Prophylactic treatment of very premature infants with human surfactant

Prophylaxis of respiratory distress syndrome by treatment with modified porcine surfactant at birth: a multicentre prospective randomized trial

The objective of this prospective, multicentre trial, carried out at 18 third level hospitals in Italy, was to evaluate efficacy of modified porcine surfactant (Curosurf), administered at birth to prevent the development of respiratory distress syndrome (RDS) in premature infants. 287 babies with a gestational age of 24-30 weeks were randomized to prophylactic treatment with Curosurf (80 mg/ml; dose 20 mg/kg) or to a control group receiving no surfactant treatment in the delivery-room. Babies in both groups were eligible for rescue treatment with surfactant (200 mg/kg) if they developed clinical symptoms of RDS and required mechanical ventilation. The main end-point was to obtain, in the prophylaxis group, a 30% reduction in the incidence of grade 3-4 RDS. Median gestational age was 28 weeks in both groups and mean birth weight 1010 and 1002 g, respectively for prophylaxis and control babies. There was a 32% reduction in the incidence of grade 3-4 RDS in the prophylaxis group (p < 0.05). This was associated with a significant reduction in mean maximum fraction of inspired oxygen (0.57 vs 0.66%; p < 0.01), a decreased incidence of pulmonary interstitial emphysema (7 vs 14%; p < 0.05) and a lowered mortality (21 vs 35%; p < 0.01). Combined unfavourable outcome (mortality + bronchopulmonary dysplasia and/or grade 3-4 intraventricular hemorrhage and/or grade 2-4 retinopathy of prematurity) was significantly lower in the prophylaxis than in the second group (41 vs 58%; p < 0.01). The favourable effects of prophylactic treatment were equally recorded in all the age groups, including the babies with the lowest gestational age (24-25 weeks). Multiple and logistic regression analysis confirmed that high gestational age and surfactant prophylaxis were, independently, associated with a lower degree of RDS (p = 0.0001 and p = 0.0008, respectively) and a lower mortality (p = 0.0001 and p = 0.0045, respectively). We conclude that prophylaxis with modified natural surfactant effectively prevents RDS in newborn babies between 24 and 30 weeks' gestation.

Efficacy of surfactant therapy in infants managed with CPAP

Surfactant rescue therapy can be utilized effectively early in the course of respiratory distress syndrome (RDS) in infants weighing > 1,000 g and treated exclusively with continuous positive airway pressure (CPAP) therapy. Thirteen infants (BW, 1,774 +/- 580 g; GA, 31 +/- 3 weeks) comprising the CPAP/SURFACTANT group were compared with 12 infants (BW, 1,753 +/- 556 g; GA, 31 +/- 2 weeks) who comprised the intermittent mandatory ventilation (IMV)/surfactant group, and with 14 infants (BW, 1,776 +/- 332 g; GA, 32 +/- 2 weeks) treated with CPAP before surfactant was clinically available. A 5 mL/kg dose of Exosurf Neonatal (Burroughs-Wellcome) was administered to infants intratracheally when the FiO2 requirement reached 0.40 to maintain the PO2 above 50 torr. Infants in the CPAP/surfactant group were intubated solely for surfactant administration and extubated within 18 +/- 6 min of treatment. The CPAP/surfactant group was treated at a mean age of 12.3 +/- 9.3 h, and the IMV/surfactant group at 10.2 +/- 9.8 h. Alveolar-arterial oxygen gradient (AaDO2), oxygenation index (OI), and mean airway pressure (MAP) were determined immediately before and after surfactant therapy, and at comparable times for the CPAP-only group. A significant difference was found in pre-treatment AaDO2, OI and MAP between the CPAP/surfactant group and IMV/surfactant group, but not between the CPAP/surfactant group and the CPAP-only group. Similarly, a significant difference in AaDO2, OI and MAP continued post-treatment was noted. However, a significant difference was also found at this time between the CPAP/surfactant group and the CPAP-only group. In addition, a significant difference was noted in AaDO2 and OI pre- and post-treatment within each surfactant-treated group. Furthermore, in the CPAP-only group AaDO2 and OI actually worsened (212 +/- 70 vs. 239 +/- 68; 4.0 +/- 1 vs. 4.5 +/- 2, respectively). There was a significant reduction in the duration of oxygen therapy (3 +/- 2 vs. 5 +/- 2 vs. 4.5 +/- 2 days, respectively) as well as in the total days of hospitalization (30 +/- 10 vs. 42 +/- 15 vs. 43 +/- 12 days, respectively). We conclude that in this small group of infants surfactant administration was effective and safe. It appeared to improve the course of RDS and shorten the duration of oxygen exposure and days of hospitalization.

An experimental model investigation of the opening of a collapsed untethered pulmonary airway

We developed an essentially two-dimensional planar benchtop model of an untethered collapsed airway to investigate the influence of fluid properties (viscosity, mu and surface tension, gamma) and the structural characteristics (effective diameter, D, longitudinal tension, T, and fluid film thickness, H) on airway reopening. This simplified model was used to quantify the relationship between wall deformation and meniscus curvature during reopening. We measured the pressure (P) required to move the meniscus at a constant velocity (U), and found the dimensionless post-startup pressure (PD/gamma) increased monotonically with the capillary number (Ca = microU/gamma). Startup pressures depend on the fluid viscosity and piston acceleration, and may significantly increase reopening pressures. Consistently stable steady-state pressures existed when Ca > 0.5. D was the most dominant structural characteristics, which caused an increase in the post-startup pressure (P) for a decrease in D. An increase in H caused a slight decrease in the reopening pressure, but a spatial variation in H resulted in only a transient increase in pressure. T did not significantly affect the reopening pressure. From our planar two-dimensional experiments an effective yield pressure of 3.69 gamma/D was extrapolated from the steady-state pressures. Based on these results, we predicted airway pressures and reopening times for axisymmetrically collapsed airways under various disease states. These predictions indicate that increasing surface tension (as occurs in Respiratory Distress Syndrome) increases the yield pressure necessary to reopen the airways, and increasing viscosity (as in cystic fibrosis) increases the time to reopen once the yield pressure has been exceeded.

Neonatal technology, perinatal survival, social consequences, and the perinatal paradox

Exogenous surfactant therapy for premature infants with respiratory distress syndrome has had a significant impact on infant mortality and on some complications of prematurity. Yet the total number of low-birthweight infants has not declined, resulting in a high-risk population who would require surfactant therapy and long-term child care. Surviving low-birthweight infants (despite surfactant therapy) remain at risk for the consequences of premature birth, such as neurosensory impairment, cerebral palsy, and chronic lung disease. In addition, because of the close association between poverty and low birthweight, surviving premature infants are at increased risk for the new morbidities such as violence, homelessness, child abuse and neglect, and addictive drug use. A goal should be to reduce the risk of being born with a low birthweight, rather than having to treat the consequences of premature gestation. Despite the marvelous advances that permit us to treat respiratory distress syndrome, the continuing high low-birthweight rate places a significant strain on our health care system. The goal should be redirected to identifying large population-based efforts to reduce the number of low-birthweight infants.

