- Clinical science
Neonatal respiratory distress syndrome (NRDS), or surfactant deficiency disorder, is a lung disorder in infants that is caused by a deficiency of pulmonary surfactant. It is most common in preterm infants, with the incidence and severity decreasing with gestational age. Surfactant deficiency causes the alveoli to collapse, resulting in impaired blood gas exchange. Symptoms manifest shortly after birth and include tachypnea, tachycardia, increased breathing effort, and/or cyanosis. The diagnosis is suspected based on clinical features and confirmed by evaluating the extent of atelectasis via chest x-ray. Blood gases show respiratory and metabolic acidosis in addition to hypoxia. Treatment primarily involves emergent resuscitative measures, which include nasal CPAP and stabilizing blood sugar levels and electrolytes. Additionally, intratracheal surfactant is administered if ventilation alone is not successful. Most cases resolve within 3–5 days of treatment. However, complications like hypoxemia, tension pneumothorax, bronchopulmonary dysplasia, sepsis, and neonatal death may still occur. NRDS can be prevented by administering antenatal glucocorticoids to the mother if premature delivery is expected.
- Pulmonary surfactant is a mixture of phospholipids and proteins produced by lamellar bodies of . These phospholipids reduce alveolar surface tension and thereby prevent the alveoli from collapsing.
- Surfactant production occurs early, at around 20 weeks' gestation. However, its distribution throughout the lungs begins around weeks 28–32 and does not reach sufficient concentration until week 35. Thus, any infant born before term is vulnerable to surfactant deficiency.
Surfactant deficiency → little or no reduction of alveolar surface tension → reduced pulmonary unfolding → atelectasis → decreased lung compliance and functional residual capacity → hypoxemia and hypercapnia
- Hypoxemia and hypercapnia → vasoconstriction of the pulmonary vessels (hypoxic vasoconstriction) and acidotic metabolism → intrapulmonary right-to-left-shunt → increased permeability due to alveolar epithelial damage → fibrinous exudation within the alveoli → development of hyaline membranes in the lungs (hyaline membrane disease)
- History of premature birth
- Onset of symptoms: usually manifests immediately after birth
Signs of increased breathing effort
- Nasal flaring and moderate to severe subcostal/intercostal and jugular retractions
- Typical expiratory “grunting”
- Auscultation: decreased breath sounds
- Cyanosis due to peripheral hypoxic vasoconstriction
- Chest x-ray: diffuse, fine, reticulogranular (ground-glass) densities, with low lung volumes and air bronchograms
- Blood gas analysis
- Prenatal testing for NRDS: Amniocentesis. Markers of fetal lung immaturity:
- Microscopic findings
- Lung hypoplasia
Transient tachypnea of the newborn (wet lung disease)
- Reversible respiratory disorder
- Most commonly occurs in full-term neonates delivered by cesarean section. These infants often have fluid-filled lungs.
- Diffuse crackles are heard on examination.
- X-ray shows fluid in the lung fissures and increased lung volumes.
- Treatment: supportive care (e.g., supplemental oxygen, neutral thermal environment, adequate nutrition)
- Meconium aspiration syndrome: Neonates with meconium aspiration are usually post-term rather than preterm infants
- Neonatal pneumonia
The differential diagnoses listed here are not exhaustive.
- Endotracheal administration of artificial surfactant within 2 hours postpartum
- Supportive measures: IV fluid replacement; stabilization of blood sugar levels and electrolytes
- Definition: chronic lung disease primarily found in premature infants exposed to prolonged mechanical ventilation and oxygen therapy for neonatal RDS
- Etiology: immature lung with exposure to ventilation → barotrauma, oxygen toxicity, inflammation
- Clinical features
- Therapy: controlled oxygenation, diuretics, consider glucocorticoids
- Cardiovascular arrest
- Neonatal sepsis
- Complications of O2 inhalation: retinopathy, bronchopulmonary dysplasia, and intraventricular hemorrhage.
We list the most important complications. The selection is not exhaustive.
- NRDS has a case fatality rate of 30% if not treated.
- Most cases that have been promptly treated resolve within 3–5 days of treatment.
- Prevent premature birth if possible. See in the Preterm labor and birth learning card.
- Antenatal corticosteroid therapy administered to the mother (stimulates infant )