Improved Anticoagulation with a Weight-Adjusted Heparin Nomogram in Patients with Acute Coronary Syndromes: A Randomized Trial.

Abstract

The optimal heparin dosing schedule to achieve rapid and therapeutic anticoagulation has not been established. The objective of this study is to determine whether an intravenous heparin dosing nomogram based on body weight achieves adequate anticoagulation more rapidly than a standard-care nomogram. Sixty-four patients requiring intravenous heparin treatment for acute coronary syndromes, but who did not receive thrombolytic therapy, were randomized to a standard-care nomogram in which heparin was given as a 5000 unit IV bolus followed by 1000 U/hr, or a weight-adjusted nomogram in which heparin was given as an 80 U/kg IV bolus and 18 U/kg/hr. Activated partial thromboplastin time (APTT) values were checked at 6, 12, 18, 24, and 48 hours and adjusted either by 100-200 U/hr (standard-care nomogram) or by 2-4 U/kg/hr (weight-based nomogram). Activated partial thromboplastin times were measured using a widely generalizable laboratory method. The primary goal was to achieve and maintain the APTT between 60 and 90 seconds. The median APTT values were higher in the weight-adjusted group compared with the standard-care group at 6, 12, 18, 24, and 48 hours: 150 versus 83 (p = 0.001), 100 versus 79 (p = 0.09), 66 versus 61 (p = 0.005), 63 versus 56 (p = 0.09), and 64 versus 56 (p = 0.11). At 18 hours only 11% of patients in the weight-adjusted group had an APTT <61 compared with 26% in the standard-care nomogram (p = 0.007). No major bleeding complications were noted in either group. A weight-adjusted heparin nomogram offers improved anticoagulation in the first 24 hours after heparin initiation compared with a standard-care nomogram in patients with acute coronary artery syndromes.