Inflammatory Alterations in a Novel Combination Model of Blunt Chest Trauma and Hemorrhagic Shock

Background: Chest trauma frequently occurs in severely injured patients and is often associated with hemorrhagic shock. Immune dysfunction contributes to the adverse outcome of multiple injuries. The aims of this study were to establish a combined model of lung contusion and hemorrhage and to evaluate the cardiopulmonary and immunologic response. Methods: Male mice were subjected to sham procedure, chest trauma, hemorrhage (35 mm Hg +/- 5 mm Hg, 60 minutes), or the combination. Respiratory rate, heart rate, and blood pressure were monitored. Plasma, Kupffer cells, blood monocytes, splenocytes, and splenic macrophages were isolated after 20 hours. Tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-6, 10, 12, 18, and macrophage inflammatory protein-2 levels in plasma and culture supernatants were determined. Results: Heart rate and blood pressure dropped in all groups, and after chest trauma and the double hit, these values remained reduced until the end of observation. Blood pressure was lower after the double hit than after the single hits. Plasma and Kupffer cell TNF-alpha concentrations were increased after lung contusion but not further enhanced by subsequent hemorrhage. Peripheral blood mononuclear cell (PBMC) TNF-alpha and IL-6 release were suppressed after the combined insult. IL-18 concentrations were increased in PBMC supernatants after chest trauma and in splenic macrophage supernatants of all groups. Conclusions: Although physiologic readouts were selectively altered in response to the single or double hits, the combination did not uniformly augment the changes in inflammation. Our results suggest that the leading insult regarding the immunologic response is lung contusion, supporting the concept that lung contusion represents an important prognostic factor in multiple injuries.