Early changes within the lymphocyte population are associated with the development of multiple organ dysfunction syndrome in trauma patients

BACKGROUND Early survival following severe injury has been improved with refined resuscitation strategies. Multiple organ dysfunction syndrome (MODS) is common among this fragile group of patients leading to prolonged hospital stay and late mortality. MODS after trauma is widely attributed to dysregulated inflammation but the precise mechanics of this response and its influence on organ injury are incompletely understood. This study was conducted to investigate the relationship between early lymphocyte responses and the development of MODS during admission. METHODS During a 24-month period, trauma patients were recruited from an urban major trauma centre to an ongoing, observational cohort study. Admission blood samples were obtained within 2 h of injury and before in-hospital intervention, including blood transfusion. The study population was predominantly male with a blunt mechanism of injury. Lymphocyte subset populations including T helper, cytotoxic T cells, NK cells and γδ T cells were identified using flow cytometry. Early cytokine release and lymphocyte count during the first 7 days of admission were also examined. RESULTS This study demonstrated that trauma patients who developed MODS had an increased population of NK dim cells (MODS vs no MODS: 22 % vs 13 %, p < 0.01) and reduced γδ-low T cells (MODS vs no MODS: 0.02 (0.01-0.03) vs 0.09 (0.06-0.12) × 10^9/L, p < 0.01) at admission. Critically injured patients who developed MODS (n = 27) had higher interferon gamma (IFN-γ) concentrations at admission, compared with patients of matched injury severity and shock (n = 60) who did not develop MODS (MODS vs no MODS: 4.1 (1.8-9.0) vs 1.0 (0.6-1.8) pg/ml, p = 0.01). Lymphopenia was observed within 24 h of injury and was persistent in those who developed MODS. Patients with a lymphocyte count of 0.5 × 10(9)/L or less at 48 h, had a 45 % mortality rate. CONCLUSIONS This study provides evidence of lymphocyte activation within 2 h of injury, as demonstrated by increased NK dim cells, reduced γδ-low T lymphocytes and high blood IFN-γ concentration. These changes are associated with the development of MODS and lymphopenia. The study reveals new opportunities for investigation to characterise the cellular response to trauma and examine its influence on recovery.