Anticoagulant prophylaxis against venous thromboembolism following severe traumatic brain injury: A prospective observational study and systematic review of the literature

A nomogram for predicting risk factors for lower limb deep venous thrombosis in elderly postoperative patients with severe traumatic brain injury in the intensive care unit

AimTo investigate the incidence and risk factors for lower limb deep venous thrombosis in elderly postoperative patients with severe traumatic brain injury in the intensive care unit.DesignA retrospective study.MethodsFour hundred and one elderly patients (defined as aged ≥60 years) with severe traumatic brain injury who had undergone surgery and were admitted to the intensive care unit were enrolled in this study. We collected data on the incidence of lower extremity deep vein thrombosis and analyzed its influencing factors. Binary logistic regression analysis was employed to assess the associations between these factors and the occurrence of DVT. A nomogram was developed, and calibration curves were utilized to evaluate the model's accuracy. Additionally, a receiver operating characteristic curve was employed to assess the model's clinical discriminatory power.ResultsThe incidence of lower limb deep venous thrombosis in elderly postoperative patients with severe traumatic brain injury in the intensive care unit was 25.69%. The final nomogram included age, intraoperative hypothermia, intraoperative bleeding volume, surgery time, D-dimer level, any organ failure, and body mass index as independent risk factors. The standard curve fit well with the calibrated prediction curve. The area under the receiver operating characteristic curve was 0.976 (95% CI: 0.958-0.994), and the model had good discrimination ability and reliability.ConclusionsThe risk factors for lower limb deep venous thrombosis in elderly postoperative patients with severe traumatic brain injury in the intensive care unit can be preliminarily assessed via the nomogram prediction model. This information may help guide medical staff in making reasonable decisions regarding the management of deep vein thrombosis prophylaxis.Patient or Public ContributionElderly postoperative patients with severe traumatic brain injury in the intensive care unit participated in the retrospective investigation of this study.

A comparative analysis of three risk assessment scales for predicting venous thromboembolism in traumatic brain injury patients

Venous thromboembolism (VTE) is a common complication in patients with traumatic brain injury (TBI). This study aimed to assess the predictive ability of the Caprini score, Risk Assessment Profile for Thromboembolism (RAPT), and Trauma Embolic Scoring System(TESS) for VTE risk assessments in TBI patients. A retrospective analysis of 460 TBI patients was conducted, categorizing them into VTE and non-VTE groups based on imaging results. The three scales were applied to assess VTE risk, and their performance was compared using receiver operating characteristic(ROC) curves and area under the curve(AUC) values. The VTE incidence was 31.7%. The RAPT scale demonstrated the highest AUC (0.826) and optimal cutoff (9.5) with balanced sensitivity (0.753) and specificity (0.771). The Caprini and TESS scales also showed moderate to high predictive value but had lower AUCs. All three scoring scales showed medium to high predictive value for the risk of VTE in patients with TBI. Among them, the RAPT scoring scale offered the highest predictive value for VTE risk in TBI patients, with fewer items, making it easier for clinical implementation. It stands as the most appropriate VTE risk assessment scale for TBI patients at present.

A systematic review and meta-analysis on the impact of early vs. delayed pharmacological thromboprophylaxis in patients with traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) poses significant health challenges, often leading to complications such as venous thromboembolism (VTE) and increased mortality rates. The administration of early post-traumatic prophylaxis (PTP) is intended to mitigate these risks and enhance overall patient recovery. This study aims to perform a systematic review and meta-analysis assessing clinical outcomes associated with early versus late pharmacologic thromboprophylaxis in TBI patients.

METHODS

We conducted a literature search across PubMed and Scopus databases from their inception to March 2024. Data from eligible studies were aggregated using the generic inverse variance method, with outcomes reported as odds ratios (OR).

RESULTS

The review encompassed 20 studies involving 87,726 patients. Early PTP was categorized based on the timing of administration: 1) within 24 h, 2) within 48 h, and 3) within 72 h of hospital admission. Our findings indicated that early prophylaxis significantly reduced the incidence of VTE, deep vein thrombosis (DVT), pulmonary embolism (PE), and overall mortality when compared to late administration. Specifically, early PTP was associated with a markedly lower risk of VTE (OR: 0.38; 95 % CI: 0.30 to 0.48; P < 0.00001), DVT (OR: 0.32; 95 % CI: 0.25 to 0.41; P < 0.00001), and PE (OR: 0.39; 95 % CI: 0.31 to 0.49; P < 0.00001). Furthermore, the analysis revealed a significant reduction in all-cause mortality within the early PTP group (OR: 0.71; 95 % CI: 0.53 to 0.97; P = 0.03). However, while statistically significant improvements were observed in the <48-hour subgroup, neither the <24-hour nor <72-hour groups achieved statistical significance.

