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.

Double-blind developmental evaluation at 1-year corrected age of 597 premature infants with birth weights from 500 to 1350 grams enrolled in three placebo-controlled trials of prophylactic synthetic surfactant. American Exosurf Neonatal Study Group I

Infants enrolled in three clinical trials of prophylactic treatment for respiratory distress syndrome with a single dose of synthetic surfactant (Exosurf Neonatal) or air placebo were monitored through 1-year adjusted age. A total of 1046 infants with birth weights from 500 to 1350 gm were enrolled in the three trials; of the 735 infants who survived to 1 year of age, follow-up evaluations were completed for 597 (80%, air placebo group; 82%, synthetic surfactant group). Infants in the air placebo and synthetic surfactant treatment groups had no differences in general health, growth, or nerodevelopmental outcomes or impairments. These follow-up results at 1-year adjusted age for infants who received a single dose of synthetic surfactant indicate that a single dose of synthetic surfactant reduces mortality without increasing the absolute number or proportion of infants with impairments at 1 year of age.

Effects of two rescue doses of synthetic surfactant in 344 infants with respiratory distress syndrome weighing 750 to 1249 grams: a double-blind, placebo-controlled multicenter Canadian trial. Canadian Exosurf Neonatal Study Group

In a multicenter, double-blind, placebo-controlled rescue trial conducted at 13 Canadian hospitals, two 5 ml/kg doses of a synthetic surfactant or air placebo were administered to 344 infants with birth weights of 750 to 1249 gm who had established respiratory distress syndrome and an arterial/alveolar oxygen tension ratio less than 0.22. The first dose was given between 2 and 24 hours of age, and the second dose was given 12 hours later to the infants remaining on mechanical ventilation. Infants were stratified at study entry by birth weight and gender. The trial was terminated short of the targeted sample size because significant reductions in mortality were observed in another rescue trial completed in the United States in the same weight class of infants. Despite premature termination of the trial, the rate of survival without bronchopulmonary dysplasia was increased (61% vs 52%; p = 0.046) in infants treated with surfactant. In addition, there was a significant reduction in the incidence of overall pulmonary air leak (46% vs 32%; p = 0.009), pneumothorax (27% vs 17%; p = 0.023), and pulmonary interstitial emphysema (40% vs 28%; p = 0.018) in infants treated with synthetic surfactant. There was no difference in the incidence of bronchopulmonary dysplasia, apnea, or pulmonary hemorrhage. Significant improvements in alveolar-arterial oxygen tension gradient, arterial/alveolar oxygen tension ratio, and oxygen and ventilator requirements through day 7 were present. These findings indicate that rescue therapy with synthetic surfactant can improve outcome for premature infants weighing 750 to 1249 gm with respiratory distress syndrome.

One-year follow-up of 66 premature infants weighing 500 to 699 grams treated with a single dose of synthetic surfactant or air placebo at birth: results of a double-blind trial. American Exosurf Neonatal Study Group I

In a multicenter, double-blind, placebo-controlled trial that enrolled 215 premature infants with birth weights of 500 to 699 gm, 106 infants were treated prophylactically with a single 5 ml/kg dose of synthetic surfactant and 109 infants were given an equivalent dose of air placebo shortly after birth. In each group, 40 children survived infancy: 36 children in the air placebo group and 30 children in the synthetic surfactant group were available for follow-up. Weight, height, and head circumference measurements were similar for both groups at 1-year adjusted age. Infants who received synthetic surfactant at birth had statistically similar Bayley Scales of Infant Development scores (mental developmental index, 92 vs 83; psychomotor developmental index, 87 vs 82) compared with controls. Mild to moderate impairments in the synthetic surfactant group were 7% versus 29% in the control group; these differences were not statistically significant. The incidence of retinopathy of prematurity, the number of hospital readmissions, the need for surgery after day 28, evidence of chronic lung disease, the need for respiratory support at 1-year adjusted age, and the incidence of allergies were also not different between the two groups. However, the proportion of infants surviving without impairment was modestly higher in the synthetic surfactant group (8%, air placebo group; 23%, synthetic surfactant group). The findings from this small study indicate that infants weighing 500 to 699 gm who receive a single prophylactic dose of synthetic surfactant at birth have neurodevelopmental outcomes at least equivalent to those of infants given air placebo at 1-year follow-up.

