PULMONARY CAUSES
Common
Transient tachypnoea of the newborn – Caused by delay in the resorption of lung fluid and is more common after birth by C-section. CXR may show fluid in the horizontal fissure and additional ambient oxygen may be required. Condition usually settles within first day of life but can take several days to resolve completely.
Less common
Meconium aspiration – Meconium is passed before birth by 8-20% of babies. Rarely passed by preterm infants and occurs increasingly the greater the gestational age, affecting 20-25% of deliveries by 42 weeks. Asphyxiated infants may start gasping and aspirate meconium before delivery. Meconium is a lung irritant and results in both mechanical obstruction and a chemical pneumonitis. In meconium aspiration the lungs are overinflated, accompanied by patches of collapse and consolidation.
Pneumonia – Prolonged rupture of the membranes, chorioamnionitis and low birthweight predispose to pneumonia. In this kind of case, we usually start broad spectrum antibiotics early
Pneumothorax – May occur spontaneously in up to 2% of deliveries. May occur secondary to meconium aspiration, RDS or as a complication of ventilation
Milk aspiration – More frequently in preterm infants and those with respiratory distress or neurological damage. Babies with bronchopulmonary dysplasia often have gastro-oesophageal reflux, which predispose to aspiration
Persistent pulmonary hypertension of the newborn – This life-threatening condition is usually associated with birth asphyxia, meconium aspiration, septicaemia, or respiratory distress syndrome. As a result of high pulmonary vascular resistance, there is right-to-left shunting within the lungs and at atrial and ductal levels. Cyanosis occurs soon after birth. CXR may show pulmonary oligaemia. Most infants require mechanical ventilation and circulatory support in order to achieve adequate oxygenation. Inhaled nitric oxide, a potent vasodilator, is often beneficial. Extracorporeal membrane oxygenation (ECMO), where infant is placed on heart and lung bypass for several days, in indicated for severe cases.
Other rare causes
Diaphragmatic hernia, Tracheo-oesophageal fistula, Pulmonary hypoplasia, Airways obstruction, Pulmonary haemorrhage
NON-PULMONARY
Congenital heart disease, Intracranial birth trauma, Encephalopathy, Severe anaemia, Metabolic acidosis
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