Double-blind, randomized trial of one versus three prophylactic doses of synthetic surfactant in 826 neonates weighing 700 to 1100 grams: effects on mortality rate. American Exosurf Neonatal Study Groups I and IIa

At 33 hospitals in the United States, a double-blind, randomized clinical trial was performed to compare one versus three prophylactic doses of synthetic surfactant in 700 to 1100 gm inborn infants. All 826 infants received an initial prophylactic dose of surfactant within 30 minutes of birth. Subsequently 410 infants received two doses of placebo (air) 12 and 24 hours later, and 416 infants received two additional doses of surfactant. By the age of 28 days, 70 infants who received one dose of surfactant and 40 infants who received three doses were dead, a 43% relative reduction in the mortality rate (30 fewer deaths; p = 0.002). By the age of 1 year after term, 87 infants who received one dose and 62 infants who received three doses were dead: a 29% relative reduction in the mortality rate (25 fewer deaths; p = 0.027). Infants who received three doses of surfactant required significantly less oxygen and less mean airway pressure for the first week of life. Necrotizing enterocolitis (9 vs 25 infants; p = 0.005), and use of high-frequency ventilation (13 vs 26 infants; p = 0.037); pancuronium (43 vs 62 infants; p = 0.045); and leukocyte transfusions (0 vs 4 infants; p = 0.042) were less frequent in the three-dose group, but air leak, bronchopulmonary dysplasia, intraventricular hemorrhage, patent ductus arteriosus, pulmonary hemorrhage, and infections were not different. These results indicate that physiologic findings, mortality rates, and probably morbidity rates are improved by two additional prophylactic doses of synthetic surfactant.

Pulmonary hypertension in respiratory distress syndrome

Pulmonary hypertension was associated with nonresponse to surfactant in six premature infants with respiratory distress syndrome. The diagnosis was suspected on the basis of a discrepancy between the X-ray findings and the severity of the clinical status as reflected by hypoxia despite maximal ventilatory support. The diagnosis of pulmonary hypertension was made by pre- and postductal oxygen saturation differences or by echodoppler cardiography, showing suprasystemic right ventricular pressures or right to left shunts through a patent foramen ovale or the ductus arteriosus. The response to surfactant was quantified by the arterial/alveolar (a/A) ratio difference before and 1 hr after therapy ("delta a/A ratio"); the delta a/A ratio was 0 +/- 0.01, which indicates a nonresponse. A single dose of 1 mg/kg tolazoline was administrated and the response assessed by a/A difference. A delta a/A ratio of 0.11 +/- 0.11 (range 0.02-0.32) represented a dramatic response and enabled oxygenation in these severely ill infants. No significant side effects were observed. We conclude that pulmonary hypertension may be an important and reversible condition in certain cases of respiratory distress syndrome and has to be considered in infants who do not respond to surfactant.

Influence of energy substrates on respiratory gas exchange during conventional mechanical ventilation of preterm infants

OBJECTIVE

The purpose of this study was to determine the optimal parenteral feeding regimen for infants with compromised respiratory function.

METHODS

We studied the influence of varying the source of energy on respiratory gas exchange in 10 infants who were supported by mechanical ventilation and who received intravenous feedings. Two isoenergetic parenteral regimens were infused consecutively; the level of fat intake was varied inversely with that of glucose. Under similar ventilator settings, transcutaneous partial pressures of oxygen and carbon dioxide, as well as indirect calorimetry were measured during each regimen.

RESULTS

Despite the higher carbon dioxide production during the glucose-rich regimen (8.9 +/- 0.7 vs 7.9 +/- 0.4 ml/kg per minute, p < 0.05 by analysis of variance), transcutaneous partial pressure of carbon dioxide remained unaffected, suggesting ventilatory compensation as documented by the increased (p < 0.002) alveolar ventilation. This was not associated with a detectable rise in oxygen consumption, but with a significant change in partial pressure of oxygen (77 +/- 5 vs 66 +/- 3 mm Hg, p < 0.05).

CONCLUSIONS

Ventilator-dependent infants with early and mild bronchopulmonary dysplasia, who receive intravenous feedings of a moderate load of glucose-based energy, can compensate for enhanced carbon dioxide production by increasing their respiratory drive, with a beneficial effect on oxygenation compared with that observed when energy is derived from lipid-based solutions.

Randomized clinical trial of surfactant prophylaxis in retinopathy of prematurity

Prophylactic lung surfactant is commonly used to reduce the severity of neonatal respiratory distress syndrome in premature infants. There is disagreement in the literature regarding the effect of prophylactic lung surfactant on the incidence of retinopathy of prematurity (ROP). Sixty-four infants, gestational age 23 to 32 weeks, birth weight 610 to 1250 g, were randomized to receive either intratracheal bovine surfactant prophylaxis or air control, at our institution, as part of a national double-masked multicenter trial. Forty-eight of these infants survived and underwent complete ophthalmologic examinations by a single masked examiner. ROP data were gathered retrospectively. ROP developed in 19 of the 23 (83%) who received surfactant and 15 of the 25 (60%) controls (P = .1). Analysis of the worst stage of ROP for each infant also revealed no difference between the surfactant and control groups (P = .4). Our retrospective analysis of ROP data in a prospective double-masked randomized study revealed no significant effect of surfactant on the incidence or severity of ROP.

Successful treatment of ARDS with two doses of synthetic surfactant

A 50-year-old man with adult respiratory distress syndrome (ARDS) was successfully treated with synthetic surfactant. The therapy rapidly improved the respiratory function; it also increased the release of endogenous surfactant. Synthetic surfactant may thus be of value in the treatment of ARDS.

High-dose versus low-dose bovine surfactant treatment in very premature infants

The aim of the study was to determine if high-dose bovine surfactant (Alveofact, initially 100 mg/kg birth weight) would improve oxygenation compared with low-dose surfactant (50 mg/kg birth weight) administered intratracheally within 1 h after birth. Inclusion criteria included gestational age 24-29 weeks and birth weight 500-1500 g, intubation and mechanical ventilation, absence of congenital malformations and bacterial infections. Retreatment was considered if the fraction of inspired oxygen (FiO2) was > 0.4 (dose 50 mg/kg birth weight). The primary endpoint was level of oxygenation (PaO2/FiO2) 2 h after treatment. The study design was a sequential analysis using a triangular test with alpha = 0.05 and 95% power to detect a 25% improvement in the endpoint. Oxygenation was improved significantly with high-dose (n = 42) compared to low-dose treatment (n = 48): 30.9 +/- 15.0 kPa (231.5 +/- 112.7 mmHg) versus 24.1 +/- 15.7 kPa (180.6 +/- 118.0 mmHg) (mean +/- SD). The survival rate was 83% in both groups and the incidence of pulmonary interstitial emphysema was 33% versus 14% with the high-dose treatment. We conclude that high-dose surfactant significantly improved oxygenation and reduced lung barotrauma. An initial dose greater than 50 mg/kg birth weight of surfactant is required for optimal acute response.

