Transient Tachypnoea Of The Newborn

Transient tachypnoea of the newborn (wet lung) is a self-limited respiratory distress syndrome of term and late preterm babies caused by delayed clearance of fetal lung fluid. It affects about 4 to 6 per 1000 term births and up to 1 to 2 percent of late preterm infants. Symptoms begin within 2 hours of birth, peak at 12 to 24 hours and resolve within 24 to 72 hours, and the prognosis is excellent.

• Mechanism: the fetal lung is fluid filled. At labour a catecholamine surge opens epithelial sodium channels and the fluid is reabsorbed. Birth by elective caesarean section without labour, or very rapid delivery, leaves interstitial and alveolar fluid that reduces compliance.
• Risk factors: elective caesarean section before labour (strongest), delivery at 35 to 38 weeks, maternal diabetes or asthma, male sex, macrosomia, maternal sedation, perinatal asphyxia, family atopy.
• It is a diagnosis of exclusion. Sepsis, pneumonia, respiratory distress syndrome, meconium aspiration, pneumothorax, congenital heart disease, persistent pulmonary hypertension and diaphragmatic hernia must be considered.
• Some affected children have transient wheeze in later infancy.

• Respiratory rate above 60 per minute (often 80 to 120), nasal flaring, grunting, mild subcostal and intercostal retraction, mild cyanosis that corrects with low flow oxygen. Air entry is good, with occasional fine crackles. The infant is alert and active.
• Gradual improvement over 24 to 48 hours without deterioration.
• Red flags: worsening distress or rising oxygen requirement after 6 hours; inspired oxygen above 0.4; apnoea; severe retractions; hypotension or poor perfusion; temperature instability; bilious vomiting; murmur or differential pulses; scaphoid abdomen (diaphragmatic hernia); meconium staining; maternal fever or prolonged membrane rupture (sepsis); grunting beyond 48 to 72 hours.

• Chest X-ray: prominent perihilar streaking (sunburst pattern), fluid in the horizontal fissure, small effusions, hyperinflation. It clears within 48 to 72 hours.
• Pulse oximetry, blood gas (normal or mild respiratory acidosis), blood glucose, full blood count, CRP and blood culture to exclude sepsis. Lung ultrasound (double lung point) is increasingly used.
• Echocardiography if cyanosis persists, there is a murmur or abnormal pulses, or oxygen need is out of proportion.
• Differentials: respiratory distress syndrome (preterm, ground glass appearance with air bronchograms), pneumonia or sepsis (group B streptococcus), meconium aspiration, pneumothorax, persistent pulmonary hypertension, congenital heart disease, diaphragmatic hernia, polycythaemia, hypoglycaemia.

• Admit to the neonatal unit with continuous monitoring of respiratory rate, heart rate, temperature, saturations and blood glucose (keep above 2.6 mmol/L).
• Keep warm in a neutral thermal environment.
• Oxygen to keep saturation 90 to 95 percent by head box or low flow nasal cannula. Use continuous positive airway pressure 5 to 6 cmH2O if inspired oxygen above 0.3 to 0.4 is needed or distress increases. Ventilation is seldom needed.
• Feeding: if respiratory rate is 60 to 80 per minute, offer breast or bottle with caution. Above 80 per minute, withhold oral feeds and give nasogastric feeds or intravenous 10 percent dextrose at 60 to 80 mL/kg/day, then reintroduce feeds as the rate improves.
• Antibiotics only if sepsis is suspected (risk factors, raised CRP, unwell): benzylpenicillin 50 mg/kg intravenously every 12 hours plus gentamicin 4 to 5 mg/kg intravenously once daily for term infants with level monitoring. Stop after 36 to 48 hours if cultures are negative and the infant has recovered.
• Diuretics, salbutamol, nebulised adrenaline and corticosteroids are not used routinely.
• Discharge when respiratory rate is below 60 per minute, feeding is established, saturations are normal in air, and parents know the warning signs (fast breathing, grunting, poor feeding, blue lips, lethargy).
• Prevention: avoid elective caesarean section before 39 weeks.
• Review in primary care at 1 to 2 weeks.