Exogenous surfactant in paediatric Acute Lung Injury and Acute Respiratory Distress Syndrome

Natural pulmonary surfactant is a complex mixture of lipids and proteins with many biological functions. Surfactant is responsible for lowering the surface tension within alveoli and maintaining the functional integrity of the distal airways. In addition to this function surfactant components represent important elements of the host defence system of the lung. Acute Respiratory Distress Syndrome (ARDS) and Acute Lung Injury (ALI) are syndromes characterised by reduced pulmonary gas exchange due to diffuse injury to the alveolar-capillary barrier. The alveoli fill with proteinaceous fluid, and there is a marked infiltrate of acute inflammatory cells. ARDS and ALI may occur after both direct lung injury such smoke inhalation, and after indirect lung injury such as in sepsis. Qualitative and quantitative surfactant deficiencies are present in individuals suffering from ARDS and ALI, and the role of exogenous surfactant treatment in these conditions has attracted considerable interest. Most clinical studies have shown only improvements in the oxygenation of patients, but a recent study has, for the first time, demonstrated a reduction in the mortality of children with ARDS and ALI treated with exogenous surfactant. Given the differences that exist in surfactant composition, dosing schedules and the pathological processes responsible for ALI, it is clear that considerable work remains to be done in this field.