Potential value of pharmacological protocols in trauma

Viscoelastic monitoring in trauma resuscitation

BACKGROUND

Traumatic injury results in both physical and physiologic insult. Successful care of the trauma patient depends upon timely correction of both physical and biochemical injury. Trauma-induced coagulopathy is a derangement of hemostasis and thrombosis that develops rapidly and can be fatal if not corrected. Viscoelastic monitoring (VEM) assays have been developed to provide rapid, accurate, and relatively comprehensive depictions of an individual's coagulation profile. VEM are increasingly being integrated into trauma resuscitation guidelines to provide dynamic and individualized guidance to correct coagulopathy.

STUDY DESIGN AND METHODS

We performed a narrative review of the search terms viscoelastic, thromboelastography, thromboelastometry, TEG, ROTEM, trauma, injury, resuscitation, and coagulopathy using PubMed. Particular focus was directed to articles describing algorithms for management of traumatic coagulopathy based on VEM assay parameters.

RESULTS

Our search identified 16 papers with VEM-guided resuscitation strategies in adult patients based on TEG, 12 such protocols in adults based on ROTEM, 1 protocol for children based on TEG, and 2 protocols for children based on ROTEM.

CONCLUSIONS

This review presents evidence to support VEM use to detect traumatic coagulopathy, discusses the role of VEM in trauma resuscitation, provides a summary of proposed treatment algorithms, and discusses pending questions in the field.

Contractile forces in platelet aggregates under microfluidic shear gradients reflect platelet inhibition and bleeding risk

Platelets contract forcefully after their activation, contributing to the strength and stability of platelet aggregates and fibrin clots during blood coagulation. Viscoelastic approaches can be used to assess platelet-induced clot strengthening, but they require thrombin and fibrin generation and are unable to measure platelet forces directly. Here, we report a rapid, microfluidic approach for measuring the contractile force of platelet aggregates for the detection of platelet dysfunction. We find that platelet forces are significantly reduced when blood samples are treated with inhibitors of myosin, GPIb-IX-V, integrin α_IIbβ_3, P2Y₁₂, or thromboxane generation. Clinically, we find that platelet forces are measurably lower in cardiology patients taking aspirin. We also find that measuring platelet forces can identify Emergency Department trauma patients who subsequently require blood transfusions. Together, these findings indicate that microfluidic quantification of platelet forces may be a rapid and useful approach for monitoring both antiplatelet therapy and traumatic bleeding risk.

Platelet aggregates generate contractile forces that contribute to their cohesion and adhesion. Here, Ting et al. develop a microfluidic device to measure contractile forces generated by platelet aggregates, and find it can detect the response of platelets to pharmacological agents and predict bleeding risk in trauma patients.

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.

The use of fibrinogen concentrate for the management of trauma-related bleeding: a systematic review and meta-analysis

Haemorrhage following injury is associated with significant morbidity and mortality. The role of fibrinogen concentrate in trauma-induced coagulopathy has been the object of intense research in the last 10 years and has been systematically analysed in this review. A systematic search of the literature identified six retrospective studies and one prospective one, involving 1,650 trauma patients. There were no randomised trials. Meta-analysis showed that fibrinogen concentrate has no effect on overall mortality (risk ratio: 1.07, 95% confidence interval: 0.83-1.38). Although the meta-analytic pooling of the current literature evidence suggests no beneficial effect of fibrinogen concentrate in the setting of severe trauma, the quality of data retrieved was poor and the final results of ongoing randomised trials will help to further elucidate the role of fibrinogen concentrate in traumatic bleeding.