Double-blind evaluation of developmental and health status to age 2 years of infants weighing 700 to 1350 grams treated prophylactically at birth with a single dose of synthetic surfactant or air placebo

In a previously published article, we reported results of a two-center study of outcome to 28 days of 385 infants with birth weights from 700 to 1350 gm who were assigned randomly to receive a single 5 ml/kg intratracheal dose of either synthetic surfactant or air placebo. Infants treated with surfactant had a higher rate of survival to 28 days without bronchopulmonary dysplasia than did control subjects given an air placebo. The present study assessed survivors in early childhood to determine neurodevelopmental outcome and late morbidity. Two hundred fifty-eight surviving infants from both centers were evaluated at 1-year adjusted age; medical histories were obtained, standard physical and neurologic examinations were performed, and Bayley Scales of Infant Development were administered. Ophthalmologic examinations were performed at various times between 28 days and 1-year adjusted age. At 2-years adjusted age, 118 infants from one center were reevaluated with the same procedures and also had hearing and speech evaluations. Neither the 1-year assessment of the entire population nor the 2-year assessment of the one center's cohort revealed physical or neurodevelopmental differences between treatment groups. We conclude that administration of a single prophylactic dose of synthetic surfactant to premature infants with birth weights from 700 to 1350 grams results in improved survival rates to 28 days without bronchopulmonary dysplasia and is not associated with adverse health or neurodevelopmental effects at 1-year or 2-years adjusted age.

One-year follow-up evaluation of 260 premature infants with respiratory distress syndrome and birth weights of 700 to 1350 grams randomized to two rescue doses of synthetic surfactant or air placebo. American Exosurf Neonatal Study Group I

A multicenter, randomized, double-blind, placebo-controlled trial of synthetic surfactant therapy for premature infants with respiratory distress syndrome (RDS) and birth weights of 700 to 1350 gm demonstrated a reduction in severity of RDS, morbidity, and neonatal and 1-year mortality. Of the 419 infants who were entered in the study, 80% of the surviving infants in both the air placebo group (122) and the synthetic surfactant group (138) returned for the follow-up evaluation at 1-year adjusted age. The only significant difference observed at follow-up was a reduction in the incidence of mild cerebral palsy in the synthetic surfactant group (air placebo group, 8 of 122 (7%); synthetic surfactant group, 3 of 138 (2%); relative risk 0.306; 95% confidence interval 0.094, 0.999). No differences were observed between the air placebo and synthetic surfactant treatment groups with respect to health status of the infants, including the incidence of retinopathy of prematurity and neurodevelopmental delays. The difference in the overall incidence of impairment among the 1-year survivors in the air placebo group (43 of 122 (35%)) and in the synthetic surfactant group (40 of 138 (29%)) was not statistically significant. The results of this 1-year follow-up study show that rescue treatment with synthetic surfactant in infants weighing 700 to 1300 gm is not associated with adverse developmental consequences despite the improvement in survival.

One-year follow-up of 273 infants with birth weights of 700 to 1100 grams after prophylactic treatment of respiratory distress syndrome with synthetic surfactant or air placebo. American Exosurf Neonatal Study Group I

A single dose of synthetic surfactant was administered prophylactically to premature neonates with birth weights between 700 and 1100 gm. The effects of this treatment on neurodevelopmental, neurologic, and ophthalmologic outcomes, impairments, and general health status were examined during a follow-up evaluation at 1-year adjusted age. The study was a multicenter, parallel, randomized, double-blind comparison of 446 infants who received either air placebo (n = 222) or synthetic surfactant (n = 224). Follow-up evaluations were completed for 82% of surviving infants in both treatment groups. Neurodevelopmental outcome and growth were equivalent in the infants treated with synthetic surfactant and in the infants given air placebo. Impairments occurred in 38% of the infants treated with air placebo compared with 31% of those given synthetic surfactant; the difference was not statistically significant (relative risk 0.809, 95% confidence interval 0.585, 1.119). The incidence of asthma was significantly higher in the group of infants given air placebo (4% vs 10% for surfactant and air placebo, respectively, relative risk 0.391, 95% confidence intervals 0.157, 0.972). Other outcomes, including retinopathy of prematurity, hospital readmissions, surgery, and evidence of chronic lung disease, were not different. Administration of a single prophylactic dose of synthetic surfactant increases survival in infants with birth weights between 700 and 110 gm without increasing the number or proportion of impaired survivors.

