Bronchoalveolar lavage with a diluted surfactant suspension prior to surfactant instillation improves the effectiveness of surfactant therapy in experimental acute respiratory distress syndrome (ARDS)

Objective: To assess whether bronchoalveolar lavage (BAL) with a diluted surfactant suspension prior to surfactant instillation prevents the only transient improvement in lung function as reported after surfactant instillation in severe acute respiratory distress syndrome (ARDS). Design: Randomized, prospective, experimental study. Setting: Laboratory and animal facility of a large university. Materials: Adult male Sprague-Dawley rats (280 ± 30 g). Interventions: All animals underwent repetitive whole lung saline lavage to induce acute lung injury. Then, animals were randomly divided into seven study groups: the first group received surfactant (150 mg/kg) within 10 min after the last lavage (early treatment), whereas in the other six groups mechanical ventilation was continued for 3 h before treatment (late treatment). Treatment consisted of: surfactant instillation at a dose of 150 mg/kg; at a dose of 250 mg/kg; BAL with saline; BAL with a diluted surfactant suspension (2.5 mg/ml); BAL with saline, immediately followed by surfactant instillation (150 mg/kg) and BAL with a diluted surfactant suspension (2.5 mg/kg), immediately followed by surfactant instillation (150 mg/kg). Measurements and results: Blood gases were measured for 6 h and then BAL was performed to measure the protein concentration and surface tension properties. Mean PaO₂ values increased immediately after surfactant instillation to pre-lavage values but remained stable only in the group that received surfactant immediately after the lavage procedure and the group that underwent BAL with a diluted surfactant suspension prior to surfactant instillation. Conclusion: BAL with a diluted surfactant suspension prior to surfactant instillation at a later time point in lung injury resulted in a stable improvement of lung function. This improvement is comparable with the results seen after surfactant instillation immediately after lung lavage.