CONCLUSION

These robust findings highlight the potential of early pharmacologic thromboprophylaxis as a crucial intervention to enhance patient outcomes following traumatic brain injuries.

Management of post-injury anticoagulation in the traumatic brain injury patient: A scoping review

Traumatic brain injury (TBI) remains a leading cause of morbidity and mortality among trauma patients. The care of these patients continues to be a complex endeavor with prevention of associated complications, often requiring as much attention as that of the treatment of the primary injury. Paramount among these are venous thromboembolic events (VTE) due to their high incidence, additive effect on the risk of morbidity and mortality, and the careful balance that must be utilized in their diagnosis and treatment to prevent progression of the brain injury itself. In this review, we have synthesized the most recent major studies detailing the ideal choice of chemoprophylactic agent, the timing of initiation, and continued monitoring and management strategies through the hospital course and beyond. Additional discussion is provided for subpopulations in which management can vary significantly, including the elderly, critically ill, and obese. Ultimately, current literature supports the use and safety of low molecular weight heparin over unfractionated heparin, especially when dosed using newer assays including anti-Xa levels. The timing of prophylaxis remains important, as the risk of VTE increases with each day that prophylaxis is held. Consensus findings favor initiation within 24-72 h, in the absence of documented progression, life threatening bleeding, or need for major surgical intervention. Despite available data, there continues to be significant variability in practice patterns which we hope to address with this review.

Venous thromboembolism chemoprophylaxis after severe polytrauma: timing and type of prophylaxis matter

In this review, we provide recommendations as well as summarize available data on the optimal time to initiate venous thromboembolism chemoprophylaxis after severe trauma. A general approach to the severe polytrauma patient is provided as well as in-depth reviews of three high-risk injury subgroups: patients with traumatic brain injury, solid organ injury, and pelvic fractures.

The safety of early pharmacological venous thromboembolism prophylaxis in patients with traumatic intracranial haemorrhage: a systematic review and meta-analysis

INTRODUCTION

In patients with traumatic intracranial haemorrhage (tICH) there is significant risk of both venous thromboembolism (VTE) and haemorrhage progression. There is a paucity of literature to inform the timing of pharmacological thromboprophylaxis (PTP) initiation.

AIM

This meta-analysis aims to summarise the current literature on the timing of PTP initiation in tICH.

METHODS

This meta-analysis followed the Methodological Expectations of Cochrane Intervention Reviews checklist and the Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines. Following the literature search, studies were matched against the criteria for inclusion. Data from included studies was pooled, analysed using random-effect analysis and presented as forest plots of risk ratios, except one result reported as difference of means. The ROBINS-I tool was used to assess the risk of bias in the studies. The GRADE approach was taken to assess the quality of included studies. Heterogeneity of studies was assessed using Tau∧2. Funnel plots were generated and used in conjunction with Harbord's test and Rucker's arcsine to assess for small-study effect including publication bias.

RESULTS

A total of 9927 ICH patients who received PTP were included from 15 retrospective observational cohort studies, 4807 patients received early PTP, the remaining 5120 received late PTP. The definition of early was dependent on the study but no more than 72-hours after admission. The mean age of the included cohort was 45.3 (std dev ±9.5) years, and the proportion of males was 71%. Meta-analysis indicated that there was a significant difference between early and late groups for the rate of VTE (RR, 0.544; p = 0.000), pulmonary embolus (RR, 0.538; p = 0.004), deep vein thrombosis (RR, 0.484; p = 0.000) and the intensive care unit length of stay (difference of means, -2.021; 95% CI, -2.250, -1.792; p = 0.000; Tau∧2 = 0.000), favouring the early group. However, the meta-analysis showed no significant difference between the groups for the rate of mortality (RR, 1.008; p = 0.936), tICH progression (RR, 0.853; p = 0.157), and neurosurgical intervention (RR, 0.870; p = 0.480).

CONCLUSION

These findings indicated that early PTP appears to be safe and effective in patients with tICH.

Venous Thromboembolism: Exploring Incidence and Utility of Screening in Individuals With Brain Injury

OBJECTIVE

To determine the incidence of VTE in the population with brain injuries (BIs) using ultrasonography, and to assess the risk of pulmonary embolism (PE) development and/or bleeding complications related to anticoagulation.

