From the Editor
The battle of the clot
In this issue we review two situations in which low-molecular-weight heparins have special advantages in pregnant women and in patients with...
Paul S. Gibson, MD
Assistant Professor, Department of Medicine and Department of Obstetrics and Gynaecology, University of Calgary, Alberta, Canada
Raymond Powrie, MD
Associate Professor of Medicine and Obstetrics and Gynecology, The Warren Alpert Medical School of Brown University, Women and Infants’ Hospital of Rhode Island, Providence
Address: Paul S. Gibson, MD, HSC-1443, 3330 Hospital Drive NW, Calgary,
AB, Canada T2N 4N1; e-mail gibsonp@ucalgary.ca
Dr. Gibson disclosed receiving honoraria from Leo Pharma Inc. for teaching and speaking.
Women on anticoagulant therapy who are at risk of recurrent venous thromboembolism should be encouraged to wear elastic compression stockings. Intermittent pneumatic compression of the legs via automated devices may be considered for women hospitalized for any reason or on bedrest.
Whichever measures are used, a high index of suspicion and a low threshold for investigating for recurrent thrombosis should be maintained throughout pregnancy and the puerperium.
PERIPARTUM AND POSTPARTUM MANAGEMENT OF ANTICOAGULATION
Heparin therapy must be interrupted temporarily during the immediate peripartum interval to minimize the risk of hemorrhage and to allow for the option of regional anesthesia. As mentioned earlier, because of the theoretical risk of paraspinal hemorrhage in women receiving heparin who undergo epidural or spinal anesthesia, the American Society of Regional Anesthesia guidelines advise waiting to insert the needle at least 10 to 12 hours after the last prophylactic dose of LMWH, and at least 24 hours after the last therapeutic dose. 31
The guidelines state that neuraxial anesthesia is not contraindicated in patients on prophylactic unfractionated heparin. 31
To facilitate use of regional anesthesia in these women, therefore, options include:
Additional advantages to using unfractionated heparin peripartum include the option of obtaining a rapid aPTT measurement to confirm the absence of a significant ongoing heparin effect prior to regional anesthesia or delivery, and the ability to completely reverse the heparin effect with protamine sulfate if major bleeding occurs. LMWHs are only partially reversible. 64
If therapeutic anticoagulation must be interrupted for labor within 1 month of the initial thrombotic event, the risk of recurrent thrombotic complications is high 65; these women must be observed very carefully and may benefit from intravenous heparin before and after delivery. They may even merit placement of a temporary vena cava filter (particularly if less than 2 weeks have elapsed since the venous thromboembolic event and in women with a large deep venous clot burden), a procedure that has been used safely but little studied in pregnant women. 66
Fluoroscopic guidance may be needed for filter placement. This exposes the fetus to radiation, but the low-level exposure at this late gestational age is unlikely to pose a significant risk. The filter may be removed within 1 to 2 weeks postpartum, assuming there are no ongoing contraindications to anticoagulation.
In the rare woman with antithrombin deficiency and a recent or prior thrombotic event, giving antithrombin concentrate during the peripartum (heparin-free) interval has been described and may be considered under the guidance of a hematologist. 67
Ongoing anticoagulation is essential postpartum, as the puerperium is the period of highest day-to-day risk of thromboembolic events: about one-third of pregnancy-associated events occur during these 6 to 12 weeks. 2 Heparin should be resumed 6 to 12 hours after delivery, once hemostasis is confirmed.
In this issue we review two situations in which low-molecular-weight heparins have special advantages in pregnant women and in patients with...