Activation of factor IX by erythrocyte membranes causes intrinsic coagulation

Hemostasis Strategies and Recent Advances in Nanomaterials for Hemostasis

The development of materials that effectively stop bleeding and prevent wound adhesion is essential in both military and medical fields. However, traditional hemostasis methods, such as cautery, tourniquets, and gauze, have limitations. In recent years, new nanomaterials have gained popularity in medical and health fields due to their unique microstructural advantages. Compared to traditional materials, nanomaterials offer better adhesion, versatility, and improved bioavailability of traditional medicines. Nanomaterials also possess advantages such as a high degree and stability, self-degradation, fewer side effects, and improved wound healing, which make them ideal for the development of new hemostatic materials. Our review provides an overview of the currently used hemostatic strategies and materials, followed by a review of the cutting-edge nanomaterials for hemostasis, including nanoparticles and nanocomposite hydrogels. The paper also briefly describes the challenges faced by the application of nanomaterials for hemostasis and the prospects for their future development.

The Role of RBC Oxidative Stress in Sickle Cell Disease: From the Molecular Basis to Pathologic Implications

Sickle cell disease (SCD) is an inherited monogenic disorder and the most common severe hemoglobinopathy in the world. SCD is characterized by a point mutation in the β-globin gene, which results in hemoglobin (Hb) S production, leading to a variety of mechanistic and phenotypic changes within the sickle red blood cell (RBC). In SCD, the sickle RBCs are the root cause of the disease and they are a primary source of oxidative stress since sickle RBC redox state is compromised due to an imbalance between prooxidants and antioxidants. This imbalance in redox state is a result of a continuous production of reactive oxygen species (ROS) within the sickle RBC caused by the constant endogenous Hb autoxidation and NADPH oxidase activation, as well as by a deficiency in the antioxidant defense system. Accumulation of non-neutralized ROS within the sickle RBCs affects RBC membrane structure and function, leading to membrane integrity deficiency, low deformability, phosphatidylserine exposure, and release of micro-vesicles. These oxidative stress-associated RBC phenotypic modifications consequently evoke a myriad of physiological changes involved in multi-system manifestations. Thus, RBC oxidative stress in SCD can ultimately instigate major processes involved in organ damage. The critical role of the sickle RBC ROS production and its regulation in SCD pathophysiology are discussed here.

Added Value of Blood Cells in Thrombin Generation Testing

The capacity of blood to form thrombin is a critical determinant of coagulability. Plasma thrombin generation (TG), a test that probes the capacity of plasma to form thrombin, has improved our knowledge of the coagulation system and shows promising utility in coagulation management. Although plasma TG gives comprehensive insights into the function of pro- and anticoagulation drivers, it does not measure the role of blood cells in TG. In this literature review, we discuss currently available continuous TG tests that can reflect the involvement of blood cells in coagulation, in particular the fluorogenic assays that allow continuous measurement in platelet-rich plasma and whole blood. We also provide an overview about the influence of blood cells on blood coagulation, with emphasis on the direct influence of blood cells on TG. Platelets accelerate the initiation and velocity of TG by phosphatidylserine exposure, granule content release and surface receptor interaction with coagulation proteins. Erythrocytes are also major providers of phosphatidylserine, and erythrocyte membranes trigger contact activation. Furthermore, leukocytes and cancer cells may be important players in cell-mediated coagulation because, under certain conditions, they express tissue factor, release procoagulant components and can induce platelet activation. We argue that testing TG in the presence of blood cells may be useful to distinguish blood cell-related coagulation disorders. However, it should also be noted that these blood cell-dependent TG assays are not clinically validated. Further standardization and validation studies are needed to explore their clinical usefulness.

Oxidative Stress and Thrombosis during Aging: The Roles of Oxidative Stress in RBCs in Venous Thrombosis

