Fibrinogen and platelet contributions to clot formation: implications for trauma resuscitation and thromboprophylaxis

Thromboelastography and Thromboelastometry in Assessment of Fibrinogen Deficiency and Prediction for Transfusion Requirement: A Descriptive Review

Fibrinogen is crucial for the formation of blood clot and clinical outcomes in major bleeding. Both Thromboelastography (TEG) and Rotational Thromboelastometry (ROTEM) have been increasingly used to diagnose fibrinogen deficiency and guide fibrinogen transfusion in trauma and surgical bleeding patients. We conducted a comprehensive and comparative review on the technologies and clinical applications of two typical functional fibrinogen assays using TEG (FF TEG) and ROTEM (FIBTEM) for assessment of fibrinogen level and deficiency, and prediction of transfusion requirement. Clot strength and firmness of FF TEG and ROTEM FIBTEM were the most used parameters, and their associations with fibrinogen levels as measured by Clauss method ranged from 0 to 0.9 for FF TEG and 0.27 to 0.94 for FIBTEM. A comparison of the interchangeability and clinical performance of the functional fibrinogen assays using the two systems showed that the results were correlated, but are not interchangeable between the two systems. It appears that ROTEM FIBTEM showed better associations with the Clauss method and more clinical use for monitoring fibrinogen deficiency and predicting transfusion requirements including fibrinogen replacement than FF TEG. TEG and ROTEM functional fibrinogen tests play important roles in the diagnosis of fibrinogen-related coagulopathy and guidance of transfusion requirements. Despite the fact that high-quality evidence is still needed, the two systems are likely to remain popular for the hemostatic management of bleeding patients.

Perhaps it's not the platelet: Ristocetin uncovers the potential role of von Willebrand factor in impaired platelet aggregation following traumatic brain injury

BACKGROUND

Injury to the blood-brain barrier exposes endothelium rich in von Willebrand factor (vWF), which may play a role in altered platelet aggregation following traumatic brain injury (TBI). Ristocetin is an antimicrobial substance that induces vWF-mediated aggregation of platelets. We examined these mechanisms in injured patients by measuring the aggregation response of platelets to stimulating agonists (including ristocetin) via whole-blood multiple-electrode platelet aggregometry. We hypothesized that patients with TBI have an altered platelet aggregation response to ristocetin stimulation compared with patients without TBI.

METHODS

Blood was collected from 233 trauma patients without thrombocytopenia. Platelet aggregation was assessed using multiple-electrode platelet aggregometry (Multiplate). Platelet aggregation response to stimulating agonists collagen, thrombin receptor-activating peptide 6, adenosine diphosphate, arachidonic acid, and ristocetin was measured. Factor activity was measured.

RESULTS

Of the 233 patients, 23% had TBI. There were no differences in platelet aggregation responses to any agonists between TBI and non-TBI patients except ristocetin. Platelet aggregation response to ristocetin stimulation was significantly lower in TBI patients (p = 0.03). Patients with TBI also had higher factor VIII activity (215% vs. 156%, p = 0.01). In multivariate analysis, there was a significant independent association of impaired platelet aggregation response to ristocetin stimulation with TBI (odds ratio, 3.05; p = 0.04).

CONCLUSIONS

Given the importance of platelets in hemostasis, understanding the mechanisms of impaired platelet aggregation following injury is critical. The impaired platelet aggregation response to ristocetin stimulation and corresponding increase in factor VIII activity in TBI patients may be secondary to a TBI-induced effect on vWF quantity (due to injury-driven consumption of vWF) or vWF function with resultant increase in circulating factor VIII activity (due to impaired carrying capacity of vWF). Given there are multiple known therapies for vWF deficits including desmopressin, purified and recombinant vWF, and estrogens, these lines of investigation are particularly compelling in patients with TBI and hemorrhage.

LEVEL OF EVIDENCE

Prognostic study, level II.

Microfluidics contrasted to thrombelastography: perplexities in defining hypercoagulability

BACKGROUND

Elevated clot strength (maximum amplitude [MA]) measured by thrombelastography (TEG) is associated with thrombotic complications. However, it remains unclear how MA translates to thrombotic risks, as this measurement is independent of time, blood flow, and clot degradation. We hypothesize that under flow conditions, increased clot strength correlates to time-dependent measurements of coagulation and resistance to fibrinolysis.

MATERIALS AND METHODS

Surgical patients at high risk of thrombotic complications were analyzed with TEG and total thrombus-formation analysis system (T-TAS). TEG hypercoagulability was defined as an r <10.2 min, angle >59, MA >66 or LY30 <0.2% (based off of healthy control data, n = 141). The T-TAS AR and PL chips were used to measure clotting at arterial shear rates. T-TAS measurements include occlusion start time, occlusion time (OT), occlusion speed (OSp), and total clot generation (area under the curve). These measurements were correlated to TEG indices (R time, angle, MA, and LY30). Both T-TAS and TEG assays were challenged with tissue plasminogen activator (t-PA) to assess clot resistance to fibrinolysis.

RESULTS

Thirty subjects were analyzed, including five controls. TEG-defined hypercoagulability by MA was detected in 52% of the inflammatory bowel disease/cancer patients; 0% was detected in the controls. There were no TEG measurements that significantly correlated with T-TAS AR and PL chip. However, in the presence of t-PA, T-TAS AR determined OSp to have an inverse relationship with TEG angle (-0.477, P = 0.012) and LY30 (-0.449, P = 0.019), and a positive correlation with R time (0.441 P = 0.021). In hypercoagulability determined by TEG MA, T-TAS PL had a significantly reduced OT (4:07 versus 6:27 min, P = 0.043). In hypercoagulability defined by TEG LY30, T-TAS PL had discordant findings, with a significantly prolonged OT (6:36 versus 4:30 min, P = 0.044) and a slower OSp (10.5 versus 19.0 kPa/min, P = 0.030).

CONCLUSIONS

Microfluidic coagulation assessment with T-TAS has an overall poor correlation with most TEG measurements in a predominantly hypercoagulable patient population, except in the presence of t-PA. The one anticipated finding was an elevated MA having a shorter time to platelet-mediated microfluidic occlusion, supporting the role of platelets and hypercoagulability. However, hypercoagulability defined by LY30 had opposing results in which a low LY30 was associated with a longer PL time to occlusion and slower OSp. These discordant findings warrant ongoing investigation into the relationship between clot strength and fibrinolysis under different flow conditions.

Optimizing transfusion strategies in damage control resuscitation: current insights

From clinical and laboratory studies of specific coagulation defects induced by injury, damage control resuscitation (DCR) emerged as the most effective management strategy for hemorrhagic shock. DCR of the trauma patient who has sustained massive blood loss consists of 1) hemorrhage control; 2) permissive hypotension; and 3) the prevention and correction of trauma-induced coagulopathies, referred to collectively here as acute coagulopathy of trauma (ACOT). Trauma patients with ACOT have higher transfusion requirements, may eventually require massive transfusion, and are at higher risk of exsanguinating. Distinct impairments in the hemostatic system associated with trauma include acquired quantitative and qualitative platelet defects, hypocoagulable and hypercoagulable states, and dysregulation of the fibrinolytic system giving rise to hyperfibrinolysis or a phenomenon referred to as fibrinolytic shutdown. Furthermore, ACOT is a component of a systemic host defense dysregulation syndrome that bears several phenotypic features comparable with other acute systemic physiological insults such as sepsis, myocardial infarction, and postcardiac arrest syndrome. Progress in the science of resuscitation has been continuing at an accelerated rate, and clinicians who manage catastrophic blood loss may be incompletely informed of important advances that pertain to DCR. Therefore, we review recent findings that further characterize the pathophysiology of ACOT and describe the application of this new information to optimization of resuscitation strategies for the patient in hemorrhagic shock.

