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PubMed2006

The effects of continuous venovenous hemofiltration on coagulation activation.

INTRODUCTION: The mechanism of coagulation activation during continuous venovenous hemofiltration (CVVH) has not yet been elucidated. Insight into the mechanism(s) of hemostatic activation within the extracorporeal circuit could result in a more rational approach to anticoagulation. The aim of the present study was to investigate whether CVVH using cellulose triacetate filters causes activation of the contact factor pathway or of the tissue factor pathway of coagulation. In contrast to previous studies, CVVH was performed without anticoagulation. METHODS: Ten critically ill patients were studied prior to the start of CVVH and at 5, 15 and 30 minutes and 1, 2, 3 and 6 hours thereafter, for measurement of prothrombin fragment F1+2, soluble tissue factor, activated factor VII, tissue factor pathway inhibitor, kallikrein-C1-inhibitor and activated factor XII-C1-inhibitor complexes, tissue-type plasminogen activator, plasminogen activator inhibitor type I, plasmin-antiplasmin complexes, protein C and antithrombin. RESULTS: During the study period the prothrombin fragment F1+2 levels increased significantly in four patients (defined as group A) and did not change in six patients (defined as group B). Group A also showed a rapid increase in transmembrane pressure, indicating clotting within the filter. At baseline, the activated partial thromboplastin time, the prothrombin time and the kallikrein-C1-inhibitor complex and activated factor XII-C1-inhibitor complex levels were significantly higher in group B, whereas the platelet count was significantly lower in group B. For the other studied markers the differences between group A and group B at baseline were not statistically significant. During CVVH the difference in the time course between group A and group B was not statistically significant for the markers of the tissue factor system (soluble tissue factor, activated factor VII and tissue factor pathway inhibitor), for the markers of the contact system (kallikrein-C1-inhibitor and activated factor XII-C1-inhibitor complexes) and for the markers of the fibrinolytic system (plasmin-antiplasmin complexes, tissue-type plasminogen activator and plasminogen activator inhibitor type I). CONCLUSION: Early thrombin generation was detected in a minority of intensive care patients receiving CVVH without anticoagulation. Systemic concentrations of markers of the tissue factor system and of the contact system did not change during CVVH. To elucidate the mechanism of clot formation during CVVH we suggest that future studies are needed that investigate the activation of coagulation directly at the site of the filter. Early coagulation during CVVH may be related to lower baseline levels of markers of contact activation.

Adult↗
PubMed2005

Identifying hypocoagulable states with a modified global assay of overall haemostasis potential in plasma.

To test the sensitivity of the global assay of overall haemostasis potential (OHP) in detecting hypocoagulation, the OHP was assayed in plasma containing exogenous thrombin (0.04 IU/ml), tissue-plasminogen activator (330 ng/ml), Ca and a platelet reagent. Commercial plasmas with factor II, V, VIII, IX, X, XI, XII or VII deficiency were mixed with normal plasma in different proportions to imitate different severities. Samples from patients with haemophilia and factor XII deficiency were also examined. No clot was found in the absence of factor II/factor X, indicating that the tiny dose of thrombin worked solely as a trigger for the intrinsic pathway activation. Changed levels of the investigated coagulants, apart from factor XII, influenced the outcome. OHPs were decreased in patients with haemophilia but were unchanged or even increased in those with factor XII deficiency. This modified OHP method may therefore be useful for estimating the bleeding tendency in haemophilic patients and to find suitable doses and intervals for prophylactic treatment. It may also be of use in investigations of the effect of antifibrinolytic drugs as well as for identifying a thrombotic tendency in patients with factor XII deficiency. For detection of other coagulation factor deficiencies, our investigations with the commercial plasmas suggest that the OHP assay is also valuable, especially when the intrinsic pathway of the coagulation cascade is impaired.

Blood Coagulation↗
PubMed1998

Assessment of Actin FS and Actin FSL sensitivity to specific clotting factor deficiencies.

We present a two centre study designed to assess the sensitivity of Actin FS and Actin FSL to deficiencies of factor VIII, IX, XI or XII. The study was undertaken at two centres to avoid bias due to the investigations being undertaken on one analyser. Samples from patients with a factor VIII (n = 36, F VIII = < 1.0-50 iu/dl), factor IX (n = 22, F IX = 2-48 iu/dl), factor XI (n = 23, F XI = 5-50 u/dl) or a factor XII (n = 18, F XII = 1-50 u/dl) deficient state were studied. Activated partial thromboplastin times (APTT) were determined using two batches of Actin FS and of Actin FSL; comparison of APTT results between centres was facilitated by the conversion of clotting times to ratios (test divided by geometric mean normal clotting time). APTT ratios were considered to be elevated if greater than two standard deviations above the mean normal. The factor deficient status of each sample was verified by assaying all samples for factors VIII, IX, XI and XII. Clotting factor assays were performed on a Sysmex CA-1000 fitted with research software, which permitted the auto-dilution and testing of three serial dilution of both a reference preparation and each patient's sample. Assay results were calculated using parallel-line Bioassay principles. This procedure allowed for variation in clotting times due to the effect of temporal drift of any of the reagents within the assay system. Actin FS and Actin FSL demonstrate acceptable sensitivity to factor VIII deficiency, however, both reagents failed to detect a large proportion of factor XI (17.4% and 30.4% of samples, respectively) and factor XII (66.7% and 72.2%, respectively) deficiencies. The detection rate with Actin FSL for factor IX deficiency was also poor (36.4% not detected). As factor IX and XI deficiencies are both associated with haemorrhagic disorders, the inability of these reagents to detect such abnormalities gave cause for concern.

