Evaluation of heparin dosing based on adjusted body weight in obese patients

Purpose. Results of a study to determine whether heparin dosing based on adjusted body weight (BWAdj) instead of actual body weight (ABW) can lead to faster achievement of therapeutic activated partial thromboplastin time (aPTT) values in obese patients are presented. Methods. A single-center retrospective cohort study was conducted to assess aPTT outcomes before and after implementation of a revised heparin protocol specifying BWAdj-based dosing for obese patients. The primary outcome was the percentage of first aPTT values within the target range after heparin initiation. Secondary outcomes included the median time to the first on-target aPTT and the rate of clinically significant bleeding. Results. After protocol implementation, there was no significant difference between obese and nonobese patients in the primary outcome (17% and 21%, respectively, had first aPTT values in the target range) or in the median time to achieve the first on-target aPTT value. Among obese patients, on-target aPTT values were achieved significantly faster with BWAdj-versus ABW-based dosing (14 hours versus 24 hours, p = 0.002). Prior to implementation of BWAdj-based heparin dosing, obese patients had a higher rate of clinically significant bleeding than nonobese patients (11% versus 1%, p = 0.01); postimplementation bleeding rates did not differ significantly. Conclusion. The percentages of first aPTT values in the targeted range did not differ significantly in obese and nonobese patients before and after protocol implementation. The use of BWAdj for dose calculation in obese patients was associated with faster achievement of an aPTT value in the target range.