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PubMed1983

Estimation of coagulation-fibrinolytic factors in DIC.

A computer analysis of the coagulation laboratory records at the first department of Hokkaido University Hospital over a three-year period (1979-1981) was performed on 553 patients with presumptive intravascular coagulation. It is indicated that the most important diagnostic tests for DIC were Fbg, FDP, and AT III. DIC may have developed not only in patients with reduced Fbg but also in patients with normal or elevated Fbg. It is necessary to estimate the actual situations in the patients with DIC by utilizing sequential laboratory tests. In DIC, SDS-PAGE patterns of Fbg indicated the marked reduction of LMW Fbg, and the activated fibrin formation must be caused by the high affinity of thrombin for HMW Fbg. Changes in the immunoprecipitative second peak of AT III may indicate the binding of different serine proteases to AT III in DIC. Rapid and simple diagnostic tests for DIC are clinically required. An analysis of the TEG pattern using normal plasma mixed with the patient's plasma can indicate the presence of procoagulant activity in patient plasma. Such a laboratory test using TEG is the most useful and rapid diagnostic test in DIC. An anticoagulant effect of heparin therapy is determined by APTT and heparin levels. The antithrombotic effect of heparin therapy is determined by FPA as an immediate index and by Fbg, FDP, and AT III as a slow index.

Antithrombin III↗
PubMed2004

The role of platelets and recombinant factor VIIa on thrombin generation, platelet activation and clot formation.

In the present study we assessed the effect of platelet counts and rFVIIa on thrombin generation, platelet activation and clot formation after tissue factor pathway activation in human plasma aiming to investigate the mechanism by which rFVIIa induces haemostasis in patients with severe thrombocytopenia. Plasma samples with platelet counts from 5 x 10(9)/l to 150 x 10(9)/l were spiked with rFVIIa (1 micro g/ml) or buffer. Clotting was initiated in the presence of diluted thromboplastin. Thrombin generation was assessed using the Thrombogram-Thrombinoscope trade mark assay. The kinetics of platelet activation was assessed using flow cytometry to measure the expression the P-selectin on platelet membrane of washed platelets suspended in defibrinated homologous PPP. Thromboelastography was used to evaluate the effect of platelets and rFVIIa on the kinetics of clot formation and clot's firmness. In the presence of low platelet counts the endogenous thrombin potential (ETP) and the maximum concentration of generated thrombin (Cmax) were reduced by 60%-70%. The lag-time of thrombin generation and the time required to reach the Cmax (Tmax) were prolonged, the velocity of platelet activation was decreased and thrombus formation was delayed. Recombinant FVIIa accelerated thrombin generation and platelet activation but it did not significantly modify ETP or Cmax. Recombinant FVIIa enhanced platelet activation in a TF and thrombin dependent manner since its effect on the studied parameters was abolished when TF was omitted or when hirudin was added into the experimental system respectively. Recombinant FVIIa normalized the velocity of clot formation but it did not modify clot firmness, which depended mainly on platelets' count. In conclusion, in experimental conditions simulating severe thrombocytopenia rFVIIa in the presence of low amounts of TF, accelerates thrombin generation, without increasing the maximum amount of generated thrombin, thus leading in enhanced platelet activation and rapid clot formation.

Blood↗
PubMed2004

In vitro comparison of the effect of fondaparinux and enoxaparin on whole blood tissue factor-triggered thromboelastography profile.

Fondaparinux and enoxaparin are both effective and safe in preventing post-operative venous thromboembolism. However, neither of them significantly influence the conventional clotting tests. We compared the influence of clinically relevant concentrations of fondaparinux and enoxaparin on normal whole blood (WB) thromboelastographic profiles after triggering TF-pathway with minimal amount of thromboplastin. Diluted thromboplastin was added to WB samples supplemented with buffer (control), fondaparinux (0.25; 0.5; 1 microg/ml), or enoxaparin (0.1; 0.5; 1 anti-Xa IU/ml). Four parameters were analyzed, R: clotting time, K: time required to reach an amplitude of 20 mm, alpha angle: measurement reflecting clot development kinetics and MA: maximal amplitude. At concentrations used in prophylaxis, both enoxaparin (0.1 anti-Xa IU/ml) and fondaparinux (0.25 microg/ml which correspond to 0.27 anti-Xa IU/ml) significantly prolonged the R and K times, but did not significantly modify the alpha angle as compared to the control. At concentrations observed after administration of curative doses for the treatment of DVT (> or = 0.5 anti-Xa IU/ml for enoxaparin and > or = 0.5 microg/ml for fondaparinux) both drugs induced a significant increase of R and K times, and a significant decrease of the alpha angle (p < 0.05). In contrast to fondaparinux, enoxaparin at concentrations equal to or higher than 0.5 anti-Xa IU/ml significantly reduced MA. The present study provides evidence that the whole blood TF-triggered TEG assay is sensitive to the presence of clinically relevant concentrations of enoxaparin or fondaparinux. Moreover, the angle may be used in order to distinguish the effect of prophylactic and therapeutic concentrations, since it was significantly reduced by the later ones. Further studies are needed to evaluate the clinical usefulness of whole blood TF-triggered TEG assay for the monitoring of treatment with enoxaparin or fondaparinux.

