Chapter 4 Respiratory Distress Syndrome

Introduction

  • Respiratory distress syndrome (RDS) is a condition in which a newborn presents with respiratory distress due primarily to a pulmonary surfactant deficiency. The chest X-ray has a characteristic “ground glass” or reticulogranular appearance.

Epidemiology

  • Earlier the child is born, higher the incidence of Respiratory distress syndrome, In other words, The incidence increases with increasing prematurity because synthesis of surfactant by Type II pneumocytes begins at 24-28 weeks gestation.

Risk Factors

  • Prematurity
    • at risk since development of Type II pneumocytes has not yet occured
  • Sepsis
    • at risk due to surfactant inactivation
  • Infants of diabetic mothers
    • at risk due to delayed maturation of Type II pneumocytes.
  • Hypoxic Ischemic Encephalopathy
    • at risk due to possible injury to the pneumocytes.

Pathophysiology

  • The role of pulmonary surfactant is to reduce alveolar surface tension - maintaining an inflated, stable alveolus. Deficiency of surfactant results in progressive alveolar collapse (atelectasis) and decreased lung compliance. Hypoxemia results from VQ mismatch. Diffuse atelectasis leads to lung inflammation, injury and possible pulmonary edema.

Clinical Presentation

  • At birth, infants present with respiratory distress (tachypnea, nasal flaring, grunting and retractions) and cyanosis. Breath sounds may be diminished. Without treatment, symptoms worsen over the first 48-72 hrs of life.

Diagnostic Evaluation

  • Blood gas – usually reveals hypoxemia and acidosis
  • CXR: classic appearance is “ground glass” – a fine, uniform, diffuse reticulogranular pattern with air bronchograms – representing diffuse microatelectasis

Management

  • Surfactant replacement (For patients on non-invasive support consider intubation for >40% FiO2 needs with ground glass appearance on Xray for surfactant administration)
    • Curosurf Initial dose 2.5 ml/kg of BirthWeight. Two repeat doses of 1.25 ml/kg birth weight may be administered at approximately 12-Hour intervals.
    • Survanta 4 mL/kg via ETT Q6hrs as needed up to 4 doses (if FiO2 > 0.4)
  • Respiratory support – Most require mechanical ventilation or NCPAP. The goal is to use lowest but adequate pressures possible to avoid air leak syndromes (i.e. pnemumothorax)
  • Fluid/Nutrition – IVF/TPN support should be provided until enteral feeds can be established
  • Empiric antibiotics – Treat with ampicillin and gentamicin while awaiting culture results

Prognosis RDS accounts for 20% of neonatal deaths. Outcome is related to BW. Under 750grams, many will develop bronchopulmonary dysplasia (BPD)/chronic lung disease (CLD) and there is higher risk of advanced retinopathy of prematurity (ROP). In infants born >1000 grams, fewer will have BPD and there is lower risk of advanced ROP.