Anti-Factor Xa Activity of Prophylactic Enoxaparin Regimens in Critically Ill Patients

Enoxaparin is frequently used as prophylaxis for deep venous thrombosis in critically ill patients.

To evaluate three enoxaparin prophylactic regimens in critical care patients with and without administration of a vasopressor.

Patients admitted to intensive care units (general and post-cardiothoracic surgery) without renal failure received, once daily, a subcutaneous fixed dose of 40 mg enoxaparin, a subcutaneous dose of 0.5 mg/kg enoxaparin, or an intravenous dose of 0.5 mg/kg enoxaparin. Over 5 days anti-activated factor X levels were collected before the daily administration and 4 hours after the injection.

Overall, 16 patients received the subcutaneous fixed dose, 15 received the subcutaneous weight-based dosage, and 8 received the dose intravenously. Around two-fifths (38%) of the patients received vasopressors. There was no difference between anti-activated factor X levels regarding vasopressor administration. However, in all three groups the levels were outside the recommended range of 0.1 IU/ml and 0.3 IU/ml.

Although not influenced by vasopressor administration, the enoxaparin regimens resulted in blood activity levels outside the recommended range.