Efficacy of Thromboelastography (TEG) in Predicting Acute Trauma-Induced Coagulopathy (ATIC) in Isolated Severe Traumatic Brain Injury (iSTBI)

To evaluate the efficacy of point-of-care thromboelastography (TEG) to predict acute trauma-induced coagulopathy (ATIC) in isolated severe TBI (iSTBI). We conducted an observational diagnostic cohort. Patients for whom TEG was performed before blood transfusion were stratified by conventional coagulation tests (CCTs) on admission and classified as "ATIC" (prothrombin time ≥ 16.70 s; international normalized ratio ≥ 1.27; activated partial thromboplastin time ≥ 28.80 s) (n = 24) or "no ATIC" (n = 34). Univariate analysis to compare groups, receiver operating characteristic analysis to establish cut-off and diagnostic validation was done. Fifty-eight patients were included [32(25-45) years; 97% male; GCS 6.3 ± 1.5]. 41% developed ATIC. Compared to no-ATIC, ATIC group had significantly prolonged κ-time (4.6 vs. 2.5 min; p = 0.01) and shortened α-angle (40.2° vs. 56.3°; p = 0.03). A cut-off for κ-time ≥ 3.7 (AUC 0.68 95% CI 0.54-0.82, specificity 70%, sensitivity 63%) and α angle ≤ 48.0 (AUC 0.66, 95% CI 0.51-0.81, specificity 67%, sensitivity 67%) was established. The diagnostic accuracy of this cut-off for identifying ATIC, was 55.6% with sensitivity (81.8%) and specificity (14.3%). TEG may be a clinically sensitive test for identifying the underlying coagulopathy following TBI. However confirmation with CCTs is recommended.

Fibrinogen supplementation ex vivo increasesclot firmness comparable to platelet transfusion in thrombocytopenia

BACKGROUND

Fibrinogen concentrate can improve clot firmness and offers a better safety profile than platelet concentrates. Reduction or avoidance of blood transfusions represents a strategy to reduce associated risks. We investigated whether supplementation of fibrinogen concentrate ex vivo can compensate for clot strength as compared with platelet transfusion in vivo METHODS: One hundred patients in need of platelet transfusion (PT) were enrolled. Blood samples were collected immediately before PT and at 1 h and 24 h after PT. Fibrinogen concentrate was added to these citrated whole blood samples at concentrations of 50, 100, 200 and 400 mg kg^-1 and the maximum clot firmness (MCF) was analysed using ROTEM thromboelastometry.

RESULTS

Fibrinogen supplementation increased MCF significantly and dose-dependently before and after PT. The effect of fibrinogen concentrate (equivalent to doses of 100 and 200 mg kg^-1) ex vivo was comparable to that of PT in vivo, whereas 400 mg kg^-1 fibrinogen significantly improved MCF compared with PT (P < 0.001).

CONCLUSIONS

Fibrinogen concentrate can match the effect of PT on MCF in thrombocytopenia. This potential alternative haemostatic intervention should be evaluated in clinical trials.

Amicus or Adversary Revisited: Platelets in Acute Lung Injury and Acute Respiratory Distress Syndrome

Platelets are essential cellular effectors of hemostasis and contribute to disease as circulating effectors of pathologic thrombosis. These are their most widely known biologic activities. Nevertheless, recent observations demonstrate that platelets have a much more intricate repertoire beyond these traditional functions and that they are specialized for contributions to vascular barrier integrity, organ repair, antimicrobial host defense, inflammation, and activities across the immune continuum. Paradoxically, on the basis of clinical investigations and animal models of disease, some of these newly discovered activities of platelets appear to contribute to tissue injury. Studies in the last decade indicate unique interactions of platelets and their precursor, the megakaryocyte, in the lung and implicate platelets as essential effectors in experimental acute lung injury and clinical acute respiratory distress syndrome. Additional discoveries derived from evolving work will be required to precisely define the contributions of platelets to complex subphenotypes of acute lung injury and to determine if these remarkable and versatile blood cells are therapeutic targets in acute respiratory distress syndrome.

Contemporary thromboprophylaxis of trauma patients

PURPOSE OF REVIEW

The traumatically injured patient is at high risk for developing venous thromboembolism. Clinical practice guidelines developed by the American College of Chest Physicians and the Eastern Association for the Surgery of Trauma recognize the importance of initiating thromboprophylaxis, but the guidelines lack specific recommendations regarding the timing and dose of pharmacologic thromboprophylaxis. We review the literature regarding initiation of thromboprophylaxis in different injuries, the use of inferior vena cava filters, laboratory monitoring, dosing regimens, and the use of antiplatelet therapy.

RECENT FINDINGS

Use of pharmacologic thromboprophylaxis with invasive intracranial monitors is not associated with increased bleeding complications. The initiation of low-molecular-weight heparin (LMWH) prophylaxis 48 h postinjury in blunt solid organ injury is not associated with an increase in the rate of failed nonoperative management. Antiplatelet therapy in conjunction with LMWH may help to prevent venous thromboembolism.

SUMMARY

In the setting of blunt traumatic brain and solid organ injury, initiation of pharmacologic thromboprophylaxis 48 h after injury is not associated with increased bleeding complications. There is no consensus or clear data showing which dosing regimen of LMWH is most effective or whether routine laboratory measurements are beneficial for determining effective thromboprophylaxis.

Thromboelastometry profile in critically ill patients: A single-center, retrospective, observational study

Background

Transfusion therapy is associated with increased morbidity, mortality and costs. Conventional coagulation tests (CCT) are weak bleeding predictors, poorly reflecting coagulation in vivo. Thromboelastometry (ROTEM) provides early identification of coagulation disorders and can guide transfusion therapy by goals, reducing blood components transfusion.

Objective

The aim of this study is to describe coagulation profile of critically ill patients using ROTEM and evaluate the association between CCT and thromboelastometry.

Methods

This is a retrospective, observational study conducted in medical-surgical intensive care unit (ICU). Adult patients (≥18 years) admitted to ICU between November 2012 and December 2014, in whom ROTEM analyses were performed for bleeding management were included in this study. The first ROTEM and CCT after ICU admission were recorded simultaneously. Additionally, we collected data on blood components transfusion and hemostatic agents immediately after laboratory tests results.

Results

The study included 531 patients. Most ROTEM tests showed normal coagulation profile [INTEM (54.8%), EXTEM (54.1%) and FIBTEM (53.3%)] with divergent results in relation to CCT: low platelet count (51.8% in INTEM and 55.9% in EXTEM); prolonged aPTT (69.9% in INTEM and 63.7% in EXTEM) and higher INR (23.8% in INTEM and 27.4% in EXTEM). However 16,7% of patients with normocoagulability in ROTEM received platelet concentrates and 10% fresh frozen plasma.

