A term newborn born to a mother with meconium-stained amniotic fluid develops respiratory distress within 2 hours of birth. Chest X-ray shows patchy infiltrates with hyperinflation. The infant is on supplemental oxygen and mechanical ventilation. What is the drug of choice for managing the underlying pulmonary inflammation and air trapping in meconium aspiration syndrome?

## Meconium Aspiration Syndrome (MAS): Pharmacological Management ### Pathophysiology of MAS Meconium aspiration causes: 1. Mechanical airway obstruction → air trapping and hyperinflation 2. Chemical pneumonitis → inflammatory cascade 3. Surfactant inactivation → increased surface tension 4. Ventilation-perfusion mismatch ### Role of Surfactant in MAS **Key Point:** Surfactant replacement therapy is the first-line pharmacological intervention in MAS because meconium directly inactivates endogenous surfactant. **High-Yield:** Meconium contains bile salts, free fatty acids, and proteins that bind to and denature pulmonary surfactant, reducing its surface-tension-lowering properties. ### Surfactant Replacement: Mechanism & Evidence | Aspect | Details | |--------|----------| | **Mechanism** | Restores surface tension properties; improves lung compliance; reduces work of breathing | | **Timing** | Early administration (within 6 hours) shows best outcomes | | **Evidence** | Reduces need for ECMO; decreases air leak syndromes (pneumothorax, pulmonary interstitial emphysema) | | **Dosing** | Standard neonatal surfactant dose: 100–200 mg/kg | ### Why Surfactant Over Other Options **Clinical Pearl:** Surfactant replacement addresses the PRIMARY pathophysiology of MAS—surfactant inactivation—whereas other agents are adjunctive or reserved for specific complications. ### Adjunctive Therapies (NOT first-line) - **Inhaled nitric oxide (iNO):** Reserved for refractory hypoxemia and suspected pulmonary hypertension; does not treat surfactant deficiency - **Systemic corticosteroids:** No proven benefit in acute MAS; not indicated - **Aminophylline:** Bronchodilator; not specific to MAS pathophysiology ### Supportive Management Alongside Surfactant 1. Gentle ventilation (permissive hypercapnia if needed) 2. High-frequency oscillatory ventilation (HFOV) for severe cases 3. Oxygen titration to target SpO₂ 90–95% 4. Consideration of iNO if hypoxemia persists despite surfactant + optimal ventilation **Mnemonic:** **SURF** = **S**urface tension reduction, **U**se early, **R**estores compliance, **F**irst-line in MAS. [cite:Nelson Textbook of Pediatrics 21e Ch 102]