DESIGN

Retrospective study.

SETTING

Acute rehabilitation hospital.

PARTICIPANTS

238 individuals with moderate to severe BI who were routinely screened for VTE with ultrasonography on admission to rehabilitation (N=238).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Retrospective chart review was performed to identify individuals who were diagnosed with VTE at the following 3 time points: in acute care prior to admission to rehabilitation, at the time of admission diagnosed via screening examination, and after admission to rehabilitation. Additionally, risk factors for VTE, PE, and incidence of bleeding complications related to therapeutic anticoagulation were assessed.

RESULTS

123 deep vein thromboses (DVTs) were identified with 38.2% in acute care (n=47), 69.1% on admission to rehabilitation (n=85), and 7.3% during the course of rehabilitation stay (n=9). Risk factors for development of VTE included age at injury, body mass index, injury etiology, history of neurosurgical procedure, and surgery during inpatient rehabilitation. Of those who were placed on therapeutic anticoagulation due to admission diagnosis of VTE (n=50), 2% developed recurrent DVT and 2% had bleeding complications. There was zero incidence of PE.

CONCLUSION

We demonstrated a high prevalence of VTEs identified on screening ultrasonography on admission to inpatient rehabilitation among individuals with moderate to severe BIs, and low complications related to anticoagulation. Given the findings of this study, prospective research in ultrasonography screening for VTE in moderate to severe BI is needed.

Early start of thromboprophylaxis does not increase risk of intracranial hematoma progression in multiply injured patients with traumatic brain injury

BACKGROUND

Venous thromboembolism (VTE) in severely injured patients with severe traumatic brain injury (TBI) is a risk during the clinical course. Data on the safety of an early initiation of pharmacological VTE prophylaxis in severely injured patients with concomitant severe TBI is sparse.

METHODS

Admissions to our level-1-trauma center between January 2015 and December 2018 were screened. Patients suffering from severe TBI (Abbreviated Injury Scale (AIS) of the head ≥3) and at least one further AIS ≥ 3 in any other body region were included. Demographic data, thromboembolic events, and progression of the intracranial hemorrhage were extracted from the patient's charts. According to the first application of pharmacological thromboprophylaxis (VTEp), patients were categorized either to the early, the late (later than 24 h) or the no therapy group.

RESULTS

In 79 patients (early: n = 35, late: n = 29, no therapy: n = 15) the Injury Severity Score (ISS) was 36.7 ± 12.7 points (AIS_head 4.1 ± 0.8). No differences were found regarding the progression of the intracranial hemorrhage after initiation of the VTE prophylaxis (adj. p = 0.8). The VTE rate was low (n = 1, 1.6%).

CONCLUSION

In severely injured patients with severe TBI, the early administration of pharmacological thromboprophylaxis did not result in a higher rate of intracranial hematoma progression.

Effects of Early Chemoprophylaxis in Traumatic Brain Injury and Risk of Venous Thromboembolism

BACKGROUND

The optimal timing to initiate venous thromboembolism (VTE) prophylaxis in patients with a traumatic brain injury (TBI) is still unknown. We designed a study to determine the effect that timing of initiation of VTE prophylaxis has on VTE rates in TBI patients.

METHODS

Patient records were obtained from 32 level 1 and 2 trauma centers in the Michigan Trauma Quality Improvement Program from 2008 to 2018. Overall, 5589 patients with a TBI were included and split into cohorts based on VTE prophylaxis initiation time. Outcomes included rate of VTE, mortality, and serious in-hospital complications.

RESULTS

There were nine patients (1.3%) in the <24 hour group with a VTE as compared to 36 (2.6%) in the 24-48 hour group, 51 (4.1%) in the 48-72 hour group, and 181 (8.1%) in the >72 hour group (P < .001). The adjusted odds of VTE were significantly greater in patients initiated within 48-72 hours (AOR 2.861, 95% CI 1.271-6.439) and >72 hours (AOR 3.963, 95% CI 1.824-8.612) compared to <24 hours. Patients that received VTE prophylaxis within 24 hours had similar rates of serious in-hospital complication as patients initiated within 24-48 hours (AOR .956, 95% CI .637-1.434) and 48-72 hour (AOR 1.132, 95% CI .757-1.692) but less than the >72 hour group (AOR 1.662, 95% CI 1.154-2.393) groups.

DISCUSSION

Patients initiated on VTE prophylaxis within 48 hours of presentation had lower incidence of VTE without a significant increase in serious complications.

