Similarity and synergy of trauma and sepsis: Role of tumor necrosis factor-α and interleukin-6

Both trauma and infection cause a rise in body temperature, white blood cell count, acute phase proteins, fluid and sodium retention and negative nitrogen balance. This phenomenon is often described as "acute phase response" or "systemic inflammatory response syndrome" to denote a coordinated systemic response to significant tissue injury and/or microbial invasion. It is generally agreed that the acute phase response is mediated through the interaction of cytokine and neuroendocrine pathways. Tumor Necrosis Factor-α (TNF-α) and interleukin-6 (IL-6) are two of the major key cytokines involved in the generation of acute phase response. Interleukin-6 are consistently found in septic, trauma and post-operative patients and correlated well with the severity of sepsis or injury. IL-6 is responsible for the fever and metabolic changes in the acute phase. In addition to IL-6, TNF-α was proved to be the mediator that orchestrates the hemodynamic and tissue injury in septic shock. TNF-α destroys endothelial cells and induces disseminated intravascular coagulation, fluid shift, shock, multiple organ system failure and death. On many clinical occasions, both infection and trauma may happen simultaneously on the same patient. Our study demonstrated that operation on the infected patients would cause a synergistic effect on both TNF-α and IL-6 levels. The pulse increase in TNF-α and the persistent elevation of IL-6 were responsible for the post-operative unstable clinical condition in the infected patients. Should we block the cytokine signal and inflammatory response that appear to be harmful? Animal studies have shown that the septic shock to endotoxin challenge can be prevented by pretreatment with monoclonal antibody against TNF-α. The transcription of TNF-α can be blocked with corticosteroid in vivo. The post-operative increase in IL-6 and its related inflammation can be attenuated with corticosteroid, epidural anesthesia and narcotics. However, although blocking the inflammatory response has a beneficial effect of stress free it also eliminates our ability to fight with bacterial infection by lowering our immune response. How to manipulate these cytokines is a question of art more than science.