Rotational thromboelastography for monitoring of fibrinogen concentrate therapy in fibrinogen deficiency

Pharmacokinetics, efficacy and safety of a novel fibrinogen concentrate in pediatric patients with congenital afibrinogenemia

INTRODUCTION

Congenital afibrinogenemia treatment with plasma-derived fibrinogen concentrates in pediatric patients is limited. This study investigated the pharmacokinetics, surrogate efficacy, and safety of a plasma-derived fibrinogen concentrate (FIB Grifols) in pediatric patients with congenital afibrinogenemia.

METHODS

Patients aged <18 years old diagnosed with congenital afibrinogenemia were included in this prospective, multinational, phase 1-2, single-arm study. After a single dose of a plasma-derived fibrinogen concentrate (70 mg/kg body weight), pharmacokinetic parameters were determined from plasma fibrinogen activity (Clauss method) and antigen method (ELISA), and calculated by noncompartmental and population pharmacokinetic (popPK) models. Patients were followed up over 14 days. Efficacy variables were the mean change on thromboelastographic variables (maximum clot firmness [MCF], alpha angle [ α ]) and coagulation tests (prothrombin time, activated partial thromboplastin time, and thrombin time) 1 h postinfusion. Safety parameters were assessed.

RESULTS

Eleven patients with a median (range) age 8.80 (3.7-12.7) years were treated with the plasma-derived fibrinogen concentrate. Using the popPK modeling, fibrinogen activity reached a mean (standard deviation) Cmax of 1.3 (0.225) g/l, half-life ( t1/2 ) of 60.6 (4.48) h and incremental in vivo recovery (IVR) of 1.86 (0.322) (mg/dl)/(mg/kg). Surrogate efficacy was demonstrated by significant increase in MCF (9.23 [3.94] mm; P  < 0.001; 95% confidence interval 6.58, 11.87). All coagulation times were significantly shortened after fibrinogen concentrate infusion. Adverse events were mild or moderate in severity, and unrelated to fibrinogen concentrate.

CONCLUSIONS

In pediatric patients with congenital afibrinogenemia, plasma-derived fibrinogen concentrate revealed a favorable and specific pharmacokinetic profile, demonstrated efficacy in coagulation and was safe and well tolerated.

Anaesthetic-surgical guide in the treatment of ascending aorta and surgery of the ascending aorta and aortic arch. Consensus document of the Spanish Society of Cardiovascular and Endovascular Surgery and the Sociedad of Anaesthesiology, Resuscitation and Pain Therapy

Aortic pathology is always a challenge for the clinician, and must be diagnosed and treated by a multidisciplinary team due to the technical and technological complexity of the resources used. Ongoing efforts to implement a systematic, protocolized approach involving "Aortic teams" made up of cardiologists, cardiac surgeons, vascular surgeons, anaesthesiologists and radiologists, among others are now leading to improved outcomes. The aim of this consensus document drawn up by the Aortic working groups of the Spanish Society of Anaesthesiology, Resuscitation and Pain Therapy (SEDAR) and the Spanish Society of Thoracic and Cardiovascular Surgery (SECTCV) is to disseminate a set of working protocols. The latest consensus document of the European Association for Cardio-Thoracic Surgery (EACTS) and the European Society for Vascular Surgery (ESVS) define the concept of "AORTIC TEAM"(1). The aortic team should be closely involved from diagnosis to treatment and finally follow-up, and should be formed of cardiac and vascular surgeons working together with anaesthesiologists, cardiologists, radiologists and geneticists. Treatment of aortic pathologies should be centralised in large centres, because this is the only way to effectively understand the natural course of the disease, provide the entire range of treatment options under one umbrella and treat potential complications. A streamlined emergent care pathway (24/7 availability), adequate transportation and transfer capabilities, as well as rapid activation of the multidisciplinary team must be available. In light of the complexity and constant evolution of therapeutic options, we present this first version of the Anaesthesiology and surgical guidelines for surgery of the ascending aorta and aortic arch. Some questions will no doubt remain unanswered, and future versions will include new techniques that, though implemented in some centres, are still not widely recommended.

Congenital Afibrinogenemia and Hypofibrinogenemia: Laboratory and Genetic Testing in Rare Bleeding Disorders with Life-Threatening Clinical Manifestations and Challenging Management

Congenital fibrinogen disorders are rare pathologies of the hemostasis, comprising quantitative (afibrinogenemia, hypofibrinogenemia) and qualitative (dysfibrinogenemia and hypodysfibrinogenemia) disorders. The clinical phenotype is highly heterogeneous, being associated with bleeding, thrombosis, or absence of symptoms. Afibrinogenemia and hypofibrinogenemia are the consequence of mutations in the homozygous, heterozygous, or compound heterozygous state in one of three genes encoding the fibrinogen chains, which can affect the synthesis, assembly, intracellular processing, stability, or secretion of fibrinogen. In addition to standard coagulation tests depending on the formation of fibrin, diagnostics also includes global coagulation assays, which are effective in monitoring the management of replacement therapy. Genetic testing is a key point for confirming the clinical diagnosis. The identification of the precise genetic mutations of congenital fibrinogen disorders is of value to permit early testing of other at risk persons and better understand the correlation between clinical phenotype and genotype. Management of patients with afibrinogenemia is particularly challenging since there are no data from evidence-based medicine studies. Fibrinogen concentrate is used to treat bleeding, whereas for the treatment of thrombotic complications, administered low-molecular-weight heparin is most often. This review deals with updated information about afibrinogenemia and hypofibrinogenemia, contributing to the early diagnosis and effective treatment of these disorders.

Viscoelastic testing in benign hematologic disorders: Clinical perspectives and future implications of point-of-care testing to assess hemostatic competence

Viscoelastic tests (VETs) have been used routinely for liver transplantation, cardiac surgery, and trauma, but only recently have found clinical utility in benign hematologic disorders. Therefore, guidelines for diagnosis and treatment of these disorders based on viscoelastic variables have been adapted from the existing transplant, cardiothoracic surgery, and trauma resuscitation literature. As a result, diagnostic and therapeutic strategies for benign hematologic disorders utilizing VETs are not uniform. Accordingly, even though there has been a recent increase in the utilization of VET for the diagnosis and treatment of such disorders, the literature is still in its early stages. Analysis of point-of-care viscoelastic tracings from benign hematologic disorders has the potential to allow prompt recognition of disease and to guide patient-specific intervention. Here we present a review describing the application of VETs to benign hematologic disorders.