Conclusion

The predominant ROTEM profile observed in this sample of critically ill patients was normal. In contrast, CCT suggested coagulopathy leading to a possibly unnecessary allogenic blood component transfusion. ROTEM test may avoid inappropriate allogeneic blood products transfusion in these patients.

Resuscitation

Blast injuries can produce complex patterns of injury and can easily result in hemorrhagic shock. Adequate resuscitation of blast-injured patients is critical, as both under- and over-resuscitation can result in a number of fatal complications. Consideration must be given to the choice of resuscitative fluid, the volume of resuscitation, the timing of resuscitation relative to definitive surgical management, and the determination of endpoints at which resuscitation can be stopped. This chapter explores resuscitation of blast-injured patients, beginning in the prehospital phase with initial choice of fluid and continuing through definitive resuscitation at a higher echelon of care. Particular consideration is given to the effect of resuscitation on the unique physiologic derangements seen following blast injury. Drawing upon the enormous amount of literature on resuscitation from the recent coalition experiences in Iraq and Afghanistan, we advocate for the use of early hemostatic resuscitation with a high ratio of plasma, platelets, and packed red blood cells, with a transition to resuscitation guided by viscoelastic testing or coagulation status immediately following definitive control of hemorrhage.

Abnormalities of laboratory coagulation tests versus clinically evident coagulopathic bleeding: results from the prehospital resuscitation on helicopters study (PROHS)

BACKGROUND

Laboratory-based evidence of coagulopathy (LC) is observed in 25-35% of trauma patients, but clinically-evident coagulopathy (CC) is not well described.

METHODS

Prospective observational study of adult trauma patients transported by helicopter from the scene to nine Level 1 trauma centers in 2015. Patients meeting predefined highest-risk criteria were divided into CC+ (predefined as surgeon-confirmed bleeding from uninjured sites or injured sites not controllable by sutures) or CC-. We used a mixed-effects, Poisson regression with robust error variance to test the hypothesis that abnormalities on rapid thrombelastography (r-TEG) and international normalized ratio (INR) were independently associated with CC+.

RESULTS

Of 1,019 highest-risk patients, CC+ (n=41, 4%) were more severely injured (median ISS 32 vs 17), had evidence of LC on r-TEG and INR, received more transfused blood products at 4 hours (37 vs 0 units), and had greater 30-day mortality (59% vs 12%) than CC- (n=978, 96%). The overall incidence of LC was 39%. 30-day mortality was 22% vs 9% in those with and without LC. In two separate models, r-TEG K-time >2.5 min (RR 1.3, 95% CI 1.1-1.7), r-TEG mA <55 mm (RR 2.5, 95% CI 2.0-3.2), platelet count <150 x 10⁹/L (RR 1.2, 95% CI 1.1-1.3), and INR >1.5 (RR 5.4, 95% CI 1.8-16.3) were independently associated with CC+. A combined regression model was not generated because too few patients underwent both r-TEG and INR.

CONCLUSION

CC was rare compared to LC. CC was associated with poor outcomes and impairment of both clotting factor and platelet-mediated coagulation components.

The hypercoagulability paradox of chronic kidney disease: The role of fibrinogen

BACKGROUND

Chronic kidney disease (CKD) patients have increased rates of bleeding as well as thrombosis. Fibrinogen and platelets combine to generate a mature clot, but in CKD platelets are dysfunctional. Therefore, we hypothesize that CKD patients have increased clot strength due to elevated fibrinogen levels.

METHODS

Retrospective review of CKD patients (n = 84) who had rTEG and fibrinogen levels measured. They were compared to healthy controls (n = 134).

RESULTS

CKD patients had statistically significant increases in ACT, angle, MA and decreases in LY30 compared to controls. Fibrinogen levels were increased in CKD patients compared to reference range. Fibrinogen levels had a positive correlation with MA (rho = 0.709, p < 0.0001) in CKD patients.

CONCLUSIONS

Patients with CKD manifest a coagulopathy consisting of delayed clot formation, but increased final clot strength and decreased clot breakdown. Furthermore, the elevated clot strength is mediated by increased fibrinogen levels in CKD patients.

The current understanding of trauma-induced coagulopathy (TIC): a focused review on pathophysiology

The emergency management of acute severe bleeding in trauma patients has changed significantly in recent years. In particular, greater attention is now being devoted to a prompt assessment of coagulation alterations, which allows for immediate haemostatic resuscitation procedures when necessary. The importance of an early trauma-induced coagulopathy (TIC) diagnosis has led physicians to increase the efforts to better understand the pathophysiological alterations observed in the haemostatic system after traumatic injuries. As yet, the knowledge of TIC is not exhaustive, and further studies are needed. The aim of this review is to gather all the currently available data and information in an attempt to gain a better understanding of TIC. A comprehensive literature search was performed using MEDLINE database. The bibliographies of relevant articles were screened for additional publications. In major traumas, coagulopathic bleeding stems from a complex interplay among haemostatic and inflammatory systems, and is characterized by a multifactorial dysfunction. In the abundance of biochemical and pathophysiological changes occurring after trauma, it is possible to discern endogenously induced primary predisposing conditions and exogenously induced secondary predisposing conditions. TIC remains one of the most diagnostically and therapeutically challenging condition.

High level of venous thromboembolism in critically ill trauma patients despite early and well-driven thromboprophylaxis protocol

Background

Venous thromboembolism (VTE) is one of the most common preventable causes of in-hospital death in trauma patients surviving their injuries. We assessed the prevalence, incidence and risk factors for deep venous thrombosis (DVT) and pulmonary embolism (PE) in critically ill trauma patients, in the setting of a mature and early mechanical and pharmacological thromboprophylaxis protocol.

Methods

This was a prospective observational study on a cohort of patients from a surgical intensive care unit of a university level 1 trauma centre. We enrolled consecutive primary trauma patients expected to be in intensive care for ≥48 h. Thromboprophylaxis was protocol driven. DVT screening was performed by duplex ultrasound of upper and lower extremities within the first 48 h, between 5 and 7 days and then weekly until discharge. We recorded VTE risk factors at baseline and on each examination day. Independent risk factors were analysed using a multivariate logistic regression.

Results

In 153 patients with a mean Injury Severity Score of 23 ± 12, the prevalence of VTE was 30.7%, 95 CI [23.7–38.8] (29.4% DVT and 4.6% PE). The incidence was 18%, 95 CI [14–24] patients-week. The median time of apparition of DVT was 6 days [1; 4]. The global protocol compliance was 77.8% with a median time of introduction of the pharmacological prophylaxis of 1 day [1; 2]. We identified four independent risk factors for VTE: central venous catheter (OR 4.39, 95 CI [1.1–29]), medullar injury (OR 5.59, 95 CI [1.7–12.9]), initial systolic arterial pressure <80 mmHg (OR 3.64, 95 CI [1.3–10.8]), and pelvic fracture (OR 3.04, 95 CI [1.2–7.9]).

Conclusion

Despite a rigorous, protocol-driven thromboprophylaxis, critically ill trauma patients showed a high incidence of VTE. Further research is needed to tailor pharmacological prophylaxis and balance the risks and benefits.

Electronic supplementary material

The online version of this article (doi:10.1186/s13613-017-0315-0) contains supplementary material, which is available to authorized users.

Coagulation factor concentrate-based therapy for remote damage control resuscitation (RDCR): a reasonable alternative?

