Author Affiliations: Division of General Internal Medicine, Department of Medicine, UMDNJ-Robert Wood Johnson Medical School, New Brunswick, NJ.
Since 1960, when Barrett and Jordan established that anticoagulation reduced the risk of death in patients with pulmonary embolism,1 heparin has been the treatment of choice for thromboembolic disease. Heparin was initially administered by intravenous bolus every 4 hours until clinical trials showed that unfractionated intravenous infusion was associated with less bleeding.2,3 Unfractionated heparin was administered by intravenous infusion and the activated partial thromboplastin time (aPTT) was monitored to maintain a level between 1.5 to 2.5 times control. It was common practice to begin treatment with a loading dose of 5000 units and 1000 units per hour of infusion. Clinical experience revealed that many patients had subtherapeutic aPTT levels for more than 24 hours and were more likely to develop recurrent thromboembolism.4,5 Today, the standard of care is to use a weight-based algorithm6 or other heparin protocols7 that quickly achieve therapeutic targets for the aPTT.
Carson JL. Subcutaneous Unfractionated Heparin vs Low-Molecular-Weight Heparin for Acute Thromboembolic DiseaseIssues of Efficacy and Cost. JAMA. 2006;296(8):991-993. doi:10.1001/jama.296.8.991