Pharmacy-managed protocol for warfarin use in orthopedic surgery patients

A pharmacy-managed protocol for warfarin use in orthopedic surgery patients was studied. In 1990 a protocol designed to accommodate either protocol- or physician-determined dosing of warfarin for orthopedic antithrombotic prophylaxis (OAP) was implemented at a community hospital. A "protocol" group consisting of patients treated entirely under the protocol-determined dosing option was prospectively identified over a two-year period. A "physician" group consisting of patients treated by physicians in the 10 months immediately preceding implementation of the protocol was also identified. The ability of the protocol to achieve laboratory-test and clinical goals was assessed by comparing the two groups. The proportion of patients who received OAP increased from 89% for the physician group to 98% for the protocol group. Mean prothrombin times (PTs) were significantly higher in the protocol group only on postoperative day 2; 66% of all PTs beyond post-operative day 1 in the protocol group were within the targeted range, which reflected an International Normalized Ratio of 1.6-3.2. The frequencies of clinically apparent postoperative thrombotic events and bleeding episodes were low in each group and comparable to literature values. Analysis of protocol-group patients with PTs of > 20 seconds indicated that lower weight, female sex, and blood loss during surgery were associated with an elevated PT. The protocol was revised to provide for a lower initial warfarin dose in elderly women. A pharmacy-managed protocol for dosing warfarin achieved therapeutic goals and promoted nearly universal use of OAP in patients undergoing high-risk orthopedic surgery.