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[Oral contraception and surgery].


 Oral contraceptives (OCs) and surgery are both recognized risk factors for thromboembolism. Observation of a postoperative deep venous thrombosis and pulmonary embolism in a 21-year-old OC user prompted the authors to define the risk of OC use in surgical patients through a review of the literature. The patient had no other relevant risk factors except a moderate smoking habit. Surgery increases risk of thromboembolism because of the postoperative hypercoagulation state with declines in AT III, elevation of fibrinogen and products of degradation of fibrin, decline of plasminogen, and elevation of antiplasmin. The risks are greater in the immobile postsurgical phase and are increased as well by direct vascular lesions during surgery. Estimates of rates of deep venous thrombosis are very variable according to different authors because of the difficulties of diagnosis, heterogeneity of risk factors encountered, and variety of prophylactic methods employed. The most thrombogenic surgery is believed to be that on the legs; 1 literature review produced a range of estimates from 45-70% without prophylaxis and with 2% involving fatal pulmonary emboli. Another study estimated the risk of deep venous thrombosis at 2% for young subjects in good health undergoing minor surgery lasting less than 30 minutes and at 10-40% for subjects over 40 undergoing moderately serious general surgical procedures. No ideal method of prevention has been found that is well accepted by patients, nurses, and physicians. OC use entails multiple physiopathologic modifications including among others alterations of the vascular walls with endothelial proliferation and/or thickening of the media, increased blood viscosity, hyperaggregability of platelets, and increases in certain coagulation factors. Synthetic estrogens play the major role in modifications but progestins diminish venous tone and increase stasis. Large epidemiologic studies in the US and Great Britain found a significantly increased thromboembolic risk in OC users beginning in the 1st month of use and persisting until 3-4 weeks after termination of treatment. Most authors believe that OC use increases the postsurgical risk of thromboembolism by a factor of about 3. More selective choice of OC users, reduced estrogen doses, and better surveillance of users appear to have diminished the risk of thromboembolic disease with OC use. But unfortunately there are no sure predictors of thromboembolic disease. All authors recognize the reversibility of modifications caused by OCs on hemostasis by 4 weeks after termination. If therefore is recommended that OC use be interrupted 1 cycle before surgery.
