Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.21.6 (thromboplastin)
13,278 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Venous thromboembolism produces chronic sequelae in the legs and occasional immediate mortality due to pulmonary embolism. Because it occurs in certain high risk situations (for example, after surgery) its prevention is a practical proposition. This has been attempted using many different approaches. Administration of low dose heparin with or without dihydroergotamine to enhance venous return has been one of the most widely tested regimens. There is little doubt that this can prevent, in many patient groups, postoperative deep venous thrombosis and fatal pulmonary embolism, with a low incidence of adverse reactions. Some particularly high risk postoperative patient groups (for example, those undergoing hip surgery) warrant more aggressive measures to prevent thrombosis. Surveys have shown that increasing use is being made of this approach, and it is hoped that all surgeons will adopt a policy that will reduce postoperative venous thrombosis and pulmonary embolism. A reduction in the incidence of venous thromboembolism in large acute myocardial infarction is achieved by low dose heparin, although early mobilization is important. In addition, many of the patients at risk merit full dose anticoagulation to prevent intracardiac thromboembolism. Established venous thrombosis is treated effectively by intravenous heparin, followed by warfarin to keep the prothrombin time at 1.2 to 1.5 times control, as assessed using rabbit thromboplastin; most patients need three months of treatment. Anticoagulation is warranted for pulmonary embolism, with fibrinolytic therapy reserved for patients with massive embolism and hemodynamic compromise. Embolectomy is a heroic measure, which may occasionally be lifesaving.
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PMID:Preventive and therapeutic approach to venous thromboembolic disease and pulmonary embolism--can death from pulmonary embolism be prevented? 353 67

Preoperative coagulation studies are commonly employed in order to try to identify the 2-4% of all patients undergoing tonsillectomy/adenoidectomy surgery who experience hemorrhagic complications. In an atmosphere of increasing cost consciousness, evaluation of the efficacy of screening tests is warranted. The records of 994 out of 1050 patients consecutively scheduled for tonsillectomy, adenoidectomy or T&A over a 2.5-year period were retrospectively reviewed in order to determine the usefulness of partial thromboplastin (PTT) and prothrombin time (PT) screening in predicting surgical and postsurgical bleeding. For patients with no history or clinical signs indicating possible bleeding disorder, preoperative PT and PTT failed to predict bleeding as an outcome. Also no patients were identified in this series to have previously undiagnosed coagulopathies on the basis of screening PT/PTT. The purpose of any screening test is to identify disease early enough for therapeutic intervention to be effective. Although preoperative PT/PTT will occasionally identify an unsuspected von Willebrand's or other coagulopathy, the prevalence of bleeding disorders in patients with negative history and examination is low enough that PT/PTT has essentially a zero predictive value for surgical bleeding. Screening PT/PTT should therefore be reserved for patients with known or suspected coagulopathies.
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PMID:An assessment of preoperative coagulation screening for tonsillectomy and adenoidectomy. 367 79

We retrospectively compared preoperative prothrombin (PT), partial thromboplastin (PTT), dilute whole blood clot lysis and bleeding times, fibrinogen level, and platelet count with subsequent blood component administration in 92 patients who had undergone cardiac operations with cardiopulmonary bypass (CPB). Abnormal results for one or more tests were found in 34% of 71 adults and 81% of 21 children and teenagers. The patients with abnormal test(s) received no more whole blood and packed red cell units, platelets, or plasma than those with normal tests in either age group. No individual or multiple test abnormalities predicted excess blood component transfusion, even when low-grade abnormalities were excluded. The high rate of abnormal tests in patients less than 20 years of age was not due to polycythemia and may indicate a need for age-specific reference ranges. Baseline PT, PTT, and platelet count may aid in the evaluation of the potential for subsequent development of coagulopathy, but we conclude that further preoperative testing may be reserved for infants, polycythemic individuals, or others in whom history or drug use suggests potential bleeding problems.
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PMID:Do preoperative laboratory tests predict blood transfusion needs in cardiac operations? 660 Dec 13

