Low-dose warfarin prophylaxis to prevent symptomatic pulmonary embolism after total knee arthroplasty.

Pulmonary embolism poses a risk to patients undergoing total knee arthroplasty. The selection of an appropriate prophylaxis agent and its implementation have been influenced by decreased duration of hospital stay and the pressures of cost containment. The purpose of this study was to determine the inpatient and outpatient pulmonary embolism rates, the number of days required to attain the target level of anticoagulation, and complications associated with the use of a low-dose warfarin prophylaxis protocol after primary and revision total knee arthroplasty. Between 1984 and 1993, there were 815 primary and revision total knee arthroplasties that received low-dose warfarin prophylaxis at our institution. The average time to attainment of the target level of anticoagulation was 3 days. The average duration of warfarin prophylaxis was 12 days. Overall, there were a total of three symptomatic pulmonary embolisms (0.3%; 95% confidence interval, 0.08%-1.1%). There were eight (1%) symptomatic deep vein thromboses (all distal). There were two deaths (0.3%), but neither one was secondary to a pulmonary embolism. Seventeen knees (2.5%) developed a hematoma after surgery, and two of these patients required drainage of the knee. Low-dose warfarin prophylaxis is safe and effective in preventing symptomatic pulmonary embolism after total knee arthroplasty.