Actins↗
PubMed1964

WATERFALL SEQUENCE FOR INTRINSIC BLOOD CLOTTING.

A simple waterfall sequence is proposed to explain the function of the various protein clotting factors during the formation of the fibrin clot. When clotting is initiated, each cloting factor except fibrinogen is converted to a form that has enzymatic activity. This activation occurs in a sepwise sequence with each newly formed enzyme reacting with its specific substrate, converting it to an active enzyme.

Blood Coagulation↗
PubMed1995

[Measurements of the activity of the coagulation factors VIII:C, IX,XI, and XII in cats].

Using an optimized test, reference ranges were established for the activity of the coagulation factors VIII:C (72-124%), IX (81-130%), XI (69-134%) and XII (51-142%) in the cat (n = 58 cats, 2.5-97.5% quantile). Compared to a reference curve prepared by using a cat-pool plasma (n = 50), the factor VIII:C activity in humans (commercial human reference plasma) was 7.6%, i.e. the factor VIII:C activity in cats was 13 fold higher than in humans. The values for the factors IX, XI and XII depended distinctly on the dilution step of the human plasma. The activity of the cat in relation to humans was approximately 90% (factor IX), 170% (factor XI) and 135% (factor XII). Two clinically healthy cats who were conspicuous pre-operative because of a distinctly prolonged, activated partial thromboplastin time showed a decreased factor XII activity.

Animals↗
PubMed2005

Effects of coagulation factor deficiency on plasma coagulation kinetics determined via thrombelastography: critical roles of fibrinogen and factors II, VII, X and XII.

BACKGROUND: Thrombelastography (TEG) is used to assess coagulopathy. However, a comprehensive characterization of the effects of specific coagulation factor deficiencies and mode of activation on TEG data does not exist. METHODS: Thrombelastography was performed for 15 min with control plasma and plasmas deficient (<1% activity) in Factors II, V, VII, VIII, IX, X, XI, XII, or XIII activated with celite (0.28 mg ml(-1)) or tissue factor (TF, 0.1%) (n = 6 per condition). Additional fibrinogen concentration activity (75-345 mg dl(-1)) and Factor II, VII, X and XII activity-response relationships (1%, 6.25%, 12.5%, 25%, 50% and 100% activity) were obtained (n = 8 per condition). Thrombelastography parameters included reaction time (R), angle (alpha), and clot strength (A, amplitude; G, elastic modulus). RESULTS: Celite activation of FXII-deficient plasma, TF activation of FVII-deficient and FX-deficient plasma, and celite or TF activation of FII-deficient plasma resulted in an almost undetectable clot. Compared to control values, celite activation of plasmas deficient in FXI, FIX and FVIII resulted in prolonged R and decreased alpha values, whereas TF activation resulted in decreased alpha values. Celite and TF activation of FV-deficient plasma resulted in prolonged R and decreased alpha values, whereas FXIII-deficient plasma had decreased alpha, A and G-values compared to control values. CONCLUSIONS: The fundamental finding of this study is that coagulation factor deficiencies affect TEG parameters in both a factor-dependent and activation-dependent fashion. Utilizing both celite and TF activation improves the diagnostic power of TEG. Based on such TEG data, more targeted administration of blood products could potentially help improve perioperative hemostatic outcomes.

Blood Coagulation↗
PubMedDate not supplied

Pathophysiologic role of contact activation in bleeding followed by thromboembolic complications after implantation of a ventricular assist device.

The time period after implantation of a ventricular assist device in patients with end-stage heart disease is complicated by hemorrhage in the early postoperative period and by thromboembolism in the later course. To investigate the pathophysiologic role of contact activation in 12 bridging patients (10 patients with a paracorporeal Berlin Heart [Berlin Heart GmbH, Berlin, Germany], 2 patients with an intracorporeal Novacor system [Novacor N100; Baxter, Oakland, CA]), hemostatic parameters were determined until heart transplantation or at least up to the 51st postoperative day. The following were observed: 1) In the early postoperative period, until day 15, levels of contact factors XI, XII, and prekallikrein were below normal, whereas levels of plasmin-a2-antiplasmin (PAP) complexes were elevated. Thrombin-antithrombin III (TAT) complexes, as well as platelet factor 4 and beta-thromboglobulin, significantly increased immediately after surgery. 2) In the later postoperative period, starting with the third postoperative week, an increase of factors XI, XII, and prekallikrein was observed. PAP and TAT complexes, as well as platelet factor 4 and beta-thromboglobulin, remained elevated. It is concluded that, in the early postoperative period, hemostasis is influenced mainly by an activation of the intrinsic contact system dependent fibrinolytic system with consumption of contact factors and increased levels of PAP complexes, whereas later system dependent fibrinolysis becomes less important, leading to a shift of the balance toward coagulation, with sustained prothrombin and platelet activation. This is in accord with the observed clinical complications (e.g., early postoperative bleeding, and thromboembolic events later on).