Outcome at 1-year adjusted age of 957 infants weighing more than 1250 grams with respiratory distress syndrome randomized to receive synthetic surfactant or air placebo. American and Canadian Exosurf Neonatal Study Groups

This study determined outcomes at 12-months adjusted age of 957 infants weighing more than 1250 gm at birth who were subjects in a randomized, double-blind, controlled trial of synthetic surfactant or air placebo administered in a rescue trial at 23 hospitals in the United States and 13 hospitals in Canada. Follow-up results were available for 475 of 563 surviving infants who received air placebo (84%) and 482 of 571 infants who received synthetic surfactant (84%). Developmental outcome was equivalent in the two groups. Morbidity was less in the synthetic surfactant group as assessed by the need for medication for chronic lung disease (52 of 475 (11%) for the air placebo group vs 32 of 482 (7%) for the synthetic surfactant group) or respiratory support (10 of 475 (2%) for the air placebo group vs 1 of 482 (< 1%) for the synthetic surfactant group) at 1-year adjusted age. Bayley Scales of Infant Development (mental development Index: 102 for both the air placebo and synthetic surfactant groups; psychomotor development index: 95 for the air placebo group vs 94 for the synthetic surfactant group) and impairment rates (94 of 475 (20%) for the air placebo group vs 86 of 482 (18%) for the synthetic surfactant group) were similar in the two groups. Infants weighing more than 1250 gm who have respiratory distress syndrome have previously been shown to have improved survival rates and lower neonatal morbidity after treatment with synthetic surfactant. These follow-up data confirm that developmental outcome as determined at 12-months adjusted age is at least as good in those receiving synthetic surfactant.

One-year outcome in 232 premature infants with birth weights of 750 to 1249 grams and respiratory distress syndrome randomized to rescue treatment with two doses of synthetic surfactant or air placebo. Canadian Exosurf Neonatal Study Group

A randomized, double-blind, placebo-controlled trial was performed in 13 hospitals in Canada to assess whether two rescue doses of a synthetic surfactant (Exosurf Neonatal) would reduce mortality and morbidity rates in neonates with respiratory distress syndrome who weighed from 750 to 1249 gm. As part of the original trial design, double-blind follow-up evaluations were performed at 1-year adjusted age. A total of 118 patients who received air placebo and 114 patients who received synthetic surfactant were evaluated at 1 year. Growth and development in the two groups were equivalent. Scores on the Bayley Scales of Infant Development were within the normal range for both groups (mental development index, 90 +/- 22 vs 92 +/- 22; psychomotor development index, 81 +/- 19 vs 87 +/- 22 for the air placebo and synthetic surfactant groups, respectively). However, in both groups the proportion of infants with any impairment (air placebo group, 43 of 118 (36%); synthetic surfactant group, 41 of 114 (36%) and severe impairment (air placebo group, 29 of 118 (25%); synthetic surfactant group, 21 of 114 (18%)) was substantial. We conclude that two rescue doses of synthetic surfactant in infants with RDS who weighed 750 to 1249 gm had no detrimental effect on developmental outcome or late morbidity. No long-term benefits to 12-months corrected age were observed with the use of surfactant in this weight class. Larger studies or meta-analyses of existing trials will be required to determine if there are any late outcome advantages associated with rescue use of synthetic surfactant in infants weighing 700 to 1249 gm.

Health and neurodevelopmental outcome at 1-year adjusted age in 508 infants weighing 700 to 1100 grams who received prophylaxis with one versus three doses of synthetic surfactant. American Exosurf Neonatal Study Groups I and II

