Implications of excessive fibrinolysis and alpha(2)-plasmin inhibitor deficiency in patients with severe head injury

Platelet-like particles reduce coagulopathy-related and neuroinflammatory pathologies post-experimental traumatic brain injury

Coagulopathy may occur following traumatic brain injury (TBI), thereby negatively affecting patient outcomes. Here, we investigate the use of platelet-like particles (PLPs), poly(N-isopropylacrylamide-co-acrylic-acid) microgels conjugated with a fibrin-specific antibody, to improve hemostasis post-TBI. The objective of this study was to diminish coagulopathy in a mouse TBI model (controlled cortical impact) via PLP treatment, and subsequently decrease blood-brain barrier (BBB) permeability and neuroinflammation. Following an acute intravenous injection of PLPs post-TBI, we analyzed BBB permeability, ex vivo coagulation parameters, and neuroinflammation at 24 hr and 7 days post-TBI. Both PLP-treatment and control particle-treatment had significantly decreased BBB permeability and improved clot structure 24 hr post-injury. Additionally, no significant change in tissue sparing was observed between 24 hr and 7 days for PLP-treated cohorts compared to that observed in untreated cohorts. Only PLP-treatment resulted in significant reduction of astrocyte expression at 7 days and percent difference from 24 hr to 7 days. Finally, PLP-treatment significantly reduced the percent difference from 24 hr to 7 days in microglia/macrophage density compared to the untreated control. These results suggest that PLP-treatment addressed acute hypocoagulation and decreased BBB permeability followed by decreased neuroinflammation and fold-change tissue loss by 7 days post-injury. These promising results indicate that PLPs could be a potential therapeutic modality for TBI.

Age-Related Differences in the Time Course of Coagulation and Fibrinolytic Parameters in Patients with Traumatic Brain Injury

Coagulopathy and older age are common and well-recognized risk factors for poorer outcomes in traumatic brain injury (TBI) patients; however, the relationships between coagulopathy and age remain unclear. We hypothesized that coagulation/fibrinolytic abnormalities are more pronounced in older patients and may be a factor in poorer outcomes. We retrospectively evaluated severe TBI cases in which fibrinogen and D-dimer were measured on arrival and 3–6 h after injury. Propensity score-matched analyses were performed to adjust baseline characteristics between older patients (the “elderly group,” aged ≥75 y) and younger patients (the “non-elderly group,” aged 16–74 y). A total of 1294 cases (elderly group: 395, non-elderly group: 899) were assessed, and propensity score matching created a matched cohort of 324 pairs. Fibrinogen on admission, the degree of reduction in fibrinogen between admission and 3–6 h post-injury, and D-dimer levels between admission and 3–6 h post-injury were significantly more abnormal in the elderly group than in the non-elderly group. On multivariate logistic regression analysis, independent risk factors for poor prognosis included low fibrinogen and high D-dimer levels on admission. Posttraumatic coagulation and fibrinolytic abnormalities are more severe in older patients, and fibrinogen and D-dimer abnormalities are negative predictive factors.

Prognostic value of coagulation tests for in-hospital mortality in patients with traumatic brain injury

BACKGROUND

Coagulopathy is commonly observed after traumatic brain injury (TBI). However, it is not known whether using the standard independent predictors in conjunction with coagulation tests would improve their prognostic value. We determined the incidence of TBI-associated coagulopathy in patients with isolated TBI (iTBI), evaluated the prognostic value of coagulation tests for in-hospital mortality, and tested their predictive power for in-hospital mortality in patients with iTBI.

METHODS

We conducted a retrospective, observational database study on 2319 consecutive patients with iTBI who attended the Huashan Hospital Department of the Neurosurgery Neurotrauma Center at Fudan University in China between December 2004 and June 2015. Two models based on the admission characteristics were developed: model A included predictors such as age, Glasgow Coma Scale (GCS) score, pupil reactivity, type of injury, and hemoglobin and glucose levels, while model B included the predictors from model A as well as coagulation test results. A total of 1643 patients enrolled between December 2004 and December 2011 were used to derive the prognostic models, and 676 patients enrolled between January 2012 and June 2015 were used to validate the models.

RESULTS

Overall, 18.6% (n = 432) of the patients developed coagulopathy after iTBI. The prevalence of acute traumatic coagulopathy is associated with the severity of brain injury. The percentage of platelet count <100 × 109/L, international normalized ratio (INR) > 1.25, the prothrombin time (PT) > 14 s, activated partial thromboplastin time (APTT) > 36 s, D-dimer >5 mg/L and fibrinogen (FIB) < 1.5 g/L was also closely related to the severity of brain injury, significance being found among three groups. Age, pupillary reactivity, GCS score, epidural hematoma (EDH), and glucose levels were independent prognostic factors for in-hospital mortality in model A, whereas age, pupillary reactivity, GCS score, EDH, glucose levels, INR >1.25, and APTT >36 s exhibited strong prognostic effects in model B. Discrimination and calibration were good for the development group in both prediction models. However, the external validation test showed that calibration was better in model B than in model A for patients from the validation population (Hosmer-Lemeshow test, p = 0.152 vs. p = 0.046, respectively).

