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Objectives and questions: Polytrauma (PT) triggers complex immune responses that contribute to organ crosstalk and post-traumatic inflammatory complications. Circulating biomarkers may reflect trauma severity as well as post-traumatic immune responses, yet their dynamic behavior and clinical relevance across different trauma severities remain not fully understood.

Material and methods: In this multicenter prospective study, patients (n=87) were prospectively included into two groups; PT without chest trauma (PT-; n = 43) or PT with chest trauma (PT+; n = 44). Serum samples were collected at six consecutive timepoints; at admission and at 8, 24, and 48 hr, and 5 and 10 d after trauma. Nine predefined circulating biomarkers related to the post-traumatic immune response, chemotaxis, and tissue regeneration were quantified using ELISA. Cross-sectional comparisons, longitudinal mixed-effects models, correlation analyses, and multivariable linear regression were performed to evaluate associations with injury severity and Intensive Care Unit length of stay (ICU-LOS).

Results: Several biomarkers demonstrated significant trauma severity- and time-dependent expression patterns. In the acute post-traumatic phase (admission and 8 hr), levels of hepatocyte growth factor and macrophage migration inhibitory factor were increased in the PT+ group as compared to the PT-group. Furthermore, the expression of both interferon-γ–inducible protein 10 and C-C Motif Chemokine Ligand 5 showed to be dependent on trauma severity as well as the time after trauma. Although multiple biomarkers were correlated with ICU-LOS in univariate analyses, none independently predicted ICU-LOS after adjustment for the Injury Severity Score.

Discussion and conclusions: Polytrauma with concomitant chest trauma resulted in unique inflammatory marker profiles in the systemic circulation. Furthermore, several of the analyzed biomarker candidates showed trauma severity as well as time dependent circulating expression levels. This study demonstrated the relevance of dynamic biomarker monitoring over time to provide greater insight into immune dysregulation and organ crosstalk compared to singular point-of-care measurements. While anatomical injury severity remains the primary determinant of ICU-LOS, integrating time-dependent biomarker expression profiles with established clinical scores may enhance risk stratification for post-traumatic inflammatory complications after severe trauma.