Intramural hematoma of the small intestine is a relatively rare but serious complication of oral anticoagulant therapy. On the basis of a retrospective epidemiological survey the authors estimate its incidence at 1 case per 20 000 admissions to medical and surgical services or 1 case per 2500 anticoagulated patients per year. The classical trial of clinical symptoms comprises abdominal pain, small bowel obstruction and multiple hemorrhagic symptoms (hematuria, hematomas, ecchymoses, hematemesis and melaena). The most important etiologic factors appear to be overanticoagulation with vitamin K antagonists (the thromboplastin time is prolonged in over 70% of cases) or correct oral anticoagulation associated with additional impairment of hemostasis due to the administration of drugs inhibiting platelet function. Radiologic examination of the gastrointestinal tract reveals that the jejunum and the ileum are sites of predilection for intramural intestinal hematoma. The treatment of choice is conservative; surgery should be reserved for cases in which the diagnosis is doubtful and for patients who exhibit signs of bowel necrosis or peritonitis.
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PMID:[Incidence of intramural digestive system hematoma in anticoagulation. Epidemiologic study and clinical aspects of 59 cases observed in Switzerland (1970-1975)]. 660 15

Sixty-seven cases of eclampsia were managed between August 1977 and July 1980. Routinely acquired laboratory tests of these cases have been analyzed. In addition, the group of patients with eclampsia was compared with a group of 24 healthy pregnant women. There was no significant difference in platelet count, serum fibrinogen, and bilirubin values. The activated partial thromboplastin time was abnormal in 42% of patients with eclampsia. There was no clinical evidence of disseminated intravascular coagulation in any patient. Patients with eclampsia had abnormalities of lactic dehydrogenase, alkaline phosphatase, SGOT, uric acid, BUN, and creatinine. However, in any individual patients there was no single test of great clinical usefulness and no test predictive of maternal or fetal outcome. At present the authors recommend complete blood count (including blood smear and platelet count), clot observation, and serum creatinine tests. Liver function tests are reserved for the patient with upper abdominal pain. Additional tests are recommended if the diagnosis of eclampsia is questionable or if an additional disease process is suspected.
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PMID:Eclampsia II. Clinical significance of laboratory findings. 707 59

Unfractionated heparin (UH) and low-molecular-weight heparins (LMWH) are antithrombotic drugs covering virtually all indications requiring immediately effective anticoagulation. For prevention and treatment of venous thromboembolism (VTE) UH have mainly been replaced by LMWH due to their practical usefulness (one or two subcutaneous daily doses without laboratory test for dose adjustment) and their more favourable risk-benefit profile. With respect to arterial occlusions this statement is also valid for unstable angina pectoris. The risk to develop heparin-induced thrombocytopenia (HIT) appears to be ten times lower with LMWH. In hospitals the use of UH is reserved for complex cases with high bleeding risk and the necessity to interrupt heparin effects rapidly. Therapeutic doses of UH are monitored by the classical coagulation assays, activated partial thromboplastin time (aPTT) and thrombin time (TT), but also by automated chromogenic tests of anti-factor Xa activity. There are no prospective studies directly comparing the efficiency of these three approaches. Disagreements between tests are not rare in individual cases. However, dosing recommendations for UH treatment of VTE (intravenous bolus of 80 IU/kg, followed by 18 IU/kg/h infusion) and average doses used are concordant. 0.30-0.70 anti-Xa IU/ml are considered as therapeutic range for UF infusion. Higher UH activities required during extracorporeal circulation in heart surgery or during coronary angioplasty are usually guided by bedside ACT (activated clotting time). For LMWH tests of anti-Xa activities may only be necessary during weight adjusted treatment of pregnant women, children, or cases with reduced kidney function (glomerular filtration rate < 30 ml/min.) or increased bleeding risk. Expected anti-Xa activities are 0.5-1.1 IU/ml and 1.0-2.0 IU/ml 4 hours after subcutaneous LMWH for dosing intervals of 12 hours and 24 hours respectively.
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PMID:[Heparins]. 1263 71