Comparison of the effect of three doses of a synthetic surfactant on the alveolar-arterial oxygen gradient in infants weighing > or = 1250 grams with respiratory distress syndrome. American Exosurf Neonatal Study Group II

The effect of a 50% increment or decrement in the recommended 5 ml/kg dose of a commercially available surfactant (Exosurf Neonatal) on the alveolar-arterial oxygen gradient was investigated in a multicenter, double-blind, placebo-controlled rescue trial conducted at 15 hospitals in the United States. Two doses of three different volumes (2.5, 5.0, and 7.5 ml/kg) were compared with two 5.0 ml/kg doses of air in 281 infants weighing > or = 1250 gm who had respiratory distress syndrome requiring mechanical ventilation and an arterial/alveolar oxygen ratio < 0.22. The first dose was given between 2 and 24 hours of age, and the second dose was given 12 hours later to all infants who still required mechanical ventilation. Infants were stratified at entry by gender and the magnitude of the arterial/alveolar oxygen ratio. The air placebo arm of the study was terminated early when reductions in mortality rates were proved in another rescue trial of this surfactant in infants with the same birth weights. For the first 48 hours, administration of a 2.5 ml/kg dose of surfactant provided less improvement in the alveolar-arterial oxygen gradient than doses of 5.0 and 7.5 ml/kg, which were equivalent. Similar results were observed in mean airway pressure (p < 0.05). There were no significant differences among the three dosage groups in mortality rate, air leak, bronchopulmonary dysplasia, and other complications of prematurity. There were no pulmonary hemorrhages in any group. Reflux of surfactant occurred more frequently in the 5.0 and 7.5 ml/kg groups. These results indicate that more sustained improvements in oxygenation are provided, with equal safety, by the standard two 5.0 ml/kg rescue doses of this surfactant than by the 2.5 ml/kg dose. No further benefit is gained from two larger doses given 12 hours apart.

Pulmonary hemorrhage and exogenous surfactant therapy: a metaanalysis

A metaanalysis of surfactant clinical trials was carried out to assess whether or not an association exists between exogenous surfactant therapy and pulmonary hemorrhage. Trials that reported the pulmonary hemorrhage occurrence (group 1) and those that did not (group 2) were analyzed. Thirty-three treatment strategies were tested in 29 publications from 1980 through 1992. Eleven of these were group 1 trials, which reported a 3% overall incidence of pulmonary hemorrhage. The rates were significantly higher in both the treated and the control groups of natural surfactant trials than in synthetic surfactant trails (5.87% and 5.36% in the natural surfactant trials vs 2.51% and 1.04% in the synthetic surfactant trials, respectively). The pooled estimate of relative risk for pulmonary hemorrhage with any surfactant therapy was 1.47 (95% confidence interval 1.05, 2.07; p < 0.05). Logistic regression modeling revealed that the nature of surfactant, treatment strategy, and lower mean birth weight had a significant influence on the relative risk of pulmonary hemorrhage; a similar trend was seen with higher mortality rates. Variation in the rates of patent ductus arteriosus did not have an independent effect on the estimated pulmonary hemorrhage risk. Most group 2 trials were published before 1990, and the median total sample size was 73, compared with 402 for the group 1 trials (p < 0.05), most of which were published in the 1990s. In 10 (50%) of 20 group 2 trials, pulmonary hemorrhage data were collected methodically, in comparison with all group 1 trials, most of which collected data prospectively. We conclude that pulmonary hemorrhage is a rare complication of respiratory distress syndrome. An awareness of the possible association of pulmonary hemorrhage with surfactant use in later trials and the differences in definitions and reporting practices probably explain variations in the reported incidence among the trials. The risk of pulmonary hemorrhage increases slightly, on an average of 47%, with any surfactant therapy. This increased risk is small compared with the documented benefits of surfactant therapy in respiratory distress syndrome.

Surfactant replacement therapy for pulmonary diseases

Surfactant therapy has clearly been a meaningful addition to the therapeutic armamentarium in the management of premature infants with RDS. Pediatricians and others involved in the care of newborn infants should familiarize themselves with the various surfactant preparations, the indications for their use, the techniques of administration, and the possible side effects. All such care provides should also be skilled in endotracheal intubation and ventilation of neonates; recognition of the clinical and radiographic signs of RDS; and have the appropriate equipment to monitor cardiopulmonary status, oxygenation, and ventilation in these infants until transport to a tertiary care facility can be accomplished. In addition to the two current FDA-approved surfactants, several other surfactants are in various stages of evaluation. When administered to infants with established RDS, both natural and synthetic surfactants have clearly been shown to improve survival, decrease requirements for ventilatory support, and reduce the incidence of air leak complications. Although by no means conclusively demonstrated, certain infants, particularly those delivered at < 30 week gestation, may benefit from immediate treatment in the delivery room. It should be emphasized that, except under extenuating but controlled circumstances and except in the hands of an experienced physician, surfactant treatment should not be viewed as an integral part of neonatal resuscitation. Adequate treatment requires the administration of a minimum of two surfactant doses, although some infants may benefit from additional doses or treatment with an alternative preparation. Massive pulmonary hemorrhage, although rare, is observed with prophylactic and rescue treatment protocols and may result from hemorrhagic pulmonary edema due to a hemodynamically significant PDA. Currently there are no data to recommend the use of one surfactant preparation over another. The short- and long-term benefits may be similar with different products. Therefore, we must await results of trials with then necessary power (large number of subjects) and unbiased design to discern any clinically relevant differences. Results of studies directly comparing the relative efficacy of Survanta and Exosurf, conducted under the auspices of the National Institutes of Health, are expected in 1993. Multicenter trials comparing prophylactic and rescue administration of Exosurf versus CLSE and Survanta versus CLSE are currently underway. It is encouraging to note that follow-up studies up to 2 years of age do not reveal an increase in physical or neurodevelopmental handicaps, BPD, or other problems in preterm infants who received surfactant preparations either for prophylaxis or rescue therapy. Results of long-term follow-up studies, however, are not yet available.(ABSTRACT TRUNCATED AT 400 WORDS)

The effects of bedside pulmonary mechanics testing during infant mechanical ventilation: a retrospective analysis

We examined the effects of regular bedside testing of pulmonary mechanics (PM) on the outcome of 468 acutely ill, mechanically ventilated neonates. During the first of two 18-month study periods, 217 infants were mechanically ventilated without the assistance of PM measurements. During the second 18-month period, 251 infants were ventilated with the assistance of at least daily PM measurements. Using data obtained from the PM tests, we adjusted the infants' ventilators to maintain tidal volume, inspiratory time, and pressure-volume loops within predetermined limits. With the exception of the PM measurements, given the limitations of retrospective analyses, both groups of infants received identical medical and nursing care. The infants ventilated with the assistance of PM testing developed fewer pneumothoraces (4.0%; 10/251) vs. no PM testing, 10.1% (22/217); P < 0.05 by Chi-square analysis]. Infants weighing less than 1,500 g ventilated with the assistance of PM measurements had less intraventricular hemorrhage (IVH) overall, most notably, less grades I and II IVH (total IVH-PM testing, 39.1% vs. no PM testing, 65.7%; P < 0.01; Grades I-II IVH-PM testing, 30.4% vs. no PM testing, 54.9%; P < 0.01). IVH incidence was decreased independent of pneumothorax occurrence. Survival rates, incidences of bronchopulmonary dysplasia, and durations of mechanical ventilation and hospitalization were similar. This retrospective analysis suggests that PM testing during infant mechanical ventilation reduces common acute ventilator-associated complications.

