Clinical experience with exogenous natural surfactant.

More than 600 preterm babies have been enrolled in randomised controlled trials of natural surfactant replacement to prevent or treat the respiratory distress syndrome. Four types of natural surfactant, prepared from animal lungs or human amniotic fluid, have been used. Each contains mainly phospholipids and small amounts (1-5%) of apoproteins. Two types of trial have been used to test these natural surfactants. In prophylaxis studies, babies less than 30 weeks of gestation are given surfactant intratracheally at birth. These studies show a reduction in mortality and pneumothorax and an increase in survival without bronchopulmonary dysplasia (BPD) in treated babies compared to matched controls. In rescue studies, where ill babies are given surfactant about 5 h after birth, there is a reduction in mortality, pneumothorax, intraventricular haemorrhage and BPD, and an increase in survival without BPD. However, treated babies also show an increased incidence of patent ductus arteriosus which has been the only side effect noted to date. All these surfactant preparations show similar effects and studies comparing the different types are unlikely to be undertaken as large numbers of babies would need to be enrolled to show differences. Many uncertainties remain, however, and include the dose of surfactant needed, whether repeat dosing is better than single dosing, whether treatment of less-ill babies is justified, and the results of long-term follow-up studies.