TF Fok

The last decade has seen significant improvements in the understanding and management of respiratory distress syndrome in preterm infants. Extensive basic research and clinical trials have led to the widespread use of exogenous surfactant whose benefit in improving survival and reducing morbidity in preterm infants has been confirmed Nowadays, the mainstays of management of RDS include (1) oxygen, (2) assisted ventilation including mechanical ventilation and nasal prong continuous positive pressure ventilation (CPAP), (3) surfactant replacement, (4) supportive care, (5) cover/exclude other causes, (6) prevention/treatment of chronic lung disease. Oxygen therapy is administered usually via a headbox. Great care has to be taken to ensure that the infant's arterial oxygen tension is within a "safe" range since excessively high PaO₂ is associated with the development of retinopathy of prematurity. The exact "safe" range of PaO₂ is not certain but there is some evidence that it should not exceed 80mmHg. There is also emerging evidence that not only hyperoxia but also intermittent hypoxia may have a role in the pathogenesis of retinopathy of prematurity. Nasal prong CPAP has been revived after losing its popularity for almost 10 years. Its use has been associated with a reduced need for mechanical ventilation and lower incidence of bronchopulmonary dysplasia. Infant ventilators nowadays are safer and much more efficient than their previous versions. The introduction of high frequency oscillatory ventilation has provided a rescue for infants who cannot be effectively ventilated by conventional positive pressure ventilation. In preterm infants with severe RDS, it has been shown that compared to conventional ventilation, the use of HFOV is associated with less barotrauma and pulmonary airleak. Exogenous surfactant given by intratracheal instillation improves the survival, reduces the morbidity, and shorten the hospital stay of preterm infants with RDS. Both synthetic (Exosurf, Burrough Wellcome Laboratories, UK) and natural bovine (Survanta, Abbott Laboratories, USA) surfactants are equally efficacious although the latter has a faster onset of action. In contrast to what has been recommended previously, there is now evidence from an animal study that Exosurf should best be given with the lungs lying horizontally supine, and that turning the position of the chest does not result in more even distribution of the medication. Better distribution can also be achieved by giving the surfactants in large volume by rapid bolus instillation although these manoeuvres may cause transient hypoxia, fluctuation in blood pressure, and changes in cerebral blood flow. All preterm infants with RDS require supportive care to ensure homeostasis of their various systems. Fluid intake has to be carefully tailored, and excessive fluid intake may be associated with the development of chronic lung disease. Early prophylactic indomethacin for closure of the ductus arteriosus is associated with a lower incidence of intraventricular haemorrhage. Since sepsis might present as RDS, these infants are often covered with antibiotics after a "sepsis work up". There is now evidence that routine lumbar puncture in RDS infants without risk factors for sepsis has extremely low yield and should not be included in the "sepsis workup". Preventive measures against bronchopulmonary dysplasia include antenatal steroid given either alone or in combination with thyrotrophin releasing hormone, and postnatally, surfactant treatment, inositol and vitamin supplement, fluid restriction, and, for those with severe RDS, the use of HFOV. Once bronchopulmonary dysplasia is established, corticosteroid is the mainstay of treatment. There is a tendency now for neonatologists to use steroid before the infants develop frank BPD if they are at risk of the condition. There are studies underway to evaluate the usefulness of prophylactic steroid given within the first 2 days of life either parenterally or by the inhaled route in preventing BPD.