Cause of trauma-induced coagulopathy Davenport, Ross A; Brohi, Karim
Current opinion in anaesthesiology,
04/2016, Letnik:
29, Številka:
2
Journal Article
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.
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.
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.
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.
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.
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.
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.
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.
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. survived103,170 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.
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.
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.
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.
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.
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.
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.
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.
Therapeutic, level III.
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.
...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.
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.
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.
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.
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