Current antithrombotic agents include anticoagulants (unfractionated and low-molecular-weight heparin, and antivitamin K) and platelet aggregation inhibitors (aspirin, ticlopidine, clopidogrel). Two areas are under particular investigation: specific inhibition, direct or indirect, of factor Xa and factor IIa. Pentasaccharide, an indirect anti-Xa, has proved effective in curing deep-vein thrombosis and more effective than enoxaparin for prophylactic treatment after orthopedic surgery. Administered in a single subcutaneous injection daily, it has no risk of thrombocytopenia; laboratory surveillance is based on anti-Xa activity. Hirudin and melagatran act by direct thrombin inhibition. Unlike hirudin (which requires monitoring of active coagulation time or ecarin clotting time), melagatran requires no laboratory monitoring. It is not associated with an increased risk of hemorrhage. But there is no true antidote at this time. If its efficacy is confirmed, ximelagatran, the orally active prodrug of melagatran, may facilitate the long-term treatment now reserved for antivitamin K. Three antagonists of the tissue factor-factor VIIa complex are also under development: rNAPc2 (Recombinant Nematode Anticoagulant Protein C2), ASIS (Active Site Inhibitor Factor Seven) and recombinant TFPI (Tissue Factor Pathway Inhibitor). Antiplatelet drugs are the reference antithrombotic agents for the prevention and treatment of arterial thrombosis. Aspirin remains in first place (75 to 300 mg/d) but the modest superiority of the thienopyridines (clopidogrel and ticlopidine) is established. Hemogram monitoring is no longer necessary for clopidogrel. Use of aspirin + a thienopyridine after placement of a coronary stent has been validated. Laboratory monitoring of antiplatelet treatments has not been codified.
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PMID:[The new antithrombotic agents]. 1626 95

To evaluate the association of inherited coagulopathies and acquired conditions (e.g. hypertension, aspirin use) with emergency department admission due to epistaxis. Patients admitted to the emergency department with epistaxis were included. A questionnaire for personal and family history of any bleeding disorder was used. Physical examination including ear, nose and throat examination was performed. Platelet counts, International Normalized Ratio, activated partial thromboplastin time, factors VIII, IX and XI, von Willebrand factor and ristocetin cofactor activity levels were determined. Nineteen patients were included in the study. Personal history of mucocutaneous bleeding was present in four cases and family history in two cases. Only one case (5%) had a decreased von Willebrand factor level (45%), and also had a personal and family history of bleeding tendency. Ten patients (53%) had a history of aspirin use. Thirteen (68%) patients had hypertensive values on admission. Aspirin use and hypertension were the leading causes of emergency service admission in adults due to epistaxis in this study, although the number of the patients was relatively low. Regarding the low prevalence of inherited coagulopathies, detailed coagulation tests should be reserved for adult patients with positive personal and/or family history of bleeding.
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PMID:Research for bleeding tendency in patients presenting with significant epistaxis. 1717 25

No data about the use of the pentasaccharide fondaparinux, a highly selective indirect inhibitor of factor Xa, in patients treated with haemodialysis are available. Therefore, we investigated the pharmacokinetics and -dynamics of fondaparinux in 12 patients during haemodialysis. The anti-Xa activity (expressed as fondaparinux equivalent) was monitored, a semiquantitative clotting scale (SQCS) ranging from 0 (no visible traces of coagula) to 3 (complete clotting of the dialysis circuit) was applied, and the digital compression time necessary to achieve haemostasis at the puncture site was determined. After an initial period, when the regular heparin dose was replaced once weekly by fondaparinux, 0.05 mg/kg, the pentasaccharide was administered for nine consecutive haemodialysis sessions. Peak anti-Xa activity increased from 0.61 +/- 0.14 microg/l after the first dose to 0.89 +/- 0.24 microg/l after dose 9 (P < 0.001), whereas predialysis anti-Xa activity steadily rose to 0.32 +/- 0.09 microg/l (P < 0.001). A sufficient but slightly less effective anticoagulation with a mean SQCS of 1.19 +/- 0.71 (n = 121) was obtained by fondaparinux as compared with 0.65 +/- 0.58 (n = 60, P < 0.005) by 4,825 +/- 1,703 U of unfractionated heparin. Mean digital compression time rose slightly during fondaparinux from 23.7 +/- 7.4 minutes to 24.8 +/- 7.5 minutes (P < 0.05) and, more important, six of the 12 patients reported minor bleeding problems during the interdialytic interval. Thus, fondaparinux can be used to prevent circuit clotting during haemodialysis; however, accumulation results in an interdialytic increase of anti-Xa activity. Therefore, fondaparinux should be reserved for patients requiring systemic anticoagulation on the days off dialysis.
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PMID:Use of the pentasaccharide fondaparinux as an anticoagulant during haemodialysis. 1806 14