Anaesthetic-surgical guide in the treatment of ascending aorta and surgery of the ascending aorta and aortic arch. Consensus document of the Spanish Society of Cardiovascular and Endovascular Surgery and the Sociedad of Anaesthesiology, Resuscitation and Pain Therapy

Aortic pathology is always a challenge for the clinician, and must be diagnosed and treated by a multidisciplinary team due to the technical and technological complexity of the resources used. Ongoing efforts to implement a systematic, protocolized approach involving "Aortic teams" made up of cardiologists, cardiac surgeons, vascular surgeons, anaesthesiologists and radiologists, among others are now leading to improved outcomes. The aim of this consensus document drawn up by the Aortic working groups of the Spanish Society of Anaesthesiology, Resuscitation and Pain Therapy (SEDAR) and the Spanish Society of Thoracic and Cardiovascular Surgery (SECTCV) is to disseminate a set of working protocols. The latest consensus document of the European Association for Cardio-Thoracic Surgery (EACTS) and the European Society for Vascular Surgery (ESVS) define the concept of "AORTIC TEAM"(1). The aortic team should be closely involved from diagnosis to treatment and finally follow-up, and should be formed of cardiac and vascular surgeons working together with anaesthesiologists, cardiologists, radiologists and geneticists. Treatment of aortic pathologies should be centralised in large centres, because this is the only way to effectively understand the natural course of the disease, provide the entire range of treatment options under one umbrella and treat potential complications. A streamlined emergent care pathway (24/7 availability), adequate transportation and transfer capabilities, as well as rapid activation of the multidisciplinary team must be available. In light of the complexity and constant evolution of therapeutic options, we present this first version of the Anaesthesiology and surgical guidelines for surgery of the ascending aorta and aortic arch. Some questions will no doubt remain unanswered, and future versions will include new techniques that, though implemented in some centres, are still not widely recommended.

Pharmacokinetics, surrogate efficacy and safety evaluations of a new human plasma-derived fibrinogen concentrate (FIB Grifols) in adult patients with congenital afibrinogenemia

BACKGROUND AND AIMS

Congenital afibrinogenemia is a rare coagulation disorder resulting from a deficiency in fibrinogen. This study assessed the pharmacokinetics, surrogate efficacy and safety of FIB Grifols, a new human plasma-derived fibrinogen concentrate, to treat congenital afibrinogenemia.

METHODS

Eleven adult patients from a multinational, phase 1-2, prospective, open-label, single-arm, uncontrolled clinical study received a single infusion of FIB Grifols, 70 mg/kg bw. Fibrinogen pharmacokinetics (fibrinogen activity: Clauss method; antigen plasma concentrations: ELISA) and efficacy parameters were determined over 14 days after infusion. Efficacy endpoints were the mean change on plasma maximum clot firmness (MCF) on viscoelastic testing and coagulation tests 1-hour post-infusion, and correlation with fibrinogen levels throughout. Safety parameters were also assessed.

RESULTS

For the Clauss method, (mean [standard deviation]) baseline adjusted C_max was 1.99 (0.40) g/L, reached 1.76 (1.00) h after infusion, and half-life was 76.94 (20.21) h. Using ELISA, C_max after FIB Grifols infusion was 2.88 (0.86) mg/mL, with a t_max of 3.06 (2.24) h. Fibrinogen activity and antigen concentrations showed statistically significant correlation of 0.9120 (P < 0.001). Surrogate efficacy was demonstrated by a significant increase of 12.35 (3.85) mm in MCF. Prothrombin time, activated partial thromboplastin time and thrombin time, returned to normal ranges over time, indicating restoration of functionally active fibrinogen. There were no treatment-related adverse events, allergic reactions, serious adverse events, or discontinuations.

CONCLUSIONS

The pharmacokinetic profile of functionally active FIB Grifols was established, hemostasis was restored, and FIB Grifols was safe and well tolerated in fibrinogen-deficient patients.

From Routine to Research Laboratory: Strategies for the Diagnosis of Congenital Fibrinogen Disorders

Congenital fibrinogen disorders (CFDs) encompass a heterogeneous group of fibrinogen defects with a wide spectrum of biological and clinical features. An accurate diagnosis is thus essential to assure the optimal management for the patient. Diagnosis involves a multistep approach starting with routine coagulation assays and assessment of functional and antigenic fibrinogen followed by identification of the molecular anomaly. However, the diagnosis of CFD can be challenging as the sensitivity and specificity of coagulation assays depend on the fibrinogen level as well as on the fibrinogen variant. In addition, patients suffering from CFD have a heterogeneous clinical course which is often unpredictable by routine coagulation assays. To better determine the patient's clinical phenotype, global hemostasis assays and an assessment of the fibrin clot properties are performed in research laboratories. In this review, we summarize the fibrinogen work-up highlighting some common pitfalls and provide an update of the research on CFD.

Genetic Variants in the FGB and FGG Genes Mapping in the Beta and Gamma Nodules of the Fibrinogen Molecule in Congenital Quantitative Fibrinogen Disorders Associated with a Thrombotic Phenotype

Fibrinogen is a hexameric plasmatic glycoprotein composed of pairs of three chains (Aα, Bβ, and γ), which play an essential role in hemostasis. Conversion of fibrinogen to insoluble polymer fibrin gives structural stability, strength, and adhesive surfaces for growing blood clots. Equally important, the exposure of its non-substrate thrombin-binding sites after fibrin clot formation promotes antithrombotic properties. Fibrinogen and fibrin have a major role in multiple biological processes in addition to hemostasis and thrombosis, i.e., fibrinolysis (during which the fibrin clot is broken down), matrix physiology (by interacting with factor XIII, plasminogen, vitronectin, and fibronectin), wound healing, inflammation, infection, cell interaction, angiogenesis, tumour growth, and metastasis. Congenital fibrinogen deficiencies are rare bleeding disorders, characterized by extensive genetic heterogeneity in all the three genes: FGA, FGB, and FGG (enconding the Aα, Bβ, and γ chain, respectively). Depending on the type and site of mutations, congenital defects of fibrinogen can result in variable clinical manifestations, which range from asymptomatic conditions to the life-threatening bleeds or even thromboembolic events. In this manuscript, we will briefly review the main pathogenic mechanisms and risk factors leading to thrombosis, and we will specifically focus on molecular mechanisms associated with mutations in the C-terminal end of the beta and gamma chains, which are often responsible for cases of congenital afibrinogenemia and hypofibrinogenemia associated with thrombotic manifestations.

Fibrinogen concentrate for treatment of bleeding and surgical prophylaxis in congenital fibrinogen deficiency patients

BACKGROUND

Congenital fibrinogen deficiency is an ultra-rare disorder in which patients can experience severe and/or frequent bleeding episodes (BEs). Here, we present the largest prospective study to date on the treatment of this disorder.

METHODS

Hemostatic efficacy of human fibrinogen concentrate (HFC; FIBRYGA® , Octapharma AG) for treatment of bleeding or surgical prophylaxis was assessed by investigators and adjudicated by an independent data monitoring and endpoint adjudication committee (IDMEAC) according to a four-point scale, using objective criteria. Thromboelastometry maximum clot firmness (MCF) was also determined.