The concept of remote damage control resuscitation (RDCR) is still in its infancy and there is significant work to be done to improve outcomes for patients with life-threatening bleeding secondary to injury. The prehospital phase of resuscitation is critical and if shock and coagulopathy can be rapidly minimized before hospital admission this will very likely reduce morbidity and mortality. The optimum transfusion strategy for these patients is still highly debated and the potential implications of the recently published pragmatic, randomize, optimal platelet, and plasma ratios trial (PROPPR) for RDCR have been reviewed. Identifying the appropriate transfusion strategy is mandatory before adopting prehospital hemostatic resuscitation strategies. An alternative approach is based on the early administration of coagulation factor concentrates combined with the antifibrinolytic tranexamic acid (TXA). The three major components to this approach in the context of RDCR target the following steps to achieve hemostasis: 1) stop (hyper)fibrinolysis; 2) support clot formation; and 3) increase thrombin generation. Strong evidence exists for the use of TXA. The data from the prospective fibrinogen in trauma induced coagulopathy (FIinTIC) study will inform on the prehospital use of fibrinogen in bleeding trauma patients. Deficits in thrombin generation may be addressed by the administration of prothrombin complex concentrates. Handheld point-of-care devices may be able to support and guide the prehospital and remote use of intravenous hemostatic agents including coagulation factor concentrates along with clinical presentation, assessment, and the extent of bleeding. Combinations may even be more effective for bleeding control. More studies are urgently needed.

Coagulation Changes following Combined Ablative and Reconstructive Breast Surgery

BACKGROUND

This study assessed hemostatic function in cancer patients at high risk for venous thromboembolism.

METHODS

Thirty-eight female patients (age, 53 ± 9 years) undergoing immediate postmastectomy reconstruction were prospectively studied with informed consent. Blood was sampled preoperatively, on postoperative day 1, and at 1 week follow-up. Rotational thromboelastography clotting time, α-angle (clot kinetics), clot formation time, and maximum clot firmness were studied with three different activating agents: intrinsically activated test using ellagic acid, extrinsically activated test with tissue factor, and fibrin-based extrinsically activated test with tissue factor and the platelet inhibitor cytochalasin D. Thromboprophylaxis was unfractionated heparin plus sequential compression devices if not contraindicated. Hypercoagulability was defined by one or more parameters outside the reference range.

RESULTS

Preoperatively, 29 percent of patients were hypercoagulable, increasing to 67 percent by week 1 (p = 0.017). Clotting time, clot formation time, and α-angle remained relatively constant over time, but maximum clot formation increased in intrinsically activated test using ellagic acid, extrinsically activated test with tissue factor, and fibrin-based extrinsically activated test with tissue factor and the platelet inhibitor cytochalasin D (all p < 0.05). Body mass index was 28 ± 5 kg/m, 23 percent received preoperative chemotherapy, and 15 percent had a history of tobacco use, but there was no association between these risk factors and hypercoagulability.

CONCLUSIONS

Despite perioperative thromboprophylaxis, two-thirds of patients undergoing combined tumor resection and reconstructive surgery for breast cancer were hypercoagulable 1 week after surgery. Hypercoagulability was associated with increased clot strength mediated by changes in platelet and fibrin function.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Management of Trauma-Induced Coagulopathy with Thrombelastography

Viscoelastic assays, such as thrombelastography (TEG) and rotational thrombelastometry (ROTEM), have emerged as point-of-care tools that can guide the hemostatic resuscitation of bleeding injured patients. This article describes the role of TEG in contemporary trauma care by explaining this assay's methodology, clinical applications, and result interpretation through description of supporting studies to provide the reader with an evidence-based user's guide. Although TEG and ROTEM are assays based on the same viscoelastic principle, this article is focused on data supporting the use of TEG in trauma, because it is available in trauma centers in North America; ROTEM is mostly available in Europe.

Onset of Coagulation Function Recovery Is Delayed in Severely Injured Trauma Patients with Venous Thromboembolism

BACKGROUND

Altered coagulation function after trauma can contribute to development of venous thromboembolism (VTE). Severe trauma impairs coagulation function, but the trajectory for recovery is not known. We hypothesized that enhanced, early recovery of coagulation function increases VTE risk in severely injured trauma patients.

STUDY DESIGN

Secondary analysis was performed on data from the Pragmatic Randomized Optimal Platelet and Plasma Ratio (PROPPR) trial, excluding patients who died within 24 hours or were on pre-injury anticoagulants. Patient characteristics, adverse outcomes, and parameters of platelet function and coagulation (thromboelastography) were compared from admission to 72 hours between VTE (n = 83) and non-VTE (n = 475) patients. A p value < 0.05 indicates significance.

RESULTS

Despite similar patient demographics, VTE patients exhibited hypercoagulable thromboelastography parameters and enhanced platelet function at admission (p < 0.05). Both groups exhibited hypocoagulable thromboelastography parameters, platelet dysfunction, and suppressed clot lysis (low clot lysis at 30 minutes) 2 hours after admission (p < 0.05). The VTE patients exhibited delayed coagulation recovery (a significant change compared with 2 hours) of K-value (48 vs 24 hours), α-angle (no recovery), maximum amplitude (24 vs 12 hours), and clot lysis at 30 minutes (48 vs 12 hours). Platelet function recovery mediated by arachidonic acid (72 vs 4 hours), ADP (72 vs 12 hours), and collagen (48 vs 12 hours) was delayed in VTE patients. The VTE patients had lower mortality (4% vs 13%; p < 0.05), but fewer hospital-free days (0 days [interquartile range 0 to 8 days] vs 10 days [interquartile range 0 to 20 days]; p < 0.05) and higher complication rates (p < 0.05).

CONCLUSIONS

Recovery from platelet dysfunction and coagulopathy after severe trauma were delayed in VTE patients. Suppressed clot lysis and compensatory mechanisms associated with altered coagulation that can potentiate VTE formation require additional investigation.

Applying the Cell-Based Coagulation Model in the Management of Critical Bleeding

The cell-based coagulation model was proposed 15 years ago, yet has not been applied commonly in the management of critical bleeding. Nevertheless, this alternative model may better explain the physiological basis of current coagulation management during critical bleeding. In this article we describe the limitations of the traditional coagulation protein cascade and standard coagulation tests, and explain the potential advantages of applying the cell-based model in current coagulation management strategies. The cell-based coagulation model builds on the traditional coagulation model and explains many recent clinical observations and research findings related to critical bleeding unexplained by the traditional model, including the encouraging results of using empirical 1:1:1 fresh frozen plasma:platelets:red blood cells transfusion strategy, and the use of viscoelastic and platelet function tests in patients with critical bleeding. From a practical perspective, applying the cell-based coagulation model also explains why new direct oral anticoagulants are effective systemic anticoagulants even without affecting activated partial thromboplastin time or the International Normalized Ratio in a dose-related fashion. The cell-based coagulation model represents the most cohesive scientific framework on which we can understand and manage coagulation during critical bleeding.

Performance of functional fibrinogen thromboelastography in children undergoing congenital heart surgery

BACKGROUND

Functional Fibrinogen assay of the Thromboelastography (FFTEG), a whole blood viscoelastic hemostatic assay, has been used to estimate fibrinogen levels in adult patients undergoing major surgery but its performance in pediatric patients undergoing cardiac surgery requires evaluation. In this study, we evaluate the correlation between FFTEG parameters and standard laboratory tests for fibrinogen and platelet counts before and after cardiopulmonary bypass in children undergoing repair for congenital heart disease.