The diagnosis of disseminated intravascular coagulation (DIC) should encompass both clinical and laboratory information. The International Society for Thrombosis and Haemostasis (ISTH) DIC scoring system provides objective measurement of DIC. Where DIC is present the scoring system correlates with key clinical observations and outcomes. It is important to repeat the tests to monitor the dynamically changing scenario based on laboratory results and clinical observations. The cornerstone of the treatment of DIC is treatment of the underlying condition. Transfusion of platelets or plasma (components) in patients with DIC should not primarily be based on laboratory results and should in general be reserved for patients who present with bleeding. In patients with DIC and bleeding or at high risk of bleeding (e.g. postoperative patients or patients due to undergo an invasive procedure) and a platelet count of <50 x 10(9)/l transfusion of platelets should be considered. In non-bleeding patients with DIC, prophylactic platelet transfusion is not given unless it is perceived that there is a high risk of bleeding. In bleeding patients with DIC and prolonged prothrombin time (PT) and activated partial thromboplastin time (aPTT), administration of fresh frozen plasma (FFP) may be useful. It should not be instituted based on laboratory tests alone but should be considered in those with active bleeding and in those requiring an invasive procedure. There is no evidence that infusion of plasma stimulates the ongoing activation of coagulation. If transfusion of FFP is not possible in patients with bleeding because of fluid overload, consider using factor concentrates such as prothrombin complex concentrate, recognising that these will only partially correct the defect because they contain only selected factors, whereas in DIC there is a global deficiency of coagulation factors. Severe hypofibrinogenaemia (<1 g/l) that persists despite FFP replacement may be treated with fibrinogen concentrate or cryoprecipitate. In cases of DIC where thrombosis predominates, such as arterial or venous thromboembolism, severe purpura fulminans associated with acral ischemia or vascular skin infarction, therapeutic doses of heparin should be considered. In these patients where there is perceived to be a co-existing high risk of bleeding there may be benefits in using continuous infusion unfractionated heparin (UFH) due to its short half-life and reversibility. Weight adjusted doses (e.g. 10 mu/kg/h) may be used without the intention of prolonging the APTT ratio to 1.5-2.5 times the control. Monitoring the APTT in these cases may be complicated and clinical observation for signs of bleeding is important. In critically ill, non-bleeding patients with DIC, prophylaxis for venous thromboembolism with prophylactic doses of heparin or low molecular weight heparin is recommended. Consider treating patients with severe sepsis and DIC with recombinant human activated protein C (continuous infusion, 24 microg/kg/h for 4 d). Patients at high risk of bleeding should not be given recombinant human activated protein C. Current manufacturers guidance advises against using this product in patients with platelet counts of <30 x 10(9)/l. In the event of invasive procedures, administration of recombinant human activated protein C should be discontinued shortly before the intervention (elimination half-life approximately 20 min) and may be resumed a few hours later, dependent on the clinical situation. In the absence of further prospective evidence from randomised controlled trials confirming a beneficial effect of antithrombin concentrate on clinically relevant endpoints in patients with DIC and not receiving heparin, administration of antithrombin cannot be recommended. In general, patients with DIC should not be treated with antifibrinolytic agents. Patients with DIC that is characterised by a primary hyperfibrinolytic state and who present with severe bleeding could be treated with lysine analogues, such as tranexamic acid (e.g. 1 g every 8 h).
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PMID:Guidelines for the diagnosis and management of disseminated intravascular coagulation. British Committee for Standards in Haematology. 1922 77


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