CONCLUSIONS

Coagulation tests can improve the predictive power of the standard model for in-hospital mortality after TBI.

Acute Traumatic Coagulopathy Accompanying Isolated Traumatic Brain Injury is Associated with Worse Long-Term Functional and Cognitive Outcomes

BACKGROUND

Approximately one-third of patients with isolated traumatic brain injury (iTBI) present with acute traumatic coagulopathy (ATC). ATC is associated with increased morbidity and mortality. Its effects on long-term functional and cognitive outcomes are not as well characterized.

METHODS

Data from the Citicoline Brain Injury Treatment Trial (COBRIT) were analyzed retrospectively. Exclusion criteria were renal failure or malignancy, and any extracranial injury severity score >3. ATC was defined as INR > 1.3, PTT > 38 s, or platelets < 100 K, determined at baseline, and during the first 7 days of hospitalization.

RESULTS

Six hundred forty-seven patients were included; 21 % were found to have ATC. Highest incidence occurred at baseline, and Day Two. Forty-two percent of ATC patients had a GCS < 8, compared with 11.3 % of non-ATC patients (p < 0.001). A significantly higher proportion of ATC patients was transfused blood products, required greater than 4L of fluids, demonstrated hyperthermia and hypothermia, were hypotensive and demonstrated elevated lactate when compared to non-ATC patients. In-hospital mortality, mean hospital length of stay, incidence of DVT and seizures were also significantly higher in ATC patients. A significantly lower portion of ATC patients had good outcomes on the GOS-E (i.e., score > 6), and the DRS (i.e., score < 2) at 180 days, for which ATC was found to be an independent predictor with binary logistic regression. ATC patients also performed significantly worse on several components of the CVLT-II at 180 days.

CONCLUSIONS

ATC accompanying iTBI is associated with worse functional and cognitive outcomes at 180 days.

Traumatic brain injury associated coagulopathy

BACKGROUND

The presence of coagulopathy is common after severe trauma. The aim of this study was to identify whether isolated severe traumatic brain injury (TBI) is an independent risk factor for coagulopathy.

METHODS

Prospective observational cohort of adult patients admitted to a Level I Trauma Center within 6 h of injury. Patients were categorized according to the abbreviated injury scale (AIS): Group 1-isolated severe TBI (AIS head ≥ 3 + AIS non-head < 3); Group 2-severe multisystem trauma associated with severe TBI (AIS head ≥ 3 + AIS non-head ≥ 3); Group 3-severe multisystem trauma without TBI (AIS head < 3 + AIS non-head ≥ 3). Primary outcome was the development of coagulopathy. Secondary outcome was in-hospital mortality.

RESULTS

Three hundred and forty five patients were included (Group 1 = 48 patients, Group 2 = 137, and Group 3 = 160). Group 1 patients had the lowest incidence of coagulopathy and disseminated intravascular coagulopathy, and in general presented with better coagulation profile measured by either classic coagulation tests, thromboelastography or clotting factors. Isolated severe TBI was not an independent risk factor for the development of coagulopathy (OR 1.06; 0.35-3.22 CI, p = 0.92), however, isolated severe TBI patients who developed coagulopathy had higher mortality rates than isolated severe TBI patients without coagulopathy (66 vs. 16.6 %, p < 0.05). The presence of coagulopathy (OR 5.61; 2.65-11.86 CI, p < 0.0001) and isolated severe TBI (OR 11.51; 3.9-34.2 CI, p < 0.0001) were independent risk factors for in-hospital mortality.

CONCLUSION

Isolated severe TBI is not an independent risk factor for the development of coagulopathy. However, severe TBI patients who develop coagulopathy have extremely high mortality rates.