Anticoagulants↗
PubMed2006

Anti-metastatic effect of a non-anticoagulant low-molecular-weight heparin versus the standard low-molecular-weight heparin, enoxaparin.

Low-molecular-weight heparins (LMWH) exhibit potent anticoagulant efficacy via their plasmatic effects on thrombin and factor Xa. These agents are also effective in releasing endothelial tissue factor pathway inhibitor (TFPI), the natural inhibitor of tissue factor, and exhibit significant anti-metastatic effects in experimental animal models. However, the potential for bleeding complications has slowed down the more widespread adoption of LMWH therapy in cancer patients. In this study, the effect of a non-anticoagulant form of LMWH (NA-LMWH) on experimental lung metastasis and tumor cell-induced platelet aggregation in vivo was compared to the LMWH enoxaparin. Using the B16 melanoma mouse model of metastasis, subcutaneous (s.c.) injection of NA-LMWH or enoxaparin (10 mg/kg), three hours before intravenous (i.v.) injection of metastatic melanoma cells, followed by daily doses for 14 days, reduced lung tumor formation by 70% (P < 0.001). I.v. injection of tumor cells resulted in a significant (50-62%, P < 0.01) fall in platelet counts. Pre-injection (i.v.) of enoxaparin completely abolished the tumor cell-induced thrombocytopenia, whereas NA-LMWH had no effect. Four hours after a single s.c. dose, enoxaparin but not NA-LMWH prolonged the clotting time three-fold and delayed the time to clot initiation more than 10-fold as measured by a Sonoclot analyzer and by thromboelastography, respectively. Enoxaparin but not NA-LMWH demonstrated a significant anticoagulant effect in mice. Both NA-LMWH and enoxaparin caused similar TFPI release from endothelial cells in vitro. These data provide evidence to support the potential of NA-LMWH as an anti-metastatic agent without any significant impact on coagulation.

Animals↗
PubMed2000

Comparative in vitro efficacy of different platelet glycoprotein IIb/IIIa antagonists on platelet-mediated clot strength induced by tissue factor with use of thromboelastography: differentiation among glycoprotein IIb/IIIa antagonists.

In the present study, the in vitro efficacy of different platelet glycoprotein IIb/IIIa (GPIIb/IIIa) antagonists on platelet-fibrin-mediated clot strength under shear was compared with the antiaggregatory efficacy by using tissue factor (TF) thromboelastography (TEG). The ability of platelets to augment the elastic properties of blood clots under shear conditions was measured by computerized TEG under conditions of maximal platelet activation accelerated by recombinant TF. Under these conditions, platelets significantly enhance clot strength 8-fold (relative to platelet-free fibrin clots). This effect was inhibited to a different extent by various platelet GPIIb/IIIa receptor antagonists; this inhibition appears to be dependent on the transmission of platelet contractile force to fibrin via the GPIIb/IIIa receptors. The GPIIb/IIIa antagonists with high binding affinity for resting and activated platelets and slow platelet dissociation rates (class I) but not those with fast platelet dissociation rates (class II) demonstrated potent and comparable inhibition of platelet aggregation and TF-TEG clot strength. Platelet GPIIb/IIIa antagonists of class I, such as XV459 (free-acid form of roxifiban), DMP802, XV454, and c7E3, demonstrated comparable inhibitory dose responses of TF-TEG clot strength and platelet aggregation, with an IC(50) of 50 to 70 nmol/L. In contrast, platelet GPIIb/IIIa antagonists from class II, with comparable antiaggregatory efficacy, such as DMP728, YZ202 (free-acid form of orbofiban), YZ211 (free-acid form of sibrafiban), YZ751, and other antagonists, have a much lower efficacy in altering the strength of TF-mediated clot formation (IC(50) >1.0 micromol/L). These data suggest differential efficacy among different GPIIb/IIIa antagonists in inhibiting platelet-fibrin clot retraction despite of equivalent antiaggregatory potency.

