Efficacy and safety of enoxaparin, a low molecular weight heparin in the prevention of deep vein thrombosis in Nigerian patients after orthopaedic surgery.

The objective was to determine the efficacy and safety of Enoxaparin as an antithrombotic agent in orthopaedic patients at risk for thromboembolism. 49 patients who had lower limb orthopaedic surgery were studied. They received subcutaneous Enoxaparin 40mg 12 hours before surgery and subsequently, daily for one week. Blood specimens were drawn at 2 and 12 hours after the first injection, and 24 hours after the fourth injection for anti Factor Xa assay. Specimens were also taken preoperatively, 1st, 5th and 7th post operative days (POD) for determination of Packed Cell Volume (PCV), Haemoglobin level, White Blood Cell (WBC) and Platelet Counts. The mean pre-treatment, 2, 12 and 24 hours anti Factor Xa clotting times were 14.5 +/- 0.8, 36.2 +/- 5.6, 30.6 +/- 9.8 and 25.8 +/- 9.3 seconds respectively. The changes were significant, P = 8.2 x 10(-12). The 2 and 24 hours clotting times corresponded to plasma heparin concentration level of 0.12 - 0.22U/ml read off from prepared Enoxaparin standardisation curve. Significant changes were observed in haemoglobin level, PCV, WBC and Platelet Counts when preoperative, 1st, 5th and 7th POD mean values were compared by Analysis of Variance--P < 0.01 in all cases. The study showed that Enoxaparin 40 mg daily caused hypocoagulation within prophylactic range of 0.12 - 0.22U/ml of heparin in the plasma. Changes in blood counts were within the limits expected post surgery.