Mid-life stage adults are at higher risk of developing venous thrombosis (VT)/thromboembolism (VT/E). Aging is characterized by an overproduction of reactive oxygen species (ROS), which could evoke a series of physiological changes involved in thrombosis. Here, we focus on the critical role of ROS within the red blood cell (RBC) in initiating venous thrombosis during aging. Growing evidence has shifted our interest in the role of unjustifiably unvalued RBCs in blood coagulation. RBCs can be a major source of oxidative stress during aging, since RBC redox homeostasis is generally compromised due to the discrepancy between prooxidants and antioxidants. As a result, ROS accumulate within the RBC due to the constant endogenous hemoglobin (Hb) autoxidation and NADPH oxidase activation, and the uptake of extracellular ROS released by other cells in the circulation. The elevated RBC ROS level affects the RBC membrane structure and function, causing loss of membrane integrity, and decreased deformability. These changes impair RBC function in hemostasis and thrombosis, favoring a hypercoagulable state through enhanced RBC aggregation, RBC binding to endothelial cells affecting nitric oxide availability, RBC-induced platelet activation consequently modulating their activity, RBC interaction with and activation of coagulation factors, increased RBC phosphatidylserine exposure and release of microvesicles, accelerated aging and hemolysis. Thus, RBC oxidative stress during aging typifies an ultimate mechanism in system failure, which can affect major processes involved in the development of venous thrombosis in a variety of ways. The reevaluated concept of the critical role of RBC ROS in the activation of thrombotic events during aging will help identify potential targets for novel strategies to prevent/reduce the risk for VT/E or VT/E recurrences in mid-life stage adults.

The Hemocompatibility of Nanoparticles: A Review of Cell-Nanoparticle Interactions and Hemostasis

Understanding cell-nanoparticle interactions is critical to developing effective nanosized drug delivery systems. Nanoparticles have already advanced the treatment of several challenging conditions including cancer and human immunodeficiency virus (HIV), yet still hold the potential to improve drug delivery to elusive target sites. Even though most nanoparticles will encounter blood at a certain stage of their transport through the body, the interactions between nanoparticles and blood cells is still poorly understood and the importance of evaluating nanoparticle hemocompatibility is vastly understated. In contrast to most review articles that look at the interference of nanoparticles with the intricate coagulation cascade, this review will explore nanoparticle hemocompatibility from a cellular angle. The most important functions of the three cellular components of blood, namely erythrocytes, platelets and leukocytes, in hemostasis are highlighted. The potential deleterious effects that nanoparticles can have on these cells are discussed and insight is provided into some of the complex mechanisms involved in nanoparticle-blood cell interactions. Throughout the review, emphasis is placed on the importance of undertaking thorough, all-inclusive hemocompatibility studies on newly engineered nanoparticles to facilitate their translation into clinical application.

The European guideline on management of major bleeding and coagulopathy following trauma: fifth edition

BACKGROUND

Severe traumatic injury continues to present challenges to healthcare systems around the world, and post-traumatic bleeding remains a leading cause of potentially preventable death among injured patients. Now in its fifth edition, this document aims to provide guidance on the management of major bleeding and coagulopathy following traumatic injury and encourages adaptation of the guiding principles described here to individual institutional circumstances and resources.

METHODS

The pan-European, multidisciplinary Task Force for Advanced Bleeding Care in Trauma was founded in 2004, and the current author group included representatives of six relevant European professional societies. The group applied a structured, evidence-based consensus approach to address scientific queries that served as the basis for each recommendation and supporting rationale. Expert opinion and current clinical practice were also considered, particularly in areas in which randomised clinical trials have not or cannot be performed. Existing recommendations were re-examined and revised based on scientific evidence that has emerged since the previous edition and observed shifts in clinical practice. New recommendations were formulated to reflect current clinical concerns and areas in which new research data have been generated.

RESULTS

Advances in our understanding of the pathophysiology of post-traumatic coagulopathy have supported improved management strategies, including evidence that early, individualised goal-directed treatment improves the outcome of severely injured patients. The overall organisation of the current guideline has been designed to reflect the clinical decision-making process along the patient pathway in an approximate temporal sequence. Recommendations are grouped behind the rationale for key decision points, which are patient- or problem-oriented rather than related to specific treatment modalities. While these recommendations provide guidance for the diagnosis and treatment of major bleeding and coagulopathy, emerging evidence supports the author group's belief that the greatest outcome improvement can be achieved through education and the establishment of and adherence to local clinical management algorithms.

CONCLUSIONS

A multidisciplinary approach and adherence to evidence-based guidance are key to improving patient outcomes. If incorporated into local practice, these clinical practice guidelines have the potential to ensure a uniform standard of care across Europe and beyond and better outcomes for the severely bleeding trauma patient.