Adult↗
PubMed1981

The influence of cytostatic treatment on the initiation of plasma coagulation in patients with neoplastic diseases.

The above described changes in the haemostatic system in acute leukemias are well known and underlined by many authors [1, 5, 6, 9]. It should be stressed that the results of particular nonspecific hemostatic tests in some patients may be within the normal range in spite of significant alterations in the activity of some blood coagulation factors and the presence of hemorrhagic symptoms. In the observations of some authors the factor VIII level is distinctly increased in the majority of acute leukemic cases, whereas the vitamin K-dependent blood coagulation factors show a low activity in some patients [6, 9]. It is not easy to interpret the different behaviour of the factor XI and XII level especially before antileukemic treatment. In 3/4 of all studied cases the factor XI activity was low, whereas the factor XII level was high in 1/4 of patients above the normal range. It may be that there is a specific inhibitor against the factor XI that is produced in acute leukemia. It must be stressed that the level of factor XI shows normal values during hematological remission.

Antineoplastic Agents↗
PubMed1965

PATHOGENESIS OF INFLAMMATION. II. IN VIVO OBSERVATIONS OF THE INFLAMMATORY EFFECTS OF ACTIVATED HAGEMAN FACTOR AND BRADYKININ.

Activated Hageman factor, when injected into the rabbit ear chamber, produces a delayed and prolonged inflammatory response characterized by prominent sticking and emigration of leucocytes. In contrast, preformed bradykinin evokes an immediate and more transient response in which leucocytic emigration occurs less frequently. It is concluded that either Hageman factor produces its inflammatory effects by mechanisms other than kinin release, or bradykinin released endogenously has effects quite different from those resulting from a single injection of the exogenous material.

Animals↗
PubMed1990

The haemostatic balance in groups of thrombosis-prone patients. With particular reference to fibrinolysis in patients with myocardial infarction.

The concept of the haemostatic balance was reviewed, and its potential role in the regulation of tissue repair and the pathogenesis of thrombotic processes was surveyed. Physiological activation of coagulation appears to be dominated by effects of degenerated and injured cells of the vascular wall causing local release of thromboplastin and exposition of activating surfaces. Inhibition of coagulation impairs its progression and the non-thrombogenic nature of the normal endothelium is chiefly caused by the binding of inhibitory components (antithrombin-III, protein C) to specific receptor sites. Physiological activation of fibrinolysis appears to be triggered by and limited to the fibrin because of a specific affinity to fibrin of plasminogen and plasminogen activators. Systemic activation of fibrinolysis is prevented by primary (alpha 2-antiplasmin) and secondary (alpha 2-macroglobulin, alpha 1-antitrypsin) plasmin inhibitors. A plasminogen binding protein (histidine-rich glycoprotein), plasmin inhibitors and activator inhibitors appear to contribute to the regulation of the initial phase of fibrinolysis. A deviation from normal of the dynamic balance, regulating fibrin formation and resolution, may lead to a haemorrhagic and/or a thrombophilic state. Described were the optimization of selected methods for assessment of variables involved in the haemostatic balance. An overestimation of plasminogen concentrations in plasma may occur in patients with elevated levels of fibrinogen or fibrin degradation products, when using assays based on the activation of plasminogen by streptokinase followed by the hydrolysis of a synthetic chromogenic substrate. This source of error could be eliminated by presence of fibrinogen in excess in the plasminogen assay, thereby securing maximum stimulation of the plasminogen-streptokinase complex. The presence of cryoglobulin in plasma interferes with the assessment in euglobulins of plasminogen activator activities. Experiments indicate that tissue-type plasminogen activator adsorb cryoglobulins and that a cold-promoted activation of the factor XII-dependent proactivator system of fibrinolysis is related to the presence of cryoglobulins. Experiments supported the existence of an as yet not characterized factor XII-dependent proactivator. Strictly optimized procedures for the preparation of euglobulins for the accurate determination of plasminogen activators were recommended. The determination of plasminogen activator inhibition in plasma was optimized and simplified. The amidolytic assay of antithrombin-III was shown to be influenced by adsorption to laboratory utensils and aggregation of thrombin. This error could be corrected by protection with additives (Tween 80, polyethyleneglycol 6,000), which also improved the solubility of the chromogenic substrates in aqueous media. The role of thrombosis in myocardial infarction was reviewed.(ABSTRACT TRUNCATED AT 400 WORDS)

Antithrombin III↗