Generalisations on benefits of aspirin are dangerous

BMJ 2000; 321 doi: https://doi.org/10.1136/bmj.321.7260.569 (Published 02 September 2000) Cite this as: BMJ 2000;321:569
  1. Dan Quinlan, research fellow (dan.quinlan{at}kcl.ac.uk),
  2. Ander Cohen, vascular physician and epidemiologist
  1. Department of Academic Medicine, Guy's, King's and St Thomas's School of Medicine and Dentistry, London SE5 9PJ

    EDITOR—The publication of the pulmonary embolism prevention (PEP) trial has created considerable interest in the medical and lay press about the optimal thromboprophylactic strategy to minimise the substantial morbidity and mortality experienced by patients with hip fractures.1 Minerva's interpretation of the trial is misleading,2 and we wish to counter each of her four claims.

    Firstly, the claim that the trial showed clearly that aspirin prevents deep vein thrombosis and pulmonary embolism and saves lives is misleading. Although the primary efficacy end point of the trial was all vascular deaths, this primary efficacy finding is not clearly stated in the Lancet manuscript. Aspirin did not reduce vascular deaths (hazard ratio 0.72, 95% confidence interval 0.29 to 1.79), clearly disproving the assertion that aspirin saves lives.

    Secondly, the interpretation that aspirin works, whether or not patients are given other prophylactic drugs, including subcutaneous heparins, is wrong. The trial showed that patients receiving concomitant low molecular weight heparin and aspirin did not experience a reduction in symptomatic venous thromboembolism compared with heparin alone. Furthermore, bleeding in patients receiving concomitant anticoagulant treatment was a concern. Aspirin was associated with a 12 per 1000 excess of transfused bleeds among patients also receiving subcutaneous heparin (48% increase).

    Thirdly, orthopaedic surgeons who are now wondering whether or not to continue with their traditional perioperative protocols as well should consider the following: The meta-analysis of thromboprophylaxis with heparin by Collins et al showed a 67% reduction of fatal pulmonary embolism in patients having orthopaedic surgery, a 64% reduction in the rates of deep vein thrombosis in patients having traumatic surgery, and a 21% reduction in overall mortality.3 This compares with a 29% proportional reduction of deep vein thrombosis in the pulmonary embolism prevention trial with no reduction in overall mortality.

    Finally, readers may wish to consider the following when reading the assertion by the trial investigators that patients with hip fracture should be given perioperative aspirin—the main outcomes of the trial are that aspirin did not reduce vascular deaths, had no significant effect on major non-fatal vascular events other than deep vein thrombosis, but did result in an excess of 6 (SD3) per 1000 postoperative transfused bleeds.

    We believe that the pulmonary embolism prevention trial does nothing to alter accepted and proved benefits of perioperative and extended thromboprophylaxis with heparin and that commentaries on it should be carefully considered. Dangerous generalisations about the benefits of aspirin have been made that unfortunately may have dire consequences for patient care.


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