Thrombotic Prophylaxis in Orthopedic Surgery

In patients undergoing orthopedic surgery, a long-acting anti-thrombotic prophylaxis is usually performed, but is this practice really useful and necessary? Through a multinational trial, sponsored by pharmaceutical industry, the efficacy of a long-term prophylaxis in acute patients has been assessed: everybody has been treated with enoxaparin for 10 days, then all have been randomized to receive further injections of heparin or placebo for 28 further days. Controls have been made when 75% of enrolment was reached (3685 patients) and there have been no differences between enoxaparin and placebo as to thromboembolic events; there has been, instead, a greater tendency to bleeding episodes in the group treated with heparin (0.6% vs. 0.29%). Given these partial results, the trial was early stopped. Analyzing the type of patients participating to the trial, it was seen that they were mostly sick people needing long-term confinement to bed and with other thromboembolic risk factors. The final analysis, on 4995 subjects from both phases of the trial, has shown a lower rate of thromboembolisms in the heparin arm (2.5% vs. 4.0%) and an absolute reduction of 0.8% in symptomatic venous thromboembolisms (almost all deep venous thromboses and not pulmonary embolisms). There was no difference, instead, in overall mortality.

Long-term prophylaxis with heparin certainly implies some problems: according to analyses performed at half trial, it results to be dangerous rather than useful (it increases bleeding episodes without reducing thrombotic ones). Considering only patients with a high risk, instead, a decrease in thrombotic episodes of about 1.5% has been seen, even if the authors of the trial do not specify which is the period of confinement to bed of the various participants, so the conditions of thrombotic risk could have been strongly different from one subject to another. The situation being this, we cannot know yet which are the characteristics of patients doomed to a long-term prophylaxis: no doubt, the indiscriminate administration of heparin to all patients undergoing orthopedic surgery is a practice to be abandoned.