 METHODS Study Design This double blind randomized controlled trial RCT was conducted from July 2012 until July 2014 in the dialysis and transplantation unit of a Brazilian university hospital. The patients were randomly assigned to have their catheter locked with either unfractionated sodium heparin 5000 UmL or 30 trisodium citrate. The randomization was performed through a computer-generated list of random numbers in blocks of six. Patients and investigators were unaware of the treatment assignments. Allocation concealment was performed using opaque, sealed envelopes for assignment. 