REEVALUATION OF A WEIGHT-BASED HEPARIN DOSING NOMOGRAM - IS INSTITUTION-SPECIFIC MODIFICATION NECESSARY

OBJECTIVE: TO compare a heparin dosing nomogram using an initial infus ion rate of 18 units/kg/h with physician-directed heparin prescribing and with a modified version of the nomogram adjusted for institution-s pecific data. METHODS: During consecutive phases of this cohort study, patients' intravenous heparin therapies were initiated and adjusted b y using one of the following three methods: (I) physician-directed dos ing, (2) a body weight-based dosing nomogram with an initial infusion rate of 18 units/kg/h, and (3) a body weight-based dosing nomogram wit h an initial infusion rate determined by the median dose of heparin (i n units/kg/h) required to achieve therapeutic activated partial thromb oplastin times (aPTTs) during the first two phases. The time required to achieve therapeutic aPTTs as well as the percentage of initial aPTT s in the therapeutic range were compared for the three phases. RESULTS : The heparin dosing nomogram in which the initial infusion rate was a djusted for our individual institution resulted in a statistically sho rter median time until aPTTs were in the therapeutic range than did ei ther the physician-directed dosing or unmodified nomogram groups (6.1 h in the modified nomogram group, 10.5 h in the physician-directed gro up, 21.5 h in the unmodified nomogram group; p < 0.05 for all differen ces). Use of the institution-specific nomogram resulted in the greates t percentage of initial aPTTs in the therapeutic range (84% in the 13 units/kg/h nomogram group vs, 47% in the physician-directed group and 18% in the 18 units/kg/h nomogram group; p < 0.05 for all differences) , CONCLUSIONS: Use of a heparin dosing nomogram with an initial infusi on rate of 18 units/kg/h resulted in prolongation of the time to reach therapeutic aPTTs, By modifying the nomogram for use at an individual institution, we reduced the time to achieve therapeutic range of aPTT s while still reducing the likelihood of excessive anticoagulation of patients.