important functions that influence its effectiveness both in the primary function of the reduction of surface tension and also in secondary, but nonetheless just as important, role of lung defense. With greater understanding of the individual surfactant components, particularly the surfactant-associated proteins, development of newer synthetic surfactants has been made possible. Despite being an effective therapy for RDS, surfactant has failed to have a significant impact on the incidence of chronic lung disease in survivors. Paradoxically the cost of care has increased as surviving neonates are more immature and consume a greater proportion of neonatal intensive care resources. Despite this, surfactant is considered a cost-effective therapy for RDS compared with other therapeutic interventions in premature infants.

Developmental outcome of preterm infants after surfactant therapy: systematic review of randomized controlled trials

OBJECTIVES

To review neuro-developmental outcome at 1 and 2 years of age following randomized controlled trials (RCT) of neonatal surfactant therapy.

METHODS

A systematic review of the MEDLINE, Embase and Cochrane Controlled Trial Register databases, searching for RCT of surfactant replacement therapy with follow-up outcomes, was carried out. The main outcome measures were severe and mild disability at 1 and 2 years plus composite adverse outcome of death and/or severe disability.

RESULTS

A meta-analysis using odds ratios was carried out on 13 RCT. There were a total of 2218 treated and 2090 control infants who underwent follow up at 1 year of age. There were 303 treated and 292 control infants with follow up at between 18 months and 2 years of age. Surfactant therapy was associated with a lower rate of mild disability at 1 year (OR 0.79; 95% CI 0.66-0.95). There was a reduction in the combined adverse outcome (death or severe disability rate) at 1 year (OR 0.8; 95% CI 0.72-0.89). Neither the 1 year nor the 2 year follow-up examination showed a statistical difference in the severe disability rate between the control and treated group.

CONCLUSION

Surfactant therapy increases survival without an increase in subsequent morbidity at 1 and 2 years of age.

Neurodevelopmental and functional outcomes of extremely low birth weight infants in the National Institute of Child Health and Human Development Neonatal Research Network, 1993-1994

OBJECTIVES

The purposes of this study were to report the neurodevelopmental, neurosensory, and functional outcomes of 1151 extremely low birth weight (401-1000 g) survivors cared for in the 12 participating centers of the National Institute of Child Health and Human Development Neonatal Research Network, and to identify medical, social, and environmental factors associated with these outcomes.

STUDY DESIGN

A multicenter cohort study in which surviving extremely low birth weight infants born in 1993 and 1994 underwent neurodevelopmental, neurosensory, and functional assessment at 18 to 22 months' corrected age. Data regarding pregnancy and neonatal outcome were collected prospectively. Socioeconomic status and a detailed interim medical history were obtained at the time of the assessment. Logistic regression models were used to identify maternal and neonatal risk factors for poor neurodevelopmental outcome.

RESULTS

Of the 1480 infants alive at 18 months of age, 1151 (78%) were evaluated. Study characteristics included a mean birth weight of 796 +/- 135 g, mean gestation (best obstetric dates) 26 +/- 2 weeks, and 47% male. Birth weight distributions of infants included 15 infants at 401 to 500 g; 94 at 501 to 600 g; 208 at 601 to 700 g; 237 at 701 to 800 g; 290 at 801 to 900 g; and 307 at 901 to 1000 g. Twenty-five percent of the children had an abnormal neurologic examination, 37% had a Bayley II Mental Developmental Index <70, 29% had a Psychomotor Developmental Index <70, 9% had vision impairment, and 11% had hearing impairment. Neurologic, developmental, neurosensory, and functional morbidities increased with decreasing birth weight. Factors significantly associated with increased neurodevelopmental morbidity included chronic lung disease, grades 3 to 4 intraventricular hemorrhage/periventricular leukomalacia, steroids for chronic lung disease, necrotizing enterocolitis, and male gender. Factors significantly associated with decreased morbidity included increased birth weight, female gender, higher maternal education, and white race.

CONCLUSION

ELBW infants are at significant risk of neurologic abnormalities, developmental delays, and functional delays at 18 to 22 months' corrected age.

