At what gestational age are preterm infants most responsive to exogenous surfactant (surfactant) therapy for respiratory distress syndrome (RDS)?

From the Guidelines

Preterm infants born between 26-30 weeks gestational age are most responsive to exogenous surfactant therapy for respiratory distress syndrome (RDS). This gestational age range is most beneficial for surfactant replacement therapy as it reduces the incidence and severity of respiratory distress syndrome, air leaks, and mortality in preterm infants with surfactant deficiency, as shown in a study published in Pediatrics 1. At this gestational age range, infants have sufficient lung development to benefit from surfactant replacement but typically lack adequate endogenous surfactant production.

Key Considerations

• Surfactant therapy is most effective when administered early, ideally within the first 2 hours of life, with preparations like beractant (Survanta), poractant alfa (Curosurf), or calfactant (Infasurf) at their respective recommended doses.
• Infants born before 26 weeks can still benefit from surfactant, but they often have additional complications from extreme prematurity that may limit the response.
• Infants born after 30 weeks typically have more mature lungs with better surfactant production, reducing the need for exogenous therapy.
• The effectiveness of surfactant in the 26-30 week range is due to the developmental timing of type II pneumocytes, which begin producing surfactant around 24 weeks but don't reach sufficient production levels until later in gestation, as supported by the findings of a study on surfactant-replacement therapy for respiratory distress in the preterm and term neonate 1.

Surfactant Mechanism and Benefits

• Surfactant works by reducing surface tension in the alveoli, preventing atelectasis, improving lung compliance, and enhancing gas exchange.
• Surfactant replacement has been shown to decrease respiratory morbidity and mortality in preterm infants with surfactant deficiency, and both animal-derived and synthetic surfactants are effective in reducing adverse respiratory outcomes 1.
• Antenatal steroid exposure can also decrease mortality, the severity of respiratory distress syndrome, surfactant use, and intraventricular hemorrhage in infants born at less than 34 weeks’ gestation, and may reduce the need for prophylactic and early rescue surfactant replacement in infants born after 27 to 28 weeks’ gestation 1.

From the Research

Gestational Age and Responsiveness to Surfactant Therapy

The responsiveness of lungs to surfactant therapy in preterm infants is closely related to their gestational age. Studies have shown that preterm infants born at a gestational age of less than 30 weeks are more likely to benefit from surfactant therapy 2.

Surfactant Therapy in Preterm Infants

• Preterm infants with respiratory distress syndrome (RDS) born at 28-36 weeks of gestation have been shown to benefit from surfactant therapy, with improved clinical outcomes and reduced hospitalization time 3.
• A study comparing surfactant administration via thin catheter with intubation and surfactant administration found that the thin catheter method reduced the risk of death or bronchopulmonary dysplasia (BPD) at 36 weeks' postmenstrual age 4.
• Surfactant therapy has been shown to be effective in preterm infants with mild to moderate RDS, with a significant reduction in the need for mechanical ventilation and improved ventilatory index and a/A PO2 ratio 5.

Gestational Age and Surfactant Responsiveness

• Preterm infants born at a gestational age of less than 32 weeks appear to benefit more from surfactant therapy, with rapid weaning of FiO2 and decreased mortality 6.
• A study found that surfactant therapy was 70% effective in improving respiratory failure in near-term or term newborns with acute RDS 6.
• The optimal gestational age for surfactant therapy is not well established, but studies suggest that preterm infants born at 28-32 weeks of gestation may be the most responsive to surfactant therapy 2, 4.

Methods of Surfactant Administration

• Surfactant administration via thin catheter has been shown to be a effective method of surfactant delivery, with reduced risk of death or BPD and less intubation in the first 72 hours 4.
• The INtubation, SURfactant administration, and Extubation (INSURE) technique has also been shown to be effective, but may be associated with more side effects than surfactant administration via thin catheter 3.