METHODS

In this prospective observational study, whole blood samples were obtained from children less than 5 years of age undergoing congenital heart surgery with cardiopulmonary bypass before surgical incision and immediately after administration of protamine. Blood samples were analyzed for Thromboelastography, Functional Fibrinogen level measured by FFTEG (FLEV), complete blood counts with platelet count and plasma fibrinogen assay (LFib, Clauss). The primary outcome of this study was to assess the correlation between FFTEG parameters, LFib and platelet counts in neonates, infants, and small children less than 5 years old. Additionally, we studied if postbypass FFTEG parameters could predict critical thresholds of hypofibrinogenemia LFib ≤200 mg·dl^-1 .

RESULTS

One hundred and five children (22 neonates, 51 infants, and 32 small children) were included in the final analysis. FLEV estimated higher fibrinogen levels than LFib in all patients. Before bypass, FLEV was on average 133 mg·dl^-1 higher than LFib (95% confidence interval, CI, 116-150, P < 0.001) for all the patients; after bypass, FLEV was 48 mg·dl^-1 (95% CI: 37-59, P < 0.001) higher than LFib for all the patients. Linear correlation coefficients between FLEV and LFib in all patients were R = 0.41 (95% CI: 0.24-0.56, P < 0.001) before bypass and increased to R = 0.63 (95% CI: 0.51-0.74, P < 0.001) after bypass. Bland Altman analysis performed on postbypass values of FLEV and LFib showed a positive bias of FLEV in estimation of LFib. The magnitude and the variability of the bias for all the patients group was decreased with lower mean of the difference of FLEV and LFib when the average values of FLEV and LFib were <200 mg·dl^-1 . Low linear correlations were noticed between maximal amplitude of platelet contribution to FFTEG and platelet counts both before and after bypass. For predicting the clinical thresholds of postbypass hypofibrinogenemia at plasma fibrinogen levels ≤200 mg·dl^-1 , FLEV and maximal amplitude of the fibrinogen clot generated area under receiver operative curves at 0.90 (95% CI = 0.76-1.0) in neonates, 0.6 (95% CI- 0.42-0.78) in infants, and 0.97 (95% CI = 0.91-1.0) in small children. Based on the receiver operative curves, values of postbypass hypofibrinogenemia with LFib ≤200 g·dl^-1 corresponded to cutoffs of FLEV_POST ≤245 mg·dl^-1 and maximal amplitude of the fibrinogen clot ≤13.4 mm.

CONCLUSION

In pediatric patients undergoing cardiac surgery, FLEV derived from Functional Fibrinogen correlated linearly with plasma fibrinogen levels (Clauss) both before and after CPB. FLEV estimation of plasma fibrinogen was improved after CPB in neonates, infants, and small children. After CPB, FFTEG can be used to predict laboratory diagnosis of critical hypofibrinogenemia (≤200 mg·dl^-1 ) during pediatric cardiac surgery. Further studies are required to assess the impact of predictability of FFTEG on component transfusion during pediatric cardiac surgery.

Monitoring the coagulation status of trauma patients with viscoelastic devices

Coagulopathy is a physiological response to massive bleeding that frequently occurs after severe trauma and is an independent predictive factor for mortality. Therefore, it is very important to grasp the coagulation status of patients with severe trauma quickly and accurately in order to establish the therapeutic strategy. Judging from the description in the European guidelines, the importance of viscoelastic devices in understanding the disease condition of patients with traumatic coagulopathy has been widely recognized in Europe. In the USA, the ACS TQIP Massive Transfusion in Trauma Guidelines proposed by the American College of Surgeons in 2013 presented the test results obtained by the viscoelastic devices, TEG® 5000 and ROTEM®, as the standard for transfusion or injection of blood plasma, cryoprecipitate, platelet concentrate, or anti-fibrinolytic agents in the treatment strategy for traumatic coagulopathy and hemorrhagic shock. However, some studies have reported limitations of these viscoelastic devices. A review in the Cochrane Library published in 2015 pointed out the presence of biases in the abovementioned reports in trauma patients and the absence of a quality study in this field thus far. A quality study on the relationship between traumatic coagulopathy and viscoelastic devices is needed.

Alternatives to allogeneic platelet transfusion

Allogeneic platelet transfusions are widely used for the prevention and treatment of bleeding in thrombocytopenia. Recent evidence suggests platelet transfusions have limited efficacy and are associated with uncertain immunomodulatory risks and concerns about viral or bacterial transmission. Alternatives to transfusion are a well-recognised tenet of Patient Blood Management, but there has been less focus on different strategies to reduce bleeding risk by comparison to platelet transfusion. Direct alternatives to platelet transfusion include agents to stimulate endogenous platelet production (thrombopoietin mimetics), optimising platelet adhesion to endothelium by treating anaemia or increasing von Willebrand factor levels (desmopressin), increasing formation of cross-linked fibrinogen (activated recombinant factor VII, fibrinogen concentrate or recombinant factor XIII), decreasing fibrinolysis (tranexamic acid or epsilon aminocaproic acid) or using artificial or modified platelets (cryopreserved platelets, lyophilised platelets, haemostatic particles, liposomes, engineered nanoparticles or infusible platelet membranes). The evidence base to support the use of these alternatives is variable, but an area of active research. Much of the current randomised controlled trial focus is on evaluation of the use of thrombopoietin mimetics and anti-fibrinolytics. It is also recognised that one alternative strategy to platelet transfusion is choosing not to transfuse at all.

Impact of Platelets and Platelet-Derived Microparticles on Hypercoagulability Following Burn Injury

An acute burn induced coagulopathy develops after scald injury, which evolves into a subacute, hypercoagulable state. Microparticles, specifically platelet-derived MPs (PMPs), have been suggested as possible contributors. We first developed a model of burn-induced coagulopathy and then sought to investigate the role of platelets and PMPs in coagulation after burn. We hypothesized that changes in circulating platelet and PMP populations after injury would contribute to the post-burn, hypercoagulable state. A murine scald model with 28% TBSA full thickness burn injury was utilized and blood samples were collected at intervals after injury. Circulating MP populations, platelet counts, overall coagulation, and platelet function were determined. Burn injury led to hypercoagulability on post-burn day one (PBD1), which persisted 6 days after injury (PBD6). On PBD1, there was a significant decrease in platelet numbers and a decline in platelet contribution to clot formation with a concomitant increase in circulating procoagulant PMPs. On PBD6, there was a significant increase in platelet numbers and in platelet activation with no change in PMPs compared with sham. Further, on PBD1 decreased ADP-induced platelet activation was observed with a contrasting increase in ADP-induced platelet activation on PBD6. We therefore concluded that there was a temporal change in the mechanisms leading to a hypercoagulable state after scald injury, that PMPs are responsible for changes seen on PBD1, and finally that ADP-induced platelet activation was key to the augmented clotting mechanisms 6 days after burn.

Platelet adenosine diphosphate inhibition in trauma patients by thromboelastography correlates with paradoxical increase in platelet dense granule content by flow cytometry

BACKGROUND

The mechanism of platelet dysfunction in acute traumatic coagulopathy is unknown. Traumatic brain injury is hypothesized as a cause, while some investigators presume platelets become "exhausted." We hypothesized that platelet hyperstimulation and consumption resulting from trauma leads to decreased platelet function secondary to depletion of platelet granules.

