Santos, E.J.F. dos et al. 2015. Effectiveness of heparin versus 0.9% saline solution in maintaining the permeability of central venous catheters: a systematic review . Revista da Escola de Enfermagem da USP. 49, 6 (Dec. 2015), 995–1003. DOI:https://doi.org/10.1590/S0080-623420150000600017.