Heparin quick review

• Description: a sulfated glycosaminoglycan characterized by having anticoagulant activity, biosynthesized and stored in mast cells of various tissues.

• Health benefits: used as an anticoagulant in conjunction with invasive surgical procedures and dialysis procedures, to prevent clotting in intravenous lines and in the treatment of thrombolytic disorders.

• Side effects: a serious side effect of heparin is heparin induced thrombocytopenia (HIT syndrome).

Heparin

Heparin is a sulfated glycosaminoglycan with a backbone comprised of alternating hexuronic, either L-iduronic or D-glucuronic and D-glycocyamine residues joined in alternating 1, 4 linkages. Heparin is one of glycosaminoglycans and is characterized by having anticoagulant activity. Glycosaminoglycans are the polysaccharide portions of proteoglycans. Heparin is biosynthesized and stored in mast cells of various tissues, most notably liver, lung, and gut. Heparin exerts its anti-coagulant effect by increasing the rate of formation of an irreversible complex between thrombin and antithrombin III. The heterologous nature of heparin is due to the varying degree and location of sulfate substitution on these residues giving rise to at least ten different monosaccharide building blocks within the polymer. Heparin is polydisperse with a molecular weight range from 3,000-30,000 with many structural variations within a given chain. The exact composition of heparin varies depending on its source, which usually is porcine intestinal mucosa, bovine lung, bovine intestinal mucosa, or ovine intestinal mucosa and also depending on the method for its preparation and purification.

Heparin health benefits

Heparin works by potentiating the action of antithrombin III, as it is similar to the heparan sulfate proteoglycans which are naturally present on the cell membrane of the endothelium. It decreases the rate of coagulation by increasing the rate at which antithrombin III, inhibits activated coagulation factors, particularly thrombin, a key enzyme in the coagulation cascade. Because antithrombin III

inactivates many coagulation proteins, the process of coagulation will slow down. Heparin exhibits a variety of biological activities. Heparin binds to a wide variety of cell growth factors, cytokines and cell adhesion molecules.

Heparin is often used as a treatment for certain blood vessel, heart, and lung conditions. Heparin will not dissolve blood clots that have already formed, but it may prevent the clots from becoming larger and causing more serious problems. Heparin has been used for already a long time as an anticoagulant and antithrombotic agent in the treatment and prevention of venous thrombosis. Heparin is also used to prevent blood clotting during open-heart surgery, bypass surgery, and dialysis. Heparin is widely used as an anticoagulant in conjunction with invasive surgical procedures and dialysis procedures, to prevent clotting in intravenous lines and in the treatment of thrombolytic disorders. Heparin has been used in surgery of the heart and blood vessels, with organ transplants and artificial organs, for cardiovascular diagostic techniques, and for the control and prevention of thromboembolism following surgical operations. At the conclusion of these procedures, the anticoagulation effects of heparin must be neutralized or reversed in order to prevent the patient from bleeding.

Heparin protection of cellular destruction and enhancement of revascularization and heparin induced epithelialization and re-epithelialization can be favorably applied to treat dermatitides, fissures, and fistulas that are difficult to heal, or are refractory to current methods of treatment. Heparin by itself (without a steroid) enhances the intensity of angiogenesis induced by tumors and by tumor derived factors in vivo, although in the absence of tumor cells or tumor extracts or tumor derived factors neither heparin nor the mast cells which release heparin could induce angiogenesis.

Side effects (heparin induced thrombocytopenia, or HIT syndrome)

A serious side effect of heparin is heparin induced thrombocytopenia (HIT syndrome). The inadequate production of platelets or increased platelet destruction is called thrombocytopenia. There are two types of thrombocytopenia associated with heparin use. Type I or drug-induced nonimmune thrombocytopenia may occur within 48 to 72 hours of administration. Type II thrombocytopenia is a drug-induced immune thrombocytopenia (formation of antibodies against platelets). HIT is caused by an immunological reaction that makes platelets form clots within the blood vessels, thereby using up coagulation factors. Formation of platelet clots can lead to thrombosis, while the loss of coagulation factors and platelets may result in bleeding. HIT can (rarely) occur shortly after heparin is given, but also when a person has been on heparin for a long while. HIT typically develops 4-14 days after the administration of heparin. Heparin (UFH) is used in cardiovascular surgery, as prevention or treatment for deep-vein thrombosis and pulmonary embolism and in various other clinical scenarios. LMWH is increasingly used in out patient prohylaxis regimes. Immunologic tests are available for the diagnosis of HIT. There is also a benign form of thrombocytopenia associated with heparin use. Treatment of HIT type II requires immediate discontinuation of all heparin products, including heparin infusions, heparin flushes, and heparin-coated catheters used for hemodynamic monitoring. To block the thrombotic state, lepirudin (Refludan®), bivalirudin, argatroban, danaparoid or other direct thrombin inhibitors are used.