Aspirin 160mg daily reduced the risk of pulmonary embolism or deep vein thrombosis by 34 per cent in patients who had undergone hip fracture repair or hip or knee arthroplasty. This was the conclusion of Dr Anthony Rodgers (Clinical Trials Research Unit, University of Auckland, New Zealand) on behalf of the Pulmonary Embolism Prevention (PEP) trial collaborative group who have published their findings in the Lancet (2000;355:1295).
A total of 17,444 patients (13,356 of whom had had hip fracture repair and 4,088 who had undergone hip or knee arthroplasty) were given 160mg aspirin daily. Treatment was continued for a mean of 16 days post-discharge or until the patient's 35th day in hospital. Pulmonary embolism or deep-vein thrombosis or both was confirmed in 105 (1.6 per cent) of the patients who took aspirin compared with 165 (2.5 per cent) in the placebo group (P=0.0003).
The numbers of patients suffering any postoperative bleeding episode that required transfusion were 197 (2.9 per cent) and 157 patients (2.4 per cent), respectively. This represents an absolute increase of 24 per cent, say the authors. However, fatal bleeds were rare in the two groups - 13 (0.2 per cent) in the aspirin group and 15 (0.2 per cent) in the placebo group, they add.
They comment that, although unfractionated and low molecular weight heparins produce greater reductions in the incidence of venous thromboembolism than aspirin, they do so at the cost of more inconvenience and bleeding. In addition, much of aspirin's benefits occurred after the first post-operative week, a time when other prophylactic strategies have been stopped.
The investigators conclude that aspirin should be used routinely in a wide range of surgical and medical groups at high risk of venous thromboembolism and that it should be continued throughout the period of increased risk. In an accompanying editorial (2000;355:1288), Drs Hervé Sors and Guy Meyer (department of lung diseases, Paris V university, France) say that aspirin prevented four fatal pulmonary embolisms per 1,000 patients treated. However, they add that there is still uncertainty about the ideal duration of prophylaxis. In addition, it is not clear whether aspirin is as effective as low molecular weight heparin in preventing "out-of-hospital" venous thromboembolism, they say.
Professor Colin Prentice (University of Leeds) commented in a British Heart Foundation press release: "There was only a small increase in bleeding and no increase in deaths from bleeds. The benefits of aspirin demonstrated by this trial are likely to extend to patients having other types of surgery and to people at risk of pulmonary embolism for other reasons".
The British Heart Foundation part-funded the trial.