A three-dose prophylactic regimen of synthetic surfactant replacement has been shown to improve neonatal and 1-year survival rates in infants of 700 to 1100 gm birth weight when compared with a single prophylactic dose. The purpose of this study was to evaluate the growth, development, and late morbidity at 1 year adjusted age among the survivors of the 826 patients enrolled in the protocol. Complete follow-up data were obtained for 75% of the survivors in both groups. Chronic lung disease, need for respiratory support, neurologic disease requiring medication, visual or auditory impairments, and the incidence and severity of retinopathy of prematurity were equivalent in the two groups. The frequency of neurodevelopmental impairment was also comparable in the groups that received one dose versus three doses: moderate to severe cerebral palsy was found in 9% versus 6%, mental retardation assessed by Bayley Scales of Infant Development scores less than 69 was found in 16% vs 14%, and moderate to severe impairments of any kind were found in 33% vs 24%, respectively. Furthermore, the absolute number of impaired survivors was 92 in the three-dose group versus 106 in the one-dose group, despite a higher survival rate in the three-dose group. This study demonstrates that developmental outcomes of infants weighing 700 to 1100 gm who received three prophylactic doses of synthetic surfactant are at least as good as those of infants receiving a single dose, and that improving survival rates of very premature infants with synthetic surfactant does not result in increased numbers of infants with impairments.

Double-blind 1-year follow-up of 1540 infants with respiratory distress syndrome randomized to rescue treatment with two doses of synthetic surfactant or air in four clinical trials. American and Canadian Exosurf Neonatal Study Groups

Synthetic surfactant has been shown to reduce neonatal and 1-year mortality and neonatal morbidity in infants with respiratory distress syndrome. However, less is known about the effects of synthetic surfactant on developmental outcome and long-term morbidity. Four multicenter, randomized, placebo-controlled trials of synthetic surfactant administered as rescue therapy were conducted in the United States and Canada, with a total enrollment of 2224 patients. Double-blind developmental evaluations of survivors were conducted at 1 year of age (adjusted for prematurity) in all four trials. Of the 1802 patients enrolled in the placebo-controlled rescue trials who survived to 1 year, 1540 (85%) completed the 1-year follow-up evaluation. Height, weight, and head circumference measurements were not different in the treatment and control groups. Mean and median Bayley Scores of Infant Development for both the Mental Development Index and the Psychomotor Development Index were also equivalent. The incidence of impairments was not different in the two groups (mild to moderate impairment, 12% (92 of 745) for the air placebo group vs 11% (86 of 771) for the synthetic surfactant group; severe impairment, 15% (114 of 745) for the air placebo group vs 13% (102 of 771) for the synthetic surfactant group). No differences in rates of retinopathy of prematurity or hearing impairment were found in the treatment groups. The need for surgery after day 28 of life (relative risk, 0.779; 95% confidence interval, 0.665, 0.927) and the need for respiratory support at 1 year (relative risk, 0.525; 95% confidence intervals, 0.303, 0.911) were both reduced in the synthetic surfactant group. These results indicate that developmental outcome at 1 year of age is at least as good among infants with respiratory distress syndrome who received rescue therapy with synthetic surfactant as it is in infants who received air placebo; the results also indicate that the incidence of long-term morbidity is reduced.

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

Double-blind neurodevelopmental and physical evaluations were conducted at 1-year adjusted age in 89 infants with birth weights of 500 to 749 gm who had respiratory distress syndrome in the neonatal period and were randomized to receive two rescue doses of a synthetic surfactant (Exosurf Neonatal, Burroughs Wellcome Co., Research Triangle Park, N.C.) or air placebo. The trial used a common protocol and was conducted at 13 hospitals; patients were entered in the trial between February 1988 and September 1990. Ninety-five percent of surviving infants were assessed. Growth and development in the two groups were equivalent. Mean Bayley Scales of Infant Development scores were comparable (mental development index, 79 +/- 22 vs 87 +/- 20; psychomotor development index, 73 +/- 18 vs 81 +/- 19 for air placebo and synthetic surfactant, respectively). The incidence of severe retinopathy of prematurity was significantly decreased in the surfactant group compared with the air placebo group (15% vs 34%; relative risk 0.428; 95% confidence interval 0.2 to 0.9). Overall, administration of surfactant appeared to increase the probability of a favorable outcome. Confirmation of the trends observed in this study would provide a strong rationale for the rescue use of synthetic surfactant in extremely low birth weight infants with respiratory distress syndrome even if overall mortality is not reduced.