RESULTS

Twenty-five afibrinogenemia patients were treated with HFC: 24 for on-demand treatment of 89 BEs, and nine as prophylaxis for 12 surgeries. For BEs, treatment success (rating of excellent or good) evaluated by investigators was 96.6% (90% confidence interval [CI], 0.92-0.99; two missing ratings, classified as failures) and by the IDMEAC was 98.9% (90% CI, 0.95-0.999). Mean ± standard deviation (SD) increase in MCF was 5.8 ± 2.5 mm one hour after the first HFC infusion (mean ± SD dose, 61.88 ± 11.73 mg/kg). For the 12 surgeries (median [range] HFC dose/surgery, 85.80 mg/kg [34.09-225.36]), intraoperative and postoperative treatment success were both rated 100% (90% CI, 0.82-1.00) by investigators and the IDMEAC. Three adverse events were possibly treatment related, including a moderate case of thrombosis. There were no deaths, no severe allergic or hypersensitivity reactions, and no clinical evidence of neutralizing antifibrinogen antibodies.

CONCLUSIONS

Human fibrinogen concentrate was efficacious for on-demand treatment of bleeding and as surgical prophylaxis, with a favorable safety profile, in patients with congenital afibrinogenemia.

Thromboelastometry as a diagnostic tool in mild bleeding disorders: A prospective cohort study

BACKGROUND

Major guidelines emphasise the potential of visco-elastic methods to overcome the limitations of conventional laboratory assays in the peri-operative setting. Their sensitivity regarding mild bleeding disorders (MBDs), the most common bleeding disorders in the general population, is however unknown.

OBJECTIVE

The aim of this study was to investigate the sensitivity of thromboelastometry for diagnosis of MBD.

DESIGN

A single-centre prospective cohort study.

SETTING

Haematology outpatient unit of a tertiary general hospital in Central Switzerland.

PATIENTS

All consecutive patients referred over a 32-month period with a suspected bleeding disorder were included and thromboelastometry was conducted using a ROTEM delta (EXTEM, INTEM and FIBTEM). Diagnostic work-up was performed according to current guidelines including the ISTH bleeding assessment tool (ISTH BAT).

MAIN OUTCOME MEASURES

Distribution of clotting time (CT) and maximum clot firmness (MCF) results in relation to the presence of MBD.

RESULTS

Two hundred and seventeen patients were assessed; the median [IQR] age was 39 years [28 to 57]; 151 patients were women (70%). MBD was diagnosed in 97 patients (45%), no MBD was found in 100 patients (46%) and a systemic disorder recognised in 20 patients (9%). Presence of MBD was not associated with a significant difference in thromboelastometry variables (0.2 s in CT EXTEM, 95% CI -2.3 to 2.7; -0.2 mm in MCF EXTEM, 95% CI -1.8 to 1.5; -0.7 s in CT INTEM, 95% CI -12.6 to 11.2; 0.6 mm in MCF INTEM, 95% CI -1.2 to 1.3; 0.8 mm in MCF FIBTEM, 95% CI -1.6 to 1.4) and most results were within the established reference ranges.

CONCLUSION

Our data did not support the use of thromboelastometry as a diagnostic tool in patients with MBD.

Clinical pharmacology, efficacy and safety study of a triple-secured fibrinogen concentrate in adults and adolescent patients with congenital fibrinogen deficiency

Essentials A novel fibrinogen concentrate was evaluated in patients with congenital fibrinogen deficiency. An open-label, phase 2-3 trial studied pharmacology, efficacy, and safety in patients >6 years. The product offers safe and effective therapy in the treatment and prophylaxis of bleeding. Data in recovery show the need of adjusted treatment and further investigation in children. SUMMARY: Background Single-factor replacement therapy is considered the most suitable treatment option for hereditary fibrinogen deficiency. A triple-secured plasma-derived human fibrinogen product was developed to increase the safety of the former fibrinogen concentrate. Objectives This non-randomized, open-label, prospective study investigated pharmacokinetics, efficacy, and safety of a novel fibrinogen concentrate (FibCLOT® /CLOTTAFACT® LFB, France) in inherited deficiency. Patients/Methods Fourteen patients ≥40 kg received fibrinogen concentrate for pharmacology and 16 ≥ 23 kg received treatment for bleeding or surgery. Each treatment was followed by a 3-week safety observation period. Key outcomes included number of infusions, dose, bleeding control, daily assessment, hemoglobin, blood loss, transfusions, and physicians' global assessment of response. Results Incremental recovery was 2.35 mg mL-1  per mg kg-1 and maximal concentration 1.41 g L-1 (geometric mean) after 0.060 g kg-1 infusion in 14 afibrinogenemic patients. Terminal half-life was 69.3 h (non-compartmental analysis). The maximum clot firmness was increased by a mean of 10.3 mm from baseline to maximal effect. Sixteen patients participated to the efficacy phase: 32 bleeding episodes were treated in 9 patients, and 15 patients underwent 38 surgical/invasive procedures. All patients achieved appropriate hemostasis: response to treatment was successful in all bleeds (95% CI, 0.89-1.00) and procedures (95% CI, 0.91-1.00). Most (94%) bleeds were controlled with a single infusion (median 0.050 g kg-1 ). Two patients experienced asymptomatic distal venous thromboses identified by systematic ultrasound. Conclusion FibCLOT® /CLOTTAFACT® showed a pharmacokinetic profile comparable to that of other fibrinogen concentrates and provides safe and clinically effective substitution therapy for fibrinogen-deficient patients.

Correlation of plasma coagulation tests and fibrinogenClauss with rotational thromboelastometry parameters and prediction of bleeding in dogs

Background

Correlation of plasma fibrinogen concentration (fibrinogen_Clauss) with rotational thromboelastometry (ROTEM) parameters has not been investigated in dogs.

Objectives

To determine the correlation between plasma coagulation tests and fibrinogen_Clauss with ROTEM parameters and to evaluate their ability to predict bleeding in dogs.

Animals

Ninety‐seven dogs with concurrent determination of fibrinogen_Clauss and fibrin polymerization test (FIBTEM) analysis.

Methods

Signalment, pretreatment, clinical signs of bleeding, fibrinogen_Clauss, plasma coagulation test results, hematocrit, platelet count, FIBTEM, extrinsic (EXTEM) and intrinsic (INTEM) activated ROTEM assays were retrieved retrospectively. Correlations between fibrinogen_Clauss and FIBTEM maximum clot firmness (MCF_FIBTEM) and between prothrombin time (PT) or activated partial thromboplastin time (aPTT) and ROTEM parameters were determined. Dogs were further assigned to groups with or without clinical signs of bleeding. The prognostic significance of significantly different parameters to predict bleeding was evaluated.

