Surfactant replacement therapy is a life-saving treatment method used in preterm infants who were born with a surfactant deficiency. This type of therapy is often used to treat or prevent respiratory distress syndrome (RDS).
In this article, we will provide you with a general overview of surfactant replacement therapy including what it is, how it works, and when it is indicated.
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What is Surfactant?
Surfactant is a substance that forms a layer over the surface of the alveoli in the lungs. It plays an essential role in reducing surface tension and preventing alveolar collapse.
Without this substance, it becomes difficult for the lungs to expand, which causes breathing problems for infants.
The production of surfactant begins during development between 24 and 35 weeks of gestation. Therefore, if an infant is born prematurely, the production of surfactant is often inhibited.
In this case, it means that the infant must receive surfactant from outside of the body.
What is Surfactant Replacement Therapy?
Surfactant replacement therapy is a treatment modality that is often used in preterm infants with surfactant deficiency.
It involves the deliverance of exogenous surfactant, which is a lipoprotein that acts to decrease the surface tension at the air-liquid interface in the alveoli. This, in turn, prevents alveolar collapse, improves expansion, and increases lung compliance.
Surfactant replacement therapy is used to treat respiratory distress syndrome (RDS), which is a condition in preterm infants born less than 28 weeks gestational age that results in a surfactant deficiency.
Infants with this condition require the administration of exogenous surfactant until their lungs mature enough to produce it on their own.
Surfactant Replacement Therapy Practice Questions:
1. What two conditions does surfactant replacement therapy prevent and treat?
Infant Respiratory Distress Syndrome (IRDS) and Hyaline Membrane Disease (HMD).
2. What are two administration techniques of surfactant?
Prophylactic and rescue.
3. What type of surfactant technique is administered to at-risk infants immediately after birth?
Prophylactic.
4. What type of surfactant technique is administered to infants after they demonstrate signs and symptoms of RDS?
Rescue.
5. What are 6 adverse effects of surfactant replacement therapy?
Pneumothorax, bradycardia, hypotension, hypoxemia, hemorrhage, and apnea.
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6. How is surfactant replacement therapy administered?
It is instilled directly into the trachea and the infant is positioned to allow gravity to aid in distributing the surfactant throughout the lung.
7. What are 3 examples of surfactant?
Calfactant, beractant, and poractant alfa.
8. What is another name for surfactant calfactant?
Infasurf (Bovine).
9. What is another name for surfactant beractant?
Survanta (Bovine).
10. What is another name for surfactant poractant alfa?
Curosurf (Porcine).
11. What is pulmonary surfactant?
Pulmonary surfactant is a complex mixture of lipids and protein that lowers surface tension proportionally to alveolar size and prevents alveolar collapse during expiration.
12. What surfactant proteins are important components of innate immunity for inhaled pathogens?
A and D.
13. What underlies the pathophysiology of many respiratory disorders like RDS, ARDS, and Meconium Aspiration Syndrome (MAS)?
Surfactant deficiency, dysfunction, or inactivation.
14. Exogenous surfactant replacement therapy was successfully used to treat what?
Neonatal RDS.
15. Surfactant replacement therapy is also researching and investigating other patient populations like?
ARDS, asthma and cystic fibrosis.
16. What is the most abundant component of surfactant?
Dipalmitoylphosphatidylcholine (DPPC).
17. Surfactant inactivation and dysfunction have not been described in what disease?
Congenital heart disease.
18. Natural surfactant preparations come from what mammals?
Pigs, cows, and calves.
19. What air sac requires higher pressure to inflate, assuming similar surface tension?
The smaller sac.
20. What surfactant-associated protein deficiency is fatal in infancy without lung transplantation?
SP-B deficiency.
21. What surfactant proteins are important in defense against infection?
SP-A and SP-D.
22. What is the most common complication of surfactant administration in the pre-term neonate?
Hypotension.
23. What are the benefits of surfactant replacement therapy in infants with RDS?
Reduction in the severity of RDS and reduction in the incidence of air leaks – pneumothorax and pulmonary interstitial emphysema.
24. What component of natural surfactant increases efficacy compared with synthetic surfactants?
Percentage of DPPC.
25. What radiographic findings are typical of a child with RDS?
Atelectasis, air bronchograms, and ground glass pattern.
26. What does surfactant therapy treat?
It treats and reduces respiratory distress syndrome.
27. What are examples of surfactant therapy drugs?
Beractant, calfactant, and poractant alfa.
28. What is Beractant?
Decreases alveolar surface tension & stabilizes alveoli.