Abciximab↗
PubMed1969

Congenital dysfibrinogenemia: fibrinogen Detroit.

A 17 yr old female with a congenital bleeding disorder was found to suffer from dysfibrinogenemia. Whole blood and plasma coagulation times were delayed and thrombelastograms were grossly abnormal. Clottability of plasma fibrinogen by addition of thrombin was not demonstrated during the 30 min test period. Fibrinogen was revealed by turbidometric and immunologic techniques. Other coagulation factors were present in normal amounts and prothrombin activation was normal. Patient's plasma inhibited thrombin clotting times of normal plasma and purified normal fibrinogen. Fibrinolysis was not detected. The plasma fibrinogen migrated normally on paper and cellulose acetate electrophoresis, but on immunoelectrophoresis it displayed a faster mobility than normal fibrinogen. On immunodiffusion the antigenic determinants were similar to those of normal fibrinogen. The patient's fibrinogen-antifibrinogen precipitins required longer to appear and the resultant precipitin was broader and hazier than those elicited with normal fibrinogen. These findings suggest the presence of two discrete populations of fibrinogen molecules. Investigation of the family of the patient suggested that the defect has an autosomal dominant pattern of heredity. Immunologic comparisons of our patient's plasma and of her relatives with plasma of patients with "Fibrinogen Baltimore" and "Fibrinogen Cleveland" revealed certain differences in immunoelectrophoretic mobility as well as in immunodiffusion. In keeping with the nomenclatures of abnormal fibrinogens in the literature, we propose the term "Fibrinogen Detroit" for this fibrinogen.Physicochemical properties of "Fibrinogen Detroit" were investigated also and compared with those of normal fibrinogen. Purified normal fibrinogen (clottability 96.7%) and "Fibrinogen Detroit" revealed homogeneity when studied by ultracentrifugation and immunoelectrophoresis. Native and cleaved "Fibrinogen Detroit" had the same sedimentation constants and molecular weights as the normal. In fresh samples. 3 moles of free SH groups/mole of fibrinogen were titrated in both. Determination of the amino acid composition revealed a decreased content of lysine, glucosamine, and galactosamine in abnormal fibrinogen. Total carbohydrates, protein-bound hexoses, sialic acid, and hexosamine were decreased in the abnormal fibrinogen. In an investigation with Doctors Blombäck a specific molecular defect was revealed in the N-terminal disulfide knot of the alpha (A) chain in which the arginine at the 19th position was replaced by serine. It is believed that the substitution of a strongly basic amino acid with a neutral hydroxy acid may result in considerable conformational changes in the N-terminal disulfide knot of fibrinogen which might affect the "active site" for polymerization. The lower carbohydrate content observed in "Fibrinogen Detroit" may have been the result of a change in primary and tertiary structure of the protein.

Adolescent↗
PubMed1969

Factor XIII in human plasma and platelets.

Plasma and platelet factor XIII levels were measured in normal human donors and in a patient congenitally deficient in factor XIII. The purpose of these experiments was to study the role of platelet factor XIII in blood coagulation. On polyacrylamide disc electrophoresis, factor XIII activity in extracts of washed normal platelets appeared as a single peak. This peak was missing or very low when factor XIII-deficient platelet extract was used. The patient was also studied before and after transfusion of fresh frozen plasma. Before transfusion, factor XIII activity could not be detected in the patient's plasma or platelet extracts. 24 hr after transfusion the plasma factor XIII level was still at the anticipated value, but factor XIII activity could not be detected in the platelet extracts. These experiments imply that plasma factor XIII was not transported across the platelet membrane in measurable quantities in vivo. This suggests that platelet factor XIII is a true platelet component and originates in the platelet precursor, the megakaryocyte. Thrombelastographic studies suggest that platelet factor XIII participates in the coagulation process. Thrombelastograms of factor XIII-deficient samples had decreased maximum amplitude and clot elasticity values. The abnormalities were fully corrected by the addition of washed normal platelets to factor XIII-deficient plasma; preincubation of the normal platelets in the deficient plasma had no additional effect. This indicates that platelet factor XIII is immediately available during clot formation.

Adolescent↗
PubMed1971

Functional evaluation of an inherited abnormal fibrinogen: fibrinogen "Baltimore".

