My dad has an artificial heart value - for the last 30 years. He has been on Coumadin the full time and never really had any problems keeping it between the suggested level of 2.5 - 3.5. He was on 2.5 mg daily. However, over the last several months, he has had some sort of infection. pseudomonas (not sure of spelling). He has been hospitalized twice. He is home now with a pic line and has to have IV antibiotics twice a day for six weeks. The problem is that we can t seem to get his INR past 1.5. Could the problems with his immune system and infections interfere with his ability to regulate the INR? His doctors don t want to up his dose of Coumadin. My mom is quite worried as she has always been able to keep him in his desired level or, at least, very close.