Surfactant Therapy

Physiology And Rationale

• Term infants typically possess a robust surfactant storage pool of approximately 100 mg/kg.
• Preterm infants have a severely limited estimated pool of only 4 to 5 mg/kg at birth.
• Exogenous surfactant therapy acutely supplements these insufficient endogenous stores.
• It rapidly increases the pool size and improves pulmonary gas exchange.
• The therapy supports lung function until endogenous surfactant is adequately synthesized and released.

Types Of Surfactant Preparations

• Natural surfactants are clinically superior to synthetic variants.
• Animal-derived products contain surfactant proteins B and C which are essential for function.
• First-generation protein-free synthetic surfactants are obsolete and no longer used.

Comparison Of Common Natural Surfactants

Indications For Therapy

Primary Indication

• Respiratory distress syndrome (RDS) is the primary indication.
• It is indicated in neonates with increasing oxygen requirements (FiO2 >0.30) on optimal continuous positive airway pressure (CPAP).

Secondary Surfactant Inactivation

• Surfactant is frequently inactivated by blood, meconium, or inflammatory exudates.
• It is utilized as an adjunct therapy in meconium aspiration syndrome (MAS).
• Other indications include severe congenital pneumonia, pulmonary hemorrhage, and acute respiratory distress syndrome (ARDS).
• It is useful in persistent pulmonary hypertension of the newborn (PPHN) associated with underlying atelectasis.

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    %% Custom High-Contrast Styling Classes (Orange/Brown Theme)
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    classDef decisionPos fill:#E8F5E9,stroke:#2E7D32,stroke-width:2px,color:#1B5E20;
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    %% Initial Assessment Layout
    GA_Less[< 28 weeks*]
    GA_More[28 weeks or more]

    %% Left Pathway: Prophylactic Surfactant
    GA_Less --> Intubated[Intubation at birth or
No/ incomplete antenatal steroids*]
    Intubated --> Prophylactic[May consider prophylactic
surfactant after stabilization]

    %% Right Pathway: Respiratory Distress / Rescue Surfactant
    GA_Less --> RespDistress[Respiratory distress
at birth]
    GA_More --> RespDistress
    
    RespDistress --> CPAP[CPAP with FiO2
of 0.3 or more]
    RespDistress --> MechVent[Mechanical ventilation
with FiO2 of 0.3 or more]
    
    CPAP --> Rescue[Early rescue surfactant within 2 hours]
    MechVent --> Rescue

    %% Convergence Node
    Prophylactic --> StabilizationCheck
    Rescue --> StabilizationCheck

    StabilizationCheck[Good spontaneous respiration and
no hemodynamic instability]
    
    %% Stabilization Branching
    StabilizationCheck -->|Yes| Insure[Insure to
nasal CPAP]
    StabilizationCheck -->|No| ContinueVent[Continued on
mechanical ventilation]
    
    %% Final Re-evaluation
    Insure --> RepeatDose[Consider giving repeat dose after 12 hours of initial dose
If FiO2 0.4 or more or CPAP failure]
    ContinueVent --> RepeatDose

    %% Apply Themes
    class GA_Less,GA_More,Intubated,Prophylactic,RespDistress,CPAP,MechVent,Rescue,StabilizationCheck,Insure,ContinueVent,RepeatDose clinicalNode;

Strategies Of Administration

Prophylactic Surfactant

• Administered within 15 to 30 minutes of birth regardless of RDS signs.
• Recent evidence shows an increased risk of bronchopulmonary dysplasia (BPD) and mortality compared to selective administration.
• It is restricted to extreme preterm neonates (<28 weeks) who received no or incomplete antenatal steroids.
• It is also indicated if the neonate requires immediate intubation and mechanical ventilation for stabilization.

Early Rescue Surfactant

• Administered within 2 hours of life in an infant exhibiting features of RDS.
• Retained lung fluid in the early hours assists in the homogenous distribution of the surfactant.
• It prevents widespread atelectasis from becoming established.
• It reduces the risk of neonatal mortality, BPD, and air leak syndromes.

Late Rescue Surfactant

• Administered after 2 hours of life in neonates showing established RDS features.
• Frequently utilized in outborn neonates who face delayed transport to referral centers.

Methods Of Delivery

Conventional Endotracheal Administration

• The classic method requires endotracheal intubation.
• Rapid bolus administration is recommended over slow infusion.
• Rapid bolus ensures homogenous distribution and rapid improvement in oxygenation.

InSurE Technique

• InSurE stands for Intubate, Surfactant, Extubate.
• The infant is intubated solely for surfactant administration.
• Following a brief period of ventilation (usually <1 hour), the infant is rapidly extubated to CPAP.
• This minimizes ventilation-induced lung injury (VILI).

Less Invasive Surfactant Administration (LISA)

• LISA completely avoids conventional endotracheal intubation.
• Surfactant is instilled through a thin catheter (4-5 Fr) inserted into the trachea using Magill forceps.
• CPAP is maintained during the procedure to recruit alveoli and distribute the surfactant.
• LISA significantly reduces the composite risk of death or BPD and pneumothorax.
• Poractant alfa is preferred for LISA due to its smaller required volume.

Minimally Invasive Surfactant Therapy (MIST)

• MIST uses a slightly stiffer catheter (like an angiocath 16G).
• It avoids the need for Magill forceps during insertion.

Procedure And Dosing Nuances

Preparation Steps

• A physician or experienced nurse must administer the drug.
• The vial must be warmed prior to use (held in palms for 8 minutes or kept at room temperature for 20 minutes).
• Do not heat the vial or place it on a radiant warmer.
• Do not shake the surfactant.

Administration Technique

• The neonate must be monitored with a pulse oximeter continuously.
• Administer through a feeding tube inserted into the endotracheal tube or via a side port.
• Instill the dose as a bolus divided into four aliquots.
• Changing the infant's position between aliquots is unnecessary and avoided.
• Avoid endotracheal suctioning for at least 2 hours post-administration.

Dosing Parameters

• A minimum phospholipid dose of 100 mg/kg is required.
• Higher doses (200 mg/kg of poractant alfa) show superior reduction in mortality and BPD.

Criteria For Repeat Dosing

• Repeat doses are indicated if the infant still requires FiO2 >0.40 on CPAP or mechanical ventilation.
• Up to two additional doses (total three) may be administered.
• Surfactant may require redosing if inhibited by edema, soluble proteins, or inflammatory mediators.

Complications And Treatment Failures

Acute Adverse Effects

• Transient hypoxia and bradycardia often occur due to acute airway obstruction during instillation.
• Mucous plugging of the endotracheal tube and gagging may occur.
• Reflux of surfactant into the pharynx is a known procedural complication.
• Pulmonary hemorrhage risk increases (5-6% with natural surfactants) due to rapid compliance improvement and left-to-right shunting across the patent ductus arteriosus.

Differential Diagnosis Of Poor Response

• Infants failing to respond ("RDS plus") typically suffer from pre-existing or concurrent severe lung injury.
• Antenatal infections or postnatal volutrauma/barotrauma drastically reduce efficacy.
• Hemodynamic instability and shock impair the physiological response.
• Total anomalous pulmonary venous connection (TAPVC) mimics RDS radiologically but does not respond to surfactant.
• Genetic disorders of surfactant metabolism (SP-B, SP-C, or ABCA3 mutations) cause refractory respiratory failure indistinguishable from severe RDS.