Heparin is generally used for anticoagulation for the following conditions:

Acute coronary syndrome, e.g., NSTEMI
Atrial fibrillation
Deep-vein thrombosis and pulmonary embolism
Cardiopulmonary bypass for heart surgery
ECMO circuit for extracorporeal life support
Hemofiltration
Indwelling central or peripheral venous cathetersHeparin and its low-molecular-weight derivatives (e.g., enoxaparin, dalteparin, tinzaparin) are effective in preventing deep vein thromboses and pulmonary emboli in people at risk, but no evidence indicates any one is more effective than the other in preventing mortality.In angiography, 2 to 5 units/mL of unfractionated heparin saline flush is used to prevent the clotting of blood in guidewires, sheaths, and catheters, thus preventing thrombus from dislodging from these devices into the circulatory system .Unfractionated heparin is used in hemodialysis. Comparing to low-molecular-weight heparin, unfractionated heparin does not have prolonged anticoagulation action after dialysis, and low cost. However, the short duration of action for heparin would require it to maintain continuous infusion to maintain its action. Meanwhile, unfractionated heparin has higher risk of heparin-induced thrombocytopenia. Adverse effects
A serious side-effect of heparin is heparin-induced thrombocytopenia (HIT), caused by an immunological reaction that makes platelets a target of immunological response, resulting in the degradation of platelets, which causes thrombocytopenia. This condition is usually reversed on discontinuation, and in general can be avoided with the use of synthetic heparins. Also, a benign form of thrombocytopenia is associated with early heparin use, which resolves without stopping heparin. Two non-hemorrhagic side-effects of heparin treatment are known. The first is elevation of serum aminotransferase levels, which has been reported in as many as 80% of patients receiving heparin.
Siderosis is the deposition of excess iron in body tissue. When used without qualification, it usually refers to an environmental disease of the lung, also known more specifically as pulmonary siderosis or Welders disease, which is a form of pneumoconiosis. Pulmonary siderosis was first described in 1936 from X-ray images of the lungs of arc welders.The name siderosis comes from Ancient Greek word for iron, sídēr(os), and has an -osis suffix. Signs and symptoms
Pulmonary siderosis doesnt usually cause harmful scar tissue formation within the lungs, which is why it said to be non-fibrotic condition, unlike asbestosis for example, and has also been called "benign pneumoconiosis".Mild to moderate scarring of the lungs has been found in unusual cases of pulmonary siderosis. These people have had persistent breathlessness, coughing and decreased lung function. However, people in occupations where they are exposed to iron (or rust) dust are usually also exposed to other forms of dust such as silica, which upon repeated inhalation is known to cause dangerous silicosis. Because of this, it is not known for certain whether the inhalation of pure iron or rust can cause detrimental scarring of the lungs that has been seen in some cases of pulmonary siderosis. Still, studies have shown lack of silica in tissue samples collected from people with pulmonary siderosis.