The aim of the present study is to monitor anticoagulant therapy by anti-Xa assay and correlate its level to the efficacy and safety of enoxaparin in the treatment of pulmonary embolism.

This prospective randomized trial was conducted on 42 patients 18 years of age or older in ICU diagnosed to have pulmonary embolism and confirmed by the presence of intraluminal filling defect in CT pulmonary angiography and treated with subcutaneous enoxaparin 1 mg/kg/12 hours. The study was conducted from August 2013 to September 2016.

All the patients were examined daily over a period of 4 weeks for symptoms and signs of recurrent pulmonary embolism (recurrent pulmonary embolism was diagnosed if the repeat CT angiography revealed a new sudden arterial branch cutoff or a new intraluminal filling defect that was not present on the first angiogram), Platelet count (patients with platelet count less than 50,000/mm3 or those with bleeding and platelet count between 50,000 and 100,000/mm3 are considered having severe thrombocytopenia), bleeding (defined as major overt bleeding requiring blood transfusion > 2 units or marked hemoglobin drop > 2 gm/dl or if the bleeding was intracranial or retroperitoneal) and death (defined as all deaths occurring within the 4 weeks of the study) , Then the results were correlated to anti-Xa assay.

Inclusion Criteria:

• Patients in ICU and diagnosed to have pulmonary embolism and confirmed by the presence of intraluminal filling defect in CT pulmonary angiography and treated with subcutaneous enoxaparin 1 mg/kg/12 hours.

Exclusion Criteria:

• Patients who underwent thrombolysis, embolectomy or if they are unfit for anticoagulant therapy because of major bleeding or thrombocytopenia (a platelet count below 100,000 per cubic millimeter). Patients were also excluded if they had impaired kidney function with a serum creatinine level above 2 mg/dl or uncontrolled hypertension (blood pressure > 160/100 mmHg).

The study was conducted on 42 patients in ICU diagnosed to have pulmonary embolism by CT pulmonary angiography and treated by subcutaneous enoxaparin 1 mg/kg every 12 hours. Anticoagulant therapy was followed by anti-Xa assay done 4 hours after the third dose of subcutaneous enoxaparin and the results were correlated to the clinical outcome of the patients as regards complications (recurrent pulmonary embolism, bleeding, low platelet count and death).