Red blood cells aggregability measurement of coagulating blood in extracorporeal circulation system with multiple-frequency electrical impedance spectroscopy

Red blood cells (RBCs) aggregability A_G of coagulating blood in extracorporeal circulation system has been investigated under the condition of pulsatile flow. Relaxation frequency f_c from the multiple-frequency electrical impedance spectroscopy is utilized to obtain RBCs aggregability A_G. Compared with other methods, the proposed multiple-frequency electrical impedance method is much easier to obtain non-invasive measurement with high speed and good penetrability performance in biology tissues. Experimental results show that, RBCs aggregability A_G in coagulating blood falls down with the thrombus formation while that in non-coagulation blood almost keeps the same value, which has a great agreement with the activated clotting time (ACT) fibrinogen concertation (F_bg) tests. Modified Hanai formula is proposed to quantitatively analyze the influence of RBCs aggregation on multiple-frequency electrical impedance measurement. The reduction of RBCs aggregability A_G is associated with blood coagulation reaction, which indicates the feasibility of the high speed, compact and cheap on-line thrombus measurement biosensors in extracorporeal circulation systems.

Acute pulmonary thromboembolism occurring during treatment with tolvaptan in a patient with autosomal-dominant polycystic kidney disease

Autosomal-dominant polycystic kidney disease (ADPKD) is the most prevalent cystic kidney disease, with approximately half of the patients reaching end-stage renal disease by the age of 60. Tolvaptan prevents renal cyst growth by inhibiting intracellular cyclic AMP and is recommended for patients with ADPKD. Reports of thrombotic complications with tolvaptan have been limited. We report a case of a 60-year-old man who developed thromboembolisms during tolvaptan treatment for ADPKD. The patient started tolvaptan in July 2014. He was brought to our hospital in February 2015 with a sudden onset of dyspnea and chest pain after 6 days of persistent watery diarrhea. Blood tests revealed enhanced coagulation and fibrinolysis, and contrast-enhanced computed tomography confirmed the presence of multiple thromboembolisms. Venous thromboembolism (VTE) with acute pulmonary and lower extremity thrombi was diagnosed, and the patient was immediately admitted. Tolvaptan was discontinued on admission, and intravenous fluid loading and monteplase were started. Subsequently, chest pain and dyspnea resolved, with thrombi resolution occurring by day 14; the patient was discharged on day 18 in stable condition. VTE was attributed to continued tolvaptan during diarrhea and dehydration; tolvaptan itself was not associated with enhanced coagulability. Dehydrated patients with ADPKD, such as the patient in this case, are at an increased risk for thrombus formation. Proper education should be provided to maintain appropriate fluid status and discontinue tolvaptan upon volume depletion.

Effect of circulating tissue factor on hypercoagulability in type 2 diabetes mellitus studied by rheometry and dielectric blood coagulometry

BACKGROUND

Hypercoagulability in type 2 diabetes mellitus (T2DM) patients increases their risk of cardiovascular diseases.

OBJECTIVE

The aim of this work was to investigate the hypercoagulation mechanism in T2DM patients in terms of circulating tissue factor (TF).

METHODS

Whole blood coagulation tests by damped oscillation rheometry and dielectric blood coagulometry (DBCM) were performed.

RESULTS

The average coagulation time was significantly shorter for T2DM patients than for healthy controls. In vitro addition of either anti-TF or anti-activated factor VII (FVIIa) antibody to hypercoagulable blood samples prolonged coagulation times for one group of patients, while coagulation times remained short for another group. The levels of circulating TF were estimated in the former group by measuring the coagulation times for blood samples from healthy subjects with addition of various concentrations of TF and comparing them with the coagulation times for the group. The results indicated that the levels of circulating TF were on the order of subpicomolar at most.

CONCLUSIONS

Circulating TF is at least partially responsible for a hypercoagulable group of T2DM patients, while an abnormality in the intrinsic coagulation pathway probably occurs in the other group.

In Vitro Thrombogenesis Resulting from Decreased Shear Rate and Blood Coagulability

