RESUMEN
The role of the fibrinolytic system in the development of venous thrombosis (VT) is unclear. We studied the risk of first and recurrent VT associated with reduced fibrinolysis, as measured by clot lysis time (CLT). We also studied the relationship between CLT and thrombin generation to determine if any relationship between CLT and VT was affected by thrombin generation. Analyses were performed in the Thrombophilia Hypercoagulability Environmental risk for Venous Thromboembolism Study, a two-centre population-based case-control study, including 579 patients and 338 controls, with patients followed from the event to determine incidence of recurrent VT. Hypofibrinolysis was associated with a 1·8-fold increased risk of a first VT [95% confidence interval (CI) 1·2-2·7]. Adjustment for sex, age, study location and Endogenous Thrombin Potential (ETP) did not change the result. The risk of VT was 2·9-fold increased when the 90th percentiles of prolonged CLT and high ETP were combined, with the highest risk for unprovoked first events (Odds Ratio = 4·2, 95% CI 1·3-13·5). In the follow-up study the Hazard Ratio for a recurrent VT associated with hypofibrinolysis was 1·5 (95% CI 0·9-2·6). A weak dose response effect was observed in relation to prolongation of CLT and recurrent VT. Although hypofibrinolysis constitutes a risk factor for a first VT, an association with recurrence is, at best, weak.
Asunto(s)
Fibrinólisis , Trombosis de la Vena/sangre , Estudios de Casos y Controles , Femenino , Tiempo de Lisis del Coágulo de Fibrina/métodos , Humanos , Masculino , Persona de Mediana Edad , Recurrencia , Factores de Riesgo , Trombina/biosíntesis , Trombosis de la Vena/etiologíaRESUMEN
In this study, we describe a novel thrombomodulin (TM) mutation (c.1611C>A) that codes for a change from cysteine 537 to a premature stop codon (p.Cys537Stop). Three members of a family with a history of posttraumatic bleeding were identified to be heterozygous for this TM mutation. All coagulation screening tests, coagulation factor assays, and platelet function test results were within normal limits. However, the endogenous thrombin potential was markedly reduced at low-tissue factor concentration, and failure to correct with normal plasma indicated the presence of a coagulation inhibitor. Plasma TM levels were highly elevated (433-845 ng/ml, normal range 2-8 ng/ml, equating to 5 to 10 nM), and the addition of exogenous protein C further decreased thrombin generation. The mutation, p.Cys537Stop, results in a truncation within the carboxyl-terminal transmembrane helix. We predict that as a consequence of the truncation, the variant TM is shed from the endothelial surface into the blood plasma. This would promote systemic protein C activation and early cessation of thrombin generation within a developing hemostatic clot, thereby explaining the phenotype of posttraumatic bleeding observed within this family.
Asunto(s)
Trastornos de la Coagulación Sanguínea Heredados/genética , Codón sin Sentido , Proteínas Mutantes/genética , Trombomodulina/genética , Adulto , Trastornos de la Coagulación Sanguínea Heredados/sangre , Trastornos de la Coagulación Sanguínea Heredados/terapia , Factores de Coagulación Sanguínea/uso terapéutico , Pruebas de Coagulación Sanguínea , Análisis Mutacional de ADN , Femenino , Humanos , Trasplante de Riñón , Masculino , Proteínas Mutantes/sangre , Proteínas Mutantes/química , Trasplante de Páncreas , Estructura Terciaria de Proteína , Trombomodulina/sangre , Trombomodulina/químicaRESUMEN
BACKGROUND: Coagulopathy is common after cardiopulmonary bypass (CPB), and platelet dysfunction is frequently considered to be a major contributor to excessive bleeding. Exposure to hypothermia may exacerbate the platelet function defect. We assessed platelet function during and after deep hypothermia with multiple electrode aggregometry (Multiplate(®); Verum Diagnostica GmbH, Munich, Germany). METHODS: Twenty adult patients undergoing pulmonary endarterectomy for chronic pulmonary hypertension were cooled on CPB to 20°C and deep hypothermic arrest was used to facilitate surgery. We analyzed platelet aggregation in whole blood samples at 12 measuring points during and after the procedure. Platelet aggregation was stimulated via the thrombin receptor (TRAPtest) at the patient's actual body temperature (AUC-CT) and after rewarming the samples to 37°C (AUC-37). In addition, we tested samples at 2 time points after 2 minutes of in vitro incubation with 20 µg protamine (0.067 µg/µL). Results are expressed as area under the aggregation curve (AUC). RESULTS: Cooling resulted in a marked decrease of platelet aggregation to a minimum AUC-CT of 