MULTIMODAL TREATMENT APPROACHES TO COMBINED TRAUMATIC BRAIN INJURY AND HEMORRHAGIC SHOCK ALTER POSTINJURY INFLAMMATORY RESPONSE.

Introduction: The optimal management strategies for patients with polytraumatic injuries that include traumatic brain injury (TBI) are not well defined. Specific interventions including tranexamic acid (TXA), propranolol, and hypertonic saline (HTS) have each demonstrated benefits in patient mortality after TBI, but have not been applied to TBI patients with concomitant hemorrhage. The goals of our study were to determine the inflammatory effects of resuscitation strategy using HTS or shed whole blood (WB) and evaluate the cerebral and systemic inflammatory effects of adjunct treatment with TXA and propranolol after combined TBI + hemorrhagic shock. Methods: Mice underwent TBI via weight drop and were subsequently randomized into six experimental groups: three with HTS resuscitation and three with WB resuscitation. Mice were then subjected to controlled hemorrhagic shock for 1 h to a goal MAP of 25 mmHg. Mice were then treated with an i.p. dose of 4 mg/kg propranolol, 100 mg/kg TXA, or normal saline (NS) as a control. Mice were killed at 1, 6, or 24 h for serum and cerebral biomarker evaluation by multiplex ELISA and serum neuron-specific enolase, a biomarker of cerebral cellular injury. Results: Mice resuscitated with HTS had elevated serum proinflammatory cytokines compared with WB resuscitated groups at 6 and 24 h after injury, with no significant difference in cerebral cytokine levels. Within the TBI/shock + HTS groups, the addition of propranolol or TXA did not significantly alter serum cytokine concentration, but cerebral IL-2, IL-12, and macrophage inflammatory protein-1α (MIP-1α) decreased after propranolol administration. In the TBI/shock + WB cohorts, the addition of both propranolol and TXA increased systemic proinflammatory cytokine levels at 6 and 24 h after injury as demonstrated by serum IL-2, IL-12, MIP-1α, and IL-1β compared with NS control. By contrast, TBI/shock + WB mice demonstrated a significant reduction in cerebral IL-2, IL-12, and MIP-1α in propranolol treated mice 6 h after injury compared with NS group. While serum neuron-specific enolase was significantly increased 1 and 24 h after injury in TBI/shock + HTS + TXA cohorts compared with NS control, it was significantly reduced in the TBI/shock + WB + propranolol mice compared with NS control 24 h after injury. Conclusions: Whole blood resuscitation can reduce the acute postinjury neuroinflammatory response after combined TBI/shock compared with HTS. The addition of either propranolol or TXA may modulate the postinjury systemic and cerebral inflammatory response with more improvements noted after propranolol administration. Multimodal treatment with resuscitation and pharmacologic therapy after TBI and hemorrhagic shock may mitigate the inflammatory response to these injuries to improve recovery.