The complexities of therapeutic nursing require the adoption of clinical practice based on scientific evidence. In the context of optimization of the use of central venous catheters, there is much controversy regarding the use or not of heparin as a way to reduce the risk of obstruction. Therefore nurses should know about the best available scientific evidence in order to promote patient safety. In this context, the idea was to find out which solution (heparin or saline) is more effective in preventing obstruction of central venous catheters. We conducted a systematic literature review between 14 October 2012 and 15 January 2013, and analyzed scientific papers included in the databases MEDline with full text, Cochrane Central Register of Controlled Trials and CINAHL Plus with Full Text presented in PubMed and EBSCOhost Web. Normal saline solution seems to be as effective as a heparinized solution with regard to catheter patency in adult patients. The scientific evidence on the subject is limited, and there is need to conduct more randomized clinical trials comparing the use of these solutions.