Optimal weight-based enoxaparin prophylaxis for deep venous thrombosis

Takeaway

• This study demonstrates that enoxaparin dose of 0.4 mg/kg predicts a therapeutic anti-Xa level (0.2-0.5 IU/mL) for deep venous thrombosis (DVT) prophylaxis.
• When regimens of 0.3-0.4 mg/kg/dose are administered in male patients with creatinine clearance (CrCl) of >90 mL/min, the likelihood of a therapeutic assay is nearly 14 times greater, suggesting that monitoring with anti-Xa assays might be unnecessary in this subgroup.

Why this matters

• Findings provide an important addition to the literature that adds to the understanding of complexities surrounding venous thromboembolism (VTE) prophylaxis.

Study design

• Retrospective study included 622 patients admitted to the Level 1 trauma centre between March 2016 and June 2018.
• Patients followed the trauma service’s enoxaparin VTE prophylaxis protocol, which targeted anti-Xa concentrations of 0.2 to 0.5 IU/mL.
• Patients were divided into 3 groups (sub-therapeutic [anti-Xa level <0.2 IU/mL]; therapeutic [0.2 and 0.5 IU/mL]; and super-therapeutic [>0.5 IU/mL]) based on their initial anti-Xa level for prophylaxis.
• Funding: None.

Key results

• Of 634 assays performed, 536: therapeutic range, 63: super-therapeutic range and 35 were in the sub-therapeutic range.
• Receiver operating characteristic (ROC)/area under the curve (AUC) analysis failed to provide significant differences between therapeutic and sub-therapeutic assays.
• ROC/AUC analysis of dose to weight ratio successfully predicted therapeutic vs super-therapeutic assays with AUC 0.78 (95% CI, 0.73-0.84; P≤0.001) and the optimal cut-off point for dose to weight ratio was 0.40 mg/kg dose differentiating therapeutic and super-therapeutic assays.
• Logistic regression revealed enoxaparin prophylaxis within range of 0.31 to 0.40 mg/kg/dose, male sex and CrCl of >90 mL/min increased the likelihood of reaching therapeutic range by 2.6 times (OR, 2.56; 95% CI, 1.22-5.37; P=0.013), 3 times (OR, 2.98; 95% CI, 1.48-5.99; P=0.002) and 10 times (OR, 10.32; 95% CI, 1.75-61.02; P=0.010), respectively.
• Therapeutic assays were 13.76 times more likely to occur with the combined effect of these 3 variables (OR, 13.76; 95% CI, 3.43-56.96; P<0.001).

Limitations

• Supplemental data retrospectively collected.