Meconium Aspiration Syndrome (MAS)

Presentation

• Term or post-term infant with meconium-stained amniotic fluid
• Respiratory distress immediately after birth
• Barrel-shaped chest (gas trapping/hyperinflation)
• Yellow-green staining of skin, nails, and umbilical cord
• Signs of PPHN (severe cyanosis, labile oxygenation)

Initial Workup

• Chest X-ray: Coarse, patchy infiltrates with areas of hyperinflation or atelectasis, flattening of the diaphragm
• Blood gas analysis: Hypoxia, hypercarbia (mixed respiratory/metabolic acidosis)
• Echocardiogram: Essential to evaluate for concurrent PPHN (right-to-left shunting, right ventricular hypertension)
• Sepsis evaluation: Blood culture and empirical antibiotics (meconium inhibits bacteriostatic properties of amniotic fluid)

Management Framework

• Delivery Room: Routine neonatal resuscitation steps. Routine intrapartum/postpartum endotracheal suctioning is NO LONGER recommended unless the airway is obstructed.
• Respiratory support: CPAP, conventional ventilation, or HFOV (High-Frequency Oscillatory Ventilation) for severe cases to minimize barotrauma
• Surfactant therapy: Consider for severe MAS (acts as a meconium detergent and replaces inactivated surfactant)
• PPHN Management: Inhaled Nitric Oxide (iNO) if oxygenation index is high and echo confirms pulmonary hypertension
• ECMO: Consider early referral to ECMO center if failing maximum medical therapy (iNO + HFOV)

Advanced Respiratory & Ventilator Protocol

• Surfactant dosing (Poractant alfa): 2.5 mL/kg (200 mg/kg) initial dose, administer via INSURE or LISA method to minimize mechanical trauma.
• High-Frequency Oscillatory Ventilation (HFOV) starting parameters: MAP 1-2 cmH2O above conventional ventilation, Amplitude adjusted to achieve visible chest wiggle.
• Target SpO2 explicitly strictly to 90-95% for infants < 32 weeks to prevent Retinopathy of Prematurity.
• Provide aggressive tracheobronchial suctioning ONLY when clinically indicated by coarse breath sounds or desaturations, not routinely.
• Permissive hypercapnia: Allow PaCO2 up to 55-60 mmHg if pH remains > 7.25 to prevent barotrauma.

Standardized Discharge & Follow-Up Criteria

• Adequate weight gain explicitly > 15-30g/day over a continuous 3-5 day period.
• Maintenance of temperature in an open crib with standard clothing for 48 hours.
• Successful completion of the 90-120 minute Infant Car Seat Challenge.
• Caregiver successfully completed CPR training, rooming-in, and independent medication administration.
• Referrals placed for High-Risk Infant Follow-Up Clinic, Early Intervention (PT/OT), and appropriate sub-specialists.

Diagnostic & Management Algorithm

• MAS Ventilation Algorithm: [START] Thick Meconium + Respiratory Distress -> [ACTION] Intubate & Suction ONLY if non-vigorous -> [DECISION] Pulmonary Hypertension present? -> [YES] iNO + High Frequency Ventilation -> [NO] Standard lung protective ventilation

References

1. Vain NE, Szyld EG, Prudent LM, et al. Oropharyngeal and nasopharyngeal suctioning of meconium-stained neonates before delivery of their shoulders: multicentre randomised controlled trial. Lancet.
2. Dargaville PA, Copnell B. The epidemiology of meconium aspiration syndrome: incidence, risk factors, therapies, and outcome. Pediatrics.