The rate of clotting and the rate of development and degree of turbidity after addition of thrombin to plasma or purified fibrinogen from a patient with fibrinogen Baltimore was delayed when compared with normal, especially in the presence of low concentrations of thrombin. Optimal coagulation and development of translucent, rather than opaque, clots occurred at a lower pH with the abnormal fibrinogen than with normal. Development of turbidity during clotting of the abnormal plasma or fibrinogen was less than normal at each pH tested, but was maximal in both at approximately pH 6.4. The physical quality of clots formed from fibrinogen Baltimore was abnormal, as demonstrated by a decreased amplitude on thromboelastography. The morphologic appearance of fibrin strands formed from fibrinogen Baltimore by thrombin at pH 7.4 was abnormal when examined by phase contrast or electron microscopy, but those formed by thrombin at pH 6.4 or by thrombin and calcium chloride were similar to, though less compact, than normal fibrin. The periodicity of fibrin formed from fibrinogen Baltimore was similar to normal and was 231-233 A.A study of the release of the fibrinopeptides from the patient's fibrinogen and its chromatographic subfractions verified the existence of both a normally behaving and a defective form of fibrinogen in the patient's plasma. The defective form differed from normal in three functionally different ways: (a) the rate of release of fibrinopeptides A and AP was slower than normal; (b) no visible clot formation accompanied either partial or complete release of the fibrinopeptides from the defective form in 0.3 M NaCl at pH 7.4; and (c) the defective component possessed a high proportion of phosphorylated, relative to nonphosphorylated, fibrinopeptide A, while the coagulable component contained very little of the phosphorylated peptide (AP). The high phosphate content of the defective component did not appear to be the cause of the abnormality, but may be the result of an associated metabolic or genetic phenomenon.

Blood Coagulation↗
PubMed1986

Nonionic contrast medium: effects on blood coagulation and complement activation in vitro.

A nonionic contrast medium was evaluated in vitro for its effects on coagulation and complement activation in comparison to a low osmolal contrast agent. In clotting assays each contrast medium was mixed with blood and clotting parameters were analyzed by using a thromboelastographic machine. Platelet function was studied by incubating platelet-rich plasma with individual contrast medium, and the subsequent challenge of a platelet aggregating agent. Complement activation was assessed by the hydrolysis of C3 protein into C3c fragment in contrast medium-incubated serum. Immunoelectrophoresis was used to detect C3c protein. Both the nonionic contrast medium and the low osmolal contrast agent acted as anticoagulant and antiplatelet agents, however, results with the low osmolal contrast agent were more pronounced compared to the nonionic contrast medium. Even at nonphysiologic concentration of contrast medium, no significant conversion at C3 to C3c was seen. Since these two agents caused hypocoagulable states in vitro, it is likely that patients with thrombocytopenia, severe liver disease and with clotting factor deficiencies may present hemostatic complications during angiographic procedures.

Blood Coagulation↗
PubMed1997

Coagulopathic-induced membrane dysfunction during extracorporeal membrane oxygenation: a case report.

This paper describes an unusual complication of membrane dysfunction during extracorporeal membrane oxygenation (ECMO) for treatment of neonatal respiratory distress. A 2.8-kg term infant presented to our facility in severe respiratory distress and was diagnosed with primary pulmonary hypertension. After routine priming of the extracorporeal circuit, the patient was placed on veno-arterial ECMO with 8 F arterial and 12 F venous cannulae. Transfusion criteria were established which included trigger values of the following: platelet count 100,000/microliters, fibrinogen 150 mg/dl, haematocrit 40%. The ECMO course was uneventful until approximately the 132nd hour on support when the patient developed a consumptive coagulopathy, as evidenced by 55-60% reductions in both platelet count and fibrinogen concentrations, despite transfusion therapy. Total autogeneic blood product transfusion during the first 120 h of ECMO averaged 4.4 +/- 2.2 ml/h, while the transfusion rate for the final 35 h was 7.8 +/- 3.5 ml/h. Coinciding with this rise in transfusion requirements was an increase in transmembrane pressure from 0.29 to 1.52 mmHg/ml blood flow. The patient was separated from ECMO after 175 h due to a continuing coagulopathy and haemothorax. The patient was then treated with nitric oxide therapy before succumbing on the twelfth postoperative day due to refractory respiratory failure. The circuit was dissected and significant clots found in both the venous bladder and oxygenator. In addition, approximately one-third of the membrane compartment had a 'fused' circumferential pattern of dessicated clot which interrupted blood path continuity. In conclusion, this report describes an unusual complication of the ECMO oxygenator that occurred during long-term extracorporeal life support which most likely resulted from a coagulopathy.

Blood Transfusion↗