Meconium Aspiration Syndrome

Original Editor - User Name

Top Contributors - Safiya Naz and Vidya Acharya  

Introduction

The presence of meconium in the respiratory tract can lead to various complications, including atelectasis, hypoxemia, hypercapnia, persistent pulmonary hypertension (PPHN), inflammation, and surfactant inactivation. Prevention plays a critical role in the management of MAS, involving both prenatal and postnatal care

Epidemilogy

MAS primarily affects near-term, term, and post-term newborns, as meconium is rarely found in amniotic fluid before 34 weeks. Meconium-stained amniotic fluid (MSAF) occurs in 4–22% of births, with higher rates in post-term pregnancies. Only 3–12% of newborns with MSAF develop MAS, and among them, 20% are non-vigorous at birth, with some requiring mechanical ventilation. MAS accounts for 10% of neonatal respiratory failure. Incidence has declined in developed countries but remains a challenge in developing nations.

Pathophysiology

1. Inflammation and Infection: Bacterial endotoxins in MSAF can stimulate meconium passage and aspiration, causing MAS. In some cases, meconium is found in stillborn infants' lungs, indicating in utero aspiration due to hypoxia or infection.
2. Airway Obstruction: Meconium can partially or fully block airways, leading to air trapping, hyperinflation, or atelectasis, with complications like pneumothorax.
3. Surfactant Inactivation: Meconium interferes with lung surfactant, causing lung collapse and impaired gas exchange.
4. Inflammatory Response: Meconium triggers lung inflammation by attracting immune cells and releasing cytokines, which can cause chemical pneumonia and increase the risk of infection.
5. Persistent Pulmonary Hypertension (PPHN): PPHN affects 15–20% of MAS cases, worsening hypoxemia and increasing pulmonary resistance due to hypoxia and lung hyperinflation.

Management

• General Treatment: Infants with MAS are admitted to the NICU. Normothermia, metabolic correction, sedation with opioids, and targeted antibiotic use are critical.
• Respiratory Support: Oxygen therapy, CPAP, and mechanical ventilation (if needed) help manage respiratory distress. HFOV is used to prevent air leaks.
• Surfactant Therapy: Surfactant improves oxygenation and reduces the need for ECMO, though further research is required for long-term effects.
• Inhaled Nitric Oxide (iNO): iNO is used for pulmonary hypertension, enhancing oxygenation and reducing the need for ECMO.
• Steroids and Inotropes: Steroids improve outcomes, and inotropes support heart function in severe cases.
• ECMO and Hypothermia: ECMO is used when other treatments fail, and therapeutic hypothermia is given for asphyxiated infants.

Physical Therapy Management

• Chest Percussion:
  • This technique involves rhythmically tapping the chest with a cupped hand or fingers to help dislodge secretions from the lungs. The trapped air within the cupped hand softens the impact while creating a compression wave that helps loosen mucus, which then moves toward the airways for easier clearance.
• Chest Vibration:
  • Vibration is applied to the chest, either manually or mechanically, to loosen mucus in the airways. The rapid vibratory motion helps move the secretions from the smaller airways to the larger ones, making it easier for the patient to expel them.
• Postural Drainage:
  • In this technique, the patient is positioned so that gravity assists in draining mucus from the lungs. Specific positions are used to target different areas of the lungs, promoting effective mucus clearance from the bronchopulmonary segments.
• Suctioning:
  • Suctioning is often performed after chest physiotherapy to remove secretions that have been loosened. It is particularly useful for patients who are unable to cough effectively or clear mucus on their own.