Clotting prevention

Stroke A stroke occurs when there is an interruption of blood supply to the brain. An ischemic stroke occurs when a clot prevents blood flow in the brain. A hemorrhagic stroke is when there is a rupture of a blood vessel in the brain. In either case, the brain cells in the affected area die. This area is called an infarct. Medical treatment is required to arrest the damage. More effective treatment can be administered within 6 hours of the onset of stroke. A stroke may result in weakness, paralysis, impairment of speech and memory, or even death. Medical treatment includes the use of anticoagulants to treat stroke victims. 

Mechanism of Action A coumarin derivative that interferes with hepatic synthesis of vitamin K-dependent clotting factors, resulting in depletion of coagulation factors II, VII, IX, and X. Therapeutic Effect Prevents further extension of formed existing clot prevents new clot formation or secondary thromboembolic complications. Pharmacokinetics ... 

Thrombosis/embolism, diagnosis and treatment of disseminated intravascular coagulation (DIG), prophylaxis of deep vein thrombosis (DVT), clotting prevention Gearing intermittent infusion lines (heparin lock) to prevent clot formation at site... 

The coprecipitation of hyaluronic acid and acidified protein in the form of a stringy mucin clot can be prevented by the depolymerizing action of hyaluronidase. This phenomenon forms the basis of the mucin clot prevention test (M. C. P.) developed by Robertson et al. (163) and modified by McClean (104,107). The method is well suited for serial determinations but gives only relative values since the assay results vary inversely with the concentration of the substrate (104). 

For screening purposes, the mucin clot prevention test is the method of choice because of its ease and speed of performance. For quantitative determinations, the turbidimetric or viscometric methods are well suited if used within proper limits. AU three procedures are based on alterations of the high polymeric properties of the substrate. The reductometric method determines the amount of hydrolysis products and is the main tool for studying the mechanism of enz3unic action and the structure of the substrate. 

The mucin clot prevention test, the stringiness test, the AGRA test, and the viscometric assay measure changes in the high polymeric properties of hyaluronic acid. The turbidimetric method determines the amount of unreacted substrate, and the reductometric method estimates the number of glucosidic linkages which have been hydrolyzed. 

Water-soluble laminaran [a] = —12.0° (dissolves in water). Sulfuric laminaran works as a blood clotting preventative. Shows an antitumor activity. 

It gels by cooling after dissolving in hot water Blood clotting prevention. 

The concentration of t-PA in human blood is 2—5 ng/mL, ie, 2—5 ppb. Plasminogen activation is accelerated in the presence of a clot, but the rate is slow. The dissolution of a clot requites a week or more during normal repair of vascular damage (17). Prevention of irreversible tissue damage during a heart attack requires that a clot, formed by mpture of an atherosclerotic plaque, be dissolved in a matter of hours. This rapid thrombolysis (dissolution of the clot) must be achieved without significant tibrinogenolysis elsewhere in the patient. 

Plasma Collection. Human plasma is collected from donors either as a plasma donation, from which the red cells and other cellular components have been removed and returned to the donor by a process known as plasmapheresis, or in the form of a whole blood donation. These are referred to as source plasma and recovered plasma, respectively (Fig. 1). In both instances the donation is collected into a solution of anticoagulant (146) to prevent the donation from clotting and to maintain the stabiUty of the various constituents. Regulations in place to safeguard the donor specify both the frequency of donation and the volume that can be taken on each occasion (147). 

Antihemophilic factor [9001-28-9] (AHF) is a protein found in normal plasma that is necessary for clot formation. It is needed for transformation of prothrombin to thrombin. Administration of AHF by injection or infusion can temporarily correct the coagulation defect present in patients with hemophilia. Antihemophilic factor VIII (Alpha Therapeutic) has been approved by the FDA as replacement therapy in patients with hemophilia B to prevent bleeding episodes, and also during surgery to correct defective hemostasis (178). 

The condition of the curd on precipitation is important. As the milk starts to gel, agitators in the coagulation tanks are started as the temperature is raised to about 65°C. Under these conditions the protein is thrown out in fine particles. Too slow an agitation will produce large clots difficult to wash whilst too fine a curd also presents washing problems. In order to obtain the requisite consistency of the precipitate it may be necessary to add inorganic material to the skimmed milk. For example, the addition of phosphate ions will prevent undesirable flaky polymer. Similarly, calcium-deficient casein will not coagulate satisfactorily and the addition of calcium ions may be necessary. 

Coumarin/warfarin, given at a typical dosage of 4 to 5 mg/day, prevents the deleterious formation in the bloodstream of small blood clots and thus reduces the risk of heart attacks and strokes for individuals whose arteries contain sclerotic plaques. Taken in much larger doses, as for example in rodent poisons, Coumarin/warfarin can cause massive hemorrhages and death. 

Calcium ions in blood trigger clotting. To prevent that in donated blood, sodium oxalate, Na2C204, is added to remove calcium ions according to the following equation. 

Dipyridamole is a PDE5/PDE6 selective inhibitor that is used widely in conjunction with aspirin to reduce clotting and prevent stroke. More recent studies with a fixed combination of these two drugs (Aggrenox) has been shown in the recent European Stroke Prevention Study 2 to be of greatly added benefit over aspirin alone for prevention of recurrent stroke. 

Heparin inhibits the formation of fibrin clots, inhibits the conversion of fibrinogen to fibrin, and inactivates several of the factors necessary for the clotting of blood. Heparin cannot be taken orally because it is inactivated by gastric acid in the stomach therefore, it must be given by injection. Heparin has no effect on clots that have already formed and aids only in preventing the formation of new blood clots (thrombi). The LMWHs act to inhibit clotting reactions by binding to antithrombin HI, which inhibits the synthesis of factor Xa and the formation of thrombin. 

Prevention of clotting in arterial and heart surgery, in blood transfusions and dialysis procedures, and in blood samples for laboratory purposes ... 

Prevention of clotting in equipment used for extracorporeal (occurring outside the body) circulation ... 

Although the exact action of the thrombolytic dragp is slightly different, these drugs break down fibrin clots by converting plasminogen to plasmin (fibrinolysin). Plasmin is an enzyme that breaks down the fibrin of a blood clot. This reopens blood vessels after their occlusion and prevents tissue necrosis. 

Blood platelets are key players in the blood-clotting mechanism. These tiny fragments of cytoplasm are shed into the circulation from the surface of megakaryocytes located in the bone marrow. When the lining of a blood vessel is injured, activated platelets release clotting factors, adhere to each other and to damaged surfaces, and send out numerous filopodia. The shape changes that occur in activated platelets are the result of actin polymerization. Before activation, there are no microfilaments because profilin binds to G-actin and prevents its polymerization. After activation, profilin dissociates from G-actin, and bundles and networks of F-actin filaments rapidly appear within the platelet. 

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