Outcomes of children of extremely low birthweight and gestational age in the 1990s

Advances in perinatal care have improved the chances for survival of extremely low birthweight (<800 grams) and gestational age (<26 weeks) infants. A review of the world literature reveals that among regional populations, survival at 23 weeks' gestation ranges from 2 to 35%, at 24 weeks' gestation 17 to 62% and at 25 weeks' gestation 35 to 72%. These wide variations may be accounted for by differences in population descriptors, in the criteria used for starting or withdrawing treatment, in the reported duration of survival and differences in care. Major neonatal morbidity increases with decreasing gestational age and birthweight. At 23 weeks' gestation, chronic lung disease occurs in 57 to 86% of survivors, at 24 weeks in 33 to 89% and at 25 weeks' gestation in 16 to 71% of survivors. The rates of severe cerebral ultrasound abnormality range from 10 to 83% at 23 weeks' gestation, 9 to 64% at 24 weeks and 7 to 22% at 25 weeks' gestation Of 77 survivors at 23 weeks' gestation, 26 (34%) have severe disability (defined as subnormal cognitive function, cerebral palsy, blindness and/or deafness). At 24 weeks' gestation, the rates of severe neurodevelopmental disability range from 22 to 45%, and at 25 weeks' gestation 12 to 35%. When compared with children born prior to the 1990s, the rates of neurodevelopmental disability have, in general, remained unchanged. We conclude that, with current methods of care, the limits of viability have been reached. The continuing toll of major neonatal morbidity and neurodevelopmental handicap are of serious concern.

Synthetic surfactant for respiratory distress syndrome in preterm infants

BACKGROUND

This section is under preparation and will be included in the next issue.

OBJECTIVES

To assess the effect of intratracheal administration of synthetic surfactant in premature newborns with established respiratory distress syndrome (RDS).

SEARCH STRATEGY

Searches were made of the Oxford Database of Perinatal Trials, Medline (MeSH terms: pulmonary surfactants; limits: age groups, newborn infant; publication types, clinical trial), previous reviews including cross references, abstracts, conference and symposia proceedings, expert informants, and journal handsearching in the English language.

SELECTION CRITERIA

Randomized controlled trials which compared the effect of synthetic surfactant treatment to routine management in the treatment of preterm infants with respiratory distress syndrome.

DATA COLLECTION AND ANALYSIS

Data regarding clinical outcome including the incidence of pneumothorax, pulmonary interstitial emphysema, pulmonary hemorrhage, patent ductus arteriosus, necrotizing enterocolitis, apnea of prematurity, intraventricular hemorrhage (any grade, and severe intraventricular hemorrhage), bronchopulmonary dysplasia, neonatal mortality, bronchopulmonary dysplasia or death, retinopathy of prematurity (any retinopathy, and retinopathy greater than Stage 3), mortality at hospital discharge, mortality to one year of age, and cerebral palsy (any, and moderate/severe cerebral palsy) was excerpted from the report of the clinical trials by the reviewer. Data were analyzed according to the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

Six randomized controlled trials of synthetic surfactant treatment of established respiratory distress syndrome were identified. Five of the studies used Exosurf Neonatal (a synthetic surfactant composed of dipalmitoylphosphatidylcholine, hexadecanol and tyloxapol); one small study utilized a mixture of dipalmitoylphosphatidylcholine (DPPC) and phosphatidylglycerol (PG). Treatment with intratracheal Exosurf Neonatal in premature infants with established respiratory distress syndrome improves pulmonary gas exchange and decreases the requirement for ventilatory support. In individual trials, the use of Exosurf Neonatal resulted in a statistically significant reduction in pneumothorax, patent ductus arteriosus, bronchopulmonary dysplasia (BPD), BPD or death at 28 days, and mortality. Similar results are seen when these large trials of Exosurf Neonatal are analyzed in conjunction with the smaller trial of dry powdered DPPC and phosphatidylglycerol (PG). The meta-analysis supports a decrease in the risk of pneumothorax (typical relative risk 0.64, 95% CI 0.55, 0.76, typical risk difference -0.09, 95% CI -0.12,-0.06), a decrease in the risk of pulmonary interstitial emphysema (typical relative risk 0.62, 95% CI 0.54, 0.71, typical risk difference -0.12, 95% CI -0.16, -0.09), a decrease in the risk of patent ductus arteriosus (typical relative risk 0.90, 95% CI 0.84, 0.97; typical risk difference -0.06 95% CI -0.10, -0.02), a decrease in the risk of intraventricular hemorrhage (typical relative risk 0.88, 95% CI 0.77, 0.99; typical risk difference -0.04, 95% CI -0.08, -0.00), a decrease in the risk of bronchopulmonary dysplasia (typical relative risk 0.75, 95% CI 0.61, 0.92; typical risk difference -0.04, 95% CI -0.06, -0.01), a decrease in the risk of neonatal mortality (typical relative risk 0. 73, 95% CI 0.61, 0.88; typical risk difference -0.05, 95% CI -0.07, -0.02), a decrease in the risk of bronchopulmonary dysplasia or death at 28 days (typical relative risk 0.73, 95% CI 0.65, 0.83; typical risk difference -0.06, 95% CI -0.11, -0.05), a decrease in the risk of mortality prior to hospital discharge (typical relative risk 0.79, 95% CI 0.68, 0.92; typical risk difference -0.05, 95% CI -0.07, -0.02) and a decrease in the risk of mortality during the first year of life (typical relative risk 0.80, 95% CI 0.69, 0.94; typical risk difference -0.04, 95% CI -0.07, -0.01). (ABS

