Efficacy of protocol-based pharmacotherapy management on anticoagulation with warfarin for patients with cardiovascular surgery

What is known and objective: Anticoagulation therapy with warfarin requires periodic monitoring of prothrombin time-international normalized ratio (PT-INR) and adequate dose adjustments based on the data to minimize the risk of bleeding and thromboembolic events. In our hospital, we have developed protocol-based pharmaceutical care, which we called protocol-based pharmacotherapy management (PBPM), for warfarin therapy. The protocol requires pharmacists to manage timing of blood sampling for measuring PT-INR and warfarin dosage determination based on an algorithm. This study evaluated the efficacy of PBPM in warfarin therapy by comparing to conventional pharmaceutical care. METHODS: From October 2013 to June 2015, a total of 134 hospitalized patients who underwent cardiovascular surgeries received post-operative warfarin therapy. The early series of patients received warfarin therapy as the conventional care (control group, n=77), whereas the latter received warfarin therapy based on the PBPM (PBPM group, n=68). These patients formed the cohort of the present study and were retrospectively analysed. RESULTS: The indications for warfarin included aortic valve replacement (n=56), mitral valve replacement (n=4), mitral valve plasty (n=22) and atrial fibrillation (n=29). There were no differences in patients' characteristics between both groups. The percentage time in therapeutic range in the first 10 days was significantly higher in the PBPM group (47.1%) than that in the control group (34.4%, P<.005). The average time to reach the steady state was significantly (P<.005) shorter in the PBPM group compared to the control group (7.3 vs 8.6 days). What is new and conclusion: Warfarin therapy based on our novel PBPM was clinically safe and resulted in significantly better anticoagulation control compared to conventional care.