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| |  Warfarin Users More Likely to Develop Brain Haemorrhage Following Stroke Treatment CHICAGO -- March 8, 2010 -- Patients already taking warfarin who develop an acute stroke appear more likely to experience a brain haemorrhage following treatment with intravenous tissue plasminogen activator (tPA), even if their blood clotting function appears normal, according to a study published early online and appearing in the May print issue of Archives of Neurology. Intravenous tissue plasminogen activator is effective for acute ischaemic stroke and generally results in improved clinical outcomes despite a slightly higher risk of brain haemorrhage, the authors wrote as background information in the article. Risk of haemorrhage is increased in some populations, including older adults and those with more severe strokes, high blood glucose levels, lower platelet counts, and high blood pressure. Use of anti-clotting medications, such as aspirin or warfarin, before having a stroke has raised further concerns about risk of haemorrhage. However, current American Heart Association/American Stroke Association guidelines permit the use of tPA in these patients as long as their results on blood clotting tests meet an international standard (described as an international normalised ratio <1.7). Shyam Prabhakaran, MD, Rush University Medical Center, Chicago, Illinois, and colleagues studied 107 patients (mean age, 69.2 years) with acute ischaemic stroke who were treated with tPA between 2002 and 2009. Of the patients, 13 (12.1%) were taking warfarin; all had an international normalised ratio <1.7. “The overall rate of symptomatic intracerebral haemorrhage was 6.5%, but it was nearly 10-fold higher among patients taking warfarin compared with those not taking warfarin at baseline (30.8% vs 3.2%, respectively),” the authors wrote. “Baseline warfarin use remained strongly associated with symptomatic intracerebral haemorrhage after adjusting for relevant co-variates, including age, atrial fibrillation, National Institutes of Health Stroke Scale score, and international normalised ratio.” Several mechanisms may explain this association, the authors noted. The clot-dissolving effects of tPA may be enhanced by the clot-preventing effects of warfarin, even at low levels. In addition, the effects of warfarin last for an average of 3 days after the last dose, so the international normalised ratio may continue to increase following treatment with tPA. Given the small size and other limitations of the study, it should “serve as a hypothesis-generating report that requires confirmation in larger cohorts,” the authors concluded. “Further analysis including more extensive adjustment for confounding variables in larger data sets may prove useful.”
SOURCE: Archives of Neurology
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