Comparison of two nomograms of unfractionated heparin in patients with acute coronary syndrome.

Heparin has an unpredictable pharmacokinetics and the responses of individuals may vary distinctly. Therefore, different dosing nomograms have been proposed. The aim of this study was to compare two prevalent nomograms to adjust heparin doses in hospitalized patients with acute coronary syndrome.  One hundred and forty patients received heparin infusions based on one of two nomograms. Group 1 received a bolus of 80 U/Kg/h and an initial infusion rate of 17 U/Kg/h. In the second group, a bolus of 60 U/Kg (maximum of 4000 U) and an initial infusion rate of 12 U/Kg/h (maximum of 900U/h) was given. Activated partial thromboplastin time (aPTT) was measured at the beginning and every 6 h for 48 hours. The rate of heparin was changed according to each nomogram in order to maintain aPTT in the therapeutic level of 46-70 s. The time to pass threshold was on average 7.63±3.95 h for nomogram 1 and 11.05±4.41 h for the second nomogram (P<0.001). At 48 hours, the proportion of patients in the therapeutic range in group 1 was higher (72.86% vs 45.71%). The time patients stayed at the desired levels was significantly higher in nomogram 1 and they also required fewer heparin rate adjustments (3.41±1.55 vs 4.53±1.63). This study indicated that using nomogram 1 facilitated a more rapid achievement of the therapeutic threshold, higher proportion of patients in the therapeutic range for a longer time, and fewer changes of in the heparin rate.