BODY-WEIGHT DOES NOT PREDICT FOR ANTI-XA LEVELS AFTER FIXED-DOSE PROPHYLAXIS WITH ENOXAPARIN AFTER ORTHOPEDIC-SURGERY

Enoxaparin after joint arthroplasty is effective prophylaxis against v enous thromboembolism. This is usually given as a fixed dose without m onitoring of anti-Xa levels. This study assesses the relationship betw een trough anti-Xa levels, body weight, and venous thromboembolism. Co nsenting patients at three institutions were treated with Enoxaparin 3 0 mg subcutaneously bis in die postoperatively until discharge. Chromo genic anti-Xa levels were measured on the fifth postoperative day by t he method of Stachrome (Diagnostica Stage). All patients had bilateral compression doppler ultrasonography on day 10 or discharge and were f ollowed for 12 weeks for evidence of venous thromboembolism. Eleven pa tients developed objectively confirmed venous thromboembolism during t he study. In this study, there was poor correlation between weight and anti-Xa levels. In addition, body weight and anti-Xa levels of patien ts who developed venous thromboembelism were compared to those who did not and there were no significant differences between the two groups. In conclusion, this study shows that there is poor correlation of tro ugh anti-Xa levels with body weight. Recognizing the low overall event rate this study does not support the need to monitor anti-Xa levels o r adjusting the dose according to weight. (C) 1998 Elsevier Science Lt d.