Results

Fibrinogen_Clauss showed strong correlation with MCF_FIBTEM (r = 0.860, n = 97, P < .001). PT showed strong correlation with EXTEM clotting time (CT_EXTEM) (r = 0.839, n = 53, P < .001), and aPTT was strongly correlated with INTEM CT (CT_INTEM) (r = 0.664, n = 31, P < .001). Platelet count, PT/aPTT, EXTEM clot formation time (CFT_EXTEM), MCF_EXTEM, EXTEM maximum clot elasticity (MCE_EXTEM), and CT_INTEM were significantly different between groups. A CT_INTEM >149 seconds was 100% sensitive to detect bleeding.

Conclusions and Clinical Importance

The MCF_FIBTEM can be used to evaluate the effect of fibrinogen on hemostasis as an alternative to determination of fibrinogen_Clauss. In addition, CT_EXTEM and CT_INTEM are strongly correlated with PT and aPTT, respectively.

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.

Pharmacokinetics, clot strength and safety of a new fibrinogen concentrate: randomized comparison with active control in congenital fibrinogen deficiency

Essentials Congenital afibrinogenemia causes a potentially life-threatening bleeding and clotting tendency. Two human fibrinogen concentrates (HFCs) were compared in a randomized pharmacokinetic study. Bioequivalence was not shown for AUCnorm , which was significantly larger for the new HFC. Increases in clot strength were comparable, and no thromboses or deaths occurred in the study.

SUMMARY

Background Human fibrinogen concentrate (HFC) corrects fibrinogen deficiency in congenital a-/hypofibrinogenemia. Objectives To assess pharmacokinetics (PK), effects on thromboelastometry maximum clot firmness (MCF), and safety of a new double virus-inactivated/eliminated, highly purified HFC vs. active control. Patients/Methods In this multinational, randomized, phase II, open-label, crossover study in 22 congenital afibrinogenemia patients aged ≥ 12 years, 70 mg kg-1 of new HFC (FIBRYGA, Octapharma AG) or control (Haemocomplettan® P/RiaSTAP™, CSL Behring GmbH) were administered, followed by crossover to the other concentrate. Fibrinogen activity, PK and MCF in plasma were assessed. Results The concentrates were not bioequivalent for the primary endpoint, AUCnorm (mean ratio, 1.196; 90% confidence interval [CI], 1.117, 1.281). Remaining PK parameters (Cmaxnorm , IVR, t1/2 , MRT) reflected bioequivalence between concentrates, except for clearance (mean ratio, 0.836; 90% CI, 0.781, 0.895) and Vss (mean ratio, 0.886; 90% CI, 0.791, 0.994). Mean AUCnorm was significantly larger for the new HFC (1.62 ± 0.45 vs. 1.38 ± 0.47 h kg g L-1  mg-1 , P = 0.0001) and mean clearance was significantly slower (0.665 ± 0.197 vs. 0.804 ± 0.255 mL h-1  kg-1 , P = 0.0002). Mean MCF increased from 0 mm to 9.68 mm (new HFC) and 10.00 mm (control) 1-hour post-infusion (mean difference, -0.32 mm; 95% CI, -1.70, 1.07, n.s.). No deaths, thromboses, viral seroconversions or serious related adverse events occurred. Conclusions Bioequivalence was not demonstrated for AUCnorm , clearance and Vss . Larger AUCnorm and slower clearance were observed for the new HFC. Remaining pharmacokinetic parameters reflected bioequivalence to control. Safety profiles and increases in clot strength were comparable between concentrates.

Clinical Consequences and Molecular Bases of Low Fibrinogen Levels

The study of inherited fibrinogen disorders, characterized by extensive allelic heterogeneity, allows the association of defined mutations with specific defects providing significant insight into the location of functionally important sites in fibrinogen and fibrin. Since the identification of the first causative mutation for congenital afibrinogenemia, studies have elucidated the underlying molecular pathophysiology of numerous causative mutations leading to fibrinogen deficiency, developed cell-based and animal models to study human fibrinogen disorders, and further explored the clinical consequences of absent, low, or dysfunctional fibrinogen. Since qualitative disorders are addressed by another review in this special issue, this review will focus on quantitative disorders and will discuss their diagnosis, clinical features, molecular bases, and introduce new models to study the phenotypic consequences of fibrinogen deficiency.

Comparison of Thrombelastography-Derived Fibrinogen Values at Rewarming and Following Cardiopulmonary Bypass in Cardiac Surgery Patients

BACKGROUND

The inflated costs and documented deleterious effects of excess perioperative transfusion have led to the investigation of targeted coagulation factor replacement strategies. One particular coagulation factor of interest is factor I (fibrinogen). Hypofibrinogenemia is typically tested for using time-consuming standard laboratory assays. The thrombelastography (TEG)-based functional fibrinogen level (FLEV) provides an assessment of whole blood clot under platelet inhibition to report calculated fibrinogen levels in significantly less time. If FLEV values obtained on cardiopulmonary bypass (CPB) during rewarming are similar to values obtained immediately after the discontinuation of CPB, then rewarming values could be used for preemptive ordering of appropriate blood product therapy.

METHODS

Fifty-one cardiac surgery patients were enrolled into this prospective nonrandomized study to compare rewarming fibrinogen values with postbypass values using TEG FLEV assays. Baseline, rewarming, and postbypass fibrinogen values were recorded for all patients using both standard laboratory assay (Clauss method) and FLEV. Mixed-effects regression models were used to examine the change in TEG FLEV values over time. Bland-Altman analysis was used to examine bias and the limits of agreement (LOA) between the standard laboratory assay and FLEVs.

RESULTS

Forty-nine patients were included in the analysis. The mean FLEV value during rewarming was 333.9 mg/dL compared with 332.8 mg/dL after protamine, corresponding to an estimated difference of -1.1 mg/dL (95% confidence interval [CI], -25.8 to 23.6; P = 0.917). Rewarming values were available on average 47 minutes before postprotamine values. Bland-Altman analysis showed poor agreement between FLEV and standard assays: mean difference at baseline was 92.5 mg/dL (95% CI, 71.1 to 114.9), with a lower LOA of -56.5 mg/dL (95% CI, -94.4 to -18.6) and upper LOA of 242.4 mg/dL (95% CI, 204.5 to 280.3). The difference between assays increased after CPB and persisted after protamine administration.

CONCLUSIONS

Our results revealed negligible change in FLEV values from the rewarming to postbypass periods, with a CI that does not include clinically meaningful differences. These findings suggest that rewarming samples could be utilized for ordering fibrinogen-specific therapies before discontinuation of CPB. Mean FLEV values were consistently higher than the reference standard at each time point. Moreover, bias was highly heterogeneous among samples, implying a large range of potential differences between assays for any 1 patient.