Double-blind, randomized, placebo-controlled Canadian multicenter trial of two doses of synthetic surfactant or air placebo in 224 infants weighing 500 to 749 grams with respiratory distress syndrome. Canadian Exosurf Neonatal Study Group

In a multicenter, double-masked, placebo-controlled rescue trial conducted at 12 Canadian hospitals, two 5 ml/kg doses of a synthetic surfactant or air placebo were administered to 224 infants with birth weights of 500 to 749 gm who had established respiratory distress syndrome and an arterial/alveolar oxygen tension ratio of less than 0.22. The first dose was given between 2 and 24 hours of age; the second dose was given 12 hours later to the infants continuing to receive mechanical ventilation. Infants were stratified at study entry by birth weight and gender. Infants receiving synthetic surfactant showed significant improvements in alveolar-arterial oxygen tension gradient, arterial/alveolar oxygen tension ratio, and oxygen and ventilator requirements through day 7. In the group randomized to synthetic surfactant, significant improvements were seen in oxygen requirements at the first time point measured (2 hours; p = 0.02), in the alveolar-arterial oxygen tension gradient by the second time point measured (6 hours; p = 0.03), and in mean airway pressure after 6 hours. Overall mortality at 28 days was not significantly different in the two groups (50% vs 46%, air placebo group vs synthetic surfactant group; p = 0.586). Similarly, neither the incidence of bronchopulmonary dysplasia (37% vs 30%, air placebo group vs synthetic surfactant group; p = 0.089) nor the incidence of survival without BPD through 28 days (17% vs 26%, respectively; p = 0.070) was significantly different in the two groups. No significant differences in the incidence of safety-related outcomes or in adverse effects such as apnea or pulmonary hemorrhage were noted. These findings indicate that rescue therapy with synthetic surfactant results in physiologic improvements in very tiny premature infants, but improvements in overall mortality or other complications of respiratory distress syndrome were not documented in the sample evaluated.

Dopaminergic influence on the ventilatory response to sustained hypoxia in the cat

We examined the effects of the dopamine blocker haloperidol (H) on the ventilatory response to sustained hypoxia in awake cats. Ventilation (VE) was measured plethysmographically, and end-tidal PO2 (PETO2) and PCO2 were measured by sampling tracheal gas. Measurements were made before, during, and after 30 min of isocapnic hypoxia after pretreatment with 0.1 mg/kg of H and placebo (P). Experimental runs were conducted on separate days with the P day being first. Two levels of hypoxia were employed. Six cats were studied at a PETO2 of approximately 61 Torr, and six cats were studied at a PETO2 of approximately 41 Torr. In all experiments, isocapnia was maintained and end-tidal PCO2 did not differ on the H and P days. With mild hypoxia after P, VE increased to 137% of air breathing control in the first 5 min of hypoxia and then declined to 102% of control at 25 min of hypoxia. Results on the H day were similar. With more severe hypoxia after P, VE increased to 173% of control at 5 min and then declined to 127% of control. With H, VE increased to 172% of control in the first 5 min and then declined to 149% of control at 25 min. After 25 min of more severe hypoxia, both VE and tidal volume were significantly greater with H than with P (P < 0.05). H reduced the ventilatory decline observed with more severe hypoxia but had no effect on the ventilatory decline in milder hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative acute effects of adenosine and prostacyclin in primary pulmonary hypertension

Vasodilators have been a main focus of therapy for primary pulmonary hypertension. Adenosine and prostacyclin have been shown to reduce pulmonary vascular resistance acutely in these patients. In order to compare the acute hemodynamic effects of adenosine and prostacyclin, ten patients with severe primary pulmonary hypertension, unresponsive to medical therapy, were studied. After baseline hemodynamics were obtained, an adenosine infusion, 50 to 100 ng/kg/min, was begun and titrated to the maximum tolerated dose. Hemodynamics were allowed to return to baseline, and thereafter, a prostacyclin infusion was begun at 2 ng/kg/min, and titrated to the maximum tolerated dose. Overall, adenosine (200 +/- 53 ng/kg/min) produced a 33 +/- 18% (p < 0.001) fall in pulmonary vascular resistance and a 52 +/- 25% (p < 0.001) increase in cardiac output with no effect on pulmonary or systemic arterial pressures. Prostacyclin (8 +/- 4 ng/kg/min) caused a 22 +/- 18% (p < 0.01) fall in pulmonary vascular resistance and a 25 +/- 26% (p < 0.05) increase in cardiac output with a 14 +/- 6% (p < 0.001) decrease in systemic arterial pressure, but no change in pulmonary arterial pressure. The effects of adenosine and prostacyclin on pulmonary vascular resistance were similar (r = 0.70, r2 = 0.49, p = 0.02). Adenosine and prostacyclin have similar hemodynamic effects acutely in primary pulmonary hypertension. Adenosine may be useful as a test of the potential for long-term prostacyclin therapy in patients with primary pulmonary hypertension.