Thrombin@Fe3O4 nanoparticles for use as a hemostatic agent in internal bleeding

Bleeding remains one of the main causes of premature mortality at present, with internal bleeding being the most dangerous case. In this paper, magnetic hemostatic nanoparticles are shown for the first time to assist in minimally invasive treatment of internal bleeding, implying the introduction directly into the circulatory system followed by localization in the bleeding zone due to the application of an external magnetic field. Nanoparticles were produced by entrapping human thrombin (THR) into a sol-gel derived magnetite matrix followed by grinding to sizes below 200 nm and subsequent colloidization. Prepared colloids show protrombotic activity and cause plasma coagulation in in vitro experiments. We also show here using a model blood vessel that the THR@ferria composite does not cause systematic thrombosis due to low activity, but being concentrated by an external magnetic field with simultaneous fibrinogen injection accelerates local hemostasis and stops the bleeding. For instance, a model vessel system with circulating blood at the puncture of the vessel wall and the application of a permanent magnetic field yielded a hemostasis time by a factor of 6.5 shorter than that observed for the control sample. Biocompatibility of composites was tested on HELF and HeLa cells and revealed no toxic effects.

Targeted Thromboelastographic (TEG) Blood Component and Pharmacologic Hemostatic Therapy in Traumatic and Acquired Coagulopathy

Trauma-induced coagulopathy (TIC) is a recently described condition which traditionally has been diagnosed by the common coagulation tests (CCTs) such as prothrombin time/international normalized ratio (PT/INR), activated partial thromboplastin time (aPTT), platelet count, and fibrinogen levels. The varying sensitivity and specificity of these CCTs have led trauma coagulation researchers and clinicians to use Viscoelastic Tests (VET) such as Thromboelastography (TEG) to provide Targeted Thromboelastographic Hemostatic and Adjunctive Therapy (TTHAT) in a goal directed fashion to those trauma patients in need of hemostatic resuscitation. This review describes the utility of VETs, in particular, TEG, to provide TTHAT in trauma and acquired non-trauma-induced coagulopathy.

Rapid thrombelastography thresholds for goal-directed resuscitation of patients at risk for massive transfusion

BACKGROUND

Uncontrolled hemorrhage is a leading cause of mortality after trauma accounting for up to 40% of deaths. Massive transfusion protocols offer a proven benefit in resuscitation of these patients. Recently, the superiority of thrombelastography (TEG)-guided resuscitation over strategies guided by conventional clotting assays has been established. We seek to determine optimal thresholds for rapid (r)-TEG driven resuscitation.

METHODS

The r-TEG data were reviewed for 190 patients presenting to our level 1 trauma center from 2010 to 2015. Criteria for inclusion were highest level trauma activation in patients 18 years or older with hypotension presumed due to acute blood loss. Exclusion criteria included isolated gunshot wound to the head, pregnancy, and chronic liver disease. Receiver operating characteristic (ROC) analysis was performed to test the predictive performance of r-TEG for massive transfusion requirement defined by need for (1) >10 units of RBCs total or death in the first 6 hours or (2) >4 units of RBCs in any hour within the first 6 hours. Cutpoint analysis was then performed to determine optimal thresholds for TEG-based resuscitation.

RESULTS

The ROC analysis of r-TEG yielded areas under the curve (AUC) greater than 70% for all outputs with respect to both transfusion thresholds considered, with exception of activated clotting time and lysis at 30 minutes for greater than 4 U RBC in any hour in the first 6 hours. Optimal cutpoint analysis of the resultant ROC curves was performed and for each value, the most sensitive cutpoint was identified, respectively activated clotting time of 128 seconds or longer, angle (α) of 65 degrees or less, maximum amplitude of 55 mm or less, and lysis at 30 minutes of 5% or greater.

CONCLUSIONS

Through ROC analysis of prospective TEG data, we have identified optimal thresholds to guide hemostatic resuscitation. These thresholds should be validated in a prospective multicenter trial.

LEVEL OF EVIDENCE

Therapeutic study, level V.