Time Course of Coagulation and Fibrinolytic Parameters in Patients with Traumatic Brain Injury

Traumatic brain injury (TBI) has long been associated with coagulopathy; however, the time course of coagulation/fibrinolytic parameters in the acute phase of TBI remains unclear. The purpose of the study was to analyze the time course of coagulation/fibrinolytic parameters in the acute phase of TBI and to elucidate parameter relationships to prognosis. We retrospectively evaluated 234 patients with severe isolated TBI with initial blood samples obtained no more than 1 h after injury. Platelet count, prothrombin time, activated partial thromboplastin time (aPTT), plasma levels of fibrinogen, and D-dimer were measured on arrival in the emergency department and 3, 6, and 12 h after injury. Multivariate logistic regression analysis was performed to identify risk factors for poor prognosis at each time point. From hospital admission to 12 h after injury, an elevated D-dimer level was a significant negative prognostic indicator (admission: p < 0.0001; 3 h after injury: p = 0.0005; 6 h after injury: p = 0.005; 12 h after injury: p = 0.0009). An upward trend of aPTT on admission and 3 h after injury was also a significant negative prognostic indicator (admission: p = 0.0011; 3 h after injury: p = 0.013). On multivariate logistic regression analysis, which included all initial variables, independent risk factors for poor prognosis included older age (p = 0.0005), low Glasgow Coma Scale score (p < 0.0001), high Abbreviated Injury Score (p = 0.015), aPTT >30.2 sec (p = 0.019), and elevated D-dimer level (p = 0.0005). We concluded that D-dimer is the best coagulation/fibrinolytic parameter to monitor for prediction of outcome.

Microparticles impact coagulation after traumatic brain injury

BACKGROUND

The pathophysiology that drives the subacute hypercoagulable state commonly seen after traumatic brain injury (TBI) is not well understood. Alterations caused by TBI in platelet and microparticle (MP) numbers and function have been suggested as possible causes; however, the contributions of platelets and MPs are currently unknown.

MATERIALS AND METHODS

A weight-drop technique of TBI using a murine model of moderate head injury was used. Blood was collected at intervals after injury. MP enumeration and characterization were performed using Nanoparticle Tracking Analysis, and platelet counts and coagulation parameters were determined using thromboelastometry. A MP procoagulant assay was used to compare activity between injured and sham mice.

RESULTS

At 24 h after injury, there were no changes in circulating platelet numbers. However, there was a decrease in platelet contribution to clot formation. In contrast, there was a decline in circulating total MP numbers. When MPs from sham mice were added to the blood from head-injured animals, there was a normalization of platelet contribution to clot formation. Conversely, when MPs from TBI mice were added to sham blood, there was a significant decrease in platelet contribution to clot formation. Notably, there was an increase in MP procoagulant activity in head-injured mice.

CONCLUSIONS

MPs generated after TBI likely contribute to altered coagulation after head injury and may play a key role in the development of a posttraumatic hypercoagulable state in TBI patients.

Coagulopathy associated with traumatic brain injury

Coagulopathy is often observed after traumatic brain injury (TBI), but the pathogenic mechanisms of this phenomenon remain elusive. Brain injury is the leading cause of trauma deaths, and the development of coagulopathy after TBI is associated with increased morbidity and mortality in these patients. The coagulopathy after TBI comprises a hypocoagulable and a hypercoagulable state with hemorrhagic and thrombotic phenotypes that are both associated with worse outcome. Some theories of its pathogenesis include massive release of tissue factor, altered protein C homeostasis, microparticle upregulation, and platelet hyperactivity. This article aims to examine the coagulopathy associated with blunt head injury, to review its effect on progression of hemorrhagic injury, and to discuss the possible relevant pathophysiological mechanisms.

Implications of fibrinogenolysis in patients with closed head injury

The objective of this study was to determine the clinical significance of fibrinogenolysis in patients with isolated closed head injury. We correlated indices of fibrinolytic activity, fibrinogen degradation products (FgDP), and fibrin degradation products (FbDP) with outcome in order to accomplish this. This study consisted of 40 patients with isolated closed head trauma in whom blood sampling could be initiated within 3 h after injury. Patients were divided into two groups according to Glasgow Outcome Scale status at 3 months after injury, characterized as good recovery or moderate disability (group 1, n = 21); and severe disability, vegetative, or death (group 2, n = 19). The plasma fibrinogen concentration correlated with the Glasgow Coma Scale score on admission (r2 = 0.201, p < 0.01), and plasma fibrinogen concentrations in group 2 were lower than in group 1 (p < 0.05). Plasma concentrations of fibrin/fibrinogen degradation products (FDP) and plasmin-alpha2-plasmin inhibitor complex (PIC), molecular markers of activation of fibrinolysis, were higher in group 2 than in group 1 (p < 0.001), and both FgDP and FbDP concentrations in group 2 also were higher than in group 1 (p < 0.001). Both the FgDP and FbDP concentrations correlated with the PIC concentration. Moreover, the plasma FgDP concentrations correlated inversely with alpha2-plasmin inhibitor activity, a potent inhibitor of the fibrinolytic sysytem, as did the FbDP concentration. This study reveals that both fibrinolysis and fibrinogenolysis are involved in the coagulopathy that develops during the acute phase of head injury and correlate with fibrinolytic activity. Decreased activity of alpha2-plasmin inhibitor may contribute to fibrinogenolysis.