Comparison of a weight-based heparin nomogram with traditional heparin dosing to achieve therapeutic anticoagulation.

Optimum anticoagulation with heparin within the first 24 hours of a thrombotic event is critical in preventing a recurrence. We believed that traditional nonweight-based heparin dosing at our institution resulted in delayed anticoagulation. A weight-based heparin nomogram was therefore created and compared to traditional heparin dosing in patients with a diagnosis of acute deep vein thrombosis or pulmonary embolism. Fifty historical control patients were compared to 50 consecutive patients treated prospectively using the weight-based nomogram. The primary outcome assessed was time to achieve therapeutic anticoagulation, defined as an activated partial thromboplastin time (aPTT) of 46-70 seconds (1.5-2.5 times the control aPTT). The weight-based nomogram achieved an aPTT above the therapeutic threshold more rapidly than the control group (10.7 hrs nomogram vs 33.3 hrs control group, p < 0.004). Similarly, the proportion of patients who exceeded the therapeutic threshold at the first aPTT measurement, at 24 hours, and at 48 hours was significantly higher in the nomogram group. There was no difference in the frequency of bleeding complications or recurrent thrombotic events between the two groups. The initial nomogram was revised for patients weighing more than 80 kg owing to a greater frequency of excessive anticoagulation in these patients. Subsequent analysis of 29 patients using the modified nomogram revealed sustained efficacy and a reduced number of supratherapeutic aPTTs. We concluded that a weight-based heparin nomogram is superior to traditional therapy in achieving rapid therapeutic anticoagulation without an increase in adverse outcomes.