Outcomes of children of extremely low birthweight and gestational age in the 1990's

Advances in perinatal care have improved the chances for survival of extremely low birthweight (< 800 g) and gestational age (< 26 weeks) infants. A review of the world literature and our own experience reveals that at 23 weeks gestation survival ranges from 2% to 35%. At 24 weeks gestation the range is 17% to 58%, and at 25 weeks gestation 35% to 85%. Differences in population descriptors, in the initiation and withdrawal of treatment and the duration of survival considered may account for the wide variations in the reported ranges of survival. Major neonatal morbidity increases with decreasing gestational age and birthweight. The rates of severe cerebral ultrasound abnormality range at 23 weeks gestation from 10% to 83%, at 24 weeks from 17% to 64% and at 25 weeks gestation from 10% to 22%. At 23 weeks gestation, chronic lung disease occurs in 57% to 70% of survivors, at 24 weeks in 33% to 89%, and at 25 weeks gestation in 16% to 71% of survivors. When compared to children born prior to the 1990's, the rates of neurodevelopmental disability have, in general, remained unchanged. Of 30 survivors reported at 23 weeks gestation nine (30%) are severely disabled. At 24 weeks gestation the rates of severe neurodevelopmental disability (including subnormal cognitive function, cerebral palsy, blindness and deafness) range from 17% to 45%, and at 25 weeks gestation 12% to 35% are similarly affected. In Cleveland, Ohio, we compared the outcomes of 114 children with birthweight 500-749 g born 1990-1992 to 112 infants born 1993-1995. Twenty month survival was similar (43% vs 38%). The use of antenatal and postnatal steroids increased (10% vs 54% and 43% vs 84%, respectively, P< 0.001), however the rates of chronic lung disease increased from 41% to 63% (P = 0.06). There was a significant increase in the rate of subnormal cognitive function at 20 months corrected age (20% vs 48%, P < 0.02) and a trend to an increase in the rate of cerebral palsy (10% vs 16%) and neurodevelopmental impairment. We conclude that, with current methods of care, the limits of viability have been reached. The continuing toll of major neonatal morbidity and neurodevelopmental handicap are of serious concern.

Developmental outcome in very low birthweight infants. Current status and future trends

Surfactant therapy has significantly reduced mortality, but not morbidity, in the very low birthweight (VLBW) infant. Questions persist as to the edge of viability, the allocation of health care resources for the VLBW infant, and whether or not we are improving survival at the cost of contributing more handicapped individuals to society. Since surfactant alone has not reduced morbidity, other medical and behavioral treatments are being studied that may help to optimize neurodevelopmental outcome in the VLBW infant.

A risk-benefit assessment of natural and synthetic exogenous surfactants in the management of neonatal respiratory distress syndrome

