Anticoagulants

Heparin works by inhibiting or inactivating the three major clotting factors—thrombin, thromboplastin, and prothrombin. It slows the process of thromboplastin synthesis, decelerates the conversion of prothrombin to thrombin, and inhibits the effects of thrombin on fibrinogen, blocking its conversion to fibrin. The agent also causes an increase in the number of negatively charged ions in the vascular wall, which helps prevent the formation of intravascular clots.

Heparin is administered either by periodic injections or by an infusion pump. The initial dose is usually 5,000 units, followed by 1,000 units per hour, depending on the patient's weight, age, and other factors. The therapy usually lasts for seven to ten days. Heparin is also used in the treatment of deep vein thrombosis, a serious surgical complication which is also associated with traumatic injury. This condition can lead to immediate death from pulmonary embolism or produce long-term, adverse effects. Patients with pelvic or lower extremity fractures, spinal cord injuries, a previous thromboembolism, varicose veins, and those over age 40 are most at risk. Low-dose heparin is a proven therapy and is associated with only a minimal risk of irregular bleeding.