Ureaplasma urealyticum in a neonatal intensive care population

The incidence of Ureaplasma colonization at birth and its effect on the development of chronic lung disease (CLD) and on mortality was studied in a neonatal intensive care population. Ureaplasma colonization was associated with a birthweight < 1000 g (odds ratio [OR] 3.45 confidence intervals [CI] 2.13-5.60) and a gestational age < 30 weeks (OR 2.54 CI 1.71-3.79). In a case-controlled study of 112 infants, significant associations with Ureaplasma colonization were maternal pyrexia in labour (n = 38 vs 21; P = 0.015), the requirement for antibiotics in labour (n = 39 vs 16; P = 0.0005) and vaginal delivery (n = 78 vs 58; P = 0.009). Risk factors associated with the development of CLD were birthweight < 1000 g (OR 3.77 CI 2.53-5.62) and delivery by Caesarean section (OR 1.65 CI 1.11-2.43). Within the group delivered by Caesarean section. Ureaplasma colonization was also associated with an increased risk of CLD (OR 1.97 CI 1.08-3.62). Ureaplasma colonization of infants at birth is associated with factors suggestive of maternal chorioamnionitis as well as preterm birth and low birthweight. In infants delivered by Caesarean section, Ureaplasma colonization is associated with an increased risk of chronic lung disease.

Pulmonary follow-up 2.5 years after a randomized, controlled, multiple dose bovine surfactant study of preterm newborn infants

Forty-seven preterm infants, who were previously enrolled in a prospective, randomized, blinded study at birth to assess the effects of multiple doses of exogenous bovine surfactant to prevent respiratory distress syndrome, underwent lung function evaluation and review of their medical histories at 2 1/2 years of age. During their initial hospitalization there were no differences between the 17 control infants and the 30 surfactant-treated infants in the duration of ventilator or oxygen therapy and the incidence of bronchopulmonary dysplasia. At the follow-up both groups were similar in chronological and corrected ages, weights, lengths, and sex ratios and there were no differences in the occurrence of allergy, asthma, bronchiolitis, eczema, pneumonia, and wheezing. In addition, there was no significant difference regarding the incidence of chest illnesses lasting either 3 or 7 days and in the total number of required rehospitalizations. Functional residual capacity (FRC), tidal volume (VT/kg), compliance (Crs/kg), resistance (Rrs), and time constant of the respiratory system were not significantly different between the two groups at 2 1/2 years of age. We conclude that bovine surfactant, when given during the neonatal period, has little long-term effect on lung function. Neonatal bovine surfactant therapy neither improves nor produces any adverse effects on the developing respiratory system.

Long-term pulmonary consequences of respiratory distress syndrome in preterm infants treated with exogenous surfactant

The pulmonary outcome for preterm infants 1 year after synthetic surfactant replacement for respiratory distress syndrome was assessed by examining their pulmonary status and the results of pulmonary function tests. A total of 47 infants were followed: 13 infants mean +/- SD: birth weight, 1960 +/- 616 gm; gestation, 32 +/- 1.1 weeks) had been assigned to the placebo group and 34 (birth weight = 1890 +/- 530 gm; gestation = 32 +/- 2.5 weeks) to surfactant treatment. The infants were examined at 3 to 6 months of age (n = 45) and at 9 to 12 months of age (n = 36). There were no significant differences between the two groups in predisposing clinical conditions that would lead to chronic lung disease. The infants had similar patterns of growth, respiratory-related illness, and need for theophylline therapy, diuretic therapy, or both. None had hypoxemia by pulse oximetry. Mean (+/- SEM) values for pulmonary mechanics and energetics in surfactant-treated infants were significantly (p < 0.01) lower for total pulmonary resistance in late infancy (57.7 +/- 11.7 vs 35.3 +/- 4.6 cm H2O/L per second). Lower values (mean +/- SEM) of resistive work of breathing were also measured in the surfactant-treated group (60.7 +/- 12.0 vs 38.2 +/- 3.6 gm-cm/kg per breath). The dynamic pulmonary compliance values were in the low-normal range for both groups, and the mean (+/- SEM) peak-to-peak esophageal pressure values were elevated (11.47 +/- 2.26 cm H2O in the placebo group; 9.24 +/- 0.69 cm H2O in the surfactant group). Forced expiratory flow measurements in late infancy demonstrated significant (p < 0.01) improvement in expiratory reserves and reduced evidence of airflow obstruction in the surfactant-treated infants (peak flow (mean +/- SEM): 287.1 +/- 69 vs 396.9 +/- 27 ml/sec; forced expiratory flow (mean +/- SEM) at functional residual capacity: 56.3 +/- 7.5 vs 83.4 +/- 19.5 ml/sec). No significant differences in pulmonary functions were noted in early infancy. These data suggest that surfactant replacement for respiratory distress syndrome may be associated with beneficial long-term effects on the resistive airflow properties of larger preterm infants.

Reversible and irreversible inactivation of preformed pulmonary surfactant surface films by changes in subphase constituents

Several mechanisms for surfactant inactivation have been reported. In this study, we have measured the reversibility of surfactant inactivation caused by various lipid or protein constituents of plasma or by pH changes. A surfactant of bovine origin was studied in a pulsating surfactometer either when surfactants were premixed with different serum constituents (inactivators) or when inactivators were introduced into subphase fluid surrounding surfactant films formed at an air-liquid interface. Subphase exchanges with sodium bicarbonate or sodium borate raised pH and raised minimal surface tensions either when premixed with surfactant or when introduced with saline subphase beneath a preformed surfactant surface film. The pH effects on surfactant film function were reversible for sodium bicarbonate but not for sodium borate when the subphase with bicarbonate or borate was replaced with saline. Lipids (platelet-activating factor or lysophosphatidylcholine) had non-reversible effects on preformed films. Proteins (fibrinogen or C reactive protein) had reversible effects at low concentrations, but reversibility was less evident at high concentrations. Effects with whole serum were non-reversible at low protein concentrations (0.5 mg/ml). These results add evidence that surfactant inactivation can be caused by multiple mechanisms, both reversible and irreversible.

Outcome at twelve months of adjusted age in very low birth weight infants with lung immaturity: a randomized, placebo-controlled trial of human surfactant

We compared the neurodevelopmental outcome of extremely premature, surfactant-deficient infants who received either prophylactic surfactant at birth, "rescue" surfactant after the clinical diagnosis of respiratory distress syndrome was established, or placebo. Infants studied were participants in a randomized, bicenter (San Diego, Calif., and Helsinki, Finland), controlled trial of human surfactant therapy. One hundred fifty infants (prophylaxis group, 63 infants; rescue group, 57; placebo group, 30) were prospectively enrolled at 38 weeks of gestational age. There were no neonatal intergroup differences in the incidence or severity of sonographic central nervous system abnormality or retinopathy. One hundred forty-five infants were alive at 1 year of adjusted age, at which time growth, neurosensory, and neurologic outcome were similar in all three treatment groups at both centers. Cerebral palsy occurred in 20% overall. Five infants (3.5%) were functionally blind. However, infants treated at birth had lower mean mental and motor scores on the Bayley Scales of Infant Development compared with those of infants rescued with surfactant after the onset of respiratory distress syndrome (Mental Development Index: 78 vs 96, p = 0.02; Psychomotor Development Index: 73 vs 87, p = 0.04). Chronic lung disease occurred more frequently in the prophylactically treated group and contributed to the subjects' neurologic and developmental morbidity. Because prophylactic surfactant treatment offered no neurodevelopmental advantage and may contribute to poorer outcome, we currently recommend early surfactant replacement only for those infants who have postnatal evidence of respiratory distress syndrome.