In vitro antithrombogenic testing with mock circulation is a useful type of pre-evaluation in ex vivo testing of mechanical assist devices. For effective in vitro testing, we have been developing a clear quantitative thrombogenesis model based on shear stress and blood coagulability. Bovine blood was used as the test medium. The activating clotting time (ACT) was adjusted with trisodium citrate and calcium chloride from 200 to 1,000 seconds. The blood was then applied to a rheometer and subjected to shear at 50 to 2,880 s-1. Blood coagulation time and degree of thrombogenesis were measured by the torque sensor of the rheometer. Prothrombin time (PT) and activated partial thromboplastin time (APTT) of the test blood were also measured after the application of shear. Blood coagulation time increased, and the degree of thrombogenesis decreased, with increases in shear rate to between 50 and 2,880 s-1. for test bloods with ACTs of 200 to 250 seconds. An ACT of 200 to 250 seconds is thus appropriate for in vitro antithrombogenic testing under a shear rate of 2,880 s-1. APTT was prolonged, whereas PT did not change, with increasing shear rate: that is, increasing the shear rate reduced thrombogenesis related to the intrinsic clotting pathway. An ACT of 200 to 250 seconds was suitable for in vitro antithrombogenic testing, and increasing the shear stress generated in the mechanical assist device reduced thrombogenesis via the intrinsic clotting pathway.

The European guideline on management of major bleeding and coagulopathy following trauma: fourth edition

BACKGROUND

Severe trauma continues to represent a global public health issue and mortality and morbidity in trauma patients remains substantial. A number of initiatives have aimed to provide guidance on the management of trauma patients. This document focuses on the management of major bleeding and coagulopathy following trauma and encourages adaptation of the guiding principles to each local situation and implementation within each institution.

METHODS

The pan-European, multidisciplinary Task Force for Advanced Bleeding Care in Trauma was founded in 2004 and included representatives of six relevant European professional societies. The group used a structured, evidence-based consensus approach to address scientific queries that served as the basis for each recommendation and supporting rationale. Expert opinion and current clinical practice were also considered, particularly in areas in which randomised clinical trials have not or cannot be performed. Existing recommendations were reconsidered and revised based on new scientific evidence and observed shifts in clinical practice; new recommendations were formulated to reflect current clinical concerns and areas in which new research data have been generated. This guideline represents the fourth edition of a document first published in 2007 and updated in 2010 and 2013.

RESULTS

The guideline now recommends that patients be transferred directly to an appropriate trauma treatment centre and encourages use of a restricted volume replacement strategy during initial resuscitation. Best-practice use of blood products during further resuscitation continues to evolve and should be guided by a goal-directed strategy. The identification and management of patients pre-treated with anticoagulant agents continues to pose a real challenge, despite accumulating experience and awareness. The present guideline should be viewed as an educational aid to improve and standardise the care of the bleeding trauma patients across Europe and beyond. This document may also serve as a basis for local implementation. Furthermore, local quality and safety management systems need to be established to specifically assess key measures of bleeding control and outcome.

CONCLUSIONS

A multidisciplinary approach and adherence to evidence-based guidance are key to improving patient outcomes. The implementation of locally adapted treatment algorithms should strive to achieve measureable improvements in patient outcome.

Design and evaluation of a portable optical-based biosensor for testing whole blood prothrombin time

Point-of-care diagnostics (POCD) for blood coagulation benefit patients on-site, but available POCD devices are too expensive to be affordable in many countries. Optically based methodologies are cheap and reliable, and have been exploited in bench-top coagulometers to monitor coagulation with plasma, but not whole blood, which contains cellular components that cause massive interference. However, the POCD testing of whole blood gives a more accurate picture of physiological conditions than does testing plasma. In this study, a portable device for performing the prothrombin time (PT) test was designed, comprising an optical sensor, an electrical processing and control circuit to monitor the optical changes that occurred during the coagulation process in whole blood. The PT was when the slope of the first-order derivative of the coagulation curve, recorded from real-time light transmittance signals, was maximal. The POCD PT testing of 167 samples revealed that 153 (91.6%) were successfully detected and the results were highly consistent with the results of whole blood international normalized ratio (INR) (r=0.985, p<0.001) by the conventional manual method and those of plasma INR (r=0.948, p<0.001) with the ACL TOP 700 bench-top coagulometer (Beckman Colter). Hematological parameters were further analyzed, revealing that fibrinogen titers (p=0.036), red blood cell numbers (p=0.017) and distribution of red cell width (p=0.015) affected the effectiveness of the current POCD PT determination. Furthermore, a highly positive correlation was revealed between fibrinogen titers and the maximum speed of change in transmittance (v/t) (r=0.805, p<0.001), suggesting that fibrinogen might be evaluated simultaneously in this POCD testing. In conclusion, the proposed portable optical-based device performs the highly sensitive and accurate determination of whole blood PT and has commercial potential because of its small volume and low fabrication cost.