METHODS

Twenty-five trauma patients were divided into traumatic brain injury and no traumatic brain injury groups. Healthy volunteers served as controls. All had thromboelastography with platelet mapping and flow cytometric assays of mepacrine performed. Mepacrine uptake in unstimulated platelets was used for quantification of platelet content of dense granules.

RESULTS

Twelve patients with traumatic brain injury and 13 patients without traumatic brain injury were enrolled. Twenty-one trauma patients showed adenosine diphosphate inhibition (>30%) on thromboelastography with platelet mapping compared with the healthy volunteers who served as controls (P < .01). Mepacrine assay showed a difference in mean fluorescent intensity for all trauma patients of 4,259 ± 1,341 compared with controls of 3,143 ± 709 (P = .044), correlating with greater quantities of dense granules. Neither adenosine diphosphate inhibition nor average difference in mean fluorescent intensity between traumatic brain injury and no traumatic brain injury groups were significant (P = .2).

CONCLUSION

Trauma patients maintain their dense granule, contradicting the theory of platelet granule exhaustion as the etiology for platelet dysfunction in traumatic brain injury.

Aspirin as added prophylaxis for deep vein thrombosis in trauma: A retrospective case-control study

BACKGROUND

Current prophylaxis does not completely prevent deep vein thrombosis (DVT) in trauma patients. Recent data suggest that platelets may be a major contributor to hypercoagulability after trauma, indicating a potential role for antiplatelet medications in prophylaxis for DVT. We sought to determine if preinjury aspirin use was associated with a reduced incidence of lower extremity DVT in trauma patients.

METHODS

Using a retrospective case-control design, we matched 110 cases of posttrauma lower extremity DVT one-to-one with controls using seven covariates: age, admission date, probability of death, number of DVT risk factors, sex, mechanism of injury, and presence of head injury. Data collected included 26 risk factors for DVT, prehospital medications, and in-hospital prophylaxis. Logistic regression models were created to examine the relationship between prehospital aspirin use and posttrauma DVT.

RESULTS

Preinjury aspirin was used by 7.3% of cases (patients diagnosed with in-hospital DVT) compared with 13.6% of controls (p = 0.1). Aspirin was associated with a significant protective effect in multivariate analysis, with an odds ratio of 0.17 (95% confidence interval, 0.04-0.68; p = 0.012) in the most complete model. When stratified by other antithrombotic use, aspirin showed a significant effect only when used in combination with heparinoid prophylaxis (odds ratio, 0.35; 95% confidence interval, 0.13-0.93; p = 0.036).

CONCLUSION

Preinjury aspirin use seems to significantly lower DVT rate following injury. This association is strongest when heparinoid prophylaxis is prescribed after patients on preinjury aspirin therapy are admitted. Aspirin as added prophylaxis for DVT in trauma patients needs to be further evaluated.

LEVEL OF EVIDENCE

Prognostic and epidemiologic study, level III.

Advances in the understanding of trauma-induced coagulopathy

Ten percent of deaths worldwide are due to trauma, and it is the third most common cause of death in the United States. Despite a profound upregulation in procoagulant mechanisms, one-quarter of trauma patients present with laboratory-based evidence of trauma-induced coagulopathy (TIC), which is associated with poorer outcomes including increased mortality. The most common causes of death after trauma are hemorrhage and traumatic brain injury (TBI). The management of TIC has significant implications in both because many hemorrhagic deaths could be preventable, and TIC is associated with progression of intracranial injury after TBI. This review covers the most recent evidence and advances in our understanding of TIC, including the role of platelet dysfunction, endothelial activation, and fibrinolysis. Trauma induces a plethora of biochemical and physiologic changes, and despite numerous studies reporting differences in coagulation parameters between trauma patients and uninjured controls, it is unclear whether some of these differences may be "normal" after trauma. Comparisons between trauma patients with differing outcomes and use of animal studies have shed some light on this issue, but much of the data continue to be correlative with causative links lacking. In particular, there are little data linking the laboratory-based abnormalities with true clinically evident coagulopathic bleeding. For these reasons, TIC continues to be a significant diagnostic and therapeutic challenge.

Clot Formation Is Associated With Fibrinogen and Platelet Forces in a Cohort of Severely Injured Emergency Department Trauma Patients

INTRODUCTION

Anticoagulation, fibrinogen consumption, fibrinolytic activation, and platelet dysfunction all interact to produce different clot formation responses after trauma. However, the relative contributions of these coagulation components to overall clot formation remain poorly defined. We examined for sources of heterogeneity in clot formation responses after trauma.

METHODS

Blood was sampled in the emergency department from patients meeting trauma team activation criteria at an urban trauma center. Plasma prothrombin time of 18 s or longer was used to define traumatic coagulopathy. Mean kaolin-activated thrombelastography (TEG) parameters were calculated and tested for heterogeneity using analysis of means. Discriminant analysis and forward stepwise variable selection with linear regression were used to determine if prothrombin time, fibrinogen, platelet contractile force (PCF), and D-dimer concentration, representing key mechanistic components of coagulopathy, each contribute to heterogeneous TEG responses after trauma.

RESULTS

Of 95 subjects, 16% met criteria for coagulopathy. Coagulopathic subjects were more severely injured with greater shock and received more blood products in the first 8 h compared with noncoagulopathic subjects. Mean (SD) TEG maximal amplitude (MA) was significantly decreased in the coagulopathic group (57.5 [SD, 4.7] mm vs. 62.7 [SD, 4.7], t test P < 0.001). The MA also exceeded the ANOM predicted upper decision limit for the noncoagulopathic group and the lower decision limit for the coagulopathic group at α = 0.05, suggesting significant heterogeneity from the overall cohort mean. Fibrinogen and PCF best discriminated TEG MA using discriminant analysis. Fibrinogen, PCF, and D-dimer were primary covariates for TEG MA using regression analysis.

CONCLUSIONS

Heterogeneity in TEG-based clot formation in emergency department trauma patients was linked to changes in MA. Individual parameters representing fibrin polymerization, PCFs, and fibrinolysis were primarily associated with TEG MA after trauma and should be the focus of early hemostatic therapies.

Tranexamic acid: from trauma to routine perioperative use

PURPOSE OF REVIEW

Optimizing hemostasis with antifibrinolytics is becoming a common surgical practice. Large clinical studies have demonstrated efficacy and safety of tranexamic acid (TXA) in the trauma population to reduce blood loss and transfusions. Its use in patients without pre-existing coagulopathies is debated, as thromboembolic events are a concern. In this review, perioperative administration of TXA is examined in nontrauma surgical populations. Additionally, risk of thromboembolism, dosing regimens, and timing of dosing are assessed.

RECENT FINDINGS

Perioperative use of TXA is associated with reduced blood loss and transfusions. Thromboembolic effects do not appear to be increased. However, optimal dosing and timing of TXA administration is still under investigation for nontrauma surgical populations.

SUMMARY

As part of a perioperative blood management programme, TXA can be used to help reduce blood loss and mitigate exposure to blood transfusion.

