DEVELOPING AND TESTING A SYSTEM TO IMPROVE THE QUALITY OF HEPARIN ANTICOAGULATION IN PATIENTS WITH ACUTE CARDIAC SYNDROMES

We have taken a stepwise approach to improving the dosing of continuou s intravenous heparin in patients with acute coronary syndromes, Our p rimary objective was to use computer modeling to develop a nomogram fo r managing heparin therapy and to put in place a continuous quality mo nitoring system to evaluate the nomogram's effectiveness. We prospecti vely collected data on 41 patients with unstable angina or myocardial infarction who were treated with heparin. Their response to heparin wa s computer modeled and the dose to achieve an activated partial thromb oplastin time (aPTT) ratio of 2.0 was established. This dose was regre ssed against all demographic characteristics to establish predictors o f heparin dose (phase I). The regression formula was used prospectivel y in 110 patients to initiate the infusion rate of heparin and a bolus dose to achieve an aPTT ratio of 2.5. Subsequent dosage adjustments w ere achieved by computer modeling the patient's aPTT response (phase I I). A nomogram was developed that simulated the decisions achieved usi ng computer-assisted methods. This was retrospectively tested and then prospectively tested in 50 patients using nursing staff (phase IV). T he nomogram was then made generally available (phase IV) and has been tested in an additional 310 patients. Phase I: Of the original 41 pati ents, 32% of the aPTT ratios were in the therapeutic range, 36% were s upratherapeutic, and 32% were subtherapeutic after the first 24 hours, Phases II and III resulted in 85% of the aPTT ratios between 1.5 and 2.5 at 24 hours. Phase 4 had similar results in 310 patients. The use of computer-assisted or a computer-generated nomogram to adjust hepari n therapy results in better control of heparin therapy than using stan dard (C) 1998 by Excerpta Medica, Inc.