Prophylactic anticoagulation with low dose enoxaparin: is the subcutaneous route appropriate in the critically ill?

Introduction

Subcutaneously administered LMW heparins are widely used for prophylactic anticoagulation. The appropriateness of the SC route in critically ill patients who require vasopressors and mechanical ventilation has never been established.

Methods

The anti-Xa kinetic (0, 1, 3, 6, 12 hours) following 40 mg of enoxaparin SC was investigated in 16 ICU patients (group 1; age 61.1 ± 16 years; m/f 7/9, APACHE II 20.9 ± 7, mechanical ventilation n = 15, vasopressors n = 13) and 13 non critically ill patients on the general ward (group 2; age 61.7 ± 9 years, m/f 7/6) requiring prophylactic anticoagulation. Patients with impaired renal function or requiring hemofiltration and those requiring therapeutic anticoagulation were not eligible.

Results

Mean anti-Xa levels were consistently lower in group 1 vs group 2 on ANOVA (P = 0.001 between groups and over time) as was the AUC_{0–12 hours} (2.6 ± 1 vs 4.2 ± 1.7 U/ml^*h, group 1 vs 2, P = 0.008). BMI (25.7 ± 5 vs 24 ± 6 kg/m²) and creatinine clearance (67.5 ± 31 vs 67.7 ± 27 mg/dl) were comparable in both groups (P = ns). The peak anti-Xa level 3 hours after administration was negatively correlated to the BMI (r = -0.41, P < 0.03) and the norepinephrine dose (r = -0.36, P = 0.056).

Conclusion

It is cautiously concluded that the SC administration of established doses of prophylactic enoxaparin might not be appropriate in the critically ill patient requiring vasopressor support and mechanical ventilation.