Meconium aspiration syndrome
Background
- May cause meconium aspiration syndrome (MAS) in a newborn infant that was born through meconium-stained amniotic fluid (MSAF)
- The presentation can range from mild respiratory distress to life-threatening respiratory failure and to make the diagnosis the symptoms cannot be better explained otherwise.
- Incidence is 2-10% of infants born through MSAF
- Causes hypoxemia and acidosis via airway obstruction, chemical irritation/inflammation, infection, and surfactant inactivation
- Associated with persistent pulmonary hypertension of the newborn (PPHN)
Clinical Features
- Tachypnea
- Cyanosis
- Accessory muscle use (intercostal/subxiphoid retractions, paradoxical breathing, grunting, nasal flaring)
- Barrel-shaped chest
- Rales and rhonchi on lung auscultation
- Pneumothorax
- Pneumomediastinum
- Usually develop symptoms immediately after birth, but sometimes are born asymptomatic and develop symptoms as meconium moves into lower tracheobronchial tree
Differential Diagnosis
- Transient tachypnea of the newborn
- Sepsis
- Pneumonia
- Delayed transition from fetal circulation
- Pneumothorax
- Pulmonary edema
- Blood aspiration
Evaluation
- Clinical diagnosis based on the following:
- Evidence of meconium on infant
- Respiratory distress shortly after birth
- Characteristic CXR findings
- Initially, streaky, linear densities
- Next, development of hyperinflated lungs and flattened diaphragm
- Finally, diffuse patchy opacities (may appear similar to ARDS if severe)
- If intubation required, meconium visualized in trachea