|
Thrombin Time
The thrombin time (TT), also known as the thrombin clotting time (TCT), is a blood test that measures the time it takes for a clot to form in the plasma of a blood sample containing anticoagulant, after an excess of thrombin has been added. It is used to diagnose blood coagulation disorders and to assess the effectiveness of fibrinolytic therapy. This test is repeated with pooled plasma from normal patients. The difference in time between the test and the 'normal' indicates an abnormality in the conversion of fibrinogen (a soluble protein) to fibrin, an insoluble protein. The thrombin time compares the rate of clot formation to that of a sample of normal pooled plasma. Thrombin is added to the samples of plasma. If the time it takes for the plasma to clot is prolonged, a quantitative (fibrinogen deficiency) or qualitative (dysfunctional fibrinogen) defect is present. In blood samples suspected to contain heparin, a substance derived from snake venom called batroxobin (formerly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thrombin
Prothrombin (coagulation factor II) is encoded in the human by the F2-gene. It is proteolytically cleaved during the clotting process by the prothrombinase enzyme complex to form thrombin. Thrombin (Factor IIa) (, fibrose, thrombase, thrombofort, topical, thrombin-C, tropostasin, activated blood-coagulation factor II, E thrombin, beta-thrombin, gamma-thrombin) is a serine protease, that converts fibrinogen into strands of insoluble fibrin, as well as catalyzing many other coagulation-related reactions. History After the description of fibrinogen and fibrin, Alexander Schmidt hypothesised the existence of an enzyme that converts fibrinogen into fibrin in 1872. Prothrombin was discovered by Pekelharing in 1894. Physiology Synthesis Thrombin is produced by the enzymatic cleavage of two sites on prothrombin by activated Factor X (Xa). The activity of factor Xa is greatly enhanced by binding to activated Factor V (Va), termed the prothrombinase complex. Prothrombin is prod ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Direct Thrombin Inhibitors
Direct thrombin inhibitors (DTIs) are a class of medication that act as anticoagulants (delaying coagulation, blood clotting) by directly inhibiting the enzyme thrombin (factor IIa). Some are in clinical use, while others are undergoing clinical development. Several members of the class are expected to replace heparin (and derivatives) and warfarin in various clinical scenarios. Types There are three types of DTIs, dependent on their interaction with the thrombin molecule. ''Bivalent'' DTIs (hirudin and analogs) bind both to the active site and exosite 1, while univalent DTIs bind only to the active site. The third class of inhibitors, which are gaining importance recently, is the allosteric inhibitors. Bivalent Hirudin and derivatives were originally discovered in ''Hirudo medicinalis'': * Hirudin * Bivalirudin (transient inhibition - is cleaved by thrombin) * Lepirudin * Desirudin Univalent Univalent DTIs include: * Argatroban * Inogatran * Melagatran (and its prodrug ximelagatra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Partial Thromboplastin Time
The partial thromboplastin time (PTT), also known as the activated partial thromboplastin time (aPTT or APTT), is a blood test that characterizes coagulation of the blood. A historical name for this measure is the Kaolin-cephalin clotting time (KCCT), reflecting kaolin and cephalin as materials historically used in the test. Apart from detecting abnormalities in blood clotting, partial thromboplastin time is also used to monitor the treatment effect of heparin, a widely prescribed drug that reduces blood's tendency to clot. The PTT measures the overall speed at which blood clots form by means of two consecutive series of biochemical reactions known as the ''intrinsic'' pathway and common pathway of coagulation. The PTT indirectly measures action of the following coagulation factors: I (fibrinogen), II (prothrombin), V (proaccelerin), VIII (anti-hemophilic factor), X (Stuart–Prower factor), XI (plasma thromboplastin antecedent), and XII (Hageman factor). The PTT is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coagulation Cascade
Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The process of coagulation involves activation, adhesion and aggregation of platelets, as well as deposition and maturation of fibrin. Coagulation begins almost instantly after an injury to the endothelium that lines a blood vessel. Exposure of blood to the subendothelial space initiates two processes: changes in platelets, and the exposure of subendothelial platelet tissue factor to coagulation factor VII, which ultimately leads to cross-linked fibrin formation. Platelets immediately form a plug at the site of injury; this is called ''primary hemostasis. Secondary hemostasis'' occurs simultaneously: additional coagulation factors beyond factor VII ( listed below) respond in a cascade to form fibrin strands, which strengthen the platelet plug. Coagulati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reference Interval
In medicine and health-related fields, a reference range or reference interval is the range or the interval of values that is deemed normal for a physiological measurement in healthy persons (for example, the amount of creatinine in the blood, or the partial pressure of oxygen). It is a basis for comparison for a physician or other health professional to interpret a set of test results for a particular patient. Some important reference ranges in medicine are reference ranges for blood tests and reference ranges for urine tests. The standard definition of a reference range (usually referred to if not otherwise specified) originates in what is most prevalent in a reference group taken from the general (i.e. total) population. This is the general reference range. However, there are also ''optimal health ranges'' (ranges that appear to have the optimal health impact) and ranges for particular conditions or statuses (such as pregnancy reference ranges for hormone levels). Values with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vacutainer
