Shock-Driven Endotheliopathy in Trauma Patients Is Associated with Leucocyte Derived Extracellular Vesicles.

Endotheliopathy following trauma is associated with poor outcome, but the underlying mechanisms are unknown. This study hypothesized that an increased extracellular vesicle (EV) concentration is associated with endotheliopathy after trauma and that red blood cell (RBC) transfusion could further enhance endotheliopathy. In this post hoc sub study of a multicentre observational trial, 75 trauma patients were stratified into three groups based on injury severity score or shock. In patient plasma obtained at hospital admission and after transfusion of four RBC transfusions, markers for endotheliopathy were measured and EVs were labelled with anti CD41 (platelet EVs), anti CD235a (red blood cell EVs), anti CD45 (leucocyte EVs), anti CD144 (endothelial EVs) or anti CD62e (activated endothelial EVs) and EV concentrations were measured with flow cytometry. Statistical analysis was performed by a Kruskall Wallis test with Bonferroni correction or Wilcoxon rank test for paired data. In patients with shock, syndecan-1 and von Willebrand Factor (vWF) were increased compared to patients without shock. Additionally, patients with shock had increased red blood cell EV and leucocyte EV concentrations compared to patients without shock. Endotheliopathy markers correlated with leucocyte EVs (ρ = 0.263, p = 0.023), but not with EVs derived from other cells. Injury severity score had no relation with EV release. RBC transfusion increased circulating red blood cell EVs but did not impact endotheliopathy. In conclusion, shock is (weakly) associated with EVs from leucocytes, suggesting an immune driven pathway mediated (at least in part) by shock.

Coagulopathy Underlying Rotational Thromboelastometry Derangements in Trauma Patients: A Prospective Observational Multicenter Study.

BACKGROUND: Viscoelastic hemostatic assays such as rotational thromboelastometry (ROTEM) are used to guide treatment of trauma induced coagulopathy. The authors hypothesized that ROTEM derangements reflect specific coagulation factor deficiencies after trauma. METHODS: This was a secondary analysis of a prospective cohort study in six European trauma centers in patients presenting with full trauma team activation. Patients with dilutional coagulopathy and patients on anticoagulants were excluded. Blood was drawn on arrival for measurement of ROTEM, coagulation factor levels, and markers of fibrinolysis. ROTEM cutoff values to define hypocoagulability were as follows: EXTEM clotting time greater than 80 s, EXTEM clot amplitude at 5 min less than 40 mm, EXTEM lysis index at 30 min less than 85%, FIBTEM clot amplitude at 5 min less than 10 mm, and FIBTEM lysis index at 30 min less than 85%. Based on these values, patients were divided into seven deranged ROTEM profiles and compared to the reference group (ROTEM values within reference range). The primary endpoint was coagulation factors levels and fibrinolysis. RESULTS: Of 1,828 patients, 732 (40%) had ROTEM derangements, most often consisting of a combined decrease in EXTEM and FIBTEM clot amplitude at 5 min, that was present in 217 (11.9%) patients. While an isolated EXTEM clotting time greater than 80 s had no impact on mortality, all other ROTEM derangements were associated with increased mortality. Also, coagulation factor levels in this group were similar to those of patients with a normal ROTEM. Of coagulation factors, a decrease was most apparent for fibrinogen (with a nadir of 0.78 g/l) and for factor V levels (with a nadir of 22.8%). In addition, increased fibrinolysis can be present when the lysis index at 30 min is normal but EXTEM and FIBTEM clot amplitude at 5 min is decreased. CONCLUSIONS: Coagulation factor levels and mortality in the group with an isolated clotting time prolongation are similar to those of patients with a normal ROTEM. Other ROTEM derangements are associated with mortality and reflect a depletion of fibrinogen and factor V. Increased fibrinolysis can be present when the lysis index after 30 min is normal.

Trauma Laparotomy in the UK: A Prospective National Service Evaluation.

