Outcomes of weight-based heparin dosing based on literature guidelines andinstitution individualization

Study Objective. To determine whether unfractionated heparin is optimally d osed using published weight-based guidelines. Design. Six-month, prospective study. Setting. University hospital. Patients. Ninety-six patients in the weight-based unfractionated heparin-do sing group 1 (WBHD1; 37 men; mean age 66.9 +/- 15.1 years; mean weight 80.1 +/- 20.6 kg) and 68 patients in the WBHD2 (25 men; mean age 68.2 +/- 15.6 years; mean weight 82.0 +/- 19.6 kg). Interventions. The WBHD1 received a 100-U/kg intravenous bolus followed by an 18-U/kg/hour continuous intravenous infusion. After 3 months, the protoc ol was modified, and the WBHD2 received a 90-U/kg bolus followed by a 16-U/ kg/hour continuous infusion for 3 months. Measurements and Main Results. Activated partial thromboplastin times (aPTT s), frequency of bleeding episodes that required blood transfusions, and th e number of recurrent thromboembolic events were collected from both groups after 3 months on the study. In the WBHD1, 24 hours after starting heparin , 38.5% of patients had therapeutic aPTTs, and at 48 hours, 54.3% were ther apeutic. In the WBHD2, 42.6% and 51.4% of patients had therapeutic aPTTs at 24 and 48 hours, respectively. There was no statistical difference between the WBHD1 and WBHD2 in the percentage of patients with therapeutic aPTTs. Conclusions. Weight-based heparin dosing resulted in low percentages of pat ients with therapeutic aPTTs. The use of weight alone to dose heparin may n ot be adequate to optimize therapy.