A vacutainer blood collection tube is a sterile glass or plastic test tube with a colored rubber stopper creating a vacuum seal inside of the tube, facilitating the drawing of a predetermined volume of liquid. Vacutainer tubes may contain additives designed to stabilize and preserve the specimen prior to analytical testing. Tubes are available with a safety-engineered stopper, with a variety of labeling options and draw volumes. The color of the top indicates the additives in the vial. Vacutainer tubes were invented by Joseph Kleiner in 1949. ''Vacutainer'' is a registered trademark of Becton Dickinson, which manufactures and sells the tubes today. Principles The Vacutainer needle is double-ended: the inner end is encased in a thin rubber coating that prevents blood from leaking out if the Vacutainer tubes are changed during a multi-draw, and the outer end which is inserted into the vein. When the needle is screwed into the translucent plastic needle holder, the coated end ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxalate
Oxalate (systematic IUPAC name: ethanedioate) is an anion with the chemical formula . This dianion is colorless. It occurs naturally, including in some foods. It forms a variety of salts, for example sodium oxalate (), and several esters such as dimethyl oxalate (). It is a conjugate base of oxalic acid. At neutral pH in aqueous solution, oxalic acid converts completely to oxalate. Relationship to oxalic acid The dissociation of protons from oxalic acid proceeds in a determined order; as for other polyprotic acids, loss of a single proton results in the monovalent hydrogenoxalate anion . A salt with this anion is sometimes called an acid oxalate, monobasic oxalate, or hydrogen oxalate. The equilibrium constant ( ''K''a) for loss of the first proton is ( p''K''a = 1.27). The loss of the second proton, which yields the oxalate ion, has an equilibrium constant of (p''K''a = 4.28). These values imply, in solutions with neutral pH, no oxalic acid and only t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Citrate
Citric acid is an organic compound with the formula . It is a colorless weak organic acid. It occurs naturally in citrus fruits. In biochemistry Biochemistry, or biological chemistry, is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology, a ..., it is an intermediate in the citric acid cycle, which occurs in the metabolism of all aerobic organisms. More than two million tons of citric acid Commodity chemicals, are manufactured every year. It is used widely as acidifier, flavoring, preservative, and chelating agent. A citrate is a derivative of citric acid; that is, the salt (chemistry), salts, esters, and the polyatomic ion, polyatomic anion found in solutions and salts of citric acid. An example of the former, a salt is trisodium citrate; an ester is triethyl citrate. When citrate anion, trianion is part of a salt, the for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Centrifugation
Centrifugation is a mechanical process which involves the use of the centrifugal force to separate particles from a solution according to their size, shape, density, medium viscosity and rotor speed. The denser components of the mixture migrate away from the axis of the centrifuge, while the less dense components of the mixture migrate towards the axis. Chemists and biologists may increase the effective gravitational force of the test tube so that the precipitate (pellet) will travel quickly and fully to the bottom of the tube. The remaining liquid that lies above the precipitate is called a supernatant or supernate. There is a correlation between the size and density of a particle and the rate that the particle separates from a heterogeneous mixture, when the only force applied is that of gravity. The larger the size and the larger the density of the particles, the faster they separate from the mixture. By applying a larger effective gravitational force to the mixture, like ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bivalirudin
Bivalirudin, sold under the brand names Angiomax and Angiox, among others, is a specific and reversible direct thrombin inhibitor (DTI). Chemically, it is a synthetic congener of the naturally occurring drug hirudin, found in the saliva of the medicinal leech '' Hirudo medicinalis''. It is manufactured by The Medicines Company. Bivalirudin lacks many of the limitations seen with indirect thrombin inhibitors, such as heparin. A short, synthetic peptide, it is a potent and highly specific inhibitor of thrombin that inhibits both circulating and clot-bound thrombin, while also inhibiting thrombin-mediated platelet activation and aggregation. Bivalirudin has a quick onset of action and a short half-life. It does not bind to plasma proteins (other than thrombin) or to red blood cells. Therefore, it has a predictable antithrombotic response. There is no risk for heparin-induced thrombocytopenia or heparin-induced thrombosis-thrombocytopenia syndrome. It does not require a bindin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Argatroban
Argatroban is an anticoagulant that is a small molecule direct thrombin inhibitor. In 2000, argatroban was licensed by the US Food and Drug Administration (FDA) for prophylaxis or treatment of thrombosis in people with heparin-induced thrombocytopenia (HIT). In 2002, it was approved for use during percutaneous coronary interventions in people who have HIT or are at risk for developing it. In 2012, it was approved by the UK Medicines and Healthcare products Regulatory Agency for anticoagulation in people with heparin-induced thrombocytopenia Type II (HIT) who require parenteral antithrombotic therapy. Argatroban is given intravenously and drug plasma concentrations reach steady state in 1–3 hours. Argatroban is metabolized in the liver and has a half-life of about 50 minutes. It is monitored by PTT. Because of its hepatic metabolism, it may be used in patients with renal dysfunction. (This is in contrast to lepirudin, a direct thrombin inhibitor that is primarily renally c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dabigatran
Dabigatran, sold under the brand name Pradaxa among others, is an anticoagulant used to treat and prevent blood clots and to prevent stroke in people with atrial fibrillation. It is commonly used to prevent blood clots following hip or knee replacement and in those with a history of prior clots. and is used as an alternative to warfarin; it does not require monitoring by blood tests. In a meta-analysis of seven different studies, there was no benefit of dabigatran over warfarin in preventing ischemic stroke; however, dabigatran was associated with a lower hazard for intracranial bleeding compared with warfarin, but also had a higher risk of gastrointestinal bleeding. It is taken by mouth. Common side effects include bleeding and gastritis. Other side effects may include bleeding around the spine and allergic reactions such as anaphylaxis. In cases of severe bleeding, it can be reversed with the antidote, idarucizumab. Use is not recommended during pregnancy or breast ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
