Using anti-Xa level for adjusting intravenous unfractionated heparin infusion in peripartum thromboembolic disease.

Background: Intravenous unfractionated heparin infusion is often used to minimize the duration of time without anticoagulation around delivery in pregnant patients with high thrombotic risk. Activated partial thromboplastin time is commonly used to monitor and adjust heparin dose. However, using activated partial thromboplastin time is problematic in pregnancy because activated partial thromboplastin time response to unfractionated heparin is attenuated due to elevated Factor VIII levels and may lead to incorrect dosing.

Case: We report a case of deep venous thrombosis occurring in a term pregnancy managed by intravenous unfractionated heparin adjusted using anti-Xa level around the time of delivery. We modified the intravenous unfractionated heparin nomogram by using anti-Xa levels instead of activated partial thromboplastin time and observed lower dosing of unfractionated heparin than otherwise required to achieve and maintain target levels.

Conclusion: This report demonstrates the feasibility and effectiveness of using anti-Xa level to monitor and adjust intravenous unfractionated heparin infusion in pregnancy.