20.5 (95% confidence interval [CI] 8.9-32.1) at 20°C body temperature. AUC-CT was significantly different from baseline (92.8, 95% CI 82.5-103.1) for temperatures of ≤28°C (P < 0.001), whereas the change in AUC-37 only became significant at the lowest body temperature (59.4, 95% CI 41.3-77.4). After rewarming to 36°C, AUC-CT and AUC-37 had recovered to 67.6 (95% CI 53.9-81.3) and 71.7 (95% CI 52.5-90.8), respectively. The mean AUC-CT was significantly lower than the mean AUC-37 from cooling at 28°C to warming at 24°C inclusive, and the relationship with temperature during cooling was significantly different between AUC-CT and AUC-37 (regression coefficients 4.7 [95% CI 4.2-5.2] vs 1.3 [95% CI 0.7-1.9]; P < 0.0001). After administration of protamine, mean aggregation decreased significantly for both measurements by 38.2 (95% CI -27.9 to -48.5; P < 0.001) and 44.5 (95% CI -58.5 to -30.5; P < 0.001), respectively. Similarly, adding protamine in vitro resulted in a decrease of mean aggregation by 35.1 (95% CI -71.0 to 0.8; P = 0.055) when measured after administration of heparin, and 56.5 (95% CI -94.5 to -18.5; P = 0.005) at the end of CPB. CONCLUSION: Platelet aggregation, assessed by multiple electrode aggregometry (Multiplate), was severely affected during deep, whole-body hypothermia. This effect was partially reversible after rewarming, and was distinct from a general decline of platelet aggregation during CPB. Protamine also caused a significant decrease in platelet aggregation in vivo and in vitro.
Asunto(s)
Puente Cardiopulmonar/métodos , Hipotermia Inducida/métodos , Agregación Plaquetaria/efectos de los fármacos , Sistemas de Atención de Punto , Protaminas/farmacología , Adulto , Electrodos , Humanos , Agregación Plaquetaria/fisiología , Pruebas de Función Plaquetaria/métodosRESUMEN
The thrombin generation test (TGT) has demonstrated utility in evaluating overall hemostatic capacity both in bleeding and thrombotic disorders. Although the test is currently well accepted as a research tool, its role in clinical practice has not yet been defined through large prospective multicenter clinical studies. Such prospective studies have been limited by the lack of official standardization of the assay and its large inter-laboratory variability. This international study assessed the intra- and inter-assay imprecision of TGT as well as the inter-centre variability of results in one US and four European centres. Contact-inhibited plasmas from six healthy volunteers, one mild haemophilia A patient, and five patients with heterozygous prothrombin G20210 mutation were assayed. We demonstrated that, using identical equipement, standardized reagents, a carefully selected reference plasma for normalization of results and the same test procedure as described in our DVD, the assay variability was highly reduced compared to previously published data. Our results emphasize the importance of preheating on TGT results and the variability of the assay. In conclusion, our data demonstrated that the standardized TGT methodology evaluated in this study effectively reduces the variability of the assay to acceptable limits and may be used in clinical trials.
Asunto(s)
Pruebas de Coagulación Sanguínea/métodos , Pruebas de Coagulación Sanguínea/normas , Trombina/análisis , Trombina/biosíntesis , Adulto , Calibración , Estudios de Casos y Controles , Procesamiento Automatizado de Datos , Hemofilia A/sangre , Humanos , Internacionalidad , Masculino , Protrombina/genética , Estándares de Referencia , Tromboembolia Venosa/sangre , Adulto JovenRESUMEN
The thromboelastography trace provides a graphical and numerical representation of the viscoelastic changes associated with fibrin polymerization. When used with whole blood, the shape of this trace is a composite of the effects of white and red cell content and composition, platelet number and function, fibrinogen concentration, as well as coagulation protein function and balance. The trace is also influenced by pharmacological agents such as anticoagulants, antiplatelet therapy, and coagulation factor supplementation. As such the main role of this technology has been as a point-of-care device to guide transfusion of blood components. Recently the technology has moved from the cardiac and hepatic surgical settings, where most of the early work was focused, into other areas of hemostatic monitoring. New applications for pharmaceutical monitoring and patient screening are being explored. This review gives a broad overview of the applications of the technology. In particular it considers the factors that most influence the characteristics of the trace, be they preanalytical, analytical, or clinical.