Platelet- and erythrocyte-derived microparticles trigger thrombin generation via factor XIIa

BACKGROUND

The procoagulant properties of microparticles (MPs) are due to the of the presence of phosphatidylserine (PS) and tissue factor (TF) on their surface. The latter has been demonstrated especially on MPs derived from monocytes.

OBJECTIVES

To investigate the relative contribution of TF and factor (F)XII in initiating coagulation on MPs derived from monocytes, platelets and erythrocytes.

METHODS

Microparticles were isolated from calcium ionophore-stimulated platelets, erythrocytes and monocytic THP-1 cells. MPs were quantified, characterized for cell-specific antigens and analyzed for TF, PS exposure and their thrombin-generating potential.

RESULTS

The MP number was not proportional to PS exposure and the majority of the MPs exposed PS. TF activity was undetectable on platelet- and erythrocyte-derived MPs (< 1 fM nM(-1) PS), whereas monocyte-derived MPs exposed TF (32 fM nM(-1) PS). Platelet-, erythrocyte- and monocyte-derived MPs, but not purified phospholipids, initiated thrombin generation in normal plasma in the absence of an external trigger (lag time < 11 min). Deficiency or inhibition of FVII had no effect on thrombin generation induced by platelet- and erythrocyte-derived MPs, but interfered with monocyte MP-triggered coagulation. Platelet- and erythrocyte-derived MPs completely failed to induce thrombin generation in FXII-deficient plasma. In contrast, monocyte-derived MPs induced similar thrombin generation in normal vs. FXII-deficient plasma.

CONCLUSION

MPs from platelets and erythrocytes not only propagate coagulation by exposing PS but also initiate thrombin generation independently of TF in a FXII-dependent manner. In contrast, monocyte-derived MPs trigger coagulation predominantly via TF.

Simultaneous measurement of red blood cell aggregation and whole blood coagulation using high-frequency ultrasound

This study aims to investigate the feasibility of using high-frequency ultrasound (HFUS) for simultaneous monitoring of blood coagulation and red blood cell (RBC) aggregation. Using a 35-MHz ultrasound scanner, ultrasound speckle data were acquired from whole blood samples of three experimental groups of rats, including 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS)-treated, noncoagulation and normal control groups. The variations of blood echogenicity, the shape parameters of probability distribution of speckle intensity (skewness and kurtosis) and the correlation coefficient between two consecutive speckle data were calculated as a function of time starting from immediately after taking blood. The blood echogenicity increases rapidly to plateaus at the early stage of measurement for all the experimental groups caused by the formation of RBC aggregates. The DIDS-treated group exhibits the lowest echogenicity level due to the inhibitory effect of DIDS on RBC aggregation. The correlation analysis between consecutive speckle patterns seems to be useful to examine the variation of blood fluidity and the progress of clot formation. Whole blood coagulation is observed to be accelerated by DIDS treatment. In addition, the results of skewness and kurtosis analysis indicated that RBC aggregates may be disrupted during blood coagulation. The present study suggests that HFUS has good potential for simultaneous monitoring of RBC aggregation and blood coagulation to examine the relationship between them.

Blood transfusion during cardiac surgery is associated with inflammation and coagulation in the lung: a case control study

INTRODUCTION

Blood transfusion is associated with increased morbidity and mortality in cardiac surgery patients, but cause-and-effect relations remain unknown. We hypothesized that blood transfusion is associated with changes in pulmonary and systemic inflammation and coagulation occurring in patients who do not meet the clinical diagnosis of transfusion-related acute lung injury (TRALI).

METHODS

We performed a case control study in a mixed medical-surgical intensive care unit of a university hospital in the Netherlands. Cardiac surgery patients (n = 45) were grouped as follows: those who received no transfusion, those who received a restrictive transfusion (one two units of blood) or those who received multiple transfusions (at least five units of blood). Nondirected bronchoalveolar lavage fluid (BALF) and blood were obtained within 3 hours postoperatively. Normal distributed data were analyzed using analysis of variance and Dunnett's post hoc test. Nonparametric data were analyzed using the Kruskal-Wallis and Mann-Whitney U tests.