Prenatal evaluation and obstetrical management of fetuses at risk of developing lung hypoplasia

The aim of this study was to measure the fetal lung area of normal human fetuses using ultrasound and them to test the predictive values of a nomogram in the identification of fetal lung hypoplasia. A nomogram for ultrasound-measured fetal lung area were constructed from 264 normal fetuses from 17 to 39 weeks of gestation. In 19 cases running the risk of developing lung hypoplasia, the sensitivity, specificity, and positive and negative predictive values of lung area measurements below the mean -2 SD were 75%, 100%, 94% and 100%, respectively, with total lung area showing a significant relation to the combined lung weight (Y = -1.05 + 2.06 X, r2 = 0.88). These results indicate that lung area measured by ultrasound is a good indicator of lung weight, and this nomogram of lung area may be useful in evaluating lung growth prenatally, as well as in the direct obstetrical management of fetuses at risk of developing lung hypoplasia.

Comparison of clinical responses to natural and synthetic surfactants

The clinical responses to both natural and synthetic surfactants were observed in two District General Hospital Neonatal Units who were centrally randomised as part of two separate multicentre trials (OSIRIS and Curosurf 4). Forty five infants were enrolled consecutively in the OSIRIS trial using synthetic surfactant (Exosurf), while 21 infants were subsequently enrolled in the Curosurf 4 trial using natural surfactant (Curosurf). There were no significant differences between the groups for mean birth weight, gestational age, inspired oxygen (FiO2), or arterial: alveolar oxygen ratio (a/A) prior to surfactant administration. Oxygen requirements fell significantly more rapidly within the first 24 hours for patients treated with Curosurf compared to Exosurf (p < 0.001). Mean duration of > 40% oxygen requirement was significantly shorter in the Curosurf group (2.6 days) compared to 8.0 days in the Exosurf group (p < 0.01). Mean duration of oxygen therapy was also significantly shorter in the Curosurf group (10.2 days) compared to 17.1 days in the Exosurf group (p < 0.05). Ten infants (24%) in the Exosurf group developed intraventricular haemorrhage (IVH) compared to none in the Curosurf group (p < 0.05). As oxygen requirements appear to decrease more rapidly following administration of Curosurf compared to Exosurf a large prospective randomized multicentre trial needs to be performed to compare the effects of these surfactants on both short and long-term outcome.

Surfactant-producing rabbit pulmonary alveolar type II cells synthesize and secrete an antiinflammatory protein, uteroglobin

Neonatal respiratory distress syndrome (RDS) caused by surfactant deficiency is a common disorder in premature infants. Exogenous surfactant therapy improves survival in infants with RDS. However, the phospholipid component of the surfactant has been suggested to be inactivated by a phospholipid hydrolyzing enzyme, phospholipase A2 (PLA2). Although alveolar type II cells produce the surfactant, it is not known whether these cells have any mechanism to protect surfactant from PLA2 hydrolysis. Since alveolar Clara cells express uteroglobin (UG), a PLA2 inhibitory and antiinflammatory protein, and since it has been suggested that alveolar type II cells are derived from Clara cells, we sought to elucidate whether type II cells are also capable of expressing UG gene. By using radioimmunoassay, immunoprecipitation and Western blotting techniques we demonstrate for the first time that type II cells, isolated from mature rabbit lungs, synthesize and secrete UG. The transcription of the UG gene was detected by in situ hybridization using rabbit UG cDNA probe. These results imply that UG, synthesized by type II cells, may protect both endogenous and exogenous surfactant from PLA2 hydrolysis. Moreover, the antiinflammatory properties of UG may prevent the development of chronic inflammatory lung disease, a frequent complication of RDS.

Surfactant replacement therapy in premature babies with respiratory distress syndrome: factors affecting the response to surfactant and comparison of outcome from 1982-86 and 1987-91

The impact of surfactant therapy on chronic lung disease remains uncertain. During the past decade (1982-91), over 300 babies with respiratory distress syndrome (RDS) weighing 501-2,500 g at birth were consecutively treated with surfactant-TA at our neonatal intensive care unit. Data on 95 RDS babies treated in the first 5 year period (Period 1, 1982-86) were compared with those on 158 RDS babies treated in the second 5 year period (Period 2, 1987-91). Overall respiratory improvement was better in Period 2 than in Period 1. In Period 2, surfactant therapy converted 98% of the babies with moderate/severe RDS to those with 'near normal' lung by 72 hr post-treatment. In Period 2, 95% of the surfactant-treated babies weighing 501-1,750 g at birth survived, 97% of which required no supplemental oxygen at 40 weeks corrected gestational age. Increased survival rate in the surfactant-treated babies during the past decade has not been followed by a parallel increase in chronic lung disease. The severity of the initial pulmonary disease per se was not the significant risk factor for chronic lung disease. Several other variables affecting the response to surfactant therapy and outcome have been identified by stepwise logistic regression analysis and include factors related to perinatal events such as birth asphyxia and infection, and other complications of prematurity.

Delayed compliance increase in infants with respiratory distress syndrome following synthetic surfactant

Recent research has demonstrated that Exosurf (EXSF), a newly synthesized artificial surfactant, increases survival when administered endotracheally to premature infants with RDS. This study examines the effects of EXSF on static respiratory system compliance (Crs). Thirty-four patients received two doses of EXSF in this rescue protocol. Crs (mL/cmH2O/kg) did not significantly change within the first 4 hours after either dose. However, Crs values did increase significantly (paired Student's t-test, P = 0.005) when data collected after the second dose (0.36 +/- 0.13 mL/cmH2O/kg) were compared to first week follow-up data (0.51 +/- 0.21 mL/cmH2O/kg). Crs data collected between 2 and 4 weeks after treatments were again not significantly different from non-concurrent control data collected at 3-4 weeks of life. The measurement of Crs in infants receiving EXSF may have been affected by an increase in lung inflation, which could mask an increase in Crs. We speculate that improved lung inflation may occur with less barotrauma in the first week of life due to surfactant replacement treatment and may in part explain the improved Crs seen at 1 week of age. Many investigators using different surfactants, dosing schedules, and pulmonary function methodologies to evaluate lung mechanics have reported that the improvement in compliance after surfactant treatment usually follows the clinical improvement in gas exchange. Additional studies are needed to explain the mechanism of early improvement following surfactant replacement in infants with RDS.

Early treatment of respiratory distress syndrome with bovine surfactant in very preterm infants: a multicenter controlled clinical trial

OBJECTIVE

To determine the effect of bovine surfactant (SF-RI 1, Alveofact) administered during the first hour following birth to very premature infants [gestational age (GA), 25-30 weeks] in a multicenter, controlled trial.

HYPOTHESIS

Survival without bronchopulmonary dysplasia (BPD; definition: ventilator dependency or FiO2 greater than 0.3 during spontaneous respiration) at day 28 is increased in surfactant-treated infants (sequential analysis).