Congenital afibrinogenemia: from etiopathogenesis to challenging clinical management

INTRODUCTION

Congenital afibrinogenemia belongs to the group of autosomal recessive bleeding disorders and represents the absolute deficiency of fibrinogen detected by an antigenic test. This can lead to severe clinical manifestations of the disorder. Therefore, it is very important to take afibrinogenemia into account in the process of the differential diagnostics of the patients.

AREAS COVERED

The authors provide a summary of currently available literature about afibrinogenemia. They collected the information from the scientific journals dedicated to thrombosis and hemostasis and searched world-wide databases. Expert commentary: The most frequent clinical manifestation of this disorder is mucosal bleeding, but musculoskeletal bleeding pattern, gynecologic and obstetric issues, spontaneous bleeding, episodes provoked by minor injury or any other intervention, and even paradoxical thromboembolic events have been published. Afibrinogenemia is the consequence of mutations of the homozygous or compound heterozygous type in gene FGA, FGB or FGG encoding fibrinogen. Pregnant women with a family history, or with a history of consanguinity ought to be properly counselled. However, primary prophylaxis of bleeding events is not suggested. The article deals with actual information about afibrinogenemia contributing to its early diagnosis and effective treatment, which in many cases requires multidisciplinary approach.

Acquired hypofibrinogenemia: current perspectives

Acquired hypofibrinogenemia is most frequently caused by hemodilution and consumption of clotting factors. The aggressive replacement of fibrinogen has become one of the core principles of modern management of massive hemorrhage. The best method for determining the patient's fibrinogen level remains controversial, and particularly in acquired dysfibrinogenemia, could have major therapeutic implications depending on which quantification method is chosen. This review introduces the available laboratory and point-of-care methods and discusses the relative advantages and limitations. It also discusses current strategies for the correction of hypofibrinogenemia.

Thromboelastographic reference ranges for a cirrhotic patient population undergoing liver transplantation

AIM

To describe the thromboelastography (TEG) “reference” values within a population of liver transplant (LT) candidates that underline the differences from healthy patients.

METHODS

Between 2000 and 2013, 261 liver transplant patients with a model for end-stage liver disease (MELD) score between 15 and 40 were studied. In particular the adult patients (aged 18-70 years) underwent to a first LT with a MELD score between 15 and 40 were included, while all patients with acute liver failure, congenital bleeding disorders, and anticoagulant and/or antiplatelet drug use were excluded. In this population of cirrhotic patients, preoperative haematological and coagulation laboratory tests were collected, and the pretransplant thromboelastographic parameters were studied and compared with the parameters measured in a previously studied population of 40 healthy subjects. The basal TEG parameters analysed in the cirrhotic population of liver candidates were as follows: Reaction time (r), coagulation time (k), Angle-Rate of polymerization of clot (αAngle), Maximum strenght of clot (MA), Amplitudes of the TEG tracing at 30 min and 60 min after MA is measured (A30 and A60), and Fibrinolysis at 30 and 60 min after MA (Ly30 and Ly60). The possible correlation between the distribution of the reference range and the gender, age, MELD score (higher or lower than 20) and indications for transplantation (liver pathology) were also investigated. In particular, a MELD cut-off value of 20 was chosen to verify the possible correlation between the thromboelastographic reference range and MELD score.

RESULTS

Most of the TEG reference values from patients with end-stage liver disease were significantly different from those measured in the healthy population and were outside the suggested normal ranges in up to 79.3% of subjects. Wide differences were found among all TEG variables, including r (41.5% of the values), k (48.6%), α (43.7%), MA (79.3%), A30 (74.4%) and A60 (80.9%), indicating a prevailing trend to hypocoagulability. The differences between the mean TEG values obtained from healthy subjects and the cirrhotic population were statistically significant for r (P = 0.039), k (P < 0.001), MA (P < 0.001), A30 (P < 0.001), A60 (P < 0.001) and Ly60 (P = 0.038), indicating slower and less stable clot formation in the cirrhotic patients. In the cirrhotic population, 9.5% of patients had an r value shorter than normal, indicating a tendency for faster clot formation. Within the cirrhotic patient population, gender, age and the presence of hepatocellular carcinoma or alcoholic cirrhosis were not significantly associated with greater clot firmness or enhanced whole blood clot formation, whereas greater clot strength was associated with a MELD score < 20, hepatitis C virus and cholestatic-related cirrhosis (P < 0.001; P = 0.013; P < 0.001).

CONCLUSION

The range and distribution of TEG values in cirrhotic patients differ from those of healthy subjects, suggesting that a specific thromboelastographic reference range is required for liver transplant candidates.

Can the phenotype of inherited fibrinogen disorders be predicted?

Congenital fibrinogen disorders are rare diseases affecting either the quantity (afibrinogenaemia and hypofibrinogenaemia) or the quality (dysfibrinogenaemia) or both (hypodysfibrinogenaemia) of fibrinogen. In addition to bleeding, unexpected thrombosis, spontaneous spleen ruptures, painful bone cysts and intrahepatic inclusions can complicate the clinical course of patients with quantitative fibrinogen disorders. Clinical manifestations of dysfibrinogenaemia include absence of symptoms, major bleeding or thrombosis as well as systemic amyloidosis. Although the diagnosis of any type of congenital fibrinogen disorders is usually not too difficult with the help of conventional laboratory tests completed by genetic studies, the correlation between all available tests and the clinical manifestations is more problematic in many cases. Improving accuracy of diagnosis, performing genotype, analysing function of fibrinogen variants and carefully investigating the personal and familial histories may lead to a better assessment of patients' phenotype and therefore help in identifying patients at increased risk of adverse clinical outcomes. This review provides an update of various tests (conventional and global assays, molecular testing, fibrin clot analysis) and clinical features, which may help to better predict the phenotype of the different types of congenital fibrinogen disorders.

Dysfibrinogenemia: from molecular anomalies to clinical manifestations and management

Congenital dysfibrinogenemia is a qualitative congenital fibrinogen disorder characterized by normal antigen levels of a dysfunctional fibrinogen. The diagnosis is usually based on discrepancies between fibrinogen activity and antigen levels, but could require more specialized techniques for the assessment of fibrinogen function, owing to some limitations in routine assays. Molecular abnormalities, which are frequently heterozygous missense mutations localized in exon 2 of FGA and exon 8 of FGG, lead to defects in one or more phases of fibrinogen to fibrin conversion, fibrin network formation, and other important functions of fibrinogen. The clinical phenotype is highly heterogeneous, from no manifestations to bleeding and/or thrombotic events. Asymptomatic propositi and relatives with the predisposing genotype are at risk of developing adverse outcomes during the natural course of the disease. Correlations between genotype and phenotype have not yet been clearly established, with the exception of some abnormal fibrinogens that severely increase the risk of thrombosis. Functional analysis of polymerization and fibrinolysis, structural studies of the fibrin network and the viscoelastic properties of fibrin clot could help to predict the phenotype of congenital dysfibrinogenemia, but have not yet been evaluated in detail. The management is essentially based on personal and family history; however, even individuals who are still asymptomatic and without a family history should be carefully assessed and monitored. Particular situations, such as pregnancy, delivery, and surgery, require a multidisciplinary approach.

