TRATAMIENTO DE LA TROMBOSIS VENOSA PROFUNDA Y DE LA EMBOLIA PULMONAR
Guía de la American Heart Association (1996)
Diagnóstico del tromboembolismo venoso en la paciente embarazada
El diagnóstico de la TVP durante el embarazo es difícil ya que el dolor y la hinchazón de piernas son frecuentes y no siempre están ligados a una trombosis (231), siendo un problema la utilización de procedimientos radiológicos por la influencia que puedan tener sobre el feto.
Trombosis Venosa Profunda
As in the nonpregnant patient, venous ultrasonography is used as the initial diagnostic test. If venographic confirmation of an equivocal test result is required, a limited venogram can be performed without risk to the fetus by covering the patient's abdomen with a lead-lined apron. A limited venogram allows visualization of the calf veins, popliteal vein, and most of the superficial femoral vein but not the iliac vein. Therefore, a normal limited venogram does not exclude iliac vein thrombosis.
The diagnosis of PE in pregnancy is essentially the same as in the nonpregnant patient, with three exceptions designed to avoid exposure of the fetus to ionizing radiation: (1) Ventilation and perfusion scanning are performed at 50% of the usual dose; (2) pulmonary angiography, if indicated, should be performed via the brachial route rather than the femoral route; and (3) venography, if indicated, should be limited, with shielding of the abdomen. Chest radiography, perfusion, and ventilation lung scanning are performed with a reduced dose of radioisotope for the perfusion scan (1 to 2 MCi). If the perfusion scan is normal, PE is excluded; if the lung scan indicates a high probability of PE, the diagnosis is made and the patient is treated with anticoagulants. If the scan is nondiagnostic, the patient is investigated for DVT by IPG or duplex ultrasound; if the test results are abnormal, the patient should be treated with anticoagulants. If the results are normal, a pulmonary angiogram should be considered
Tratamiento del tromboembolismo venoso durante el embarazo
An excellent review of this subject has been published,232 and the recommendations outlined below follow this report, which should be read for additional details.
Heparin: A recent critical review of the literature of heparin therapy during pregnancy233 reported that, contrary to a previous report,234 heparin therapy during pregnancy is safe for the fetus. The conclusion is corroborated by a cohort study in which the rates of premature birth, spontaneous abortion, stillbirth, neonatal death, and congenital malformation were not significantly higher in 100 pregnant women treated with heparin than in the normal population.235 Because heparin does not cross the placenta, there is no increased risk of bleeding for the fetus.
Warfarina: In the review cited previously, the pooled rate of adverse effects associated with warfarin therapy was high (26.1%).233 Warfarin exposure between 6 and 12 weeks of gestation can be associated with warfarin embryopathy, which is characterized by stippled epiphyses and nasal hypoplasia. In a study by Iturbe-Alessio et al,236 10 of 35 term pregnancies in which warfarin was administered between 6 and 12 weeks were associated with warfarin embryopathy. This is likely to be an overestimate, and the true incidence of warfarin embryopathy is likely to be ~5% of infants if maternal exposure occurs between 6 and 12 weeks of gestation. Warfarin embryopathy has not been reported with warfarin exposure outside this time period. Central nervous system abnormalities, both hemorrhage and malformations, have been reported after warfarin exposure at any time during pregnancy, but the incidence is very low.233,236 Therefore, heparin is the anticoagulant of choice for treatment of VTE during pregnancy. If warfarin is used, it should be restricted to the second and early third trimesters and avoided between 6 and 12 weeks of gestation and near term to avoid delivery of an anticoagulated fetus.
Tratamiento de la TVP y EP agudas
Heparin is usually initiated with an intravenous bolus of 5000 U followed by a maintenance dose administered as a continuous intravenous infusion of 32 000 U per 24 hours to prolong the aPTT into the therapeutic range (~1.8 to 2.5 times control for most reagents) for 5 to 7 days. After the initial intravenous dose of heparin, subcutaneous heparin should be administered every 12 hours in doses adjusted to prolong a 6-hour postinjection aPTT into the therapeutic range. The aPTT should be checked regularly, because heparin requirements may vary as pregnancy progresses. The patient should be monitored three times in the first week and then at least weekly thereafter. Anticoagulant therapy should be continued throughout pregnancy and for 4 to 6 weeks after delivery. If the episode of VTE occurs late in pregnancy, anticoagulation should be continued for a total of 3 months after the episode.
Tratamiento anticoagulante crónico antes del embarazo
Patients who receive long-term warfarin therapy before pregnancy for DVT/PE or prevention of systemic embolism should be treated with subcutaneous heparin every 12 hours throughout pregnancy in doses adjusted to prolong the 6-hour postinjection aPTT to ~1.5 to 2.5 times control. Two options are available when patients receiving long-term anticoagulant therapy decide to conceive. The first is to switch the patient to heparin before conception. This has the advantage of avoiding any exposure of the fetus to warfarin but increases the duration of heparin exposure if conception is delayed. The second option is to continue warfarin and perform regular pregnancy tests when conception is attempted. As soon as the pregnancy test result is positive, warfarin should be stopped and heparin started. This is probably safe for the fetus, provided warfarin is discontinued before 6 weeks of gestation. As mentioned above, no cases of fetal embryopathy have been described with warfarin exposure before 6 weeks of gestation. Warfarin therapy can be resumed after delivery.
Tormbosis venosa profunda y embolia pulmonar previas
The optimal treatment of pregnant patients with previous DVT/PE is unknown because there are no large prospective trials to provide reliable estimates of the incidence of recurrence during pregnancy. Prophylaxis with standard heparin, 5000 U every 12 hours, is a reasonable approach and is associated with a very low recurrence rate.235 Surveillance with weekly IPG or duplex ultrasonography may be a reasonable alternative to heparin during pregnancy.
Parto y post-parto
If the patient is receiving 5000 U of heparin every 12 hours at term, heparin can be discontinued at onset of labor. No increase in bleeding is anticipated with this approach. If adjusted-dose heparin is being administered at term, some pregnant patients can have a prolonged aPTT for as long as 20 hours after their last dose of subcutaneous heparin.237 To overcome the potential risk of a long aPTT at delivery, elective induction can be planned and heparin therapy discontinued 24 hours before induction. In patients considered to be at high risk for thrombotic complications, an intravenous heparin infusion can be started after discontinuation of subcutaneous heparin. Because the half-life of intravenous heparin is short,238 heparin can be discontinued 4 to 6 hours before delivery with the expectation that the aPTT will be normal at time of delivery. After delivery, heparin and warfarin should be restarted as soon as hemostasis is obtained, and heparin can be discontinued after an appropriate period of overlap. When administered to the nursing mother, warfarin is safe for the breastfed infant.239,240
Otras modalidades terapeúticas
Existen pocos informes acerca del uso de la trombolisis durante el embarazo. Como regla general, la trombolisis es una contraindicación relativa a la terapia trombolítica y su uso se debe restringuir a pacientes con embolia pulmonar masiva (241). Las heparinas de bajo peso molecular no cruzan la placenta y han sido utilizadas con éxito durante el embarazo (169, 243, 244) . Sus ventajas sobre la heparina estándar son una respuesta más predecible, una mas larga semivida después de la inyección subcutánea que permite una única dosis al día sin la necesodad de una monitorización frecuente (244)