PATIENTS AND METHODS

Thirty-four infants [GA 28.0 +/- 1.5 SD weeks, birth weight (BW), 1,048 +/- 299 g] received 50 mg/kg BW surfactant, whereas 35 infants (GA, 27.6 +/- 1.5 weeks, BW 969 +/- 269 g) served as controls. Retreatment with surfactant (up to three identical doses) 12-24 hours after the previous dose was permitted if FiO2 was greater than 0.5.

RESULTS

Survival without BPD was significantly higher in surfactant treated infants (26/34) compared to controls (14/35; P = 0.003), but in the incidence of pulmonary air leaks, patent ductus arteriosus, intracranial hemorrhage, and nosocomial infections they were not different.

CONCLUSION

Bovine surfactant treatment improves survival without BPD in very premature infants at risk for neonatal respiratory distress syndrome (RDS).

Neonatal morbidity according to gestational age and birth weight from five tertiary care centers in the United States, 1983 through 1986

OBJECTIVES

This study details the incidence, by gestational age and birth weight, of specific neonatal morbidities in singleton neonates without major congenital anomalies.

STUDY DESIGN

Data were prospectively collected on all deliveries at five tertiary centers in the United States during the years 1983 through 1986. Pregnancies were meticulously dated and the gestational ages of the neonates at delivery were confirmed by Dubowitz score.

RESULTS

The incidence of respiratory distress syndrome gradually decreases with increasing gestational age until 36 weeks. A marked decrease in the incidence of necrotizing enterocolitis, patent ductus arteriosus, intraventricular hemorrhage, and sepsis occurs after 32 completed weeks. The number of days of mechanical ventilation for respiratory distress syndrome and newborn stay in the tertiary care facility also were significantly reduced after 32 weeks.

CONCLUSIONS

The incidence of both respiratory distress syndrome and patent ductus arteriosus is markedly decreased by both increasing gestational age and birth weight. The incidence of grade III and IV intraventricular hemorrhage, necrotizing enterocolitis, and sepsis virtually vanishes after 34 weeks. These data relating neonatal morbidities to gestational age are important to the obstetrician in the critical decision regarding the timing of delivery and to the parents, who can benefit from a realistic prediction of the neonatal course.

Immunogenicity and immunomodulatory activity of bovine surfactant (SF-RI 1)

Respiratory distress syndrome in preterm infants can be treated successfully by endotracheal administration of a bovine surfactant preparation (SF-RI 1). Before the routine use of xenogenic surfactant preparations can be recommended, their immunogenicity as well as their in-vivo and in-vitro immunomodulatory activity have to be investigated. High titers of anti-surfactant antibodies were detected by a sensitive ELISA after immunizing rats, rabbits and mice with SF-RI 1. Repeated endotracheal administration of SF-RI 1 resulted in a humoral antibody response in three out of eight rabbits. After treatment of 34 preterm infants with SF-RI 1 (50-200 mg/kg), a humoral immune response to SF-RI 1 could not be detected. In-vitro restimulation of peripheral blood lymphocytes with SF-RI 1 after primary in-vivo administration did not result in cell proliferation as measured by 3H-thymidine incorporation. SF-RI 1 did not stimulate peripheral blood lymphocytes of neonates in vitro. The mitogenic response of these cells to stimulation with PHA, ConA or PWM was heavily impaired in the presence of SF-RI 1 concentrations increasing from 0.04 to 4 mg/ml. These data indicate that SF-RI 1 is immunogenic and that it may have an influence on lymphocyte proliferation in vivo.

Relative likelihood of bronchopulmonary dysplasia based on pulmonary mechanics measured in preterm neonates during the first week of life

We studied 143 low birth weight infants (less than or equal to 1500 gm) with respiratory distress syndrome who required mechanical ventilation, and determined the efficacy of using the alterations in pulmonary mechanics (measured at 1 to 3 days, 4 to 7 days, 2 weeks, and 4 weeks) as possible predictors for the subsequent diagnosis of bronchopulmonary dysplasia (BPD). The sensitivity and specificity of pulmonary compliance and resistance as predictors of BPD were ascertained by logistic regression correlation (p less than 0.01) and receiver operating characteristic curves. With these pulmonary mechanics data and logistic discriminant analysis techniques, we developed BPD prediction models based on pulmonary mechanics, measured between 4 and 7 days of age, to define the likelihood ratio for the subsequent diagnosis of BPD. Eight different BPD prediction models were developed by using combinations of four vectors (pulmonary compliance, total pulmonary resistance, birth weight, gestational age), and each model was validated in a subsequent low birth weight study population (n = 53). All models were deemed accurate for negative prediction of BPD. The models dependent on gestational age and dynamic pulmonary compliance had the highest positive predictive accuracy. The predictive impact of total pulmonary resistance appeared to be minimal. These prediction models may be used to calculate the likelihood ratio for a subsequent BPD diagnosis and thereby objectively categorize both the risk and the magnitude of acute lung injury by the first week of life.

Calf lung surfactant extract prophylaxis and retinopathy of prematurity

Retinopathy of prematurity (ROP) is an important cause of blindness among extremely low birth weight infants (birth weight less than or equal to 1000 g). In the 1990s, greater numbers of extremely low birth weight infants will survive, in part due to routine surfactant replacement therapy for neonatal respiratory distress syndrome. Few studies have evaluated the effect of surfactant therapy on the incidence and severity of ROP. The authors performed a review of the records of extremely low birth weight infants born in two 2-year intervals before and after initiation of a clinical protocol in which all extremely low birth weight infants received prophylactic treatment with calf lung surfactant extract (Infasurf). Surfactant therapy was associated with a significant improvement in survival to discharge (79% [88 of 112] versus 63% [82 of 131]; P = 0.01). Compared with control infants, surfactant-treated infants had a significantly lower incidence of any stage of ROP (64% [56 of 87] versus 85% [68 of 80]; P less than 0.004). The incidence of threshold (Stage 3 plus or greater) ROP was substantially reduced (3.4% [3 of 87] versus 10% [8 of 80]; P = 0.16)). The surfactant-associated reduction in ROP was independent of birth weight, gestational age, race, or sex. These data suggest that Infasurf may substantially reduce the incidence and severity of ROP in the extremely low birth weight population.

Energy expenditure and severity of respiratory disease in very low birth weight infants receiving long-term ventilatory support

We attempted to determine whether the hypermetabolism of infants with bronchopulmonary dysplasia was detectable during assisted ventilation. Respiratory gas exchange variables were measured with a metabolic gas monitor in 10 infants under similar nutritional conditions. Oxygen consumption increased linearly with the need for ventilatory support (R2 = 0.75), as documented by the ventilatory index.

