Biomarkers to Guide the Timing of Surgery: Neutrophil and Monocyte L-Selectin Predict Postoperative Sepsis in Orthopaedic Trauma Patients.

Deciding whether to delay non-lifesaving orthopaedic trauma surgery to prevent multiple organ failure (MOF) or sepsis is frequently disputed and largely based on expert opinion. We hypothesise that neutrophils and monocytes differentially express activation markers prior to patients developing these complications. Peripheral blood from 20 healthy controls and 162 patients requiring major orthopaedic intervention was collected perioperatively. Neutrophil and monocyte L-selectin, CD64, CD11, CD18, and CXCR1 expression were measured using flow cytometry. The predictive ability for MOF and sepsis was assessed using the Receiver Operating Characteristic (ROC) comparing to C-reactive protein (CRP). Neutrophil and monocyte L-selectin were significantly higher in patients who developed sepsis. Neutrophil L-selectin (AUC 0.692 [95%CI 0.574-0.810]) and monocyte L-selectin (AUC 0.761 [95%CI 0.632-0.891]) were significant predictors of sepsis and were not significantly different to CRP (AUC 0.772 [95%CI 0.650-0.853]). Monocyte L-selectin was predictive of MOF preoperatively and postoperatively (preop AUC 0.790 [95%CI 0.622-0.958]). CD64 and CRP were predictive of MOF at one-day postop (AUC 0.808 [95%CI 0.643-0.974] and AUC 0.809 [95%CI 0.662-0.956], respectively). In the perioperative period, elevated neutrophil and monocyte L-selectin are predictors of postoperative sepsis. Larger validation studies should focus on these biomarkers for deciding the timing of long bone/pelvic fracture fixation.

The source of cell-free mitochondrial DNA in trauma and potential therapeutic strategies.

Mitochondria play a key role in the pathophysiology of post-injury inflammation. Cell-free mitochondrial DNA (cf-mtDNA) is now understood to catalyse sterile inflammation after trauma. Observations in trauma cohorts have identified high cf-mtDNA in patients with systemic inflammatory response syndrome and multiple organ failure as well as following major surgery. The source of cf-mtDNA can be various cells affected by mechanical and hypoxic injury (passive mechanism) or induced by inflammatory mechanisms (active mechanism). Multiple forms of cf-mtDNA exist; mtDNA fragments, mtDNA in microparticles/vesicles and cell-free mitochondria. Trauma to cells that are rich in mitochondria are believed to release more cf-mtDNA. This review describes the current understanding of the mechanisms of cf-mtDNA release, its systemic effects and the potential therapeutic implications related to its modification. Although current understanding is insufficient to change trauma management, focussed research goals have been identified to pave the way for monitoring and manipulation of cf-mtDNA release and effects in trauma.