Interventional Algorithms for the Control of Coagulopathic Bleeding in Surgical, Trauma, and Postpartum Settings: Recommendations From the Share Network Group

Several clinical settings are associated with specific coagulopathies that predispose to uncontrolled bleeding. With the growing concern about the need for optimizing transfusion practices and improving treatment of the bleeding patient, a group of 9 Portuguese specialists (Share Network Group) was created to discuss and develop algorithms for the clinical evaluation and control of coagulopathic bleeding in the following perioperative clinical settings: surgery, trauma, and postpartum hemorrhage. The 3 algorithms developed by the group were presented at the VIII National Congress of the Associação Portuguesa de Imuno-hemoterapia in October 2013. They aim to provide a structured approach for clinicians to rapidly diagnose the status of coagulopathy in order to achieve an earlier and more effective bleeding control, reduce transfusion requirements, and improve patient outcomes. The group highlights the importance of communication between different specialties involved in the care of bleeding patients in order to achieve better results.

Factor concentrates in trauma

PURPOSE OF REVIEW

Recent advances in the understanding of transfusion practices during hemorrhagic shock in trauma have led to early administration of thawed plasma in increased ratios to packed red blood cells and have improved survival in the most severely injured patients. As an appreciation for the sequelae of massive transfusion continues to mature, it is becoming apparent that a more targeted approach to coagulation deficiencies may offer an advantage.

RECENT FINDINGS

Factor concentrate therapy offers the advantage of smaller volumes of resuscitative fluids directed at specific phases of coagulation identified by alternative laboratory assays (e.g., viscoelastic testing). Case reports, animal studies, and retrospective reviews offer encouraging data on the ability of factor concentrates to reverse coagulopathy and reduce blood product usage.

SUMMARY

The use of factor concentrates to target specific phases of coagulation may offer benefit over blood product ratio-driven transfusion. The outcome benefit of factor concentrates, however, has not yet been demonstrated in well powered prospective trials.

Effect of coagulation factor concentrate administration on ROTEM® parameters in major trauma

BACKGROUND

Purified coagulation factor concentrates, such as fibrinogen concentrate (FC) and prothrombin complex concentrate (PCC) are increasingly used as haemostatic therapy for trauma-induced coagulopathy (TIC). The impact of FC and PCC administration on ROTEM parameters among patients with TIC has not been adequately investigated.

METHODS

In this retrospective observational study, changes to ROTEM parameters, induced by three different therapeutic interventions, were investigated: patients receiving FC only (FC-group); patients treated with FC and PCC (FC + PCC-group) and patients treated with PCC only (PCC-group).

RESULTS

The study population comprised 96 patients who were predominately male (69 [71.9 %]), median age was 45.0 (26.3-60.0) years, and the median injury severity score was 34.0 (25.0-44.5). Administration of FC resulted in a significant reduction of the clotting time (CT) in both the EXTEM and FIBTEM assays but had no effect on INTEM CT. Clot amplitude (CA) increased significantly in the FIBTEM assay but remained unchanged in the EXTEM and INTEM assays. The combined administration of FC and PCC increased FIBTEM maximum clot firmness (MCF) and normalized EXTEM CT but did not change either INTEM or FIBTEM CT. Following PCC therapy, EXTEM and FIBTEM CT normalized; CA at 10 min after CT measurements decreased significantly in EXTEM, INTEM and FIBTEM.

CONCLUSIONS

Administration of FC alone or in combination with PCC resulted in a significant improvement of fibrin polymerisation as measured by an increase in FIBTEM MCF. CT is dependent not only on thrombin generation but also on the availability of substrate (fibrinogen). Accelerated fibrin polymerisation rate results in earlier clot formation and consequently shorter CT. PCC administration normalised EXTEM CT below the upper threshold of 80 s. This study was performed at the AUVA Trauma Centre Salzburg, Salzburg, Austria.

