Perfluorochemical rescue after surfactant treatment: effect of perflubron dose and ventilatory frequency.

To test the hypotheses that perfluorochemical (PFC) liquid rescue after natural surfactant (SF) treatment would improve pulmonary function and histology and that this profile would be influenced by PFC dose or ventilator strategy, anesthetized preterm lambs (n = 31) with respiratory distress were studied using nonpreoxygenated perflubron. All animals received SF at 1 h and were randomized at 2 h as follows and studied to 4 h postnatal age: 1) conventional mechanical gas ventilation (n = 8), 2) 30 ml/kg perflubron with gas ventilation [partial liquid ventilation (PLV)] at 60 breaths/min (n = 8), 3) 10 ml/kg perflubron with PLV at 60 breaths/min (n = 7), and 4) 10 ml/kg perflubron with PLV at 30 breaths/min (n = 8). All animals tolerated instillation without additional cardiopulmonary instability. All perflubron-rescued groups demonstrated sustained improvement in gas exchange, respiratory compliance, and reduction in pressure requirements relative to animals receiving SF alone. Improvement was directly related to perflubron dose and breathing frequency; peak inspiratory pressure required to achieve physiological gas exchange was lower in the higher-dose and -frequency groups, and mean airway pressure was lower in the lower-frequency group. Lung expansion was greater and evidence of barotrauma was less in the higher-dose and -frequency group; regional differences in expansion were not different as a function of dose but were greater in the lower-frequency group. Regional differences in lung perflubron content were reduced in the higher-dose and -frequency groups and greatest in the lower-dose and -frequency group. The results suggest that, whereas PLV of the SF-treated lung improves gas exchange and lung mechanics, the protective benefits of perflubron in the lung may depend on dose and ventilator strategy to optimize PFC distribution and minimize exposure of the alveolar-capillary membrane to a gas-liquid interface.

Brain-stem auditory evoked responses to hypercarbia in preterm infants.

To determine the effect of acute hypercarbia on brain-stem function in preterm neonates, we compared brain-stem auditory evoked responses (BAERs) during 8% CO2 breathing to those elicited during room air breathing in 12 healthy preterm infants during the first week of life. End-tidal CO2 (ETpCO2), respiratory rate and depth were monitored throughout the protocol. Absolute wave latencies and interpeak intervals of the BAERs were analyzed from duplicate trials. During 8% CO2 breathing, ETpCO2, respiratory rate and depth of respiration increased significantly (P < 0.05). The absolute latency of wave V was prolonged (P < 0.025) in the hypercarbic state as compared to baseline. Interpeak interval III-V was also prolonged (P < 0.025). Values of absolute peak latencies I and III were unaffected by the hypercarbic state. These data demonstrate that elevations in pCO2 which elicit ventilatory responses also effect the BAER. The specific effects on ventilatory pattern, peak V latency and interpeak interval III-V indicate brain-stem responsiveness and alterations in the more central components of the auditory pathway. These findings raise important considerations regarding the influence of hypercarbia on brain-stem function in preterm infants and the clinical management of such infants with abnormalities of gas exchange.

Prophylactic administration of calf lung surfactant extract is more effective than early treatment of respiratory distress syndrome in neonates of 29 through 32 weeks' gestation.

OBJECTIVE: Although numerous trials have demonstrated the efficacy of exogenous surfactant for prophylaxis or treatment of neonatal respiratory distress syndrome (RDS), optimum timing of administration remains controversial. One previous study showed that administration of calf lung surfactant extract immediately following birth, to neonates born before 30 weeks postconceptional age, was preferable to delaying administration until after development of RDS. The current study was designed to test a similar hypothesis for babies born between 29 and 32 weeks gestational age. DESIGN: One thousand three hundred ninety-eight neonates with obstetric estimates of 29 through 32 weeks' gestation were randomized to receive CLSE at birth or to wait until development of mild RDS. After exclusions for malformations and other factors, data from 1248 were analyzed. RESULTS: Prophylaxis was associated with less development of moderate RDS (7% vs 12%), less need for retreatment (5% vs 9%), less need for mechanical ventilation or supplemental oxygen during the first 4 days, and fewer deaths or less requirement for supplemental oxygen at 28 days (5% vs 9%). Although 1-minute Apgar scores were significantly lower in the prophylaxis group, the difference disappeared by the 5-minute score and there was no difference in the incidence of asphyxia-related complications. Sixty percent of the neonates assigned to early treatment received endotracheal intubation and 43% received calf lung surfactant extract at a median age of 1.5 hours. When data were analyzed by gestational age and birth weight subgroups, most of the differences could be attributable to babies born at 30 weeks or less or weighing less than 1500 g, probably because of the higher incidence of surfactant deficiency in this more immature subgroup.

Plasma fibronectin concentrations in breast fed and formula fed neonates.

Plasma fibronectin concentration was measured in neonates of 2 to 5 days of age. Although breast fed and formula fed infants were similar in demographic characteristics, the mean (SD) plasma concentration of fibronectin in 26 breast fed infants, 237 (117) mg/l, was significantly higher than in 27 formula fed infants (171 (91) mg/l). Fibronectin was detected in five colostrum specimens (mean concentration 13.4 mg/l). Similar bands were detected after gel electrophoresis of purified adult plasma fibronectin and whole plasma from breast fed and formula fed neonates after staining or immunoblotting. Fibronectin isolated from breast milk also appeared similar to purified plasma fibronectin. It is possible, although unlikely, that fibronectin is absorbed intact from ingested colostrum. Alternatively, a factor(s) might be present in colostrum that contributes to the regulation of plasma fibronectin concentration.