Exsanguination following severe injury remains the most common preventable cause of traumatic death. One third of these patients exhibit trauma-induced coagulopathy (TIC) with an associated significant morbidity and mortality. A key feature of damage control resuscitation (DCR) is early diagnosis and direct targeting of TIC with blood component therapy combined in major haemorrhage protocols (MHPs). The impact and efficacy of high-dose blood component therapy on TIC is currently unknown. The overall aim of this thesis is to address these specific areas of uncertainty. A prospective observational cohort study of 106 severely injured, bleeding trauma patients was performed over a three-year period. Blood samples for coagulation testing and clotting factor analysis were drawn on arrival and during the acute bleeding (resuscitative) phase after administration of every 4 U of PRBCs, up to 12 U. The quantity of blood products administered within each interval was recorded. Following implementation of MHP significantly higher ratios of blood component therapy were observed. FFP:PRBC transfusion improved from 1:3 to 1:2 (p < 0.01) and CRYO:PRBCs from 1:10 to 1:7 (p < 0.05). There was a six-fold reduction in platelets wastage (14% to 2%, p < 0.01). On admission, 43% of patients were coagulopathic and increased to 49% by PRBC 4, 62% by PRBC 8 and 68% by PRBC 12, despite adherence to DCR strategies. In shock, lactate clearance did not occur until haemorrhage control was achieved with no further PRBC requirement. Only the combination of high-dose FFP, CRYO and platelet therapy with a high total fibrinogen load produced a consistent improvement in ROTEM parameters. 4 The body of work within this thesis supports the need for larger studies to determine the clinical benefits of early fibrinogen supplementation in treating severely injured trauma patients suffering from life threatening haemorrhage.