BACKGROUND: Trauma patients requiring abdominal operation have considerable morbidity and mortality, yet no specific quality indicators are measured in the trauma systems of the UK. The aims of this study were to describe the characteristics and outcomes of patients undergoing emergency abdominal operation and key processes of care. STUDY DESIGN: A prospective multicenter service evaluation was conducted within all of the major trauma centers in the UK. The study was conducted during 6 months beginning in January 2019. Patients of any age undergoing laparotomy or laparoscopy within 24 hours of injury were included. Existing standards for related emergent conditions were used. RESULTS: The study included 363 patients from 34 hospitals. The majority were young men with no comorbidities who required operation to control bleeding (51%). More than 90% received attending-delivered care in the emergency department (318 of 363) and operating room (321 of 363). The overall mortality rate was 9%. Patients with blunt trauma had a greater risk of death compared with patients with penetrating injuries (16.6% vs 3.8%; risk ratio 4.3; 95% CI, 2.0 to 9.4). Patients in which the Major Hemorrhage Protocol (MHP) was activated and who received a blood transfusion (n = 154) constituted a high-risk subgroup, accounting for 45% of the study cohort but 97% of deaths and 96% of blood components transfused. The MHP subgroup had expedited timelines from emergency department arrival to knife to skin (MHP: median 119 minutes [interquartile range 64 to 218 minutes] vs no MHP: median 211 minutes [interquartile range 135 to 425 minutes]; p < 0.001). CONCLUSIONS: The majority of trauma patients requiring emergency abdominal operation received a high standard of expedited care in a maturing national trauma system. Despite this, mortality and resource use among high-risk patients remains considerable.

A Delphi study to establish consensus on a definition of major bleeding in adult trauma.

BACKGROUND: The majority of potentially preventable deaths in trauma are due to uncontrolled hemorrhage and occur early after injury. How major bleeding is defined is integral to early identification and treatment of this group of high-risk patients. However, there is no consensus on a definition of major bleeding in trauma. The aim of this Delphi study was to develop a consensus definition for research, with transfusion used as a surrogate marker of bleeding. STUDY DESIGN AND METHODS: Trauma experts from three international groups were invited to take part in an online Delphi survey. Over the course of four rounds, the group developed a number of definitions of major bleeding and reached consensus on a new definition. RESULTS: Forty-four trauma experts agreed to become members of the Delphi panel, and 30 of 44 (68%) completed all four rounds. The panel agreed to exclude the historical massive transfusion definition (≥10 units of red blood cells within 24 hours). Consensus was reached on a new definition for use in clinical research: 4 or more units of any blood component within 2 hours of injury. CONCLUSION: This Delphi process has yielded a pragmatic transfusion-based definition of major bleeding. The consensus definition differs from historical definitions: a shorter time frame to reflect the acuity of bleeding, and multiple blood components in keeping with a balanced approach to resuscitation. The definition developed may be best suited to mature trauma systems (reflecting the demographics of the expert panel), and could be used to guide registry data recording and to characterize patients at risk of major bleeding.

What's new for trauma haemorrhage management?

Uncontrolled haemorrhage is the leading cause of preventable death from injury and is a major contributor to the global burden of disease. The majority of deaths resulting from bleeding occur within the first 3 hours of hospital admission, and the window for meaningful intervention is therefore extremely small. Resuscitative efforts during active bleeding should focus on maintaining haemostatic function with blood product transfusion and early administration of tranexamic acid. Achieving control of haemorrhage is the overarching treatment priority and may require temporising measures before definitive surgical or radiological intervention. This review summarizes the contemporary approaches to resuscitation of bleeding trauma patients, options for achieving haemorrhage control, and current areas of active research including organ protective resuscitation and suspended animation.

The S100A10 Pathway Mediates an Occult Hyperfibrinolytic Subtype in Trauma Patients.

OBJECTIVE: To determine the characteristics of trauma patients with low levels of fibrinolysis as detected by viscoelastic hemostatic assay (VHA) and explore the underlying mechanisms of this subtype. BACKGROUND: Hyperfibrinolysis is a central component of acute traumatic coagulopathy but a group of patients present with low levels of VHA-detected fibrinolysis. There is concern that these patients may be at risk of thrombosis if empirically administered an antifibrinolytic agent. METHODS: A prospective multicenter observational cohort study was conducted at 5 European major trauma centers. Blood was drawn on arrival, within 2 hours of injury, for VHA (rotation thromboelastometry [ROTEM]) and fibrinolysis plasma protein analysis including the fibrinolytic mediator S100A10. An outcomes-based threshold for ROTEM hypofibrinolysis was determined and patients grouped by this and by D-dimer (DD) levels. RESULTS: Nine hundred fourteen patients were included in the study. The VHA maximum lysis (ML) lower threshold was determined to be <5%. Heterogeneity existed among patients with low ML, with survivors sharing similar clinical and injury characteristics to patients with normal ML values (5-15%). Those who died were critically injured with a preponderance of traumatic brain injury and had a 7-fold higher DD level (died vs. survived: 103,170 vs. 13,672 ng/mL, P < 0.001). Patients with low ML and high DD demonstrated a hyperfibrinolytic biomarker profile, low tissue plasminogen activator levels but high plasma levels of S100A10. S100A10 was negatively correlated with %ML (r = -0.26, P < 0.001) and caused a significant reduction in %ML when added to whole blood ex-vivo. CONCLUSIONS: Patients presenting with low ML and low DD levels have low injury severity and normal outcomes. Conversely, patients with low ML but high DD levels are severely injured, functionally coagulopathic and have poor clinical outcomes. These patients have low tissue plasminogen activator levels and are not detectable by ROTEM. S100A10 is a cell surface plasminogen receptor which may drive the hyperfibrinolysis in these patients and which when shed artificially lowers %ML ex-vivo.