29. What is Calfactant?
Pre-ventilatory treatment or post-ventilatory treatment. Source- from calf lung.
30. What is Poractant Alfa?
Rescue treatment. Source- porcine lung surfactant.
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31. Describe the administration of surfactant drugs?
It is administered via the endotracheal tube. Head should be elevated and do not suction for 2 hours after giving.
32. When should a surfactant be discontinued?
If child dusky, agitated, bradycardic, O2 sat less than 95%, and CO2 less than 30 mm Hg.
33. What is the function of surfactant?
It reduces surface tension and increases lung compliance. Also, the physiological condition is maintained by a normal surfactant level.
34. What is the composition of surfactant?
Type II pneumocytes produce surfactant– 90% lipids and 10% protein.
35. What is the most important component of surfactant?
DPPC (Dipalmitoylphosphatidylcholine).
36. If there were no surfactant, what two things would happen?
Without surfactant every breath would require a considerable amount of pressure to expand the lung with each inspiration ( -80 to -90 cmH20). The lungs would rapidly collapse during exhalation.
37. What should be given to expectant mothers who are in the 24th-34th week of pregnancy who are at risk of preterm delivery within 7 days?
Systemic corticosteroids.
38. How do you determine lung maturity?
Measurement of phospholipids in the amniotic fluid help determine fetal lung maturity.
39. What is the best measurement to determine lung maturity?
PG– PG and lecithin increase while sphingomyelin decrease during lung gestation.
40. What are the benefits of administering prophylactic surfactant replacement therapy to preterm infants in the first 15 minutes of birth?
It decreases the risk of mortality, reduces the threat of pneumothorax, and reduces the risk of developing interstitial emphysema.
41. What is the beginning dose and delivery of surfactant?
75-100 ml/kg given through the ETT which delivers as fast as possible while turning the newborn.
42. What should be monitored during the administration of surfactant?
Heart rate, oxygenation (cyanosis, bradycardia, reflux, airway obstruction), and presence of surfactant in ETT.
43. What is included in synthetic surfactants?
EXOSURF-
44. What is included in modified natural surfactants?
Survanta, Infasurf, and Curosurf.
45. What are the inactivators of surfactant?
Pulmonary hemorrhage, meconium aspiration syndrome, and pneumonia and sepsis.
46. What are the findings from use of surfactant?
Congenital diaphragmatic hernia (very little benefit from surfactant), Extracorporeal membrane oxygenation (could
47. What does surfactant do?
It keeps alveoli from collapsing.
48. When must surfactant be given?
Within the 1st hour and before
49. How is surfactant given?
Usually through the ET tube.
50. How often is surfactant given?
4 times within a 24-hour period.
51. How will you confirm that the lungs are open?
Chest X-ray.
52. What else may be needed in addition to surfactant?
C-pap machine or intubation.
53. What is surfactant made up of?
95% phospholipid – mixture and 5% protein.
54. Where is surfactant made and stored?
Type II alveolar cells – electron-dense bodies (lamellar bodies) where surfactant is stored in a highly structured way before being secreted.
55. What is the non-polar tail of phospholipids and what is it derived from?
Carbon chain length up to 18. It is derived from glucose and/or glycerol.
56. What are some examples of polar phospholipid heads?
Choline, Inositol, Serine, Glycerol, and Ethanolamine.
57. What proteins are found in surfactant?
SP-A, B, C, and D.
58. What is the use of SP-A and D?
Regulatory and host defense. Large hydrophilic.
59. What is the use of SP-B and C?
Formation and stabilization of phospholipid monolayer. Small lipophilic.
60. How is the monolayer formed?
In lamellar bodies, it needs to be broken into tubular myelin which needs SPA, B and Ca2+. SPA, B and C form monolayer.
61. What is the phospholipid turnover rate?
3-11 hours.
62. What happens to phospholipids just before degradation?
Taken up by type II cells. Transported to ciliated airways due to surface tension gradients.
63. What degrades phospholipids?
Extracellular enzymatic activity e.g. macrophages.
64. What happens after phospholipid degradation?
Macrophage phagocytosis. Epithelial reabsorption into either lymph or blood.
65. What does surfactant do?
Phospholipids moving into the surface layer aren’t attracted to each other, so they reduce surface tension (intermolecular forces between water molecules).
66. What is compliance defined as?
The degree to which the lung will distend per unit change in pressure.
