Continuous Subcutaneous Heparin Infusion During Pregnancy In A Patient With A Prosthetic Mitral Valve. Clinical And Laboratory Consideration

Administration of heparin for prolonged periods during pregnancy has usually been by the intravenous route when full anticoagulant dosages are required. Bolus subcutaneous injection of heparin has also been used, however this requires medical supervision and proper laboratory control. We have administered heparin (Elkins - Sinn) to a pregnant patient by the subcutaneous route utilizing an infusion pump (Auto-Syringe ^RModel AS3A) for 15 weeks, maintaining an activated partial thromboplastin time (APTT) of approximately 50 sec (N=22-35) using “ACTIN” (Dade) brand ellagic acid cephaloplastin reagent. The average heparin dose has been 26,000 units/24 hours during the 4th to 19th week of her pregnancy. In order to establish the presence of circulating heparin we also performed Xa and thrombin-based amidolytic assays for the absolute levels of heparin in patient’s plasma. A poor correlation was seen between the heparin levels and the APTT values. These data indicate that absolute levels of heparin may not be taken as an index of heparinization in certain clinical conditions. Lack of serious complications and ease of administration has prompted us to continue heparin by this route during the remainder of her pregnancy.