Lung injury and recovery in a murine model of unilateral acid aspiration

Background' Acid aspiration is a complication of general anesthesia. Most animal models developed to define Its patho-physiology have focused on the acute (≤24 h) phase of the Injury. The authors describe a model of acid aspiration allowing the study of this type of lung Injury over time. Methods: The authors instilled hydrochloric acid (0.1 M, 1.5 m1/kg) or normal saline In the right bronchus of mice. Lung Injury was evaluated at 6 h, 12 h, 24 h, and 2 weeks by assessing arterial blood gases, respiratory system compliance, lung wet weight normalized by body weight, lung myeloperoxidase activity, and histology. Twelve hours and 2 weeks after Injury, a computed tomography scan was obtained. Results: In the hydrochloric acid group, arterial oxygen tension decreased (P < 0.05) at 12 and 24 h, whereas It recovered at 2 weeks; respiratory system compliance was lower both at 24 h and 2 weeks (P < 0.05). Lung weight increased at 12 and 24 h (P < 0.05). Myeloperoxidase activity peaked between 6 and 12 h. Computed tomography at 12 h showed that almost 30% of the Injured lung was abnormally aerated. Although reduced, the abnormalities were still present at 2 weeks as confirmed by a fibrotic scar well evident at histologic examination. Conclusion: The authors characterized a murine model of regional acid aspiration allowing long-term survival. Despite a partial recovery, at 2 weeks the Injury persisted, with evidence of fibrosis and lung compliance reduction. This long-term, low-mortality model seems suitable for assessment of the effects of different therapies on lung Injury and repair. Copyright © 2008, the American Society of Anesthesiologists, Inc.