The most effective and safe method of maintaining peripheral intravenous lock in children is an important clinical question that has been identified by the researchers. The results of recent studies comparing saline versus 10 units/ml of heparin saline flush using a 24-gauge catheter in neonatal and pediatric populations are conflicting and inconclusive. The objectives of this study were to evaluate the effectiveness and safety of three flush solutions: normal saline, 1 unit/ml of heparin saline and 10 units/ml of heparin saline for maintaining peripheral intravenous locks in children, and to establish a research-based practice in the study hospital. In a prospective, randomized controlled, double-blind trial, one hundred and twenty-three subjects ranging in age from 1–10 years with 123 intravenous locks were randomly chosen to receive 1 unit/ml of heparin saline, 10 units/ml of heparin saline and normal saline to evaluate length of catheter use, survival rate and incidence of intravenous complications. The study found no statistically significant differences in length of catheter use, estimated catheter survival and the incidence of intravenous complications among the three groups. The group that received 1 unit/ml of heparin saline demonstrated the highest rate of survival. The mean length of catheter use of the group that received 1 unit/ml of heparin saline (49.8 hours) was 17 hours longer than the group that received normal saline (32.5 hours). There are no significant differences among the three types of flushing solution in terms of the catheter longevity and incidence of intravenous complications.