General Medical Information

Thromboembolic Diseases

David M. Barrs

Deep vein thrombosis and pulmonary embolization are significant postoperative problems. The major risk factors are immobilization, prior history of thromboembolic disease (especially in the presence of varicose veins), oral contraceptives and estrogen compounds, age older than 40 years, and hypercoagulable states, including erythrocytosis, thrombocytosis, and inherited deficiencies of the substances antithrombin III, protein C, and protein S resulting in decreased lysis of clots.

Preventive Measures
The pharmacologic methods of prevention of thromboembolic complications, such as heparin, aspirin, or warfarin, are quite effective, but they require starting the patient on treatment before surgery, which increases the risk of bleeding during surgery. Mechanical preventative measures usually are used first in otolaryngology patients. Any method designed to increase lower extremity blood return is helpful. Traditional measures include early mobilization, leg elevation, elastic stockings, and physical therapy. A newer innovation is the external pneumatic compression boot, which is applied to the calf and thigh. The boot is intermittently inflated, the pressure held, and then deflated to massage blood up from the lower extremity. These boots have been highly effective in preventing thromboembolic disease and should be considered for any patient who may not be mobilized early or who is undergoing a neurotologic, neurosurgical, or airway procedure in which heparin may not be indicated for thromboembolic control. Caution with these devices should be observed for patients who have severe peripheral arterial vascular disease, because vascular supply to the lower extremity may be compromised.

Diagnosis
The risk of embolization from calf vein thrombosis is usually small, but thrombosis propagation to the more proximal femoral and iliac veins markedly increases the chance of pulmonary embolization. Accurate diagnosis of postoperative deep vein thrombosis is difficult but important to prevent unnecessary anticoagulant therapy. A positive Homan’s sign, unexplained fever, pitting edema, and localized discomfort or discoloration over leg veins may indicate underlying deep vein thrombosis. These signs, however, are quite insensitive and may give little indication of a serious deep vein thrombosis. When it is suspected, objective testing should be performed. Contrast venography, with contrast material injected into a foot vein, is the definitive test, but it is associated with a significant number of complications. The most accurate noninvasive test is real-time (duplex) ultrasound, which is less sensitive to calf thrombosis than the more proximal femoral and iliac thrombosis.

Pulmonary Embolism
Despite preventive measures, deep vein thrombosis and subsequent pulmonary embolization may develop. The diagnosis is difficult, but pulmonary embolization should be suspected in patients with sudden onset of tachypnea, dyspnea, chest pain, hemoptysis, hypnoxia, or arrhythmias. A ventilation-perfusion scan is obtained. A normal result indicates little likelihood of a pulmonary embolization, but any other result on the perfusion scan may require the use of pulmonary angiography, depending on the degree of risk for emboli in the patient.

Management
Anticoagulation with heparin followed by oral anticoagulants is necessary in all patients with proximal deep vein thrombosis and pulmonary embolization. In neurotologic, skull base, or procedures in the airway, the risk of bleeding must be considered. In other cases, heparin should be given immediately and continued for 7 to 10 days. A loading dose of 5,000 to 10,000 U of heparin is given intravenously, followed by 1,000 to 2,000 U/h through an infusion. The PTT should be maintained in a range of 1.5 to 2 times control. Oral warfarin anticoagulant therapy is initiated and overlapped to maintain control. In severe cases, streptokinase, urokinase, or recombinant tissue plasminogen activator should be considered as thrombolytic therapy. All bleeding times are prolonged with thrombolytic therapy, and concurrent heparin therapy should not be used. Heparin should be started, however, after discontinuation of thrombolytic therapy, which usually lasts for 1 to 3 days. Inferior vena caval interruption is used when anticoagulation is contraindicated or there are recurrent emboli in adequately anticoagulated patients.