A 6-hour-old term newborn (born through thick meconium-stained amniotic fluid) presents with severe respiratory distress (RR 95/min, severe intercostal and subcostal retractions, nasal flare), SpO₂ 78% on 60% FiO₂, and a blood gas showing pH 7.18, PaCO₂ 58 mmHg, PaO₂ 52 mmHg. Chest X-ray shows extensive bilateral infiltrates with hyperinflation. The infant is irritable and has poor perfusion. What is the most appropriate immediate next step in management?