The association of timing of pharmacological prophylaxis and venous thromboembolism in patients with moderate-to-severe traumatic brain injury: A retrospective cohort study

OBJECTIVES:

Patients with traumatic brain injury (TBI) have an increased risk for venous thromboembolism (VTE). The current guidelines recommend pharmacologic prophylaxis, but its timing remains unclear.

METHODS:

In this retrospective cohort study, patients with moderate-to-severe TBI admitted to a tertiary care intensive care unit between 2016 and 2019 were categorized into two groups according to the timing of pharmacologic prophylaxis: early if prophylaxis was given within 72 h from hospital admission and late if after 72 h.

RESULTS:

Of the 322 patients in the cohort, 46 (14.3%) did not receive pharmacological prophylaxis, mainly due to early brain death; 152 (47.2%) received early pharmacologic prophylaxis and 124 (38.5%) received late prophylaxis. Predictors of late pharmacologic prophylaxis were lower body mass index, intracerebral hemorrhage (odds ratio [OR], 3.361; 95% confidence interval [CI], 1.269–8.904), hemorrhagic contusion (OR, 3.469; 95% CI, 1.039–11.576), and lower platelet count. VTE was diagnosed in 43 patients on a median of 10 days after trauma (Q1, Q3: 5, 15): 6.6% of the early prophylaxis group and 26.6% of the late group (P < 0.001). On multivariable logistic regression analysis, the predictors of VTE were Acute Physiology and Chronic Health Evaluation II score, subarachnoid hemorrhage, and late versus early pharmacologic prophylaxis (OR, 3.858; 95% CI, 1.687–8.825). The late prophylaxis group had higher rate of tracheostomy, longer duration of mechanical ventilation and stay in the hospital, lower discharge Glasgow coma scale, but similar survival, compared with the early group.

CONCLUSIONS:

Late prophylaxis (>72 h) was associated with higher VTE rate in patients with moderate-to-severe TBI, but not with higher mortality.

Venous thromboembolism prophylaxis and related outcomes in patients with traumatic brain injury and prolonged intensive care unit stay

Objective: Traumatic brain injury (TBI) patients with prolonged intensive care unit (ICU) stay are at risk of secondary intracranial haemorrhage (ICH) and venous thromboembolism (VTE). We aimed to study VTE prophylaxis, secondary ICH, and VTE prevalence and outcomes in this population. Design: Retrospective observational study. Setting: Level 1 trauma centre ICU. Patients: One hundred TBI patients receiving prolonged ICU treatment (≥ 7 days). Interventions: We collected data from medical records, pathology and radiology systems, and hospital and ICU admission databases. We analysed patient characteristics, interventions, episodes and types of secondary ICH and VTE, and timing and dosage of VTE prophylaxis. Results: Data from the 100 patients in our study showed that early use of compression stockings and pneumatic calf compression was common (75% and 91% in the first 3 days, respectively). VTE chemoprophylaxis, however, was only used in 14% of patients by Day 3 and > 50% by Day 10. We observed VTE in 12 patients (10 as pulmonary embolism), essentially all after Day 6. Radiologically confirmed secondary ICH occurred in 43% of patients despite normal coagulation. However, 72% of ICH events (42/58) were radiologically mild, and the median time of onset of ICH was Day 1, when only 3% of patients were on chemical prophylaxis. Moreover, 82% of secondary ICH events (48/58) occurred in the first 3 days, with no severe ICH thereafter. Conclusions: In TBI patients receiving prolonged ICU treatment, early chemical VTE prophylaxis was uncommon. Early secondary ICH was common and mostly radiologically mild, whereas later secondary ICH was essentially absent. In contrast, early VTE was essentially absent, whereas later VTE was relatively common. Earlier chemical VTE prophylaxis and/or ultrasound screening in this population appears logical.

Venous Thromboembolism Chemoprophylaxis in Trauma and Emergency General Surgery Patients: A Systematic Review

BACKGROUND

Appropriate venous thromboembolism (VTE) chemoprophylaxis in trauma and emergency general surgery (EGS) patients is crucial.

OBJECTIVE

The purpose of this study is to review the recent literature and offer recommendations for VTE chemoprophylaxis in trauma and EGS patients.

METHODS

We conducted a literature search from 2000 to 2021 for articles investigating VTE chemoprophylaxis in adult trauma and EGS patients. This study was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines.

