Neonatal Respiratory Distress Syndrome

Introduction

Pathophysiology
- aka hyaline membrane disease
- immature fetal lungs have a deficiency in surfactant
- reduced surfactant results in low lung compliance and subsequent atelectasis, intrapulmonary shunting, and acute lung injury
Causes
- prematurity (most important)
  - type II pneumocytes not developed
    - normal source of surfactant production
- Cesarean section
  - lack of vaginal compression stress on the infant during delivery results in reduced fetal cortisol production and resultant reduction in surfactant production
- maternal diabetes
  - high insulin levels decrease surfactant production
increased fetal blood glucose results in increased fetal insulin production

Presentation

Symptoms
- dyspnea, tachypnea during first hours of life
- nasal flaring
- expiratory grunting,
- intercostal, subxiphoid retractions
Physical exam
- severe hypoxemia
  - not responsive to 100% O₂
    - atelectasis results in intrapulmonary (right-to-left) shunting
perfusion without ventilation

Evaluation

Treatment

Prevention
- corticosteroids given to mother between 23 and 34 weeks gestation at increased risk for preterm delivery within 7 days
  - results in increased surfactant production
Treatment
- nasal CPAP
surfactant replacement (endotracheal, so intubation is needed)

Complications

Bronchopulmonary dysplasia
- still very common
Patent ductus arteriosus
- normally closed by increased O₂tension at birth
  - hypoxia keeps shunt open
100% O₂ therapy damage
- free radical damage of eyes and lungs
  - may result in blindness and pulmonary dysplasia
- damage also when the neonate is taken off oxygen therapy
  - upregulation of VEGF due to relative hypoxia results in neovascularization in the retina (retinopathy of prematurity)