The weight-based heparin dosing nomogram compared with a "standard care" nomogram. A randomized controlled trial.

OBJECTIVE

To determine whether an intravenous heparin dosing nomogram based on body weight achieves therapeutic anticoagulation more rapidly than a "standard care" nomogram.

DESIGN

Randomized controlled trial.

SETTING

Two community teaching hospitals in Phoenix, Arizona, and Rochester, New York.

PARTICIPANTS

One hundred fifteen patients requiring intravenous heparin treatment for venous or arterial thromboembolism or for unstable angina.

INTERVENTION

Patients were randomized to the weight-based nomogram (starting dose, 80 units/kg body weight bolus, 18 units/kg per hour infusion) or the standard care nomogram (starting dose, 5000-unit bolus, 1000 units per hour infusion). Activated partial thromboplastin time (APTT) values were monitored every 6 hours, and heparin dose adjustments were determined by the nomograms.

MEASUREMENTS

Activated partial thromboplastin times were measured using a widely generalizable laboratory method. The primary outcomes were the time to exceed the therapeutic threshold (APTT > 1.5 times the control) and the time to achieve therapeutic range (APTT, 1.5 to 2.3 times the control). Bleeding complications and recurrent thromboembolism were also compared.

RESULTS

Kaplan-Meier curves for the primary outcomes favored the weight-based nomogram (P < 0.001 for both). In the weight-based heparin group, 60 of 62 patients (97%) exceeded the therapeutic threshold within 24 hours, compared with 37 of 48 (77%) in the standard care group (P < 0.002). Only one major bleeding complication occurred (in a standard care patient). Recurrent thromboembolism was more frequent in the standard care group; relative risk, 5.0 (95% CI, 1.1 to 21.9).

CONCLUSIONS

The weight-based heparin nomogram is widely generalizable and has proved to be effective, safe, and superior to one based on standard practice.