Obstetric Anesthesia Venous Thromboembolic Disease and Pregnancy

Venous thromboembolism (VTE) is more common and is more difficult to diagnose in pregnant patients compared with nonpregnant women. The incidence of VTE is 0.76 to 1.72 per 1000 pregnancies, approximately 4 times the risks that are encountered in nonpregnant women. Although deep vein thrombosis (DVT) occurs mostly in the antepartum period, evenly distributed in all 3 trimesters, 43% to 60% of pulmonary embolisms (PEs) occur in the puerperium. Pulmonary embolism is the leading cause of maternal death in developed countries, with these deaths related to delayed diagnosis, delayed or inadequate treatment, and inadequate thromboprophylaxis. Pregnancy results in a hypercoagulable state owing to the increased levels of coagulation factors and fibrin and to decreased fibrinolytic activity and free protein S levels. In uncomplicated pregnancies, these changes are accompanied by hemostatic activation. Venous flow velocity is reduced in the legs by 25 to 29 weeks’ gestation and lasts until 6 weeks postpartum. Up to 50% of VTEs in pregnant women are associated with an inherited or acquired thrombophilia. Although these conditions have a high incidence, VTE is rare, rendering universal screening of pregnant women not cost-effective. Diagnosis of VTE is based on clinical suspicion, although many signs and symptoms of DVT and PE are normal in pregnancy. Pregnant women with features suggesting VTE should have testing performed as soon as feasible. Treatment with lowYmolecular weight heparin (LMWH) may be started until the diagnosis is ruled out. Compression ultrasonography is the noninvasive test of choice in pregnant women with suspected VTE. Management of VTE during pregnancy includes the use of unfractionated heparin or LMWH (both of which do not cross the placenta); warfarin does cross the placenta and is a teratogen. LowYmolecular weight heparin is now recommended because it has predictable pharmacokinetics without requiring monitoring and has a reduced risk of heparin-induced thrombocytopenia. A twice-daily weight-based regimen is recommended, although once-daily dosing is possible. Management guidelines for patients during labor and delivery suggest that spinal anesthesia may be performed 12 hours after the last dose of prophylactic LMWH and 24 hours after the last dose of therapeutic LMWH. Once women begin labor, no additional heparin should be provided. After delivery, LMWH may be used if the patient has no persistent bleeding, but its initiation should be delayed for 12 hours or longer after the epidural catheter is removed. After neuraxial anesthesia, therapeutic LMWH should not be given for at least 24 hours postoperatively or postpartum or in the presence of inadequate hemostasis. Anticoagulation therapy with LMWH or warfarin is recommended for at least 6 weeks postpartum and sometimes for as long as 6 months. Postthrombotic syndrome occurs in up to 60% of patients after DVT; compression stockings decrease the risk and should be worn on the affected leg for 2 years after the immediate event. Thrombolytic therapy in patients with massive PE can begin 1 hour after vaginal delivery and within 12 hours after cesarean delivery. Patients with PE late in pregnancy and during labor should be treated with oxygen and intravenous heparin. When the patient goes into active labor if a cesarean delivery is anticipated, heparin should be stopped. If a patient is in a fully anticoagulated state, cesarean delivery may be associated with uncontrolled bleeding and maternal death. For women who have had a previous VTE, graduated compression stockings are recommended both antepartum and postpartum because these women have a high risk of a recurrent VTE during pregnancy. Postpartum LMWH or warfarin treatment is recommended for at least 6 weeks. Aspirin is not recommended. Antepartum pharmacologic prophylaxis is more controversial and depends on the patient’s status and history. Women with 2 or more previous VTEs or with high-risk thrombophilias, whether they have had a previous VTE, should receive antenatal thromboprophylaxis. Close clinical monitoring is needed for women who decide against thromboprophylaxis. Venous thromboembolism after cesarean delivery is uncommon, but it can cause serious complications and death. The incidence of PE after cesarean delivery is greater than after vaginal delivery. For those with 1 risk factor for thromboembolism (age 935 years, obesity, parity 93, gross varicose veins, infection, preeclampsia, immobility for 94 days before operation, major current illness, and emergency cesarean delivery during labor), LMWH or compression stockings should be used. Those with more than 2 risk factors, those have undergone cesarean hysterectomy, and those with previous DVT or known thrombophilia are considered to be high-risk individuals, and LMWH and compression stockings are recommended.