Comparison of fibrin-based clot elasticity parameters measured by free oscillation rheometry (ReoRox ®) versus thromboelastometry (ROTEM ®)

Background. Whole blood viscoelastic tests such as the fibrin-based thromboelastometry (ROTEM^®) test FIBTEM are increasingly used in the perioperative setting to quickly identify deficits in fibrin quality, and to guide hemostatic therapy. The recently developed FibScreen2 test of the ReoRox^® method, based on free oscillation rheometry, also provides an evaluation of fibrin clot quality. To date, little information is available on the performance of this test in hemodiluted blood, by comparison to FIBTEM. Methods. Whole blood samples from eight healthy volunteers were analyzed using FIBTEM and Fibscreen2. Native and diluted (to 33% and 50% using saline, gelatin or hydroxyethyl starch [HES]) samples were analyzed. Clot strength parameters, including FIBTEM maximum clot firmness (MCF), FIBTEM maximum clot elasticity (MCE) and Fibscreen2 maximum elasticity (G'max), were measured. Results. In repeatedly measured samples from two volunteers, FIBTEM MCF and Fibscreen2 G'max revealed a coefficient of variation (CV) of 5.3 vs. 16.3% and 5.6 vs. 31.7% for each volunteer, respectively. Hemodilution decreased clot strength. Both Fibscreen2 G'max and FIBTEM parameters decreased proportionally to the dilution ratio when saline was used. The observed reductions in FIBTEM and Fibscreen2 parameters were more severe in samples diluted with gelatin and HES, compared to saline. Finally, a regression analysis between FIBTEM MCE and Fibscreen2 G'max revealed a poor goodness of fit (r² = 0.37, p < 0.0001). Conclusions. ReoRox^® Fibscreen2 test has a high coefficient of variation, and its application in various hemodilution conditions showed limited comparability with the ROTEM^® FIBTEM test.

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.

Plasma viscosity, functional fibrinogen, and platelet reactivity in vascular surgery patients

BACKGROUND

Platelet reactivity changes with shear stress, which in turn depends on whole blood and plasma viscosity (PV). Platelets interact with fibrinogen during thrombus formation, and fibrinogen is a determinant of PV. The respective role of PV and fibrinogen on platelet function is still unclear.

METHODS

30 patients undergoing vascular surgery were admitted to this study. In each patient we measured PV using a cone-on-plate viscosimeter, functional fibrinogen using thromboelastometry, and platelet reactivity to thrombin receptor activating peptide (TRAP) stimulation using multi-electrode aggregometry. Routine coagulation parameter were measured.

RESULTS

At the univariate analysis, platelet reactivity was positively associated with mean platelet volume (R2 = 0.15, P = 0.033) and PV (R2 = 0.35, P = 0.0006), and negatively associated with serum bilirubin (R2 = 0.20, P = 0.013) and international normalized ratio (INR) (R2 = 0.19, P = 0.017). At the multivariable analysis, only PV (P = 0.001) and INR (P = 0.019) remained independent predictors of platelet reactivity.

CONCLUSION

PV is directly and independently associated with platelet reactivity, whereas functional fibrinogen is not. Aspirin treatment is inadequate to correct thrombin-induced platelet aggregation. In presence of hyperviscosity, patients at high cardiovascular risk, may benefit from more aggressive anti-platelet treatments.

Optimal management of the critically ill: anaesthesia, monitoring, data capture, and point-of-care technological practices in ovine models of critical care

Animal models of critical illness are vital in biomedical research. They provide possibilities for the investigation of pathophysiological processes that may not otherwise be possible in humans. In order to be clinically applicable, the model should simulate the critical care situation realistically, including anaesthesia, monitoring, sampling, utilising appropriate personnel skill mix, and therapeutic interventions. There are limited data documenting the constitution of ideal technologically advanced large animal critical care practices and all the processes of the animal model. In this paper, we describe the procedure of animal preparation, anaesthesia induction and maintenance, physiologic monitoring, data capture, point-of-care technology, and animal aftercare that has been successfully used to study several novel ovine models of critical illness. The relevant investigations are on respiratory failure due to smoke inhalation, transfusion related acute lung injury, endotoxin-induced proteogenomic alterations, haemorrhagic shock, septic shock, brain death, cerebral microcirculation, and artificial heart studies. We have demonstrated the functionality of monitoring practices during anaesthesia required to provide a platform for undertaking systematic investigations in complex ovine models of critical illness.

The effectiveness of different functional fibrinogen polymerization assays in eliminating platelet contribution to clot strength in thromboelastometry

BACKGROUND

Viscoelastic tests such as functional fibrinogen polymerization assays (FFPAs) in thrombelastography (TEG®) or thromboelastometry (ROTEM®) measure clot elasticity under platelet inhibition. Incomplete platelet inhibition influences maximum clot firmness (MCF) of FFPAs. We compared the ability of existing and newly developed FFPAs to eliminate the platelet contribution to clot strength.

METHODS

MCF of whole blood (WB), platelet-rich plasma (PRP), and platelet-poor plasma samples was recorded using a ROTEM device with different FFPAs, including the TEG functional fibrinogen test (FFTEG) and different ROTEM-based assays: the standard fib-tem reagent (FIBTEM), a lyophilized single-portion reagent fib-tem S (FIBTEM-S), a newly developed reagent FIBTEM PLUS, as well as FIBTEM or the standard extrinsic activation reagent ex-tem® (EXTEM) combined with 10-μg abciximab (FIBTEM-ABC/EXTEM-ABC).

RESULTS

In WB (platelet count [mean ± SD], 183 ± 37 × 10/μL; plasma fibrinogen concentration, 2.49 ± 0.58 g/L), FFTEG and EXTEM-ABC showed higher MCF (15.7 ± 2.8 mm) than FIBTEM or FIBTEM-S (11.4 ± 3.3 mm, P < 0.001), whereas FIBTEM-ABC and FIBTEM PLUS resulted in lower MCF (9.3 ± 2.8 mm, P < 0.001). In 2 different PRP samples, with platelet counts of 407 ± 80 × 10/μL and 609 ± 127 × 10/μL, FIBTEM-ABC and FIBTEM PLUS reduced platelet contribution to clot strength within 95% confidence interval limits of -1.4 to 0.1 mm and -1.2 to 0.4 mm, respectively. Using all FFPAs it was observed that the Pearson correlation coefficient between plasma fibrinogen concentration and WB MCF was high (range, 0.75-0.93) and significant, regardless of the underlying platelet inhibiting component. Evaluating differences in the interception of regression lines by using analysis of covariance, we compared platelet-poor plasma and both PRP samples within the same assays and found that in contrast to the FIBTEM-ABC and FIBTEM PLUS assays, the FFTEG, EXTEM-ABC, FIBTEM, and FIBTEM-S methods still detected residual platelet activity and grossly overestimated fibrin clot strength in samples with high platelet counts.

