Evaluation of 2 Weight-Based Protocols

18 Dec



In recent years, significant focus has been placed on establish­ing weight-based protocols for administration of heparin to optimize patient outcomes in the treatment and prevention of conditions such as deep vein thrombosis, pulmonary embolism, and acute coronary syndrome. In 1996, the authors’ hospital developed a weight-based heparin protocol. A formal assessment revealed that, relative to traditional non-weight-based dosing, the weight-based protocol was superior in terms of the time required to achieve a minimum level of therapeutic anticoagulation, without an increase in adverse events.

Over the subsequent 10 years, several modifications were introduced to the original weight-based protocol, which had been accepted as standard of practice since its initial evaluation. These modifications were (1) determination of the therapeutic range of partial thromboplastin time (PTT) on the basis of anti-Xa units per millilitre, rather than a range based on PTT levels 1.5—2.5 times above baseline; (2) changes to the incremental adjustments in heparin dose for patients with supratherapeutic and subtherapeutic PTT; (3) use of newer, more sensitive reagents for laboratory assessment of PTT levels; and (4) introduction of a protocol with a lower target PTT in August 2006. As a result, physicians now have a choice between 2 weight-based heparin protocols. The standard heparin protocol (Appendix 1), which is analogous to the original 1996 protocol, is intended for patients with active thromboembolic disease. It targets anti-Xa levels of 0.3-0.7 units/mL, corresponding to therapeutic PTT values of 70-130 s. The lower-target protocol (Appendix 2) replaced a previously existing protocol that was used in the hospital’s cardiac care unit. Its application was expanded to include patients with acute coronary syndrome or neurologic indications for anticoagulation (e.g., stroke) and early postsurgical patients who require anticoagulation but who have no active deep vein thrombosis, pulmonary embolism, or peripheral arterial thrombosis. This protocol targets anti-Xa levels of 0.2-0.5 units/mL, corresponding to a PTT range of 60-100 s. This lower anti-Xa range has been recommended for the treat­ment of acute myocardial infarction and is achieved by using a lower initial bolus dose (70 units/kg to a maximum of 5000 units, rather than 75-100 units/kg to a maximum of 9000 units in the standard protocol), as well as lower initial mainte­nance doses.
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The heparin protocol used in the cardiac care unit, which formed the basis of the lower-target protocol, had never been formally evaluated, and the standard heparin protocol had been substantially revised since its initial analysis. Therefore, the objective of this study was to determine and compare the efficacy and safety of the two 2006 heparin protocols and to descriptively compare these results to the results of the original 1996 study.