Development and Characterization of a Rat Model of Blast Polytrauma and Hemorrhagic Shock for Evaluating Innate Immunotherapies During Prolonged Damage Control Resuscitation.

BACKGROUND

A major challenge in developing effective immunological damage-control therapies for traumatic hemorrhage (TH) is the lack of animal models that accurately reproduce the immune and pathophysiological responses observed in humans. In this study, we established a clinically relevant rat model that combines blast injury with hemorrhagic shock in a simulated prolonged damage control resuscitation environment.

METHODS

Male Sprague Dawley rats were anesthetized and subjected to moderate blast overpressure, followed by controlled hemorrhage equivalent to 40% of the estimated total blood volume. Animals then received hypotensive resuscitation with Plasma-Lyte A at twice the shed blood volume. Plasma-Lyte A was used in our study to correct hypovolemia and electrolyte imbalances, thereby helping to standardize the traumatic hemorrhage model.

RESULTS

Four of six rats in the blast-plus-hemorrhage (B + H) group survived the 25 h observation period. During resuscitation, mean arterial pressure remained markedly below baseline for at least 4 h. The B + H insult triggered a rapid innate immune response, characterized by elevated circulating HMGB1, terminal complement activation, and increased myeloperoxidase levels. Complement deposition (C4d, C5a, and C5b-9) was evident in lung tissue, accompanied by multi-organ histopathological injury, including pronounced inflammatory cell infiltration, hemorrhage, and cellular degeneration, apoptosis, or necrosis. Metabolic disturbances, including acidosis, hyperkalemia, and dilutional anemia, were also observed.

CONCLUSIONS

Overall, this model reproduced key features of inflammation-driven multi-organ dysfunction syndrome seen in human polytrauma, supporting its utility for studying TH-related immunopathology and therapeutic interventions during prolonged damage control resuscitation.