Asunto(s)
Anticoagulantes/uso terapéutico , Tromboelastografía/métodos , Hemostasis , HumanosRESUMEN
BACKGROUND: Methylene blue (MB) treatment of plasma is known to reduce the activity of clotting factors, but its effect on thrombin generation and clot formation is not well documented. STUDY DESIGN AND METHODS: Individual clotting factors and inhibitors and global tests of thrombin generation and clot formation using rotational thrombelastometry (ROTEM) were assessed in a paired study of standard or MB plasma and cryoprecipitate (n = 20 each). RESULTS: MB treatment resulted in a 10 percent reduction in endogenous thrombin potential and 30 percent decrease in peak thrombin as well as the expected 20 to 35 percent loss of Factor (F)VIII, fibrinogen, and FXI activity. MB treatment had no effect on the rate of clot formation and increased the clot firmness by 20 percent as assessed by ROTEM. There were minimal further changes in either coagulation factor levels or thrombin generation when thawed plasma was stored for an additional 24 hours. FVIII and fibrinogen content of MB cryoprecipitate was reduced by 30 and 40 percent, respectively, but this was not associated with altered clot time or rate of clot formation by ROTEM and only an 8 percent decrease in clot firmness. CONCLUSIONS: It is concluded that MB treatment is associated with a reduction in the thrombin-generating capacity of plasma, but has very little effect on the strength of clot formation as assessed by thrombelastometry. The thrombin-generating capacity of standard and MB plasma is relatively unaltered by subsequent storage of thawed plasma at 4 degrees C for 24 hours.
Asunto(s)
Coagulación Sanguínea/efectos de los fármacos , Sangre/efectos de los fármacos , Factor VIII/efectos de los fármacos , Fibrinógeno/efectos de los fármacos , Azul de Metileno/farmacología , Trombina/metabolismo , Algoritmos , Coagulación Sanguínea/fisiología , Pruebas de Coagulación Sanguínea , Conservación de la Sangre/efectos adversos , Conservación de la Sangre/métodos , Frío , Factor VIII/metabolismo , Fibrinógeno/metabolismo , Fármacos Hematológicos/farmacología , Humanos , Estabilidad Proteica/efectos de los fármacosRESUMEN
Transmittance waveform (TW) analysis has been proposed as a method of both prediction and monitoring of non-overt and overt disseminated intravascular coagulation. This study assessed the use of the rapidTW of the activated partial thromboplastin time in the detection of sepsis in 49 consecutive neutropenic haemato-oncology patients. A slope 1 cut-off value of -0.050 was found to be optimum giving 85% sensitivity with 92% specificity and positive and negative predictive values of 62% and 98%, respectively. Furthermore a worsening slope 1 value at 24 hours was indicative of a 60% increase in mortality risk. Haemato-oncology patients have a significantly increased risk of developing sepsis during intensive chemotherapy, exacerbated by the resultant neutopenia. This sepsis may progress extremely rapidly and is associated with a high mortality. Early diagnosis is therefore critical and is currently made on a predominantly clinical basis with supporting microbiological evidence 2-3 days later. This study showed that TW offers an early marker, predictive of sepsis in neutropenic patients. It correlates with subsequent microbiological results and may identify patients at greater risk of clinical deterioration who may require more intensive early therapy or observation. It may also provide a useful marker to monitor the effects of treatment.