Assessing the Methodology for Calculating Platelet Contribution to Clot Strength (Platelet Component) in Thromboelastometry and Thrombelastography

The viscoelastic properties of blood clot have been studied most commonly using thrombelastography (TEG) and thromboelastometry (ROTEM). ROTEM-based bleeding treatment algorithms recommend administering platelets to patients with low EXTEM clot strength (e.g., clot amplitude at 10 minutes [A10] <40 mm) once clot strength of the ROTEM® fibrin-based test (FIBTEM) is corrected. Algorithms based on TEG typically use a low value of maximum amplitude (e.g., <50 mm) as a trigger for administering platelets. However, this parameter reflects the contributions of various blood components to the clot, including platelets and fibrin/fibrinogen. The platelet component of clot strength may provide a more sensitive indication of platelet deficiency than clot amplitude from a whole blood TEG or ROTEM® assay. The platelet component of the formed clot is derived from the results of TEG/ROTEM® tests performed with and without platelet inhibition. In this article, we review the basis for why this calculation should be based on clot elasticity (e.g., the E parameter with TEG and the CE parameter with ROTEM®) as opposed to clot amplitude (e.g., the A parameter with TEG or ROTEM®). This is because clot elasticity, unlike clot amplitude, reflects the force with which the blood clot resists rotation within the device, and the relationship between clot amplitude (variable X) and clot elasticity (variable Y) is nonlinear. A specific increment of X (ΔX) will be associated with different increments of Y (ΔY), depending on the initial value of X. When calculated correctly, using clot elasticity data, the platelet component of the clot can provide a valuable insight into platelet deficiency in emergency bleeding.

Coagulation Profile Changes Due to Thromboprophylaxis and Platelets in Trauma Patients at High-Risk for Venous Thromboembolism

We hypothesize there are coagulation profile changes associated both with initiation of thromboporphylaxis (TPX) and with change in platelet levels in trauma patients at high-risk for venous thromboembolism (VTE). A total of 1203 trauma intensive care unit patients were screened with a VTE risk assessment profile. In all, 302 high-risk patients (risk assessment profile score ≥ 10) were consented for weekly thromboelastography. TPX was initiated between initial and follow-up thromboelastography. Seventy-four patients were analyzed. Upon admission, 87 per cent were hypercoagulable, and 81 per cent remained hypercoagulable by Day 7 ( P = 0.504). TPX was initiated 3.4 ± 1.4 days after admission; 68 per cent received unfractionated heparin and 32 per cent received low-molecular-weight heparin. The VTE rate was 18 per cent, length of stay 38 (25–37) days, and mortality of 17.6 per cent. In all, 76 per cent had a rapid clotting time at admission versus 39 per cent at Day 7 ( P < 0.001); correcting from 7.75 (6.45–8.90) minutes to 10.45 (7.90–15.25) minutes ( P < 0.001). At admission, 41 per cent had an elevated maximum clot formation (MCF) and 85 per cent had at Day 7 ( P < 0.001); increasing from 61(55–65) mm to 75(69–80) mm ( P < 0.001). Platelets positively correlated with MCF at admission (r = 0.308, R2 = 0.095, P = 0.008) and at Day 7 (r = 0.516, R2 = 0.266, P < 0.001). Change in platelet levels correlated with change in MCF (r = 0.332, R2 = 0.110, P = 0.005). In conclusion, hypercoagulability persists despite the use of TPX. Although clotting time normalizes, MCF increases in correlation with platelet levels. As platelet function is a dominant contributor to sustained trauma-evoked hypercoagulability, antiplatelet therapy may be indicated in the management of severely injured trauma patients.

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.

Obesity and clotting: Body mass index independently contributes to hypercoagulability after injury

BACKGROUND

Although obese patients have high thrombosis rates following injury, the role of obesity in coagulation after trauma remains unknown. We hypothesized that body mass index (BMI) is independently associated with increased measures of hypercoagulability longitudinally after injury.

METHODS

Data were prospectively collected for 377 consecutive highest-level trauma activation patients with a BMI of 18.5 kg/m² or greater. Standard coagulation measures, citrated kaolin and functional fibrinogen thromboelastography, as well as clotting factors were measured at 0 hour to 120 hours. BMI categories were defined as normal weight (18.5-24.99 kg/m²), overweight (25-29.99 kg/m²), and obese (≥30 kg/m²).

RESULTS

The 377 patients were mostly male (81%) and had blunt injury (61%), with a median BMI of 25.8 kg/m². Of the patients, 42% were normal weight (median BMI, 22.5 kg/m²). There were no differences in age, sex, Injury Severity Score (ISS), or base deficit between groups. There were no differences in admission international normalized ratio/partial thromboplastin time or factors II, V, VII, VIII, and X; antithrombin III; or protein C. However, obese patients had higher admission platelet counts (303 × 10⁹/L vs. 269 × 10⁹/L, p = 0.004), lower D-dimer (1.88 μg/mL vs. 4.00 μg/mL, p = 0.004), and a trend toward higher factor IX (134% vs. 119% activity, p = 0.042) compared with normal weight patients. Measured by thromboelastography, clot strength (maximum amplitude) and functional fibrinogen level (FLEV) were also higher on admission for obese patients (maximum amplitude, 65.7 mm vs. 63.4 mm, p = 0.016; FLEV, 407 mg/dL vs. 351 mg/dL, p = 0.008). In multiple linear regression, the relationship of BMI to clot strength, FLEV, and factor IX persisted through 24 hours. Similarly, the relationship of BMI and platelet count persisted through 120 hours (all p < 0.05). In multiple logistic regression, for every 5-kg/m² increase in BMI, there was an 85% increase in odds of thromboembolic complication (odds ratio, 1.85; 95% confidence interval, 1.13-3.08; p = 0.017).

CONCLUSION

Obese trauma patients are hypercoagulable compared with their similarly injured normal-weight counterparts, which persists longitudinally after injury. The significance of this hypercoagulability requires elucidation for guidance of anticoagulation in this at-risk group.

LEVEL OF EVIDENCE

Prognostic study, level III.

Taking the Blood Bank to the Field: The Design and Rationale of the Prehospital Air Medical Plasma (PAMPer) Trial

Hemorrhage and trauma induced coagulopathy remain major drivers of early preventable mortality in military and civilian trauma. Interest in the use of prehospital plasma in hemorrhaging patients as a primary resuscitation agent has grown recently. Trauma center-based damage control resuscitation using early and aggressive plasma transfusion has consistently demonstrated improved outcomes in hemorrhaging patients. Additionally, plasma has been shown to have several favorable immunomodulatory effects. Preliminary evidence with prehospital plasma transfusion has demonstrated feasibility and improved short-term outcomes. Applying state-of-the-art resuscitation strategies to the civilian prehospital arena is compelling. We describe here the rationale, design, and challenges of the Prehospital Air Medical Plasma (PAMPer) trial. The primary objective is to determine the effect of prehospital plasma transfusion during air medical transport on 30-day mortality in patients at risk for traumatic hemorrhage. This study is a multicenter cluster randomized clinical trial. The trial will enroll trauma patients with profound hypotension (SBP ≤ 70 mmHg) or hypotension (SBP 71-90 mmHg) and tachycardia (HR ≥ 108 bpm) from six level I trauma center air medical transport programs. The trial will also explore the effects of prehospital plasma transfusion on the coagulation and inflammatory response following injury. The trial will be conducted under exception for informed consent for emergency research with an investigational new drug approval from the U.S. Food and Drug Administration utilizing a multipronged community consultation process. It is one of three ongoing Department of Defense-funded trials aimed at expanding our understanding of the optimal therapeutic approaches to coagulopathy in the hemorrhaging trauma patient.