RESULTS

Restrictive transfusion increased BALF levels of interleukin (IL)-1β and D-dimer compared to nontransfused controls (P < 0.05 for all), and IL-1β levels were further enhanced by multiple transfusions (P < 0.01). BALF levels of IL-8, tumor necrosis factor α (TNFα) and thrombin-antithrombin complex (TATc) were increased after multiple transfusions (P < 0.01, P < 0.001 and P < 0.01, respectively) compared to nontransfused controls, but not after restrictive transfusions. Restrictive transfusions were associated with increased pulmonary levels of plasminogen activator inhibitor 1 compared to nontransfused controls with a further increase after multiple transfusions (P < 0.001). Concomitantly, levels of plasminogen activator activity (PAA%) were lower (P < 0.001), indicating impaired fibrinolysis. In the systemic compartment, transfusion was associated with a significant increase in levels of TNFα, TATc and PAA% (P < 0.05).

CONCLUSIONS

Transfusion during cardiac surgery is associated with activation of inflammation and coagulation in the pulmonary compartment of patients who do not meet TRALI criteria, an effect that was partly dose-dependent, suggesting transfusion as a mediator of acute lung injury. These pulmonary changes were accompanied by systemic derangement of coagulation.

Management of bleeding following major trauma: an updated European guideline

INTRODUCTION

Evidence-based recommendations are needed to guide the acute management of the bleeding trauma patient, which when implemented may improve patient outcomes.

METHODS

The multidisciplinary Task Force for Advanced Bleeding Care in Trauma was formed in 2005 with the aim of developing a guideline for the management of bleeding following severe injury. This document presents an updated version of the guideline published by the group in 2007. Recommendations were formulated using a nominal group process, the Grading of Recommendations Assessment, Development and Evaluation (GRADE) hierarchy of evidence and based on a systematic review of published literature.

RESULTS

Key changes encompassed in this version of the guideline include new recommendations on coagulation support and monitoring and the appropriate use of local haemostatic measures, tourniquets, calcium and desmopressin in the bleeding trauma patient. The remaining recommendations have been reevaluated and graded based on literature published since the last edition of the guideline. Consideration was also given to changes in clinical practice that have taken place during this time period as a result of both new evidence and changes in the general availability of relevant agents and technologies.

CONCLUSIONS

This guideline provides an evidence-based multidisciplinary approach to the management of critically injured bleeding trauma patients.

Important regulatory role of activated platelet-derived procoagulant activity in the propagation of thrombi formed under arterial blood flow conditions

BACKGROUND

The functional links between the activation of platelets and the coagulation system have not been clarified.

METHODS AND RESULTS

Immobilized collagen fibrils were perfused with human blood containing fluoresceinated platelets in the presence of various concentrations of thrombin inhibitor. Coagulant activity around platelet thrombi was detected using a FITC-conjugated antibody against the fibrin monomer complex (F-405). Intra-cytosolic calcium ion concentrations ([Ca(2+)](i)) in individual platelets and the volume of thrombi were detected with an ultrafast confocal laser microscope equipped with a piezo-motor control unit. The volume of platelet thrombi formed after 8 min of blood perfusion in the presence of 10, 25, 50, and 100 micromol/L argatroban was 7.69+/-0.46 microm(3), 6.61+/-1.96 microm(3), 3.63+/-1.54 microm(3), and 1.67+/-0.75 microm(3), respectively. There was a positive correlation between the volume of platelet thrombi and the amount of fibrin monomer complex produced around them. The [Ca(2+)](i) of the platelets forming the thrombi oscillated between a minimum of 92.0+/-57.4 nmol/L, 120.1+/-68.1 nmol/L, and a maximum of 217.6+/-131.5 nmol/L, 367.6+/-189.1 nmol/L, respectively, in the presence of 100 and 10 mumol/L argatroban.

CONCLUSIONS

The results suggest a crucial role of coagulant activity in both the generation of fibrin and the growth of platelet thrombi.

Coagulopathy in trauma: optimising haematological status

It is estimated that 10 000 people per year die following trauma in England and Wales and 30—40% do so due to uncontrolled haemorrhage. By the time the patient reaches hospital, coagulopathy is often already installed and needs to be corrected promptly to prevent further haemorrhage and allow effective treatment of injuries. The coagulopathy is multifactorial with the leading causes being acidosis, hypothermia and massive transfusion. Early recognition of the condition is imperative using standard coagulation testing; however, there are limitations in this setting. Newer methods of testing `global haemostasis' using thromboelastography are becoming more popular but need further validation. Treatment of coagulopathy requires a multidisciplinary approach. Blood product transfusion remains the cornerstone of management but newer pharmacological agents such as recombinant factor VIIa are increasingly being used. Here we review the pathogenesis, investigation and management of the coagulopathy of trauma.