Asunto(s)
Antineoplásicos/efectos adversos , Neoplasias Hematológicas/tratamiento farmacológico , Neutropenia/complicaciones , Tiempo de Tromboplastina Parcial , Sepsis/diagnóstico , Biomarcadores/sangre , Diagnóstico Precoz , Neoplasias Hematológicas/sangre , Humanos , Neutropenia/sangre , Neutropenia/inducido químicamente , Valor Predictivo de las Pruebas , Curva ROC , Medición de Riesgo , Sensibilidad y Especificidad , Sepsis/sangre , Sepsis/etiología , Sepsis/mortalidadRESUMEN
Haemostatic changes in septic patients are complex, with both procoagulant and anticoagulant changes. Thirty-eight patients with severe sepsis and 32 controls were investigated by coagulation screens, individual factor assays, calibrated automated thrombography (CAT), whole blood low-dose-tissue factor activated (LD-TFA) Rotem and LD-TFA waveform analysis. Thirty-six of 38 patients had an abnormal coagulation screen. The mean levels of factors II, V (P < 0.05), VII, X, XI and XII, antithrombin and protein C (P < 0.01) was decreased in sepsis compared with controls. The mean factor VIII and fibrinogen level (P < 0.001) was increased. CAT in platelet rich and poor plasma showed a prolonged lag time (P < 0.02), decreased peak thrombin (P < 0.02) and delayed time to peak thrombin (P < 0.001) in sepsis patients, however, the endogenous thrombin potential was equivalent in sepsis and controls. In LD-TFA Rotem, septic patients had delayed clot times (P = 0.04) but an increased maximum velocity of clot formation (P < 0.01) and area under the clot elasticity curve (P < 0.01). LD-TFA waveform analysis showed a delayed onset time but an increased rate of clot formation (P < 0.005). In conclusion, global tests of haemostasis suggest that in this patient group, activation of haemostasis is delayed but once initiated thrombin generation and clot formation are normal or enhanced.
Asunto(s)
Hemostasis , Síndrome de Respuesta Inflamatoria Sistémica/sangre , Adulto , Anciano , Anciano de 80 o más Años , Factores de Coagulación Sanguínea/metabolismo , Pruebas de Coagulación Sanguínea/métodos , Proteína C-Reactiva/metabolismo , Humanos , Persona de Mediana Edad , Proteína C/metabolismo , Tromboelastografía/métodos , Trombina/biosíntesis , Tromboplastina/metabolismoRESUMEN
The thrombin-platelet feedback loop was examined at low concentration tissue factor using calibrated automated thrombography in combination with the elimination of contact factor activation by corn trypsin inhibitor. The results indicated that, when contact factor activation was eliminated, the thrombin-platelet feedback loop was a major determinant of thrombin generating capacity and that platelets had a greater role in regulating the propagation of thrombin generation than its initiation. This method has potential application to the measurement of platelet-dependent thrombin generation in clinical diagnostic laboratories and hence the investigation of patients with apparent hypo- or hypercoagulable phenotypes.
Asunto(s)
Plaquetas/metabolismo , Hemofilia A/sangre , Trombina/biosíntesis , Tromboplastina/metabolismo , Adulto , Área Bajo la Curva , Estudios de Casos y Controles , Retroalimentación Fisiológica , Femenino , Humanos , Masculino , Persona de Mediana Edad , Activación Plaquetaria , Trombina/análisis , Factores de TiempoRESUMEN
BACKGROUND: Stratification for risk of recurrence after a first episode of venous thromboembolism (VTE) would affect the duration of anticoagulant therapy. We aimed to determine the incidence of recurrence of VTE in relation to clinical risk factors and standard laboratory testing for heritable thrombophilic defects. METHODS: We established a database to prospectively follow-up a cohort of unselected patients who had had a first episode of objectively proven VTE. We excluded patients with malignant disease and antiphospholipid syndrome. All patients were offered testing for heritable thrombophilia. FINDINGS: At 2 years, the cumulative recurrence rate in 570 patients was 11%. Incidence was lowest after surgery-related VTE (0%) and highest after unprecipitated VTE (19.4%) (p<0.001). 85% of patients were tested for heritable thrombophilic defects. Recurrence rates were not related to presence or absence of laboratory evidence of heritable thrombophilia (hazard ratio 1.50 [95% CI 0.82-2.77]; p=0.187). In patients with a first event that was unprecipitated or was associated with a non-surgical trigger, recurrence rates did not differ in patients with or without thrombophilia (1.34 [0.73-2.46]; p=0.351). INTERPRETATION: In unselected patients who have had a first episode of VTE, testing for heritable thrombophilia does not allow prediction of recurrent VTE in the first 2 years after anticoagulant therapy is stopped. However, assessment of clinical risk factors associated with the first episode of VTE does predict risk of recurrence. Patients with postoperative VTE have a very low rate of recurrence.