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Apparent heparin resistance from elevated factor VIII during pregnancy
R A Raschke1, J R Guidry, M R Foley
1Department of Internal Medicine, Critical Care, Good Samaritan Regional Medical Center, Phoenix, Arizona, USA. robertr@samaritan.edu
Obstetrics and Gynecology
|November 30, 2000
Summary
Pregnancy can cause heparin resistance due to elevated factor VIII. Monitoring heparin with anti-Xa levels, not APTT, is crucial for effective treatment and preventing complications like hematuria.
Area of Science:
- Obstetrics and Gynecology
- Hematology
- Pharmacology
Background:
- Heparin resistance is defined as requiring over 35,000 units of heparin daily for therapeutic activated partial thromboplastin time (APTT).
- Elevated factor VIII levels can falsely suggest heparin resistance by interfering with APTT results without impacting heparin's antithrombotic activity.
Observation:
- A 41-year-old pregnant patient at 25 weeks gestation with a twin pregnancy presented with deep venous thrombosis requiring high heparin doses, leading to hematuria.
- The patient was diagnosed with apparent heparin resistance attributed to elevated factor VIII.
Findings:
- Heparin dosage was adjusted based on anti-Xa heparin monitoring, leading to the resolution of deep venous thrombosis and hematuria.
- Factor VIII levels increase significantly during pregnancy, potentially causing apparent heparin resistance.
Implications:
- Anti-Xa heparin level monitoring is superior to APTT for managing heparin therapy in pregnant patients with apparent heparin resistance.
- Accurate heparin monitoring is essential for optimizing treatment and preventing adverse events in pregnancy.