Management of bleeding following major trauma: a European guideline

INTRODUCTION

Evidence-based recommendations can be made with respect to many aspects of the acute management of the bleeding trauma patient, which when implemented may lead to improved patient outcomes.

METHODS

The multidisciplinary Task Force for Advanced Bleeding Care in Trauma was formed in 2005 with the aim of developing guidelines for the management of bleeding following severe injury. Recommendations were formulated using a nominal group process and the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) hierarchy of evidence and were based on a systematic review of published literature.

RESULTS

Key recommendations include the following: The time elapsed between injury and operation should be minimised for patients in need of urgent surgical bleeding control, and patients presenting with haemorrhagic shock and an identified source of bleeding should undergo immediate surgical bleeding control unless initial resuscitation measures are successful. A damage control surgical approach is essential in the severely injured patient. Pelvic ring disruptions should be closed and stabilised, followed by appropriate angiographic embolisation or surgical bleeding control, including packing. Patients presenting with haemorrhagic shock and an unidentified source of bleeding should undergo immediate further assessment as appropriate using focused sonography, computed tomography, serum lactate, and/or base deficit measurements. This guideline also reviews appropriate physiological targets and suggested use and dosing of blood products, pharmacological agents, and coagulation factor replacement in the bleeding trauma patient.

CONCLUSION

A multidisciplinary approach to the management of the bleeding trauma patient will help create circumstances in which optimal care can be provided. By their very nature, these guidelines reflect the current state-of-the-art and will need to be updated and revised as important new evidence becomes available.

Resuscitation With Normal Saline (NS) vs. Lactated Ringers (LR) Modulates Hypercoagulability and Leads to Increased Blood Loss in an Uncontrolled Hemorrhagic Shock Swine Model

BACKGROUND

Lactated ringers (LR) and normal saline (NS) are used interchangeably in many trauma centers. The purpose of this study was to compare the effects of LR and NS on coagulation in an uncontrolled hemorrhagic swine model. We hypothesized resuscitation with LR would produce hypercoagulability.

METHODS

There were 20 anesthetized swine (35 +/- 3 kg) that underwent central venous and arterial catheterization, celiotomy, and splenectomy. After splenectomy blinded study fluid equal to 3 mL per gram of splenic weight was administered. A grade V liver injury was made and animals bled without resuscitation for 30 minutes. Animals were resuscitated with the respective study fluid to, and maintained, at the preinjury MAP until study end. Prothrombin Time (PT), Partial Thromboplastin Time (PTT), and fibrinogen were collected at baseline (0') and study end (120'). Thrombelastography was performed at 0'and postinjury at 30', 60', 90', and 120'.

RESULTS

There were no significant baseline group differences in R value, PT, PTT, and fibrinogen. There was no significant difference between baseline and 30 minutes R value with NS (p = 0.17). There was a significant R value reduction from baseline to 30 minutes with LR (p = 0.02). At 60 minutes, R value (p = 0.002) was shorter while alpha angle, maximum amplitude, and clotting index were higher (p < 0.05) in the LR versus the NS group. R value, PT, and PTT were significantly decreased at study end in the LR group compared with the NS group (p < 0.05). Overall blood loss was significantly higher in the NS versus LR group (p = 0.009).

CONCLUSIONS

This data indicates that resuscitation with LR leads to greater hypercoagulability and less blood loss than resuscitation with NS in uncontrolled hemorrhagic shock.

The effect of red blood cells on thrombin generation

We have developed an assay of thrombin generation in clotting whole blood. Because our goal was to study patients with red blood cell diseases that are associated with thrombosis, the initial evaluation of this assay analysed the effect of the haematocrit and haemolysate on the total amount of thrombin activity generated and the maximal concentration of thrombin achieved. Both of these parameters were proportional to the haematocrit throughout a wide range of clinically relevant cell concentrations. Red cell lysate also augmented thrombin generation. Because this effect was removed by filtration of the lysate, we propose that it was related to red cell microparticles.

