Severe Traumatic Head Injury Affects Systemic Cytokine Expression

Abstract

The neuroimmunologic effect of traumatic head injury remains ill-defined. This study aimed to characterize systemic cytokine profiles among traumatically injured patients to assess the effect of traumatic head injury on the systemic inflammatory response. For 5 years, 1,022 patients were evaluated from a multi-institutional Trauma Immunomodulatory Database. Patients were stratified by presence of severe head injury (SHI; head Injury Severity Score ≥4, n = 335) vs nonsevere head injury (NHI; head Injury Severity Score ≤3, n = 687). Systemic cytokine expression was quantified by ELISA within 72 hours of admission. Patient factors, outcomes, and cytokine profiles were compared by univariate analyses. SHI patients were more severely injured with higher mortality, despite similar ICU infection and ventilator-associated pneumonia rates. Expression of early proinflammatory cytokines, interleukin-6 (p < 0.001) and tumor necrosis factor-α (p = 0.02), was higher among NHI patients, and expression of immunomodulatory cytokines, interferon-γ (p = 0.01) and interleukin-12 (p = 0.003), was higher in SHI patients. High tumor necrosis factor-α levels in NHI patients were associated with mortality (p = 0.01), increased mechanical ventilation (p = 0.02), and development of ventilator-associated pneumonia (p = 0.01). Alternatively, among SHI patients, high interleukin-2 levels were associated with survival, decreased mechanical ventilation, and absence of ventilator-associated pneumonia. The presence of severe traumatic head injury significantly alters systemic cytokine expression and exerts an immunomodulatory effect. Early recognition of these profiles can allow for targeted intervention to reduce patient morbidity and mortality.