(Ivanhoe Newswire) — The blood thinner warfarin can prevent strokes in most people with abnormal heart rhythms such as atrial fibrillation, but the drug may have the opposite effect in kidney disease patients on dialysis, according to a new study. The results suggest warfarin should be prescribed with caution in patients with kidney failure.
Kevin Chan, MD, Michael Lazarus, MD, Raymond Hakim, MD, PhD of Fresenius Medical Care North America, and Ravi Thadhani, MD of Massachusetts General Hospital, studied 1,671 end stage renal disease (ESRD) patients with a diagnosis of atrial fibrillation who started dialysis in clinics operated by Fresenius Medical Care North America. Their health was monitored for an average of 1.6 years after dialysis began.
The researchers found patients who took warfarin had an increased risk of stroke that was directly related to the degree of blood thinning in response to the drug. Dialysis patients whose blood warfarin levels were not monitored had the highest risk of stroke, almost three-fold higher than patients not on warfarin. Notably, two other types of blood thinner — clopidogrel and aspirin — did not increase dialysis patients’ risk of stroke.
Additional research is needed to determine why warfain has a negative effect on stroke risk in kidney disease patients on dialysis. One possible explanation may be that bleeding is a well known complication of kidney failure and the concomitant use of blood thinners may exaggerate the risk of stroke. The researchers concluded, “Physicians should be cognizant of the possible risks associated with warfarin use for atrial fibrillation in ESRD patients, with careful evaluation of the risks and benefits of intervention at the individual patient level.”
SOURCE: Journal of the American Society Nephrology (JASN), August 27, 2009