Lesson 2

Respiratory Distress Syndrome (RDS)

  • Surfactant Production:

    • Initiated by type 2 pneumocytes between 22-26 weeks; peak at 35-36 weeks.

  • Risks:

    • Insufficient surfactant leads to RDS, hypoxemia, hypercarbia, mixed acidosis, hemodynamic instability, and death.

  • Preventive Treatment (Pre-Delivery):

    • Maternal corticosteroids (e.g., betamethasone) to expedite fetal lung maturity.

  • Post-Delivery Treatment:

    • CPAP, mechanical ventilation, and exogenous surfactant.

  • Monitoring:

    • Preductal & postductal oxygen saturation to check for pulmonary hypertension and cardiac shunts.

Surfactant and Alveolar Function

  • Functionality of Surfactant:

    • Reduces surface tension, preventing alveolar collapse as per Laplace's Law (P = 2T/R).

  • Surfactant Concentration:

    • Larger alveoli: lower surfactant concentration.

    • Smaller alveoli: higher surfactant concentration.

Diagnosis of RDS

  • Symptoms (Immediate after birth):

    • Grunting, tachypnea, retractions, nasal flaring.

    • Blood gas shows hypoxemia, hypercarbia, mixed acidosis.

  • Complications:

    • Progressive respiratory failure, hemodynamic instability, death.

Risk Factors for RDS

  • Low birth weight.

  • Low gestational age.

  • Oxygen toxicity.

  • Endotracheal intubation.

  • Barotrauma from ventilation.

  • Maternal diabetes.

Treatment Considerations

  • Corticosteroids:

    • Administer to laboring mothers with preterm fetal risk; effects peak at 48 hours.

  • Lecithin/Sphingomyelin (L/S) Ratio:

    • L/S ratio > 2 indicates adequate lung development; < 2 suggests increased RDS risk.

  • Post-Delivery Management:

    • Start with CPAP, may need mechanical ventilation and surfactant delivery via endotracheal tube.

Anesthetic Considerations

  • Oxygen Management:

    • Monitor SpO2; avoid hyperoxia to minimize risk of retinopathy of prematurity (ROP).

  • Oxygen Saturation Monitoring:

    • Use preductal (right upper extremity) and postductal monitoring (lower extremity) to assess circulation.

  • Arterial Lines:

    • Required for frequent ABG and hemodynamic assessment (preferably preductal).

  • Ventilation Risks:

    • Positive pressure ventilation increases pneumothorax risk.