RESULTS

Our search resulted in 34 articles. Most studies showed low-molecular-weight heparin (LMWH) is similar to unfractionated heparin (UFH) for VTE prevention; however, LMWH was more commonly used. Adjusted chemoprophylaxis dosing did not change the VTE rate but the timing did. Direct oral anticoagulants (DOACs) have been shown to be safe and effective in trauma and traumatic brain injury (TBI)/spinal cord injury (SCI). Studies showed VTE prophylaxis in EGS can be inconsistent and improves with guidelines that lower VTE events.

CONCLUSIONS

There may be no benefit to receiving LMWH over UFH in trauma patients. In addition, different drugs under the class of LMWH do not change the incidence of VTE. Adjusted dosing of enoxaparin does not seem to affect VTE incidence. The use of DOACs in the trauma TBI and SCI setting has been shown to be safe and effective in reducing VTE. One important consideration with VTE prophylaxis may be the timing of prophylaxis initiation, specifically as it relates to TBI, with a higher likelihood of developing VTE as time progresses. EGS patients are at a high risk of VTE. Improved compliance with clinical guidelines in this population is correlated with decreased thrombotic events.

Time Course of Hemostatic Disruptions After Traumatic Brain Injury: A Systematic Review of the Literature

Almost two-thirds of patients with severe traumatic brain injury (TBI) develop some form of hemostatic disturbance, which contributes to poor outcome. While the initial head injury often leads to impaired clot formation, TBI is also associated with an increased risk of thrombosis. Most likely there is a progression from early bleeding to a later prothrombotic state. In this paper, we systematically review the literature on the time course of hemostatic disruptions following TBI. A MEDLINE search was performed for TBI studies reporting the trajectory of hemostatic assays over time. The search yielded 5,049 articles, of which 4,910 were excluded following duplicate removal as well as title and abstract review. Full-text assessment of the remaining articles yielded 33 studies that were included in the final review. We found that the first hours after TBI are characterized by coagulation cascade dysfunction and hyperfibrinolysis, both of which likely contribute to lesion progression. This is then followed by platelet dysfunction and decreased platelet count, the clinical implication of which remains unclear. Later, a poorly defined prothrombotic state emerges, partly due to fibrinolysis shutdown and hyperactive platelets. In the clinical setting, early administration of the antifibrinolytic agent tranexamic acid has proved effective in reducing head-injury-related mortality in a subgroup of TBI patients. Further studies evaluating the time course of hemostatic disruptions after TBI are warranted in order to identify windows of opportunity for potential treatment options.

Traumatic Brain Injury: Does Admission Service Matter?

BACKGROUND

Traumatic brain injury (TBI) is common, and significant institutional variation exists with regards to structure and processes of care. Affected patients may be admitted to one of several different services, and this may drive differential care and outcomes. We sought to evaluate differential care and outcomes for patients with isolated mild-to-moderate traumatic brain injury based on admission service.

MATERIALS AND METHODS

This is a single-institution retrospective study of all adult (≥18 y old) patients admitted with isolated TBI (AIS ≤1 in all other body regions) over a 3-year period (6/2015-6/2018). Patients who underwent neurosurgical intervention (craniectomy/craniotomy) and those with a head AIS ≥4 were excluded. Patients were assigned to one of three groups based upon admission service: Trauma Surgery, Neurology/Medicine or Neurosurgery. Outcomes evaluated included in-hospital mortality and markers of differential care. We performed multivariate analyses adjusting for patient demographics and clinical characteristics.

RESULTS

A total of 401 isolated mild-to-moderate TBI patients were identified. Overall mortality was 1.7%. Adjusted multivariate logistic regression analysis demonstrated no difference in mortality. Patients admitted to Neurosurgery underwent more repeat head CTs and were more likely to receive antiseizure medication in the absence of seizure activity, and those admitted to Neurology/Medicine were less likely to receive venous thromboembolism chemoprophylaxis compared to those admitted to Trauma Surgery.

CONCLUSIONS

We identify several important metrics of variation in care received by patients with an isolated mild-to-moderate TBI based upon admission service. These findings deserve further study, and this study may lay the foundation for future efforts at protocolizing care in an evidence-based fashion for this patient cohort.

