Weight-Based Enoxaparin Achieves Adequate Anti-Xa Levels More Often in Trauma Patients: A Prospective Study.

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.

Prospective Evaluation of Weight-Based Prophylactic Enoxaparin Dosing in Critically Ill Trauma Patients: Adequacy of AntiXa Levels Is Improved.

Venous thromboembolism (VTE) is a leading cause of death in multisystem trauma patients; the importance of VTE prevention is well recognized. Presently, standard dose enoxaparin (30 mg BID) is used as chemical prophylaxis, regardless of weight or physiologic status. However, evidence suggests decreased bioavailability of enoxaparin in critically ill patients. Therefore, we hypothesized that a weight-based enoxaparin dosing regimen would provide more adequate prophylaxis (as indicated by antifactor Xa levels) for patients in our trauma intensive care unit (TICU).These data were prospectively collected in TICU patients admitted over a 5-month period given twice daily 0.6 mg/kg enoxaparin (actual body weight). Patients were compared with a historical cohort receiving standard dosing. Anti-Xa levels were collected at 11.5 hours (trough, goal ≥ 0.1 IU/mL) after each evening administration. Patient demographics, admission weight, dose, and daily anti-Xa levels were recorded. Patients with renal insufficiency or brain, spine, or spinal cord injury were excluded. Data were collected from 26 patients in the standard-dose group and 37 in the weight-based group. Sixty-four trough anti-Xa measurements were taken in the standard dose group and 74 collected in the weight-based group. Evaluating only levels measured after the third dose, the change in dosing of enoxaparin from 30 to 0.6 mg/kg resulted in an increased percentage of patients with goal antifactor Xa levels from 8 per cent to 61 per cent (P < 0.0001). Examining all troughs, the change in dose resulted in an increase in patients with a goal anti-Xa level from 19 to 59 per cent (P < 0.0001). Weight-based dosing of enoxaparin in trauma ICU patients yields superior results with respect to adequate anti-Xa levels when compared with standard dosing. These findings suggest that weight-based dosing may provide superior VTE prophylaxis in TICU patients. Evaluation of the effects of this dosing paradigm on actual VTE rate is ongoing at our institution.