Is interleukin 6 an early marker of injury severity following major traumain humans?

Hypothesis: Interleukin 6 (IL-6), a multifunctional cytokine, is expressed by various cells after many stimuli and underlies complex regulatory contro l mechanisms. Following major trauma, IL-6 release correlates with injury s everity, complications, and mortality. The IL-6 response to injury is suppo sed to be uniquely consistent and related to injury severity. Therefore, we designed a prospective study starting as early as at the scene of the unin tentional injury to determine the trauma-related release of plasma IL-6 in multiple injured patients. Patients and Methods: On approval of the local ethics committee, 94 patient s were enrolled with different injuries following trauma (Injury Severity S core [ISS] median, 19; range, 3-75). The patients were rescued by a medical helicopter. Subsets were performed according to the severity of trauma-4 g roups (ISS, <9, 9-17, 18-30, and >32)-and survival vs nonsurvival. The firs t blood sample was collected at the scene of the unintentional injury befor e cardiopulmonary resuscitation, when appropriate. Then, blood samples were collected in hourly to daily intervals. Interleukin 6 plasma levels were d etermined using a commercial enzyme-linked immunosorbent assay test. The sh ort-term phase protein, C-reactive protein, was measured to characterize th e extent of trauma and to relate these results to IL-6 release. Results: As early as immediately after trauma, elevated IL-6 plasma levels occurred. This phenomenon was pronounced in patients with major trauma (ISS , >32). Patients with minor injury had elevated concentrations as well but to a far lesser extent. In surviving patients, IL-6 release correlated with the ISS values best during the first 6 hours after hospital admission. All patients revealed increased C-reactive protein levels within 12 hours foll owing trauma, reflecting the individual injury severity. This was most pron ounced in patients with the most severe (ISS, >32) trauma. Conclusions: To our knowledge, this is the first study that elucidates the changes in the IL-6 concentrations following major trauma in humans as earl y as at the scene of the unintentional injury. The results reveal an early increase of IL-6 immediately after trauma. Moreover, patients with the most severe injuries had the highest IL-6 plasma levels. There is strong eviden ce that systemic IL-6 plasma concentrations correlate with ISS values at ho spital admission. Therefore, IL-6 release can be used to evaluate the impac t of injury early regardless of the injury pattern.