Fibrinolysis and antifibrinolytic treatment in the trauma patient.

PURPOSE OF REVIEW: The role of antifibrinolytics in trauma haemorrhage and early coagulopathy remains controversial with respect to patient selection, dosage, timing of treatment, and risk of thrombotic complications. This review presents our current understanding of the mechanisms of fibrinolysis in trauma, diagnostic evaluation, and the evidence base for treatment. RECENT FINDINGS: Excessive fibrinolysis following severe injury is a major component of acute traumatic coagulopathy and contributes to the high mortality from trauma haemorrhage. The protein C pathway, endothelial dysfunction, platelet activity, shock, and tissue injury are key to the development of hyper fibrinolysis in trauma. D-dimer and viscoelastic haemostatic assays (rotational thromboelastometry, TEG) remain the best available diagnostic modalities but have a number of limitations compared with plasma biomarkers of fibrinolytic activation, for example, plasmin-α2-antiplasmin complex. Current evidence supports the continued empiric use of tranexamic acid in major trauma haemorrhage. SUMMARY: Improving the outcomes for bleeding trauma patients requires a deeper understanding of the mechanisms driving hyperfibrinolysis and the subsequent switch toward a prothrombotic state. Discovering the interplay between platelet activity, fibrinogen utilization, the immune response, and the fibrinolytic system may lead to development of novel therapeutics.

Platelet transfusions reduce fibrinolysis but do not restore platelet function during trauma hemorrhage.

BACKGROUND: Platelets play a critical role in hemostasis with aberrant function implicated in trauma-induced coagulopathy. However, the impact of massive transfusion protocols on platelet function during trauma hemorrhage is unknown. The aim of this study was to characterize the effects of platelet transfusion on platelet aggregation and fibrinolytic markers during hemostatic resuscitation. METHODS: Trauma patients enrolled into the prospective Activation of Coagulation and Inflammation in Trauma study between January 2008 and November 2015 who received at least four units of packed red blood cells (PRBCs) were included. Blood was drawn in the emergency department within 2 hours of injury and at intervals after every four units of PRBCs transfused. Platelet aggregation was assessed in whole blood with multiple electrode aggregometry. Plasma proteins were quantified by enzyme-linked immunosorbent assay. RESULTS: Of 161 patients who received four or more PRBCs as part of their initial resuscitation, 44 received 8 to 11 units and 28 received 12 units or more. At each timepoint during bleeding, platelet aggregation was similar in patients who had received a platelet transfusion compared with those who had only received other blood products (p > 0.05 for all timepoints). Platelet transfusion during the four PRBC intervals was associated with a decrease in maximum lysis on rotational thromboelastometry (start of interval, 6% [2-12] vs. end of interval, 2% [0-5]; p = 0.001), an increase in plasminogen activator inhibitor-1 (start of interval, 35.9 ± 14.9 vs. end of interval, 66.7 ± 22.0; p = 0.007) and a decrease in tissue plasminogen activator (start of interval, 26.2 ± 10.5 vs. end of interval, 19.0 +/- 5.1; p = 0.04). No statistically significant changes in these parameters occurred in intervals which did not contain platelets. CONCLUSION: Current hemostatic resuscitation strategies do not appear to restore platelet aggregation during active hemorrhage. However, stored platelets may attenuate fibrinolysis by providing an additional source of plasminogen activator inhibitor-1. Further investigation into the effects of early platelet transfusion on platelet function, hemostatic, and clinical outcomes during bleeding are warranted. LEVEL OF EVIDENCE: Therapeutic, level III.

Diagnosis and Treatment of Hyperfibrinolysis in Trauma (A European Perspective).