CONCLUSIONS

FFPAs based solely on glycoprotein-IIb/IIIa inhibition, such as FFTEG or EXTEM-ABC, are less effective than cytochalasin D-based assays, such as FIBTEM or FIBTEM-S, at inhibiting the platelet component of clot strength. The FIBTEM PLUS assay, and the combination of FIBTEM and abciximab, sufficiently inhibits platelet contribution to clot elasticity. The combination of a glycoprotein-IIb/IIIa receptor blocker and cytochalasin D allows evaluation of functional fibrinogen polymerization without platelet "noise." In a clinical setting, the significance of potent platelet inhibition ensures a more accurate assessment of MCF and therefore the need for fibrinogen supplementation therapy. Further studies are necessary to investigate the application and impact of these tests in a clinical situation.

FIBTEM PLUS provides an improved thromboelastometry test for measurement of fibrin-based clot quality in cardiac surgery patients

BACKGROUND

The viscoelastic functional fibrinogen (FF) and FIBTEM assays measure the contribution of fibrin to clot strength. Inhibition of platelet function is a necessary precondition for these tests to work. We investigated a novel test for measuring fibrin-based clotting, FIBTEM PLUS, in cardiac surgery and compared it with FF and FIBTEM.

METHODS

A prospective, observational study was performed which included 30 patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). Blood samples were drawn at the beginning of surgery (pre-CPB), approximately 20 minutes before weaning from CPB and 5 minutes after heparin neutralization. FF, FIBTEM, and FIBTEM PLUS tests were performed in duplicate for all blood samples. Additional coagulation parameters, including platelet count, plasma fibrinogen levels, factor XIII activity, and heparin concentration, were also recorded for each sample.

RESULTS

At all time points, the lowest mean maximum clot firmness (MCF) was observed with FIBTEM PLUS, although a statistically significant difference between FIBTEM and FIBTEM PLUS was observed only at baseline (mean values 22 vs 19 mm, P = 0.01; FF value for comparison: 27.7 mm). FF maximum amplitude (MA) values were significantly higher than FIBTEM MCF and FIBTEM PLUS MCF pre-CPB, during CPB and after heparin neutralization (P ≤ 0.001 for FF MA versus FIBTEM MCF and for FF MA versus FIBTEM PLUS MCF at all time points). The difference between FIBTEM MCF and FIBTEM PLUS MCF correlated with platelet count (r = 0.46;P < 0.001), whereas differences between FF MA and FIBTEM MCF, or FF MA and FIBTEM PLUS MCF did not (r = -0.07, P = 0.51; r = 0.16, P = 0.12, respectively). Differences between the assays were unrelated to heparin levels, which decreased considerably after protamine administration compared with heparin levels recorded before weaning from CPB (decrease from 2.1 to 0.1 U/mL and from 2.8 to 0.2 U/mL for anti-factor IIa and anti-factor Xa, respectively). Agreement between duplicate measurements was similar with FIBTEM and FIBTEM PLUS assays and lower with FF. Significant positive correlations were found between MCF or MA and fibrinogen concentration (all P < 0.001); the highest correlation was with FIBTEM PLUS MCF (r = 0.70).

CONCLUSION

The FIBTEM PLUS assay produces precise results. At baseline, it provides greater inhibition of platelets than FIBTEM, but there is no meaningful difference between FIBTEM PLUS and FIBTEM in patients with low platelet counts.

Fibrinogen concentrate in bleeding patients

BACKGROUND

Hypofibrinogenaemia is associated with increased morbidity and mortality, but the optimal treatment level, the use of preemptive treatment and the preferred source of fibrinogen remain disputed. Fibrinogen concentrate is increasingly used and recommended for bleeding with acquired haemostatic deficiencies in several countries, but evidence is lacking regarding indications, dosing, efficacy and safety.

OBJECTIVES

We assessed the benefits and harms of fibrinogen concentrate compared with placebo or usual treatment for bleeding patients.

SEARCH METHODS

We searched the following electronic databases: the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2013, Issue 8); MEDLINE (1950 to 9 August 2013); EMBASE (1980 to 9 August 2013); International Web of Science (1964 to 9 August 2013); CINAHL (1980 to 9 August 2013); LILACS (1982 to 9 August 2013); and the Chinese Biomedical Literature Database (up to 10 November 2011), together with databases of ongoing trials. We contacted trial authors, authors of previous reviews and manufacturers in the field.

SELECTION CRITERIA

We included all randomized controlled trials (RCTs), irrespective of blinding or language, that compared fibrinogen concentrate with placebo/other treatment or no treatment in bleeding patients, excluding neonates and patients with hereditary bleeding disorders.

DATA COLLECTION AND ANALYSIS

Three review authors independently abstracted data; we resolved any disagreements by discussion. Our primary outcome measure was all-cause mortality. We performed subgroup and sensitivity analyses to assess the effects of fibrinogen concentrate in adults and children in terms of various clinical and physiological outcomes. We presented pooled estimates of the effects of intervention on dichotomous outcomes as risk ratios (RRs) and on continuous outcomes as mean differences, with 95% confidence intervals (CIs). We assessed the risk of bias through assessment of trial methodological components and the risk of random error through trial sequential analysis.

MAIN RESULTS

We included six RCTs with a total of 248 participants; none of the trials were determined to have overall low risk of bias. We found 12 ongoing trials, from which we were unable to retrieve any data. Only two trials provided data on mortality, and one was a zero event study; thus the meta-analysis showed no statistically significant effect on overall mortality (2.6% vs 9.5%, RR 0.28, 95% CI 0.03 to 2.33). Our analyses on blood transfusion data suggest a beneficial effect of fibrinogen concentrate in reducing the incidence of allogenic transfusions (RR 0.47, 95% CI 0.31 to 0.72) but show no effect on other predefined outcomes, including adverse events such as thrombotic episodes.

AUTHORS' CONCLUSIONS

In the six available RCTs of elective surgery, fibrinogen concentrate appears to reduce transfusion requirements, but the included trials are of low quality with high risk of bias and are underpowered to detect mortality, benefit or harm. Furthermore, data on mortality are lacking, heterogeneity is high and acute or severe bleeding in a non-elective surgical setting remains unexplored. Currently, weak evidence supports the use of fibrinogen concentrate in bleeding patients, as tested here in primarily elective cardiac surgery. More research is urgently needed.