Alveolar surfactant is central to pulmonary physiology. Quantitative and qualitative surfactant abnormalities appear to be the primary aetiological factors in neonatal respiratory distress syndrome (RDS) and exogenous replacement of surfactant is a rational treatment. Available exogenous surfactants have a natural (mammal-derived lung surfactants) or synthetic origin. Pharmacodynamic and clinical studies have demonstrated that exogenous surfactants immediately improve pulmonary distensibility and gas exchange; however, this is achieved more slowly and with more failures with synthetic surfactants. The ensuing advantageous haemodynamic effects are not so striking and they include an inconvenient increased left to right ductal shunt. Two strategies of administration have been used: prophylactic or rescue therapy to treat declared RDS. All methods of instillation require intubation. In addition to the early benefits (improved gas exchange and reduced ventilatory support) the incidence of classical complications of RDS, especially air leak events, is decreased except for the uncommon problem of pulmonary haemorrhage. The incidence of bronchopulmonary dysplasia is neither uniformly nor significantly reduced although the severity appears to be lessened. The overall incidence of peri-intraventricular haemorrhages is not diminished although separate trials have shown a decreased rate. The most striking beneficial effect of exogenous surfactants is the increased survival (of about 40%) of treated very low birthweight neonates. A small number of adverse effects has been described. The long term outcome of survivor neonates with RDS treated with surfactants versus control neonates with RDS not treated with surfactants is similar in terms of physical growth, at least as good in terms of respiratory status, with a similar or slightly better neurodevelopmental outcome. There is not clear benefit of exogenous surfactant therapy in extremely premature infants (< 26 weeks gestational age, birthweight < 750 g). The potential risks of contamination, inflammatory and immunogenic reaction and the inhalation of platelet activating factor remain a theoretical concern of surfactant therapy which has not been confirmed in clinical practice. The optimal timing of treatment favours prophylaxis over rescue treatment and early rescue treatment rather than delayed therapy. Meta-analyses suggest the clinical superiority of natural surfactant extracts over a synthetic one (colfosceril palmitate). The economic impact of surfactant therapy is favourable and the costs per quality-adjusted life year (QALY) for surviving surfactant treated infants are low. In conclusion, the mid and long term benefit/risk ratio clearly favours the use of exogenous surfactants to prevent or to treat RDS in neonates who have a gestational age of > 26 weeks or a birthweight of > 750 g, especially with the prophylactic strategy using natural surfactant extracts.

Neuropsychological and functional outcomes of very low birth weight infants

Advances in perinatal and neonatal management have resulted in a significant increase in the survival of fragile extremely low birth weight (ELBW) infants > 1,000 g at birth. The evaluation and reporting of the outcome of these infants aids in assessing the efficacy of interventions, provides data to aid in policy decisions, and provides critical information for parents and primary care providers. Comprehensive assessment of multiple domains including neurologic/neurosensory, developmental-cognitive, visual perceptual, speech/language, motor, functional skills for daily living, and Kindergarten readiness permit a total view of the child within the context of the family. Survival of VLBW infants < 800 g has steadily improved from 0% (1943 to 1945) to 49% to 70% (1994 to 1995). Rates of cerebral palsy, mental retardation, blindness, and deafness have remained stable in the 1980s and 1990s. There is evidence, however, that the percent of functional limitations may be increasing. A requirement for Special Education Resources among VLBW infants remains high at 44% to 56%. As increasing numbers of infants at the limits of viability survive, the medical community must remain vigilant in its surveillance and advocate both humanistically and scientifically for comprehensive strategies that optimize long-term functional, academic, and family outcomes.

Less severe retinopathy of prematurity induced by surfactant replacement therapy

To assess the effect of surfactant replacement therapy (SRT) on the prevalence and severity of retinopathy of prematurity (ROP), we compared data from 160 SRT-treated preterm infants with data from 230 historic controls. The prevalence of ROP was 30.6% in the treatment group and 23.4% in the control group. Severe ROP (stages 3-4) was seen in 6.1% of the infants with ROP in the treatment group and 20.3% of the ROP patients in the control group. Surfactant therapy had no influence on the prevalence of ROP (odds ratio 1.4, 95% confidence interval 0.797-2.459, p = 0.242). However, SRT was associated with a decreased risk for severe ROP, compared to mild ROP (odds ratio 0.226, 95% confidence interval 0.056-0.905, p = 0.036). These data suggest that SRT is associated with a decreased risk for severe ROP.

Role of lipid polymorphism in pulmonary surfactant

The development of artificial surfactants for the treatment of respiratory distress syndrome (RDS) requires lipid systems that can spread rapidly from solution to the air-water interface. Because hydration-repulsion forces stabilize liposomal bilayers and oppose spreading, liposome systems that undergo geometric rearrangement from the bilayer (lamellar) phase to the hexagonal II (HII) phase could hasten lipid transfer to the air-water interface through unstable transition intermediates. A liposome system containing dipalmitoylphosphatidylcholine was designed; the system is stable at 23 degrees C but undergoes transformation to the HII phase as the temperature increases to 37 degrees C. The spreading of lipid from this system to the air-water interface was rapid at 37 degrees C but slow at 23 degrees C. When tested in vivo in a neonatal rabbit model, such systems elicited an onset of action equal to that of native human surfactant. These findings suggest that lipid polymorphic phase behavior may have a crucial role in the effective functioning of pulmonary surfactant.