Effects of Fibrinogen Concentrate on Thrombin Generation, Thromboelastometry Parameters, and Laboratory Coagulation Testing in a 24-Hour Porcine Trauma Model

Introduction:

In a 24-hour porcine model of liver injury, we showed that fibrinogen supplementation does not downregulate endogenous fibrinogen synthesis. Here we report data from the same study showing the impact of fibrinogen on coagulation variables.

Materials and Methods:

Coagulopathy was induced in 20 German land race pigs by hemodilution and blunt liver injury. Animals randomly received fibrinogen concentrate (100 mg/kg) or saline. Coagulation parameters were assessed and thromboelastometry (ROTEM) was performed.

Results:

Fibrinogen concentrate significantly reduced the prolongations of EXTEM clotting time, EXTEM clot formation time, and prothrombin time induced by hemodilution and liver injury. A decrease in clot strength was also ameliorated. Endogenous thrombin potential was significantly higher in the fibrinogen group than in the control group, 20 minutes (353 ± 24 vs 289 ± 22 nmol/L·min; P < .05) and 100 minutes (315 ± 40 vs 263 ± 38 nmol/L·min; P < .05) after the start of infusion. However, no significant between-group differences were seen in other thrombin generation parameters or in d-dimer or thrombin–antithrombin levels. Fibrinogen–platelet binding was reduced following liver injury, with no significant differences between groups. No significant between-group differences were observed in any parameter at ∼12 and ∼24 hours.

Conclusion:

This study suggests that, in trauma, fibrinogen supplementation may shorten some measurements of the speed of coagulation initiation and produce a short-lived increase in endogenous thrombin potential, potentially through increased clotting substrate availability. Approximately 12 and 24 hours after starting fibrinogen concentrate/saline infusion, all parameters measured in this study were comparable in the 2 study groups.

Prehospital coagulation monitoring of resuscitation with point-of-care devices

A variety of point-of-care monitors for the measurement of hematocrit, hemoglobin, blood gas with electrolytes, and lactate can be used also in the prehospital setting for optimizing and individualizing trauma resuscitation. Point-of-care coagulation testing with activated prothrombin test, prothrombin test, and activated coagulation/clotting time tests is available for prehospital use. Although robust, battery driven, and easy to handle, many devices lack documentation for use in prehospital care. Some of the devices correspond poorly to corresponding laboratory analyses in acute trauma coagulopathy and at lower hematocrits. In trauma, viscoelastic tests such as rotational thromboelastometry and thromboelastography can rapidly detect acute trauma coagulopathy and give an overall dynamic picture of the hemostatic system and the interaction between its different components: coagulation activation, fibrin polymerization, fibrin platelet interactions within the clot, and fibrinolysis. Rotational thromboelastometry is shock resistant and has the potential to be used outside the hospital setting to guide individualized coagulation factor and blood component therapies. Sonoclot and Rheorox are two small viscoelastic instruments with one-channel options, but with less documentation. The point-of-care market for coagulation tests is quickly expanding, and new devices are introduced all the time. Still they should be better adopted to prehospital conditions, small, robust, battery charged, and rapid and use small sample volumes and whole blood.

Fibrinogen Concentrate Does Not Suppress Endogenous Fibrinogen Synthesis in a 24-hour Porcine Trauma Model

Background:

Fibrinogen concentrate may reduce blood loss after trauma. However, its effect on endogenous fibrinogen synthesis is unknown. The authors investigated the effect of exogenous human fibrinogen on endogenous fibrinogen metabolism in a 24-h porcine trauma model.

Methods:

Coagulopathy was induced in 20 German Landrace pigs by hemodilution and blunt liver injury. Animals were randomized to receive fibrinogen concentrate (100 mg/kg; infusion beginning 20 min postinjury and lasting approximately 10 min) or saline. Fibrinogen concentration, thromboelastometry, and quantitative reverse transcriptase polymerase chain reaction of fibrinogen genes in liver tissue samples were recorded. Internal organs were examined histologically for emboli.