Traumatic rupture of the tracheobronchial tree in a 2 year old

Tracheobronchial tree injuries occur in a small number of patients after blunt chest trauma, and their occurrence is even more uncommon in the pediatric trauma population. The authors present the case of a 2-year-old boy who presented with rupture of the trachea and disruption of the right upper lobe bronchus and bronchus intermedius.

Ventilatory responses to CO2 and hypoxia after sustained hypoxia in awake cats

In humans and cats the ventilatory response to 30 min of isocapnic hypoxia is biphasic with an initial increase followed by a decrease, termed "hypoxic depression." In humans, 30 min of hypoxia reduces the initial response to a subsequent hypoxic exposure. These experiments were to determine whether the same occurred in cats. Cats were studied while awake. End-tidal Po2 and Pco2 were measured by sampling tracheal gas, and ventilation was measured plethysmographically. In seven cats we measured ventilatory responses to two 30-min periods of isocapnic hypoxia (end-tidal Po2 = 60-65 Torr) separated by 5 min of room air breathing. The first hypoxic response was biphasic, with ventilation increasing to 149% of control at 5 min and decreasing to 117% of control at 25 min. During the second exposure, ventilation was 119% of control at 5 min and 113% of control at 25 min; 30 min of hypoxia depressed the subsequent hypoxic response. Hypoxic depression outlasted the hypoxia, suggesting that it was mediated by relatively slow neurochemical events. In five cats ventilatory responses to 5% CO2 were measured before and 5 min after 30 min of isocapnic hypoxia and before and after 30 min of room air breathing. Hypoxia did not affect CO2 responses. Thus the neurochemical events that cause hypoxic depression appear not to involve the neurons generating the response to CO2 and may be specific to those involved in the hypoxic 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.

Synthetic surfactant

The mortality reductions after prophylactic and rescue use of synthetic and animal surfactants are identical, so the critical issue in surfactant replacement is safety, not efficacy. Synthetic surfactant has been shown to reduce both BPD and IVH, whereas animal surfactants have not. The reduction in the former may be related to synthetic surfactant's more sustained effect on lung function, and the reduction in the latter may be due to synthetic surfactant's slower onset of action. Synthetic surfactant carries no known antigenic or infectious risks, and does not increase the incidence of sepsis. For these reasons, synthetic surfactant is a particularly attractive therapeutic option for premature infants in need of surfactant replacement.

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.

Production of germ-line chimeras in zebrafish by cell transplants from genetically pigmented to albino embryos

To determine whether embryonic cells transplanted from one zebrafish embryo to another can contribute to the germ line of the recipient, and to determine whether pigmentation can be used as a dominant visible marker to monitor cell transplants, we introduced cells from genetically pigmented (donor) embryos to albino recipients at midblastula stage. By 48 hr many of the resulting chimeras expressed dark pigment in their eyes and bodies, characteristics of donor but not albino embryos. By 4-6 weeks of age pigmentation was observed on the body of 23 of 70 chimeras. In contrast to fully pigmented wild-type fish, pigmentation in chimeras appeared within transverse bands running from dorsal to ventral. Pigmentation patterns differed from one fish to another and in almost every case were different on each side of a single fish. At 2-3 months of age chimeras were mated to albino fish to determine whether pigmented donor cells had contributed to the germ line. Of 28 chimeric fish that have yielded at least 50 offspring each, 5 have given rise to pigmented progeny at frequencies of 1-40%. The donor cells for some chimeras were derived from embryos that, in addition to being pigmented, were transgenic for a lacZ plasmid. Pigmented offspring of some germ-line chimeras inherited the transgene, confirming that they descended from transplanted donor cells. Our ability to make germ-line chimeras suggests that it is possible to introduce genetically engineered cells into zebrafish embryos and to identify the offspring of these cells by pigmentation at 2 days of age.