Pulmonary mechanics and energetics in preterm infants who had respiratory distress syndrome treated with synthetic surfactant

Pulmonary mechanics and energetics were determined in 32 neonates with respiratory distress syndrome, who were randomly assigned to receive treatment with an exogenous synthetic surfactant, Exosurf Neonatal, or air placebo. Pulmonary mechanics were measured before and 2 hours after surfactant (n = 13) or air placebo (n = 19) treatment, then longitudinally at 24, 48, and 72 hours after treatment, and again at 7, 14, and 28 days of age. There were no significant differences in the values for pulmonary mechanics or energetics 2 hours after the first dose of surfactant. Improvement in pulmonary mechanics was apparent 24 hours after surfactant treatment, when dynamic compliance was 36% greater than in the placebo group (p less than 0.03). Lung compliance values were also higher in surfactant-treated infants 48 and 72 hours after treatment, with a maximal increase of 64% at 7 days of age (p less than 0.03). Surfactant treatment also caused a significant decrease in total pulmonary resistance at 48 and 72 hours after initial treatment and at 14 days of age (p less than 0.04). Similarly, a decrease in flow-resistive work of breathing was demonstrated 24, 48, and 72 hours after surfactant treatment. At 28 days of age, pulmonary mechanics were not different in the two groups. We conclude that beneficial effects of surfactant on pulmonary mechanics were not apparent 2 hours after dosing but were evident 24 hours after dosing and persisted for the first 7 to 14 days of life.

Energy expenditure during synthetic surfactant replacement therapy for neonatal respiratory distress syndrome

Little information is available on the energy expenditure of infants with increased work of breathing from respiratory distress syndrome (RDS). A study was carried out to determine whether surfactant replacement therapy modifies respiratory gas exchange in newborn infants with RDS and an arterial-alveolar oxygen tension ratio of less than 0.22. In a double-blind, placebo-controlled, rescue trial, infants received either two 5 ml/kg doses of a synthetic surfactant, Exosurf Neonatal, or air placebo. Of 23 infants ventilated for RDS, 11 were randomly assigned to receive air and 12 to receive surfactant. Oxygen consumption, carbon dioxide production, respiratory quotient, and metabolic rate were measured by computerized, closed-circuit, indirect calorimetry. Concomitantly, transcutaneous oxygen and carbon dioxide tension were continuously recorded. Oxygen consumption and carbon dioxide production remained constant during the period infants received surfactant. In patients randomly assigned to surfactant, a decrease in respiratory quotient was observed after the first (p less than 0.025) but not the second dose. This decrease was possibly related to a change in substrate utilization. The improved clinical outcomes reported among infants receiving surfactant were not accompanied by changes in energy expenditure.

Pulmonary hemorrhage in premature infants after treatment with synthetic surfactant: an autopsy evaluation. The American Exosurf Neonatal Study Group I, and the Canadian Exosurf Neonatal Study Group

In an across study analysis of five multicenter, placebo-controlled trials of the synthetic surfactant, Exosurf Neonatal in infants weighing at least 700 gm, the incidence of clinical pulmonary hemorrhage was 1.9% in treated infants and 1.0% in control infants. To investigate whether a similar increase was also present histologically at postmortem examination, a blinded retrospective review of all autopsy reports from infants dying during these five trials was conducted. Pulmonary hemorrhage was present in 55% of 159 infants undergoing autopsy; the incidence was not different in infants treated with surfactant or air placebo. Birth weight was inversely related to the incidence of pulmonary hemorrhage in both groups. Pulmonary pathologic findings significantly associated with pulmonary hemorrhage included pulmonary interstitial emphysema and necrotizing laryngotracheitis in both groups. In the surfactant group, patent ductus arteriosus, intraventricular hemorrhage, and pneumothorax were significantly more frequent among those who developed pulmonary hemorrhage. In contrast to clinical diagnosis, pathologic diagnosis of pulmonary hemorrhage at autopsy was not more common in infants treated with Exosurf Neonatal.

Controlled trial of a single dose of synthetic surfactant at birth in premature infants weighing 500 to 699 grams. The American Exosurf Neonatal Study Group I

In a multicenter, double-blind, placebo-controlled trial conducted at 23 hospitals in the United States, a single prophylactic 5 ml/kg dose of a synthetic surfactant (Exosurf Neonatal) or air placebo was administered shortly after birth to 215 infants with birth weights of 500 to 699 gm. Despite stratification at entry by birth weight and gender, by chance female infants predominated in the air placebo group and male infants predominated in the surfactant group. Among infants receiving synthetic surfactant, improvements in oxygen requirements were significant at 2 hours after birth (p = 0.014) and persisted for 3 days (p = 0.001); improvements in the alveolar-arterial partial pressure of oxygen gradient were significant at 6 hours after birth (p = 0.01) and persisted for 3 days (p = 0.008). Improvements in mean airway pressure were not significant at 2 or at 6 hours after birth (p = 0.622 and 0.083, respectively), but became significant thereafter and persisted for 3 days (p = 0.002). Pneumothorax was reduced by slightly more than half (25 vs 11; p = 0.014); death from respiratory distress syndrome (RDS) was also reduced (26 vs 15; p = 0.046). Overall neonatal mortality, however, was not significantly reduced (58 vs 46; p = 0.102). Other complications of RDS and prematurity were not altered, except that pulmonary hemorrhage occurred significantly more frequently in infants receiving synthetic surfactant (2 vs 12; p = 0.006). These findings indicate that a single prophylactic dose of synthetic surfactant in infants weighing 500 to 699 gm at birth improves lung function, incidence of air leak, and death from RDS but not overall mortality. The only safety problem identified was an increase in pulmonary hemorrhage.

Natural surfactant for neonatal respiratory distress syndrome in very premature infants: a 1992 update

Natural surfactant (Surfactant TA, Survanta, CLSE, SF-RI 1, Curosurf and human surfactant obtained from amniotic fluid) therapy for RDS in very premature infants has been evaluated in 17 controlled clinical trials. Uniformly intratracheal surfactant administration caused a decreased intensity of mechanical ventilation during the first hours (reduced inspiratory pressure, reduced oxygen requirements) as an immediate effect of surfactant administration. Metanalysis reveals barotraumatic pulmonary complications mainly, pneumothorax and pulmonary interstitial emphysema to occur less frequently in surfactant-treated infants in virtually all trials; an increased incidence of survival without bronchopulmonary dysplasia following surfactant treatment was observed in 10 controlled clinical trials. The incidence of other complications of prematurity (intracranial hemorrhage, patent ductus arteriosus and necrotizing enterocolitis) was unchanged following natural surfactant treatment. Dosing of natural surfactant is still under investigation, however recent data indicate that the initial dose should not be less than 100 mg/kg b.w. and retreatment should be given to infants with unsatisfactory response (i.e. fraction of inspired oxygen (FiO2) > 40%). Timing of surfactant treatment still remains controversial. Prophylactic treatment shortly following birth has been compared with rescue-treatment, i.e. surfactant administration to infants suffering from manifest RDS in most studies 4-8 h after birth. Conflicting data from 5 controlled trials may be interpreted as follows: prophylactic treatment seems to be favourable for extremely premature infants (GA < or = 26 weeks) and rescue treatment seems to be adequate for infants of 27-30 weeks of gestation. Intratracheal surfactant instillation in very premature infants did not result in an improved lung function for 24 h to 48 h in all patients. Ten--25% of study infants were reported to be "non-responders", i.e. infants without sustained decrease in oxygen requirements (i.e. FiO2 > 40%). Various factors may be operative including congenital bacterial infections (sepsis or pneumonia), lung hypoplasia and cardiac failure. Inactivation of surface properties of natural surfactant caused by a leakage of proteins across the alveolar-capillary membrane was observed in experimental and clinical studies. Current investigations focus on a combination of postnatal steroids and surfactant treatment to improve lung function and outcome in "non-responders". As long as any controlled clinical studies are being published, this approach remains experimental. Up to now, any controlled clinical trials have been performed to assess different modes of artificial ventilation (e.g. high frequency oscillating ventilation versus conventional ventilation) combined with surfactant therapy. Data obtained from premature animals given natural surfactant indicate any advantage with respect to gas exchange and lung histology to result from high frequency ventilation.(ABSTRACT TRUNCATED AT 400 WORDS)