Coagulopathy and blood component transfusion in trauma

Trauma is a serious global health problem, accounting for approximately one in 10 deaths worldwide. Uncontrollable bleeding accounts for 39% of trauma-related deaths and is the leading cause of potentially preventable death in patients with major trauma. While bleeding from vascular injury can usually be repaired surgically, coagulopathy-related bleeding is often more difficult to manage and may also mask the site of vascular injury. The causes of coagulopathy in patients with severe trauma are multifactorial, including consumption and dilution of platelets and coagulation factors, as well as dysfunction of platelets and the coagulation system. The interplay between hypothermia, acidosis and progressive coagulopathy, referred to as the 'lethal triad', often results in exsanguination. Current management of coagulopathy-related bleeding is based on blood component replacement therapy. However, there is a limit on the level of haemostasis that can be restored by replacement therapy. In addition, there is evidence that transfusion of red blood cells immediately after injury increases the incidence of post-injury infection and multiple organ failure. Strategies to prevent significant coagulopathy and to control critical bleeding effectively in the presence of coagulopathy may decrease the requirement for blood transfusion, thereby improving clinical outcome of patients with major trauma.

Rheological analyses of coagulation of blood from different individuals with special reference to procoagulant activity of erythrocytes

In our previous papers, we reported that factor IX (FIX), when activated by erythrocyte membranes, causes coagulation. We have identified and characterized the FIX-activating enzyme located in normal human erythrocyte membranes. In this paper, to examine physiological and pathological significances of procoagulant activity of erythrocytes, coagulation of blood obtained from different individuals was analyzed by means of a rheological technique. In more than 65% of subjects including normals and patients, the initiation of coagulation seemed to be governed by erythrocytes. Coagulation of whole blood and platelet-free plasma supplemented with erythrocytes had a tendency to occur rapidly in the elderly. It was suggested that the concentration of FIX-activating enzyme on erythrocyte membranes for aged donors was somewhat higher than that for young ages. Propagation reactions on erythrocyte membranes (i.e. factor X activation leading to thrombin generation after FIX activation) was slower than that on platelet membranes. Moreover, the propagation reaction on erythrocyte membranes was greatly dependent on individuals, whereas that on platelet membranes was not so much. Our study demonstrates that the activation of FIX by erythrocytes and subsequent propagation reaction on platelet membranes may be important for initiating and controlling blood coagulation reactions.

Hematological Change in Venous Blood of the Lower Leg during Prolonged Sitting in a Low Humidity and Hypobaric Environment

The present study examined the effects of low humidity and hypobaric conditions on hematological change in venous blood of the lower leg during quiet prolonged sitting. Ten healthy male students participated as the subjects after singing a consent form to participate in this study. Their diet and water intake were controlled from 19:00 on the day before the experiments. The subjects sat for 130 min in a climatic chamber. Four experimental conditions in the chamber were designed from a combination of relative humidity (20% or 60%) and air pressure (sea level or equivalent to an altitude of 2,000 m). Ambient temperature was maintained at 24 degrees C in every condition. Venous blood was sampled from the lower leg before and after exposure to the experimental conditions, and was analyzed for blood viscosity and hematological indices. Also, body weight and leg circumference were measured as indices of total water loss and edema, respectively. Regarding the results of ANOVA, significant interactions between humidity and time were observed in blood viscosity, red blood cell count and hematocrit (each p<0.05). However, there were no significant differences in these indices among the conditions. Significant increases were observed in leg circumference (p<0.01), platelet count (p<0.05) and total protein (p<0.05) after the exposure compared with those before the exposure. There were no noticeable effects of hypobaric conditions in every measurement. In conclusion, prolonged sitting seems to be a more hazardous factor for thrombogenesis low humidity and hypobaric conditions during a long-distance flight.

Purification, identification, and characterization of elastase on erythrocyte membrane as factor IX-activating enzyme

In our previous papers, we reported that factor IX (F-IX), when activated by erythrocyte membranes, causes coagulation. We report on purification, identification, and characterization of F-IX-activating enzyme extracted from human erythrocyte membranes. The enzyme whose amino acid sequence is almost in accord with neutrophil elastase was found in normal erythrocyte membrane. The molecular mass was slightly smaller than that of neutrophil elastase. The content of the enzyme in erythrocyte membranes was estimated to be 3.0-3.7 ng per 10(6)erythrocytes. The F-IX sites cleaved by the enzyme were slightly different from those by the ordinary coagulation reaction. The ability of F-IX cleaved by the enzyme to cause coagulation was estimated to be approximately 1/10 as high as that of the F-IX cleaved by activated F-XI. These findings provide evidence that F-IX is activated by erythrocyte membrane, which may serve as a triggering mechanism for blood coagulation.