Results:

Coagulation parameters were impaired and plasma fibrinogen concentrations were reduced before starting infusion of fibrinogen concentrate/saline. Twenty minutes after starting infusion, exogenous fibrinogen supplementation had increased plasma fibrinogen concentration versus controls (171 ± 19 vs. 63 ± 10 mg/dl [mean ± SD for Multifibren U]; 185 ± 30 vs. 41 ± 4 mg/dl [Thrombin reagent]; P &lt; 0.05 for both comparisons). The between-group difference in plasma fibrinogen concentration diminished thereafter, with maximum concentrations in both groups observed at approximately 24 h, that is, during the acute-phase reaction after trauma. Fibrinogen supplementation did not down-regulate endogenous fibrinogen synthesis (no between-group differences in fibrinogen messenger RNA). Total postinjury blood loss was significantly lower in the fibrinogen group (1,062 ± 216 vs. 1,643 ± 244 ml; P &lt; 0.001). No signs of thromboembolism were observed.

Conclusions:

Administration of human fibrinogen concentrate did not down-regulate endogenous porcine fibrinogen synthesis. The effect on plasma fibrinogen concentration was most pronounced at 20 min but nonsignificant at approximately 24 h.

Do all trauma patients benefit from tranexamic acid?

BACKGROUND

This study tested the hypothesis that early routine use of tranexamic acid (TXA) reduces mortality in a subset of the most critically injured trauma intensive care unit patients.

METHODS

Consecutive trauma patients (n = 1,217) who required emergency surgery (OR) and/or transfusions from August 2009 to January 2013 were reviewed. At surgeon discretion, TXA was administered at a median of 97 minutes (1-g bolus then 1-g over 8 hours) to 150 patients deemed high risk for hemorrhagic death. With the use of propensity scores based on age, sex, traumatic brain injury (TBI), mechanism of injury, systolic blood pressure, transfusion requirements, and Injury Severity Score (ISS), these patients were matched to 150 non-TXA patients.

RESULTS

The study population was 43 years old, 86% male, 54% penetrating mechanism of injury, 25% TBI, 28 ISS, with 22% mortality. OR was required in 78% at 86 minutes, transfusion was required in 97% at 36 minutes, and 75% received both. For TXA versus no TXA, more packed red blood cells and total fluid were required, and mortality was 27% versus 17% (all p < 0.05). The effects of TXA were similar in those with or without TBI, although ISS, fluid, and mortality were all higher in the TBI group. Mortality associated with TXA was influenced by the timing of administration (p < 0.05), but any benefit was eliminated in those who required more than 2,000-mL packed red blood cells, who presented with systolic blood pressure of less than 120 mm Hg or who required OR (all p < 0.05).

CONCLUSION

For the highest injury acuity patients, TXA was associated with increased, rather than reduced, mortality, no matter what time it was administered. This lack of benefit can probably be attributed to the rapid availability of fluids and emergency OR at this trauma center. Prospective studies are needed to further identify conditions that may override the benefits from TXA.

LEVEL OF EVIDENCE

Therapeutic study, level IV.

Restoring hemostasis: fibrinogen concentrate versus cryoprecipitate

Fibrinogen plays a key role in the coagulation process, and therefore maintaining adequate quantities of fibrinogen is an essential step in achieving satisfactory hemostasis in patients with acquired hypofibrinogenemia. Potential options for treating acquired hypofibrinogenemia in patients with uncontrolled bleeding include the use of cryoprecipitate or fibrinogen replacement therapy. This review provides a brief overview of the hemostatic process and the methods for assessing coagulopathy and discusses the efficacy and safety of cryoprecipitate and fibrinogen concentrate in restoring fibrinogen levels, achieving hemostasis and reducing transfusion requirements in different patient populations requiring rapid hemostasis. Other issues relevant to the clinical use of these agents in restoring hemostasis, including variations in product composition, preparation time and cost, are also examined.

