RESUMO
BACKGROUND: Recent trials have demonstrated an association between high activated partial thromboplastin time (aPTT) and bleeding, intracranial hemorrhage, reinfarction, and death in patients with acute coronary syndromes treated with heparin. Of all the factors that affect aPTT in patients treated with heparin, body weight is most strongly correlated. METHODS: We compared the efficacy of 2 weight-adjusted heparin regimens (groups 2 and 3) and the standard (group 1) non-weight-adjusted 5000-U intravenous bolus/1000 U/hr infusion to achieve an aPTT between 45 and 70 seconds in a nonrandomized prospective cohort of 80 patients admitted with unstable angina and non-ST elevation myocardial infarction. RESULTS: Patients treated with the lower dose of weight-adjusted heparin (60 U/kg intravenous bolus, maximum of 4000 U; 12 U/kg/hr, maximum 900 U/kg), group 3, were more often within the target range for aPTT at 6 hours (34% vs 5% vs 0%) and required fewer heparin infusion changes (1.0 +/- 1.0 vs 1.9 +/- 1.0 vs 2.0 +/- 0.9) within the first 24 hours compared with the other regimens. Patients in groups 1 and 2 were overwhelmingly above target range at 6 hours (95% and 84%, respectively, compared with 48% in group 3). CONCLUSIONS: Traditional heparin dosing regimens result in marked initial overanticoagulation in patients with acute coronary syndromes, which may place these patients at higher risk of adverse outcomes. A lower dose weight-adjusted heparin regimen is superior in achieving early aPTTs within the target range and reducing the need for infusion changes over the ensuing 24 hours.