Efficacy and safety of postdischarge administration of enoxaparin in the prevention of deep venous thrombosis after total hip replacement. A prospective randomised double-blind placebo-controlled trial.

Although venous thromboembolism has occasionally been reported after hospital discharge in patients who have undergone total hip replacement (THR), this risk has not been fully quantified and the usefulness of a prophylactic treatment has not been evaluated. We conducted a single-centre prospective randomised double-blind clinical trial in 2 parallel groups of patients who had undergone THR and were free of deep venous thrombosis (DVT) at discharge, as assessed by bilateral ascending venography. During hospitalisation, all patients received a low molecular weight heparin, enoxaparin (enoxaparin sodium), as a prophylactic treatment for venous thromboembolism. Just before hospital discharge (15 +/- 1 days from surgery) 179 consecutive patients were randomly assigned to receive subcutaneous enoxaparin 40mg (n = 90) or placebo (n = 89) once daily for 21 +/- 2 days. The primary efficacy outcome was defined as the occurrence of DVT and/or documented pulmonary embolism (PE). DVT was assessed by ascending bilateral venography performed 21 +/- 2 days after randomisation or earlier if necessary. Secondary efficacy outcomes were the occurrence of proximal and distal DVT. Safety outcomes were defined as the occurrence of major and minor haemorrhage, other adverse events and changes in laboratory parameters. All patients underwent a 3-month follow-up. There were no deaths or cases of clinical PE during the study and the follow-up periods. In 173 patients with evaluable venograms, analysis of efficacy on an intention-to-treat basis showed that the incidence of DVT at day 21 was significantly lower in the enoxaparin group (6 of 85; 7.1%) than in the placebo group (17 of 88; 19.3%; p = 0.018), a risk reduction of 63%. Distal DVT was less frequent in the enoxaparin group than in the placebo group (1.2 vs 11.4%; p = 0.006) but there was no significant difference between groups in the incidence of proximal DVT. A 'per-protocol' analysis of efficacy in 155 patients confirmed the results for total and distal DVT, but also showed a trend in efficacy in favour of enoxaparin with regard to the incidence of proximal DVT (p = 0.064). Enoxaparin was safe in comparison with placebo: only 2 minor bleedings occurred in the enoxaparin group and there was no difference in the incidence of other adverse events between the 2 groups. In patients undergoing THR, the risk of late-occurring DVT remained high during the 21 days after hospital discharge in the placebo group. Prophylactic treatment with enoxaparin reduced the risk and was well tolerated in this context.