Use of an algorithm for administering subcutaneous heparin in the treatment of deep venous thrombosis

Background: Despite the widespread use of subcutaneous heparin in the initial treatment of deep venous thrombosis, there are no guidelines for achieving adequate anticoagulation with this drug. Objective: To implement a weight-based algorithm for the administration of subcutaneous unfractionated heparin after an intravenous loading dose. Design: Prospective cohort study. Setting: University hospital. Participants: 70 outpatients with proximal venous thrombosis. Intervention: An intravenous bolus of heparin followed by a subcutaneous injection of heparin in doses adjusted for body weight. Subsequent adjustments of the subcutaneous heparin dose were scheduled twice daily according to the algorithm; the activated partial thromboplastin time (aPTT) was measured in the mid-interval (target range, 50 to 90 seconds). Results: The therapeutic threshold aPTT (greater than or equal to 50 seconds) was achieved in 61 patients (87%) within 24 hours and in 69 patients (99%) within 48 hours. In 7 patients (10%), a supratherapeutic aPTT lasted more than 12 hours. No major bleeding episodes or cases of heparin-induced thrombocytopenia were seen. Three patients (4.3% [95% CI, 0.9 % to 12.0 %]) had recurrent thromboembolism during 3 months of follow-up. Conclusion: The administration of subcutaneous heparin according to a weight-based algorithm allows the rapid achievement of effective and safe anticoagulation in patients with deep venous thrombosis.