Even with the resources available in the most modern intensive care units, the mortality in patients with respiratory distress syndrome remains high. Therapy is supportive, and there is no pharmacological therapy that demonstrably improves outcome.
Dr. Giacomo Bellani, Department of Health Science, University of Milano-Bicocca, Monza, Italy, and Department of Emergency, San Gerardo Hospital, Monza, Italy, and colleagues explored the effect of surfactant on acid-induced ARDS in a mouse model. The results of their analysis are summarized in the article “The Effects of Exogenous Surfactant Treatment in a Murine Model of Two-Hit Lung Injury,” which was published in this month’s issue of Anesthesia & Analgesia.
Many studies have examined the relationship between surfactant and lung injury. This study differs because it examines the interactions between surfactant, acid injury to the lung, and ventilator-induced lung injury in the directly injured as well as adjacent normal lung.
Following instillation of hydrochloric acid in the right bronchus mice were mechanically ventilated for 7 hours. Mice in the treatment group received surfactant at 3 hours. 41 of 58 mice survived for more than 6 hours. The survival rate was 83% in the surfactant group and 59% in the untreated group, though the differences were not significant. There was an overall improvement in global indices of lung function, specifically gas exchange and lung compliance, in those mice that were administered surfactant. These changes were attributed to improved elastic properties of the lung. In addition, there were increases in inflammation in the lung treated with surfactant, evidenced primarily by increased protein and also based on cellular and humoral indices. However, there was less inflammation in the non-exposed lung of animals that received surfactant compared to mice that received the acid instillation but were not administered surfactant. This suggests that the benefits of surfactant may be partly due to its effects on the uninjured lung.
Surfactant reduces the severity of lung injury in this model of aspiration. This paper is a preclinical study, and as such it will not change practice. If supplemented by additional studies, or human clinical trials it could lead to a renewed interest in testing surfactant as a potential therapy for ARDS.