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BACKGROUND: Animal-derived, protein-containing surfactants seem to be superior to protein-free surfactants. Lucinactant, a synthetic surfactant containing a surfactant protein-B peptide analog, has been shown to be effective in animal models and phase II clinical trials. To date, lucinactant has not been compared with an animal-derived surfactant in a premature animal model. OBJECTIVE: The objective was to compare the acute and sustained effects of lucinactant among premature lambs with respiratory distress syndrome (RDS) with the effects of a natural porcine surfactant (poractant-alpha). METHODS: After 5 minutes of mechanical ventilation twin premature lambs were assigned randomly to the lucinactant group (30 mg/mL, 5.8 mL/kg) or the poractant-alpha group (80 mg/mL, 2.2 mL/kg). Heart rate, systemic arterial pressure, arterial pH, blood gas values, and lung mechanics were recorded for 12 hours. RESULTS: Baseline fetal pH values were similar for the 2 groups (pH 7.27). After 5 minutes of mechanical ventilation, severe RDS developed (pH: <7.08; Paco2: >80 mm Hg; Pao2: <40 mm Hg; dynamic compliance: <0.08 mL/cm H2O per kg). After surfactant instillation, similar improvements in gas exchange and lung mechanics were observed for the lucinactant and poractant-alpha groups at 1 hour (pH: 7.3 +/- 0.1 vs 7.4 +/- 0.1; Paco2: 8 +/- 18 mm Hg vs 40 +/- 8 mm Hg; Pao2: 167 +/- 52 mm Hg vs 259 +/- 51 mm Hg; dynamic compliance: 0.3 +/- 0.1 mL/cm H2O per kg vs 0.3 +/- 0.1 mL/cm H2O per kg). The improvements in lung function were sustained, with no differences between groups. Cardiovascular profiles remained stable in both groups. CONCLUSIONS: Among preterm lambs with severe RDS, lucinactant produced improvements in gas exchange and lung mechanics similar to those observed with a porcine-derived surfactant. [ABSTRACT FROM AUTHOR]

Objective: Extracorporeal membrane oxygenation (ECMO) is a technique used for cardiorespiratory support in the treatment of newborns with severe respiratory insufficiency. ECMO has not been used yet in newborns in Spain. The aim of this work was to develop an experimental veno-arterial ECMO model in newborn lambs for training the NICU medical and nursing staff before the clinical application of this technique., Material and Methods: Six newborn lambs were anesthetized, traqueotomized and connected to a neonatal ventilator. The right jugular vein and left carotid artery were cannulated and the catheters were located in the right atrium and aortic arch, respectively. A venous-arterial ECMO was performed during three hours, with an experimental ECMO circuit developed by us. Arterial pH and blood gases, systemic and airway pressures, heart rate, and rectal temperature were monitored., Results: The experimental ECMO circuit developed by use had a very low cost, but was capable of maintaining adequate gas exchange, acid-base balance and a normal rectal temperature., Conclusions: The development of an experimental ECMO model in newborn lambs may allow the establishment of an initial training program and to maintain the expertise of the NICU staff of a perinatal center planning to start an ECMO program.

Objective: Continuous hemofiltration is an extracorporeal technique used to eliminate water and solutes by convective transport through a hemofilter. The aim of this study was to develop an experimental model of arterio-venous and veno-venous continuous hemofiltration in order to gain experience before its clinical application in human neonates., Materials and Methods: Twelve white New Zealand adult rabbits were anesthetized, tracheotomized and connected to a continuous flow neonatal ventilator. Continuous arterio-venous hemofiltration (n = 6) was performed via catheters placed in the carotid artery and jugular vein and veno-venous hemofiltration (n = 6) by a double-lumen catheter located in the inferior vena cava. Heart rate, arterial pressure, pH and blood gases, and the volume of ultra-filtrate were monitored and recorded for a three hour period., Results: In both groups a high rate of ultrafiltration was achieved. The volume of ultrafiltration decreased somewhat during the second hour and remained stable thereafter. No hemodynamic changes were detected., Conclusions: The development of an experimental model for continuous arterio-venous and veno-venous hemofiltration in rabbits, facilitated the implantation of these techniques in human neonates. The model may be used to train the staff of the Neonatal Intensive Care Unit and to eliminate difficulties with vascular access and the care of extracorporeal lines.

From September 1989 to September 1990, a total of 25 newborn infants with severe RDS (on mechanical ventilation and with a FiO2 above 0.6) were treated with porcine surfactant (Curosurf), since its efficacy has been demonstrated in a prior clinical trial (Pediatrics 1988; 82: 683-91). The mean birth weight and gestational age were 1,327 +/- 566 g and 29.5 +/- 3.8 weeks, respectively. Twenty-four percent of the babies had an arterial pH below 7.1. At a mean postnatal age of 9.1 +/- 10.7 hours, a dose of 200 mg/Kg of Curosurf was given by the tracheal route. Mean paO2 rose from 47 +/- 14 mm Hg to 166 +/- 64 mm Hg (p less than 0.001). The paO2 increased in 24 of the 25 cases and in 20 (80%) the post-treatment paO2 was a least two times higher than the pre-treatment value. An hour after surfactant treatment, the paCO2 decreased from 58 +/- 21 mm Hg to 45 +/- 16 mm Hg (p less than 0.01) and the pH increased from 7.19 +/- 0.15 to 7.28 less than 0.11 (p less than 0.001). The following complications were observed: pulmonary interstitial emphysema (16%), pneumothorax (8%), patent ductus arteriosus (36%), intraventricular hemorrhage (28%) and bronchopulmonary dysplasia (24%). The neonatal survival rate and the survival rate after discharge from the hospital were 76% and 64%, respectively. The combined survival and absence of DBP was 32%. Nonsurvivors had lower birth weights and gestation ages, as well as lower paO2 5 min after treatment and higher FiO2 24 hours after surfactant treatment than did the survivors.

Pulmonary function was measured by computerized pneumotacography in 26 preterm-newborn infants without respiratory problems. Mean (+/- SD) for birth weight, gestation and postnatal age were 2,034 +/- 412 g, 34.1 +/- 1.7 weeks, and 2.2 +/- 1.6 days, respectively. An esophageal balloon, a differential transducer and nasal prongs were used to measure pressure and flow. The following parameters were measured in each respiration by the mean squares method: Dynamic compliance (Cdyn), total respiratory resistance (RRt) and work (WRt), respiratory time constant (KTt), rate (f) and maximal inspiratory and expiratory flows (PIF, PEF). Replication of the method was found to be good, as the differences between two determinations were not significant (p less than 0.05). The mean differences were less than 6.26%. The mean (+/- SD) and the 3rd and 97th percentiles for each parameter were the following: f: 52 +/- 7 (39-66) r.p.m., Tv: 6.6 +/- 1.1 (4.5-8.7) ml/kg, Vmin: 342 +/- 82 (128-502) ml/min, Cdin: 3.7 +/- 1.1 (1.5-6) ml/cm, RRt: 83 +/- 47 (37-204) cm/L/sec, TRt: 27 +/- 15 (2-57.1) g/cm/kg, PIF: 2.2 +/- 0.5 (1.1-3.2) L/min and PEF: 1.9 +/- 0.6 (0.7-3) L/min.