Background Previous research demonstrates that twice-daily enoxaparin is inadequate for venous thromboembolic (VTE) prophylaxis in critically ill trauma patients prompting dose adjustment based on anti-Xa levels. Most studies evaluate peak anti-Xa levels; however, data suggest that trough levels are associated with decreased VTE. We evaluated trough anti-Xa levels in noncritically ill trauma patients receiving fixed or weight-based enoxaparin. Methods Peak and trough anti-Xa levels were prospectively collected from patients receiving at least 3 consecutive doses of enoxaparin (PRE). A performance improvement project prompted a change to weight-based dosing. Peak and trough levels were subsequently prospectively collected from the weight-based group (POST). Adequate peak was defined as ≥0.2 IU/mL and adequate trough as ≥0.1 IU/mL. PRE and POST groups were compared. Results 200 patients were evaluated (100 PRE, 100 POST). In the PRE group, only 34% of trough and 61% of peak anti-Xa levels were adequate compared with 82% and 97%, respectively, in the POST group ( P < .01). Median trough improved from 0.07 IU/mL to 0.2 IU/mL ( P < .01). Median peak improved from 0.22 IU/mL to 0.47 IU/mL ( P < .01). More patients achieved adequate peak and trough levels in the POST group (79% vs 31%, P < .01). 95% of patients with adequate troughs also had adequate peaks, whereas 75% with adequate peaks had adequate troughs. Discussion Traditional enoxaparin dosing in noncritically ill trauma patients results in suboptimal anti-Xa levels. Weight-based enoxaparin improves both trough and peak anti-Xa levels obviating dose adjustment. Furthermore, troughs better predict adequate anti-Xa levels.

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