Management and Challenges of Severe Traumatic Brain Injury

Traumatic brain injury (TBI) is the leading cause of death and disability in trauma patients, and can be classified into mild, moderate, and severe by the Glasgow coma scale (GCS). Prehospital, initial emergency department, and subsequent intensive care unit (ICU) management of severe TBI should focus on avoiding secondary brain injury from hypotension and hypoxia, with appropriate reversal of anticoagulation and surgical evacuation of mass lesions as indicated. Utilizing principles based on the Monro-Kellie doctrine and cerebral perfusion pressure (CPP), a surrogate for cerebral blood flow (CBF) should be maintained by optimizing mean arterial pressure (MAP), through fluids and vasopressors, and/or decreasing intracranial pressure (ICP), through bedside maneuvers, sedation, hyperosmolar therapy, cerebrospinal fluid (CSF) drainage, and, in refractory cases, barbiturate coma or decompressive craniectomy (DC). While controversial, direct ICP monitoring, in conjunction with clinical examination and imaging as indicated, should help guide severe TBI therapy, although new modalities, such as brain tissue oxygen (PbtO₂) monitoring, show great promise in providing strategies to optimize CBF. Optimization of the acute care of severe TBI should include recognition and treatment of paroxysmal sympathetic hyperactivity (PSH), early seizure prophylaxis, venous thromboembolism (VTE) prophylaxis, and nutrition optimization. Despite this, severe TBI remains a devastating injury and palliative care principles should be applied early. To better affect the challenging long-term outcomes of severe TBI, more and continued high quality research is required.

Intracranial pressure monitors associated with increased venous thromboembolism in severe traumatic brain injury

Background

Utilization of intracranial pressure monitors (ICPMs) has not been consistently shown to improve mortality in patients with severe traumatic brain injury (TBI). A single-center analysis concluded that venous thromboembolism (VTE) chemoprophylaxis (CP) posed no significant bleeding risk in patients following ICPM implementation; however, there is still debate about the optimal use and timing of CP in patients with ICPMs for fear of worsening intracranial hemorrhage. We hypothesized that ICPM use is associated with increased time to VTE CP and thus increased VTE in patients with severe TBI.

Methods

A retrospective analysis of the Trauma Quality Improvement Program (2010–2016) was performed to compare severe TBI patients with and without ICPMs. A multivariable logistic regression analysis was completed.

Results

From 35,673 patients with severe TBI, 12,487 (35%) had an ICPM. Those with ICPMs had a higher rate of VTE CP (64.3% vs. 49.4%, p < 0.001) but a longer median time to CP initiation (5 vs. 4 days, p < 0.001) as well as a longer hospital length of stay (LOS) (18 vs. 9 days, p < 0.001) compared to those without ICPMs. After adjusting for covariates, ICPM use was found to be associated with a higher risk of VTE (9.2% vs 4.3%, OR = 1.75, CI = 1.42–2.15, p < 0.001).

Conclusions

Compared to patients without ICPMs, those with ICPMs had a longer delay to initiation of CP leading to an increase in VTE. In addition, there was a nearly two-fold higher associated risk for VTE in patients with ICPMs even when controlling for known VTE risk factors. Improved adherence to initiation of CP in the setting of ICPMs may help decrease the associated risk of VTE with ICPMs.

Does Complement-Mediated Hemostatic Disturbance Occur in Traumatic Brain Injury? A Literature Review and Observational Study Protocol

Despite improvements in medical triage and tertiary care, traumatic brain injury (TBI) remains associated with significant morbidity and mortality. Almost two-thirds of patients with severe TBI develop some form of hemostatic disturbance, which contributes to poor outcome. In addition, the complement system, which is abundant in the healthy brain, undergoes significant intra- and extracranial amplification following TBI. Previously considered to be structurally similar but separate systems, evidence of an interaction between the complement and coagulation systems in non-TBI cohorts has accumulated, with the activation of one system amplifying the activation of the other, independent of their established pathways. However, it is not known whether this interaction exists in TBI. In this review we summarize the available literature on complement activation following TBI, and the crosstalk between the complement and coagulation systems. We demonstrate how the complement system interacts with the coagulation cascade by activating the intrinsic coagulation pathway and by bypassing the initial cascade and directly producing thrombin as well. This crosstalk also effects platelets, where evidence points to a relationship with the complement system on multiple levels, with complement anaphylatoxins being able to induce disproportionate platelet activation and adhesion. The complement system also stimulates thrombosis by inhibiting fibrinolysis and stimulating endothelial cells to release prothrombotic microparticles. These interactions see clinical relevance in several disorders where a deficiency in complement regulation seems to result in a prothrombotic clinical presentation. Finally, based on these observations, we present the outline of an observational cohort study that is currently under preparation and aimed at assessing how complement influences coagulation in patients with isolated TBI.