My dad has a blood clot in his neck and has been put on Coumadin for the last 3 months. Now he is having some kidney abnormalities develop. Is there medication to counteract the affects of blood thinners on the kidneys? He is 76, 5'-6", 160 lbs., active, recent successful heart surgery for thoracic aneurism- 3 mos ago. He quit smoking 18 years ago, but was heavy smoker.