- Patient has an abnormal PT (INR) or a PTT (>1.2 times normal). Low-dose warfarin (1 to 2 mg P.O. q.d.) or heparin (the equivalent of 5000 IU SQ b.i.d.) administered to maintain catheter patency is acceptable. Patients administered higher doses of anticoagulants may be considered on an individual basis pending discussion between the clinical monitor and investigator. Such patients will require more intensive monitoring of PT (INR) and aPTT (at least every other day).