Developmental intervention during neonatal hospitalization. Critiquing the state of the science

Recent investigations, such as those discussed, focus attention on the need for additional studies that explore the emerging neuroregulatory mechanisms in premature infants. Data from these investigations may augment current high standards of neonatal medical care that now focus on treating the heart, lungs, and digestive systems. The various studies of early developmental processes encourage clinicians to recognize and treat premature infants as individuals, a principle acknowledged long ago about full-term infants and parents. Through understanding the critical role of parents in guiding the continued health and development of infants after hospital discharge, hospital staff are exploring methods for helping parents feel involved, respected, and supported as primary caregivers. Similarly, staff are reacting to the growing realization that optimal developmental outcome requires close coordination between hospital and community services for infants and families. Continued attention to the developmental needs of hospitalized infants and their parents, along with further integration of medical, developmental, and emotional care, will surely succeed in bringing early hope to the fragile beginning of life after high-risk birth.

Influence of intratracheal application of fluorocarbon 72 and different lipid-mixtures on mechanical behavior of isolated immature pig lungs

Substitution of surfactant in immature lungs has two functional targets: the reduction of the overall alveolar surface tension and the mechanical stabilization of the system of alveoli having different diameters. Indeed, the lowering of the surface tension facilitates the inflation of the lungs, but according to Laplace's law small and large alveoli are not in pressure equilibrium as long as the surface tension is equal in both small and large alveoli. In the present work, we tried to stabilize the lungs and to compare the effect of bolus surfactant substitution with the two-step substitution of fluorocarbons and surfactant. In all, 24 fetal immature lungs were used. For our experiments we used fluorocarbon 72 (FC-72) with a surface tension of 12 mN/m. In groups 1 and 2, a mixture of dipalmitoylphosphatidylcholine (DPPC): cholesterol 9:1 (molar ratio) or DPPC: phosphatidylglycerol (PG) 9:1 (molar ratio) was administered intratracheally as a bolus. In the case of groups 3 and 4, the immature lungs were rinsed first with FC-72. After removing the fluorocarbon, the lungs were artificially ventilated and the DPPC: cholesterol 9:1 (group 3) or DPPC:PG 9:1 mixture (group 4) was given in aerosol form. Static pressure-volume curves (p-v) of the mean values of the 6 lungs in each group were registered at the beginning (0 min) and after 20 and 40 min of artificial ventilation. Airway opening pressure, weight-specific end-inspiratory lung compliance, and phospholipid contents were investigated.(ABSTRACT TRUNCATED AT 250 WORDS)

Factors affecting surfactant responsiveness

There is a wide variability in the therapeutic responsiveness to exogenous surfactant, a drug that has become generally available for the treatment of lung immaturity and respiratory distress syndrome. Recent studies have demonstrated evidence that therapies decreasing lung edema improve the effectiveness of surfactant substitution. In addition, exogenous surfactant may acutely decrease pulmonary perfusion since the airway pressures are effectively transmitted to airspaces, compressing alveolar capillaries, especially in hypovolemia. Therapies aimed at decreasing lung edema, improving cardiac output, and stepwise weaning from oxygen and ventilatory pressures are cornerstones in the successful management of patients undergoing surfactant therapy.

Surfactant analysis and replacement therapy: a future tool of the lung transplant surgeon?

From 1965 to 1974 extensive research was carried out concerning the effects of experimental lung reimplantation and allografting on the surface tension properties of pulmonary surfactant. Since then, surfactant has been more rigorously examined in terms of its composition and function, and the potential roles of three surfactant-associated proteins have been established. Furthermore, surfactant replacement therapy for neonatal respiratory distress syndrome has come of age. The efficacy of surfactant treatment for adult respiratory distress syndrome is currently under clinical scrutiny, and experimental work on alterations in surfactant after lung transplantation has resumed after a 15-year hiatus. This article reviews current knowledge of the pulmonary surfactant system, as well as previous studies of the changes in surfactant after experimental lung transplantation. The experience in surfactant replacement therapy for the neonatal and adult respiratory distress syndromes is briefly described. Suggestions are made concerning the potential experimental and clinical applications of surfactant analysis and replacement therapy in lung transplantation.

Reduced mortality in small premature infants treated at birth with a single dose of synthetic surfactant

A randomized controlled trial of Exosurf Neonatal, a synthetic exogenous surfactant, was performed. Exosurf was given to premature infants weighing 700-1350 g, by instillation down the endotracheal tube during mechanical ventilation, within 1 h of birth. Control infants were treated with air. Dose administration was performed in secrecy by clinicians who maintained the blind for 2 years. A total of 109 infants received air and 109 received Exosurf; 19 infants with congenital pneumonia or major malformations were excluded from the primary efficacy analysis. By the age of 28 days there were 14 deaths in the air group and 4 deaths in the Exosurf group, a 69% reduction with Exosurf (P = 0.020). Survival without bronchopulmonary dysplasia at the age of 28 days was significantly improved by 15% (P = 0.050). By the age of 1 year post-term there were 19 deaths in the air group and 10 deaths in the Exosurf group, a 42% reduction with Exosurf (P = 0.104). There were no significant changes in the incidence of bronchopulmonary dysplasia, pulmonary air leaks, intraventricular haemorrhage, patent ductus arteriosus, necrotizing enterocolitis or infection. The reduction in mortality indicates important results in high risk premature infants treated soon after birth with a single dose of Exosurf.

Quality of life as outcome measures in randomized clinical trials. An overview of three general medical journals

A survey of 75 randomized trials published in 1986 in the Annals of Internal Medicine, American Journal of Medicine, and New England Journal of Medicine was carried out by two observers using predetermined criteria about the importance of health status as an outcome measurement and the quality-of-health status measurement that was used. The kappa statistic was used to measure agreement among the two observers. Although a number of investigators used well-established quality-of-life measurements, in only 10 of 55 trials in which health status was judged crucial or important were measures with established validity and responsiveness used. Despite the fact that reliable measurement of quality of life is now feasible, it is underutilized in randomized clinical trials.

Respiratory compliance in premature babies treated with artificial surfactant (ALEC)

In a randomised trial of artificial surfactant (ALEC) given at birth to 294 babies less than 34 weeks' gestation, the respiratory compliance was measured at 1, 6, 24, 48, and 168 hours after birth. In babies less than 29 weeks' gestation ALEC significantly improved the mean (SEM) compliance at 6 hours from 0.54 (0.06) to 0.91 (0.13) ml/cm H2O/kg and at 24 hours from 0.57 (0.04) to 0.92 (0.10) ml/cm H2O/kg. The improvements at 1, 48, and 168 hours were not significant. In babies of over 29 weeks' gestation the compliance was lower in the ALEC treated babies. This was significant only at one hour: 0.52 (0.03) compared with 0.71 (0.07) ml/cm H2O/kg and only occurred in babies who were not ventilated.