Impact of fibrinogen concentrate alone or with prothrombin complex concentrate (+/- fresh frozen plasma) on plasma fibrinogen level and fibrin-based clot strength (FIBTEM) in major trauma: a retrospective study

Background

Low plasma fibrinogen concentration is a predictor of poor outcome in major trauma patients. The role of fibrinogen concentrate for rapidly increasing fibrinogen plasma levels in severe trauma is not well defined.

Methods

In this retrospective study we included severe trauma patients treated with fibrinogen concentrate alone (FC group), fibrinogen concentrate with prothrombin complex concentrate (FC–PCC group) or fibrinogen concentrate with PCC and fresh frozen plasma (FC–PCC–FFP group). PCC was generally administered as the second step of intraoperative therapy, while FFP was only administered as a third step. All patients received ≥1 g fibrinogen concentrate within 24 hours. Plasma fibrinogen concentration and ROTEM parameters upon emergency room (ER) admission, intensive care unit (ICU) admission, and after 24 hours were analysed.

Results

Among 157 patients fulfilling the inclusion criteria, 83% were male; mean age was 44 years and median injury severity score (ISS) was 29. Standard coagulation tests reflected increasing severity of coagulopathy with increasing complexity of haemostatic therapy (highest severity in the FC–PCC–FFP group; p < 0.0001). Total 24-hour fibrinogen concentrate dose also increased with complexity of haemostatic therapy. Plasma fibrinogen concentration was maintained, with no significant difference between ER admission and ICU admission in all patient groups. FIBTEM clot firmness at 10 minutes (CA₁₀) was similarly maintained, albeit with a small increase in the FC–PCC group. Fibrinogen concentration and FIBTEM CA₁₀ were within the normal range in all groups at 24 hours. The ratio of fibrinogen concentrate to red blood cells (g:U) ranged between 0.7:1.0 and 1.0:1.0.

Conclusion

Fibrinogen concentrate therapy maintained fibrinogen concentration and FIBTEM CA₁₀ during the initial phase of trauma care until ICU admission. After 24 hours, these parameters were comparable between the three groups and within the normal range for each of them. Further studies are warranted to investigate the effect of fibrinogen concentrate on clinical outcomes.

Optimal trauma resuscitation with plasma as the primary resuscitative fluid: the surgeon's perspective

Over the past century, blood banking and transfusion practices have moved from whole blood therapy to components. In trauma patients, the shift to component therapy was achieved without clinically validating which patients needed which blood products. Over the past 4 decades, this lack of clinical validation has led to uncertainty on how to optimally use blood products and has likely resulted in both overuse and underuse in injured patients. However, recent data from both US military operations and civilian trauma centers have shown a survival advantage with a balanced transfusion ratio of RBCs, plasma, and platelets. This has been extended to include the prehospital arena, where thawed plasma, RBCs, and antifibrinolytics are becoming more widely used. The Texas Trauma Institute in Houston has followed this progression by putting RBCs and thawed plasma in the emergency department and liquid plasma and RBCs on helicopters, transfusing platelets earlier, and using thromboelastogram-guided approaches. These changes have not only resulted in improved outcomes, but have also decreased inflammatory complications, operations, and overall use of blood products. In addition, studies have shown that resuscitating with plasma (instead of crystalloid) repairs the "endotheliopathy of trauma," or the systemic endothelial injury and dysfunction that lead to coagulation disturbances and inflammation. Data from the Trauma Outcomes Group, the Prospective Observational Multicenter Major Trauma Transfusion (PROMMTT) study, and the ongoing Pragmatic Randomized Optimal Platelet and Plasma Ratios (PROPPR) trial represent a decade-long effort to programmatically determine optimal resuscitation practices, balancing risk versus benefits. With injury as the leading cause of death in patients age 1 to 44 years and hemorrhage the leading cause of potentially preventable death in this group, high-quality data must be obtained to provide superior care to the civilian and combat injured.