67. What are some of the key functions of surfactant?
Fluid balance, Host defense, and Compliance. It also reduces
68. What does surfactant do in terms of fluid balance?
Reduces the tendency for fluid to be sucked into airspace.
69. How does surfactant maintain fluid balance?
Rigid alveoli structure wants to collapse – creates slightly negative pressure around it which creates a hydrostatic pressure gradient to draw fluid into the lung.
70. What does surfactant do in terms of host defense?
Movements of particulate matter towards ciliated regions
71. How are the surfactant proteins involved in host defense?
Both SPA and D bind to pathogens to promote action of macrophages in an immune response.
72. What condition is surfactant involved in premature infants?
NRDS – neonatal respiratory distress syndrome.
73. What infectious diseases is surfactant involved in?
Pneumonia, HIV (pneumocystis carinii pneumonia), and pulmonary edema.
74. What obstructive lung diseases is surfactant involved in?
Asthma, bronchiolitis, and COPD.
75. What congenital diseases is surfactant involved in?
Cystic fibrosis and surfactant protein B deficiency (lethal).
76. What non-specific respiratory diseases is surfactant involved in?
ARDS – acute respiratory distress syndrome.
77. What happens in NRDS?
High pressure but low volume inhaled at birth. Hyaline membrane disease destroys the membranes.
78. What was used in the 70s for NRDS?
Specialized neonatal ventilators.
79. What was a key development in NRDS?
Antenatal steroids.
80. What was introduced in the 90s for NRDS?
Exogenous pulmonary surfactant therapy.
81. What is the brand name of calfactant?
Infasurf.
82. What is the brand name of poractant alpha?
Curosurf.
83. What is the brand name of beractant?
Survanta.
84. Which surfactant is a modified natural surfactant?
Beractant.
85. Which surfactant is from a calf?
Calfactant.
86. Which surfactant is from porcine?
Poractant alpha.
87. Which surfactant is from bovine?
Beractant.
88. Which surfactant cannot be used for prophylaxis?
Poractant alpha.
89. At what age can you use calfactant for prophylaxis?
Less than 29 weeks.
90. At what weight can you use beractant for prophylaxis?
1,250 g.
91. What is the recommended dose of calfactant?
3 mL/kg.
92. What is the recommended dose of poractant?
2.5 mL/kg.
93. What is the recommended dose of beractant?
4 mL/kg.
94. Which surfactant is recommended to be used within 30 minutes of birth?
Calfactant.
95. Which surfactant is recommended to be used within 15 minutes of birth?
Beractant.
96. Which surfactant has an age limit associated with rescue therapy?
Calfactant (less than or equal to 72 hours of age).
97. Which surfactant can be administered through side-port of ETT adapter via ventilator?
Calfactant.
98. In which surfactant is warming to room temperature not necessary?
Calfactant.
99. In which surfactant may gentle swirling of the vial be necessary?
Calfactant.
100. Which surfactant is the least expensive?
Calfactant.
Final Thoughts
Surfactant is a substance that is produced by the body to prevent alveolar collapse and improve lung expansion. When an infant is born prematurely, they may not have developed the ability to produce surfactant on their own.
In this case, exogenous surfactant must be administered in order to prevent respiratory distress syndrome.
This requires the administration of surfactant replacement therapy, which is often performed by respiratory therapists. Be sure to check out our guide on fetal lung development if you want to learn more. Thanks for reading!
Written by:
John Landry is a registered respiratory therapist from Memphis, TN, and has a bachelor's degree in kinesiology. He enjoys using evidence-based research to help others breathe easier and live a healthier life.
References
- Faarc, Walsh Brian PhD Rrt-Nps Rrt-Accs Rpft. Neonatal and Pediatric Respiratory Care. 5th ed., Saunders, 2018.
- Faarc, Kacmarek Robert PhD Rrt, et al. Egan’s Fundamentals of Respiratory Care. 12th ed., Mosby, 2020.
- “History of Pulmonary Surfactant Replacement Therapy for Neonatal Respiratory Distress Syndrome in Korea.” PubMed Central (PMC), 1 July 2019, www.ncbi.nlm.nih.gov/pmc/articles/PMC6597488.
- Stevens, Timothy. “Surfactant Replacement Therapy.” PubMed, May 2007, pubmed.ncbi.nlm.nih.gov/17494810.
- Banerjee, Sujoy. “Surfactant Replacement Therapy for Respiratory Distress Syndrome in Preterm Infants: United Kingdom National Consensus.” PubMed, July 2019, pubmed.ncbi.nlm.nih.gov/30780152.