Surfactant Replacement Therapy
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Direct answer
Surfactant replacement therapy instils exogenous surfactant into the lungs of preterm infants with respiratory distress syndrome, a disease caused by surfactant deficiency. It reduces alveolar collapse, improves oxygenation and lowers the need for prolonged mechanical ventilation and the risk of air leak. Natural animal-derived preparations are preferred over synthetic ones in most neonatal units.
What you must remember
- Indication: respiratory distress syndrome in a preterm infant, with an oxygen requirement and a classic ground-glass radiograph with air bronchograms.
- Prophylaxis: given soon after birth to very preterm infants, usually below 28 weeks (the threshold varies with unit policy and antenatal steroid cover), who are intubated.
- Natural preparations: beractant, poractant alfa and calfactant, derived from animal lungs and containing surfactant proteins B and C.
- Synthetic preparations: lab-made agents that lack animal-derived proteins or use peptide mimics, and generally have less supporting evidence.
- LISA: less invasive surfactant administration, given through a thin catheter to a spontaneously breathing infant on CPAP, avoiding intubation.
- INSURE: intubate, give surfactant, extubate promptly and support the infant with nasal CPAP.
- Complications: bradycardia and desaturation during instillation, pulmonary haemorrhage, pneumothorax and blockage of the endotracheal tube.
- Antenatal link: antenatal corticosteroids given before an anticipated preterm birth reduce the need for surfactant.
Giving surfactant in practice
A 28-week infant is born with grunting, subcostal recession and an oxygen requirement, and the chest radiograph shows a ground-glass pattern. The decision is confirmed, and the route is chosen, before the first dose is drawn up.
- Confirm the diagnosis: check for the typical signs and radiograph changes, because surfactant helps when deficiency is the cause of distress.
- Choose the route: use intubation for prophylaxis or rescue, or LISA where the infant can breathe spontaneously on CPAP.
- Instil the dose: give the measured dose in aliquots, repositioning the infant between them, as the product instructions require.
- Monitor during and after: watch heart rate and saturations closely, since bradycardia and desaturation are common during instillation.
- Wean support early: reduce oxygen and ventilatory pressures as soon as the infant improves, to limit lung injury.
- Watch for complications: check for pneumothorax, pulmonary haemorrhage and blocked tubes in the hours that follow.
Where the exam tries to catch you
Surfactant is a targeted therapy, and the MCQs test its boundaries.
- Trap: giving surfactant to a term baby with pneumonia or meconium aspiration. Correct: surfactant is indicated for the deficiency of prematurity, and its benefit in term infants is not established.
- Trap: choosing a synthetic preparation for its purity. Correct: natural preparations containing surfactant proteins B and C have stronger evidence and are preferred for most preterm infants.
- Trap: believing that surfactant alone is curative. Correct: it supports the lung, but ventilation, oxygen and antenatal steroids remain part of management.
Frequently asked questions
Which infants are the usual candidates for surfactant replacement therapy?
Preterm infants with respiratory distress syndrome are the usual candidates, most often those born below 30 weeks who need oxygen or ventilation. Ground-glass changes on the chest radiograph support the diagnosis. Surfactant may be given as prophylaxis or as rescue treatment.
What is the difference between natural and synthetic surfactant?
Natural surfactants such as poractant alfa, beractant and calfactant are extracted from animal lungs and contain surfactant proteins B and C. Synthetic surfactants are lab-made and either lack these proteins or use peptide mimics. Natural preparations have stronger evidence in preterm infants.
What is LISA and why is it used?
LISA stands for less invasive surfactant administration, in which surfactant is given through a thin catheter to a spontaneously breathing infant on CPAP. It avoids intubation and mechanical ventilation, which reduces ventilator-associated lung injury. The approach is useful for infants who can be supported without a ventilator.
What complications can follow surfactant administration?
Bradycardia and desaturation during instillation are the common immediate problems. Pulmonary haemorrhage, pneumothorax and blockage of the endotracheal tube can also occur. Heart rate and oxygen saturation are monitored closely for the first hours after the dose.