Fibrinolysis activation occurs almost universally after severe trauma. Systemic hyperfibrinolysis is a key component of acute traumatic coagulopathy and associated with poor clinical outcomes, although controversy exists over optimal treatment strategies. The mechanistic drivers and dynamics of fibrinolytic activation in response to injury and trauma resuscitation are currently unclear. Furthermore, therapeutic triggers are compounded by the lack of a sensitive and rapid diagnostic tool, with discrepancy between hyperfibrinolysis diagnosed by viscoelastic hemostatic assays versus biomarkers for fibrinolysis. Rotational thromboelastometry and thromboelastography appear capable of detecting the severest forms of hyperfibrinolysis but are relatively insensitive to moderate, yet clinically significant fibrinolytic activation. Rapid evaluation of the current status of the fibrinolytic system remains a challenge and therefore the decision whether to administer an antifibrinolytic agent should be based on available evidence from clinical trials. In line with current European guidelines, we recommend that all bleeding trauma patients, and in particular, severely injured patients with evidence of hemorrhagic shock, should receive early empiric tranexamic acid. This review explains our current knowledge of the pathophysiological pathways which induce hyperfibrinolysis in trauma hemorrhage, evaluates the available diagnostic modalities, and describes current treatment strategies.

Activated Protein C Drives the Hyperfibrinolysis of Acute Traumatic Coagulopathy.

BACKGROUND: Major trauma is a leading cause of morbidity and mortality worldwide with hemorrhage accounting for 40% of deaths. Acute traumatic coagulopathy exacerbates bleeding, but controversy remains over the degree to which inhibition of procoagulant pathways (anticoagulation), fibrinogen loss, and fibrinolysis drive the pathologic process. Through a combination of experimental study in a murine model of trauma hemorrhage and human observation, the authors' objective was to determine the predominant pathophysiology of acute traumatic coagulopathy. METHODS: First, a prospective cohort study of 300 trauma patients admitted to a single level 1 trauma center with blood samples collected on arrival was performed. Second, a murine model of acute traumatic coagulopathy with suppressed protein C activation via genetic mutation of thrombomodulin was used. In both studies, analysis for coagulation screen, activated protein C levels, and rotational thromboelastometry (ROTEM) was performed. RESULTS: In patients with acute traumatic coagulopathy, the authors have demonstrated elevated activated protein C levels with profound fibrinolytic activity and early depletion of fibrinogen. Procoagulant pathways were only minimally inhibited with preservation of capacity to generate thrombin. Compared to factors V and VIII, proteases that do not undergo activated protein C-mediated cleavage were reduced but maintained within normal levels. In transgenic mice with reduced capacity to activate protein C, both fibrinolysis and fibrinogen depletion were significantly attenuated. Other recognized drivers of coagulopathy were associated with less significant perturbations of coagulation. CONCLUSIONS: Activated protein C-associated fibrinolysis and fibrinogenolysis, rather than inhibition of procoagulant pathways, predominate in acute traumatic coagulopathy. In combination, these findings suggest a central role for the protein C pathway in acute traumatic coagulopathy and provide new translational opportunities for management of major trauma hemorrhage.

Cause of trauma-induced coagulopathy.

PURPOSE OF REVIEW: Trauma-induced coagulopathy (TIC) is a multifactorial, global failure of the coagulation system to sustain adequate haemostasis after trauma haemorrhage. Damage control resuscitation is associated with improved outcomes although the mechanisms of how it corrects TIC have yet to be fully characterized. Identification of predominant pathophysiological pathways in TIC is required to develop effective treatment algorithms for trauma haemorrhage. RECENT FINDINGS: TIC is described by varying degrees of dysfibrinogenaemia, hyperfibrinolysis, endothelial dysfunction and impaired platelet activity, dependent on the magnitude of trauma, and severity of haemorrhagic shock. Acute traumatic coagulopathy is the early endogenous process mediated by the protein C pathway in response to tissue injury and hypoperfusion. Thrombin generation appears maintained with altered fibrinogen utilization and activation of fibrinolytic pathways representing key components of TIC. Shedding of the endothelial glycocalyx appears capable of triggering systemic thrombin generation, protein C activation and hyperfibrinolysis and may itself represent a therapeutic target. SUMMARY: Further advances in TIC treatment require an enhanced understanding of the dynamic changes in the equilibrium between pro and anticoagulant factors, downstream effectors, and the host response. Delineating the interaction between fibrinolysis, fibrinogen utilization, platelet activity, and thrombin generation may provide opportunity for targeted intervention.

Transfusion strategies for traumatic coagulopathy.

Uncontrolled bleeding is the most common preventable cause of death for patients with severe injury. Coagulopathy inevitably accompanies severe bleeding, exacerbated by the ongoing blood loss and the treatments administered. There is debate about the underlying pathophysiological mechanisms of early traumatic coagulopathy and uncertainty about whether injury induces a unique coagulopathy when compared to other forms of major haemorrhage. This review describes current understanding of the coagulopathy of major blood loss and focuses on the early coagulation changes that occur following severe injury. It then reports on the contemporary management of coagulopathic bleeding using new transfusion strategies. Finally this review presents some practical points to the delivery of transfusion for major blood loss in the modern hospital setting.

