Surfactant Agents in Respiratory Therapy

Objectives

  • Define key terms related to surfactant agents.
  • List exogenous surfactant agents used in respiratory therapy.
  • Describe the mode of action for exogenous surfactant agents.
  • Discuss the route of administration for exogenous surfactant agents.
  • Recognize hazards and complications of exogenous surfactant therapy.
  • Assess the use of surfactant therapy.

Physical Principles

  • Surfactants are administered to replace missing pulmonary surfactant in respiratory distress syndrome (RDS) of newborns.
  • They regulate surface tension in films at gas-liquid interfaces, affecting how liquids behave.
  • Laplace's law describes the interrelationship of surface tension, drop or bubble size, and pressure.

What is a Surfactant?

  • A surfactant is a surface-active agent that reduces surface tension at liquid-gas interfaces.
  • Surface tension is the force of attraction between like molecules at the liquid surface.

Application to the Lung

  • Higher surface tension within alveoli can cause collapse or difficulty in opening;
  • Lowering surface tension helps ease alveolar opening.

Clinical Indications for Exogenous Surfactants

  • Treatment/Prevention of RDS:
    • Prophylactic: for very-low-birth-weight infants at risk of RDS.
    • Rescue: for infants already showing RDS symptoms.

Types of Exogenous Surfactant Preparations

  • Natural/Modified Natural Surfactants:
    • Beractant (Survanta)
    • Calfactant (Infasurf)
    • Poractant alfa (Curosurf)
  • Synthetic Surfactants:
    • Free from infectious contaminants, but may lack equivalent performance of natural surfactant proteins.

Specific Surfactant Agents

  • Beractant (Survanta): 4 mg/kg; indicated for prophylaxis up to 15 minutes after birth and rescue within 8 hours.
  • Calfactant (Infasurf): 3 mL/kg; indicated for prophylaxis no more than 30 minutes after birth and rescue for infants ≤72 hours old.
  • Poractant (Curosurf): 2.5 mL/kg; maximum total dose 5 mL/kg; indicated to reduce mortality and pneumothoraces in RDS.

Hazards and Complications of Surfactant Therapy

  • Potential complications include:
    • Airway occlusion, desaturation, bradycardia
    • High arterial oxygen values, overventilation, and apnea
    • Pulmonary hemorrhage

Future Directions in Surfactant Therapy

  • Investigational uses include:
    • Meconium aspiration syndrome
    • Acute respiratory distress syndrome (ARDS) in adults
    • Pneumonia
    • Aerosolization of surfactant

Monitoring During Surfactant Therapy

  • Monitor for cardiac rhythm, signs of airway occlusion, chest rise, and arterial oxygen saturation.
  • Maintain awareness to prevent hyperoxia and hypoxia.