The Committee on Practice Bulletins—Gynecology of the American College of Obstetricians and Gynecologists (ACOG) has developed a practice bulletin on the prevention of deep venous thrombosis (DVT) and pulmonary embolism (PE). ACOG Practice Bulletin No. 21 appears in the October 2000 issue of Obstetrics and Gynecology.

The ACOG bulletin reviews the following areas of prevention of thromboembolism in gynecologic patients: background, including detection of DVT; prophylaxis in surgery; hypercoagulable states; prophylaxis alternatives (graduated compression stockings, pneumatic compression, low-dose heparin and low-molecular-weight heparin); anesthesia concerns; and clinical considerations and recommendations.

The ACOG committee makes the following recommendations for alternatives to thromboprophylaxis in moderate-risk patients undergoing gynecologic surgery based on good and consistent scientific evidence:

• Thigh-high graduated compression stockings should be placed intraoperatively and continued until the patient is fully ambulatory.

• Pneumatic compression should be placed intraoperatively and continued until the patient is fully ambulatory.

• Unfractionated heparin (5,000 U) should be administered two hours before surgery and continued postoperatively every eight hours until the patient is discharged.

• Low-molecular-weight heparin (dalteparin, 2,500 antifactor-Xa U, or enoxaparin, 40 mg) should be admin istered 12 hours before surgery and once a day postoperatively until the patient is discharged.

In high-risk patients, especially those undergoing gynecologic surgery for malignancy, the ACOG committee recommends the following alternatives:

• Pneumatic compression should be placed intraoperatively and continued until the patient is fully ambulatory.

• Unfractionated heparin (5,000 U) should be administered eight hours before surgery and continued postoperatively until discharge.

• Dalteparin (5,000 antifactor-Xa U) should be administered 12 hours before surgery and once a day thereafter.

• Enoxaparin (40 mg) should be administered 12 hours before surgery and once a day thereafter.

The ACOG committee also makes the following recommendations based primarily on consensus and expert opinion:

• Low-risk patients undergoing gynecologic surgery do not require specific prophylaxis other than early ambulation.

• Postoperative prophylaxis should be continued for seven days or until the patient is discharged.

Clinical Considerations and Recommendations

Who are candidates for perioperative DVT thromboprophylaxis? Candidates include patients who have protein C, protein S or antithrombin III deficiencies; those who have the factor V Leiden or prothrombin gene mutation G20210A without a personal history of thrombosis; or those who experience orthopedic trauma, especially if there is a family history of thrombosis.

Which prophylactic methods should be considered for low-, moderate- and high-risk patients undergoing gynecologic surgery? Low-risk patients usually do not need prophylaxis if they are quickly mobilized. Patients in the moderate-risk category would most likely benefit from graduated compression stockings, pneumatic compression, low-dose unfractionated heparin, with the first dose given before surgery, or low-dose low-molecular-weight heparin. The length and complexity of surgery, the patient's age and the evaluation of other risk factors should also be considered. High-risk patients should be given standard heparin in a dosage of 5,000 U every eight hours. Adding graduated compression stockings or pneumatic compression to anticoagulant therapy may also benefit patients.

Should oral contraceptives or hormone replacement therapy be discontinued before surgery? There are no studies confirming a clinical benefit from discontinuing oral contraceptives or hormone replacement therapy before surgery. However, it takes four to six weeks for hypercoagulable changes to return to normal after discontinuing oral contraceptives. The risk of stopping therapy must be balanced against the risk of pregnancy, which carries a much higher risk of DVT, the effects of surgery and anesthesia on pregnancy, and the subsequent possibility of miscarriage.

Who should be tested for clotting abnormalities, and which tests should be ordered? All white patients (i.e., all patients who are not Hispanic, Asian or black) who have a history of DVT may be tested for the factor V Leiden mutation. In nonwhite patients, the decision to test should be individualized. Depending on the patient's history, testing for the prothrombin gene mutation G20210A, deficiencies in the natural inhibitors, antiphospholipid antibodies and fasting plasma homocystine levels may also be beneficial.

Should patients receiving prolonged heparin therapy be evaluated for heparin-induced osteoporosis or heparin-induced thrombocytopenia? Heparin-induced osteoporosis appears to occur predominantly in patients taking heparin for seven weeks or longer, and it is not an issue for those taking prophylactic or short-term doses. Heparin-induced thrombocytopenia is uncommon with the use of porcine heparin and is less common with low-molecular-weight heparin. Platelet counts should be monitored for up to 15 days to avoid the consequences of immune-related thrombocytopenia.

Should low-molecular-weight heparin be used in patients undergoing regional anesthesia? No regional anesthesia should be employed within 12 hours of an injection of low-molecular-weight heparin, and low-molecular-weight heparin should be withheld at least two hours after removal of an epidural catheter.

Which prophylactic methods are considered cost-effective? Approximately one half of patients with proximal DVT and one third of patients with distal DVT develop a post-thrombotic syndrome with pain, swelling and occasional ulceration of the skin and legs. Prophylaxis with graduated compression stockings, pneumatic compression, low-dose standard heparin or low-molecular-weight heparin is less expensive than no prophylaxis in patients undergoing general abdominal surgery. Routine surveillance is the most expensive strategy because of the lack of sensitivity of non-invasive tests. A cost analysis in the United States deter mined that pneumatic compression was more cost-effective than low-molecular-weight heparin or unfractionated heparin.