Treatment of Afibrinogenemia in a Chihuahua

This report discusses the diagnosis and treatment of afibrinogenemia in a Chihuahua. Prolongations of prothrombin time (PT), activated partial thromboplastin time (aPTT), and thrombin clotting time (TCT) together with fibrinogen assay results of either no or trace amounts of fibrinogen support a diagnosis of afibrinogenemia. Differential diagnoses include common coagulopathies, liver failure, and disseminated intravascular coagulation (DIC). Either aggressive cryoprecipitate or plasma transfusions are required to treat afibrinogenemia. The current guidelines for treatment of coagulopathies include plasma transfusions (either 15–30 mL/kg or until both PT and aPTT are normalized). This report describes a case in which bleeding persisted 2 days after standard plasma transfusion levels were administered and PT and aPTT levels had normalized. In this case, the bleeding was stabilized for up to 2 mo after administering &gt; 54 mL/kg plasma. In human medicine, either cryoprecipitate or fibrinogen concentrate is used to increase blood fibrinogen levels to 100 mg/dL for minor bleeding and 200 mg/dL for major bleeding. Further studies are needed; however, the author of this report suggests that aggressive transfusions and monitoring are needed in veterinary afibrinogenemia cases.

Effect of haematocrit on fibrin-based clot firmness in the FIBTEM test

BACKGROUND

Point-of-care thromboelastometry (ROTEM(®)) can be used to assess coagulation in whole blood. In the ROTEM(®) FIBTEM test, cytochalasin D eliminates the contribution of platelets to the whole blood clot; hence, only the remaining elements, including fibrinogen/fibrin, red blood cells and factor XIII, contribute to clot strength. We investigated the relationships between FIBTEM maximum clot firmness (MCF), whole blood fibrinogen concentration and plasma fibrinogen concentration to determine the impact of haematocrit on these parameters during cardiac surgery.

MATERIALS AND METHODS

The relationships between FIBTEM MCF and both whole blood fibrinogen concentration and plasma fibrinogen concentration (Clauss assay) were evaluated pre-operatively and after cardiopulmonary bypass/protamine administration in haematocrit-based subgroups.

RESULTS

The study included 157 patients. The correlation coefficient rho between FIBTEM MCF and plasma fibrinogen concentration was 0.68 at baseline and 0.70 after protamine, while that between FIBTEM MCF and whole blood fibrinogen concentration was 0.74 at baseline and 0.72 after protamine (all P <0.001). In subgroup analyses based on haematocrit levels, pre-operative FIBTEM MCF and whole blood fibrinogen concentration were both significantly higher (P <0.05) for the lowest haematocrit subgroup, but plasma fibrinogen concentration was similar in all groups. After protamine, no significant differences were observed between the lowest haematocrit group and the other groups for any of the three parameters.

CONCLUSIONS

The effect of haematocrit on blood clotting is not reflected by plasma fibrinogen concentration, in contrast to FIBTEM MCF which incorporates the contribution of haematocrit to whole blood clot firmness. This effect does, however, appear to be negligible in haemodiluted patients.

Use of point-of-care testing for plasma therapy

Use of point-of-care testing (POCT) has been driven by limitations of laboratory-based testing as a tool for decisions for transfusions of blood components. Clinical settings such as liver transplantation, cardiothoracic surgery, and trauma are particularly in need of such diagnostic tests because of the complex coagulopathies that can develop in these settings of substantial hemorrhage and need for blood component support. Successful implementation of POCT requires collaboration between surgery, anesthesia, critical care, and the laboratory to ensure proper quality control of equipment, operator training and competency, medical records test results, billing procedures, and consensus-derived transfusion algorithms for cost-effective, targeted blood component transfusion support. In this review we summarize clinical evidence for the effectiveness of POCT, along with some future directions for this strategy.

Comparison of whole blood fibrin-based clot tests in thrombelastography and thromboelastometry

BACKGROUND

Fibrin-based clot firmness is measured as maximum amplitude (MA) in the functional fibrinogen (FF) thrombelastographic assay and maximum clot firmness (MCF) in the FIBTEM thromboelastometric assay. Differences between the assays/devices may be clinically significant. Our objective was to compare clot firmness parameters through standard (FF on a thrombelastography device [TEG®]; FIBTEM on a thromboelastometry device [ROTEM®]) and crossover (FF on ROTEM®; FIBTEM on TEG®) analyses.

METHODS

Whole-blood samples from healthy volunteers were subjected to thrombelastography and thromboelastometry analyses. Samples were investigated native and following stepwise dilution with sodium chloride solution (20%, 40%, and 60% dilution). Samples were also assessed after in vitro addition of medications (heparin, protamine, tranexamic acid) and 50% dilution with hydroxyethyl starch, gelatin, sodium chloride, and albumin.

RESULTS

FF produced higher values than FIBTEM, regardless of the device, and TEG® produced higher values than ROTEM®, regardless of the assay. With all added medications except heparin 400 U/kg bodyweight, FF MA remained significantly higher (P < 0.05) than FIBTEM MCF, which was largely unchanged. FF MA was significantly reduced (P = 0.04) by high-dose heparin and partially restored with protamine. Fifty percent dilution with hydroxyethyl starch, albumin, and gelatin decreased FIBTEM MCF and FF MA by >50%.

CONCLUSIONS

These results demonstrate differences when measuring fibrin-based clotting via the FF and FIBTEM assays on the TEG® and ROTEM® devices. Point-of-care targeted correction of fibrin-based clotting may be influenced by the assay and device used. For the FF assay, data are lacking.

Viscoelastic coagulation testing: technology, applications, and limitations

Use of viscoelastic point-of-care (POC) coagulation instrumentation is relatively new to veterinary medicine. In human medicine, this technology has recently undergone resurgence owing to its capacity to detect hypercoagulability. The lack of sensitive tests for detecting hypercoagulable states, along with our current understanding of in vivo coagulation, highlights the deficiencies of standard coagulation tests, such as prothrombin and partial thromboplastin times, which are performed on platelet-poor plasma. Viscoelastic coagulation analyzers can provide an assessment of global coagulation, from the beginning of clot formation to fibrinolysis, utilizing whole blood. In people, use of this technology has been reported to improve management of hemostasis during surgery and decrease usage of blood products and is being used as a rapid screen for hypercoagulability. In veterinary medicine, clinical use of viscoelastic technology has been reported in dogs, cats, foals, and adult horses. This article will provide an overview of the technology, reagents and assays, applications in human and veterinary medicine, and limitations of the 3 viscoelastic POC analyzers in clinical use.