Reappraising the concept of massive transfusion in trauma.

INTRODUCTION: The massive-transfusion concept was introduced to recognize the dilutional complications resulting from large volumes of packed red blood cells (PRBCs). Definitions of massive transfusion vary and lack supporting clinical evidence. Damage-control resuscitation regimens of modern trauma care are targeted to the early correction of acute traumatic coagulopathy. The aim of this study was to identify a clinically relevant definition of trauma massive transfusion based on clinical outcomes. We also examined whether the concept was useful in that early prediction of massive transfusion requirements could allow early activation of blood bank protocols. METHODS: Datasets on trauma admissions over a 1 or 2-year period were obtained from the trauma registries of five large trauma research networks. A fractional polynomial was used to model the transfusion-associated probability of death. A logistic regression model for the prediction of massive transfusion, defined as 10 or more units of red cell transfusions, was developed. RESULTS: In total, 5,693 patient records were available for analysis. Mortality increased as transfusion requirements increased, but the model indicated no threshold effect. Mortality was 9% in patients who received none to five PRBC units, 22% in patients receiving six to nine PRBC units, and 42% in patients receiving 10 or more units. A logistic model for prediction of massive transfusion was developed and validated at multiple sites but achieved only moderate performance. The area under the receiver operating characteristic curve was 0.81, with specificity of only 50% at a sensitivity of 90% for the prediction of 10 or more PRBC units. Performance varied widely at different trauma centers, with specificity varying from 48% to 91%. CONCLUSIONS: No threshold for definition exists at which a massive transfusion specifically results in worse outcomes. Even with a large sample size across multiple trauma datasets, it was not possible to develop a transportable and clinically useful prediction model based on available admission parameters. Massive transfusion as a concept in trauma has limited utility, and emphasis should be placed on identifying patients with massive hemorrhage and acute traumatic coagulopathy.

Coagulopathy in trauma patients: importance of thrombocyte function?

PURPOSE OF REVIEW: Trauma-induced coagulopathy results from a complex interplay between shock resuscitation and impaired clotting protease function. A pathophysiological role of platelets in this condition remains as yet undefined. This review examines our current knowledge of platelet function in haemostasis, possible mechanisms for aberrant activity in trauma and the role of platelet transfusions in exsanguinating haemorrhage. RECENT FINDINGS: Platelet adhesion and aggregation enable a haemostatic plug to form at the site of vessel injury. As described within cell-based models of thrombin generation, platelet membranes provide a platform to amplify clot formation. There is evidence to suggest platelet activity may be of greater importance than platelet number for clot integrity. Analysis of platelet function is limited by currently available devices. Therefore, the precise role and triggers for platelet transfusion in trauma have yet to be fully characterized. Retrospective studies show that early high-volume platelet transfusion in trauma may be associated with similar outcome benefits observed in high ratio plasma: red blood cell replacement. SUMMARY: Platelets undoubtedly play a pivotal role in haemostasis and trauma-induced coagulopathy. However, their specific dysfunction in trauma remains to be elucidated. Further research to characterize the dysfunctional pathways of the platelet response is required, together with clinical trials of the optimal timing and dose of platelet transfusions.

Acute coagulopathy of trauma: mechanism, identification and effect.

PURPOSE OF REVIEW: Acute coagulopathy of trauma has only been described relatively recently. Developing early in the postinjury phase, it is associated with increased transfusion requirements and poor outcomes. This review examines the possible initiators, mechanism and clinical importance of acute coagulopathy. RECENT FINDINGS: Acute coagulopathy of trauma occurs in patients with shock and is characterized by a systemic anticoagulation and hyperfibrinolysis. Dilution, acidemia and consumption of coagulation proteases do not appear to be significant factors at this stage. There is evidence to implicate activation of the protein C pathway in this process. Diagnosis of acute coagulopathy currently relies on laboratory assessment of clotting times. These tests do not fully characterize the coagulopathy and have significant limitations, which reduce their clinical utility. SUMMARY: Acute coagulopathy results in increased transfusion requirements, incidence of organ dysfunction, critical care stay and mortality. Recognition of an early coagulopathic state has implications for the care of shocked patients and the management of massive transfusion. Identification of novel mechanisms for traumatic coagulopathy may lead to new avenues for drug discovery and therapeutic intervention.