Flushes with saline solution are used for maintaining patency of peripheral intermittent intravenous catheters in many institution based on the results of previous studies showing that 10 U heparin/mL is not better than saline in this respect. The latest meta-analysis investigated also safety and efficacy of heparin concentrations of 100 U/ml used as an intermittent flush, but no firm conclusion was reached because of limitations of the few available studies.