Infasurf is a medication used to help premature infants breathe more easily. It is a lung surfactant derived from calf lungs, designed to treat or prevent respiratory distress syndrome (RDS) in these newborns. This treatment aims to improve lung function by addressing a natural deficiency often present in very early births.
Understanding Respiratory Distress Syndrome
Respiratory Distress Syndrome (RDS) is a breathing problem that commonly affects premature babies, appearing within hours of birth. It is caused by the underdeveloped state of a premature infant’s lungs, specifically their inability to produce enough natural lung surfactant. This deficiency is more pronounced in infants born at earlier gestational ages.
Natural lung surfactant is a complex mixture of fats (lipids) and proteins that lines the tiny air sacs in the lungs, called alveoli. Its main function is to lower the surface tension at the air-liquid interface within these alveoli. This reduction in surface tension prevents the alveoli from collapsing completely when an infant exhales, making it easier for them to inflate with each subsequent breath.
Without sufficient natural surfactant, the alveoli collapse after each breath, requiring the baby to exert significant effort to reopen them. This increased work of breathing can lead to hypoxemia (low blood oxygen), hypercarbia (high blood carbon dioxide), and respiratory acidosis. The widespread collapse of alveoli can also trigger inflammation and pulmonary edema, further complicating the infant’s ability to breathe and exchange gases effectively.
How Infasurf Aids Lung Function
Infasurf, also known as calfactant, is an intratracheal suspension extracted from calf lungs. This preparation contains phospholipids, neutral lipids, and specific hydrophobic surfactant-associated proteins, particularly SP-B and SP-C. Infasurf is designed to mimic the properties of natural surfactant to help premature infants with RDS.
When administered, Infasurf rapidly spreads across the air-liquid interface within the infant’s alveoli. By adsorbing to this surface, it effectively reduces the surface tension, similar to how natural surfactant functions. This action helps to stabilize the alveoli, preventing them from collapsing at the end of exhalation and allowing them to remain open for easier gas exchange.
The presence of Infasurf improves lung compliance, which refers to the lungs’ ability to stretch and expand. This makes it less difficult for the infant to breathe, reducing the overall work of breathing. Infasurf can restore the pressure-volume mechanics of surfactant-deficient lungs and improve respiratory gas exchange. It provides the necessary surface activity that the premature infant’s own lungs are unable to produce in adequate amounts.
Administering Infasurf and Expected Outcomes
Infasurf is administered directly into the infant’s lungs through an endotracheal tube, a tube inserted into the windpipe. This procedure is performed by clinicians experienced in the care of newborns with respiratory failure. The recommended dose is 3 mL per kilogram of the infant’s birth weight.
The medication can be given as a preventative measure within 30 minutes after birth for premature infants less than 29 weeks gestational age. For infants who have already developed RDS, Infasurf can be administered as a rescue treatment within 72 hours of age. Doses may be repeated every 12 hours, up to a total of three doses, depending on the infant’s response and needs.
Following Infasurf administration, rapid improvements in oxygenation and lung compliance are observed. This means the infant’s blood oxygen levels increase, and their lungs become more flexible, requiring less pressure to inflate. Due to these swift changes, careful monitoring of the infant’s oxygen therapy and ventilator settings is necessary to adjust support as their respiratory status improves. While Infasurf significantly aids breathing, it is a component of comprehensive neonatal intensive care, not a replacement for it.
During the administration procedure, some temporary observations may occur, such as changes in heart rate (bradycardia), a bluish tint to the skin (cyanosis), or temporary airway obstruction. There might also be a reflux of the medication back into the endotracheal tube. If any of these occur, the administration of Infasurf is temporarily paused, and appropriate measures are taken to stabilize the infant before continuing.