Postoperative Deep Venous Thrombosis
Deep venous thrombosis is a known complication of surgery. The risk of developing deep venous thrombosis increases with age, prolonged surgery, pelvic surgery, obesity, and cancer, amongst other factors. Chemical and mechanical prophylactic measures are indicated in these patients. In addition, it is well-known that patients such as the ones described above are still at risk for developing deep venous thrombosis after discharge from the hospital. Chemical prophylaxis in the form of low molecular weight heparin given subcutaneously on a daily basis or oral anticoagulants are commonly prescribed for two to three weeks after discharge.
Deep venous thrombosis in the postoperative period may occur despite mechanical and chemical prophylaxis in the hospital. Early signs of deep venous thrombosis of the lower extremity veins include pain and swelling. The swelling is worse if the veins involved are proximal. A known complication of proximal deep venous thrombosis of the lower extremities is the development of a pulmonary embolus. Clot forming in the proximal veins of the leg may break off and travel to the right side of the heart and out of the right ventricle into the main pulmonary artery and then into the branches of this vessel. A large clot may go into the right and left branches of the pulmonary artery. This causes sudden obstruction to the outflow of the blood from the right ventricle leading to right ventricular strain and life-threatening arrhythmias. The blockage of blood flow into the lungs may interfere with the blood picking up oxygen as it travels through the lungs, leading to acute hypoxia and possible death. Early recognition of deep venous thrombosis is, therefore, critical as immediate administration of therapeutic anticoagulation is required to prevent clot propagation and embolization.
If untreated, thrombus forming in the proximal veins of the lower extremities can continue to build up and the clot extend more proximally into the iliac veins. This thrombus is unstable and may fragment and travel to the lungs resulting in a pulmonary embolus. The fragments of thrombus embolizing to the pulmonary artery from proximal vein thrombus tend to be larger than emboli coming from more distal veins in the legs. The chances of causing more damage to the heart and lungs is, therefore, greater when a proximal thrombus embolizes. Due to the risk of embolization, it is imperative that patients found to have proximal vein thrombus be therapeutically anticoagulated as soon as possible to prevent more thrombus from forming and prevent the thrombus from embolizing.