Systemic inflammatory response syndrome and platelet count ≥250×10(9) are associated with venous thromboembolic disease

Introduction

Prior research has demonstrated that platelet count and inflammation are dominant contributors to hypercoagulability. Our objective is to determine whether elevated platelet count and systemic inflammatory response syndrome (SIRS) have an association with the development of venous thromboembolism (VTE) in hospitalized patients with a high clinical index of suspicion for thromboembolic disease.

Methods

We performed a retrospective medical record review of 844 medical and surgical patients with suspected VTE hospitalized from July 2012 to May 2013 who underwent screening by venous duplex and computed tomography pulmonary angiogram. For our purposes, thrombocytosis was arbitrarily defined as platelet count ≥250×10⁹/L.

Results

Venous thromboembolic disease was detected in 229 patients (25.9%). Thrombocytosis was present in 389 patients (44%) and SIRS was present in 203 patients (23%) around the time of imaging. Thrombocytosis and SIRS were positively correlated with VTE (P<0.001). There was no correlation between thrombocytosis and SIRS. Multivariate analysis revealed that SIRS (odds ratio 1.91, 95% confidence interval 1.36–2.68, P<0.001) and thrombocytosis (odds ration 1.67, 95% confidence interval 1.23–2.26, P=0.001) were independently associated with VTE.

Conclusion

Patients at high risk for VTE should be routinely assessed for thrombocytosis (≥250×10⁹/L) and SIRS; if either is present, consideration for empiric anticoagulation should be given while diagnostic imaging is undertaken.

Platelet dysfunction in injured patients

A renewed understanding of Trauma Induced Coagulopathy (TIC) has implicated platelets as a crucial mediator and potential therapeutic target in hemostasis. While the importance of abnormal coagulation tests is well described in trauma, there is a paucity of data regarding the role of platelets in coagulopathy. New coagulation models, namely the cell-based-model of hemostasis, have refocused attention toward the platelet and endothelium as key regulators of clot formation. Although platelet dysfunction has been associated with worse outcomes in trauma, the mechanisms which platelet dysfunction contributes to coagulopathy are poorly understood. The goal of this review article is to outline recent advances in understanding hemostasis and the ensuing cellular dysfunction that contributes to the exsanguination of a critically injured patient.

Platelet dysfunction in injured patients

A renewed understanding of Trauma Induced Coagulopathy (TIC) has implicated platelets as a crucial mediator and potential therapeutic target in hemostasis. While the importance of abnormal coagulation tests is well described in trauma, there is a paucity of data regarding the role of platelets in coagulopathy. New coagulation models, namely the cell-based-model of hemostasis, have refocused attention toward the platelet and endothelium as key regulators of clot formation. Although platelet dysfunction has been associated with worse outcomes in trauma, the mechanisms which platelet dysfunction contributes to coagulopathy are poorly understood. The goal of this review article is to outline recent advances in understanding hemostasis and the ensuing cellular dysfunction that contributes to the exsanguination of a critically injured patient.

Effect of thromboelastography (TEG®) and rotational thromboelastometry (ROTEM®) on diagnosis of coagulopathy, transfusion guidance and mortality in trauma: descriptive systematic review

Introduction

The understanding of coagulopathies in trauma has increased interest in thromboelastography (TEG®) and thromboelastometry (ROTEM®), which promptly evaluate the entire clotting process and may guide blood product therapy. Our objective was to review the evidence for their role in diagnosing early coagulopathies, guiding blood transfusion, and reducing mortality in injured patients.

Methods

We considered observational studies and randomized controlled trials (MEDLINE, EMBASE, and Cochrane databases) to February 2014 that examined TEG®/ROTEM® in adult trauma patients. We extracted data on demographics, diagnosis of early coagulopathies, blood transfusion, and mortality. We assessed methodologic quality by using the Newcastle-Ottawa scale (NOS) for observational studies and QUADAS-2 tool for diagnostic accuracy studies.

Results

Fifty-five studies (12,489 patients) met inclusion criteria, including 38 prospective cohort studies, 15 retrospective cohort studies, two before-after studies, and no randomized trials. Methodologic quality was moderate (mean NOS score, 6.07; standard deviation, 0.49). With QUADAS-2, only three of 47 studies (6.4%) had a low risk of bias in all domains (patient selection, index test, reference standard and flow and timing); 37 of 47 studies (78.8%) had low concerns regarding applicability. Studies investigated TEG®/ROTEM® for diagnosis of early coagulopathies (n = 40) or for associations with blood-product transfusion (n = 25) or mortality (n = 24). Most (n = 52) were single-center studies. Techniques examined included rapid TEG® (n =12), ROTEM® (n = 18), TEG® (n = 23), or both TEG® and rapid TEG® (n = 2). Many TEG®/ROTEM® measurements were associated with early coagulopathies, including some (hypercoagulability, hyperfibrinolysis, platelet dysfunction) not assessed by routine screening coagulation tests. Standard measures of diagnostic accuracy were inconsistently reported. Many abnormalities predicted the need for massive transfusion and death, but predictive performance was not consistently superior to routine tests. One observational study suggested that a ROTEM®-based transfusion algorithm reduced blood-product transfusion, but TEG®/ROTEM®-based resuscitation was not associated with lower mortality in most studies.

Conclusions

Limited evidence from observational data suggest that TEG®/ROTEM® tests diagnose early trauma coagulopathy and may predict blood-product transfusion and mortality in trauma. Effects on blood-product transfusion, mortality, and other patient-important outcomes remain unproven in randomized trials.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-014-0518-9) contains supplementary material, which is available to authorized users.

Trauma-Induced Coagulopathy

Trauma is the leading cause of death among people under the age of 44. Hemorrhage is a major contributor to deaths related to trauma in the first 48 h. Accordingly, the management of these patients is a time-sensitive and critical affair that anesthesiologists responsible for surgical resuscitation will face. Coagulopathy associated with trauma exists in one-third of all severely injured patients upon presentation to the hospital. Trauma patients presenting with coagulopathy have significantly higher mortality. This trauma-induced coagulopathy (TIC) must be managed adroitly in the resuscitation of these patients. Recent advancements in our understanding of TIC have led to new protocols and therapy guidelines. Anesthesiologists must be aware of these to effectively manage this form of shock. TIC driven by a combination of endogenous biological processes, as well as iatrogenic causes, can ultimately lead to the lethal triad of hypothermia, acidemia, and coagulopathy. Providers should understand how to promptly diagnose TIC and be aware of the early indicators of massive transfusion. The use of common laboratory studies and patient vital signs serve as our current guide, but the importance of each is still under debate. Thromboelastography is a tool used often in the diagnosis of TIC and can be used to guide blood product transfusion. Certain pharmaceutical strategies and non-transfusion strategies also exist, which aid in the management of hemorrhagic shock. Damage control surgery, rewarming, tranexamic acid, and 1:1:1 transfusion protocols are promising methods used to treat the critically wounded. Though protocols have been developed, controversies still exist on the optimal resuscitation strategy.