The effectiveness of 4-, 6-, and 8-hour heparin flushing intervals on the logevity of 22- and 24-gauge intermittent i.v. catheters was examined in 83 pediatric patients. Catheters lasted 18-20 hours longer with 6- and 8-hour flushing intervals than with 4-hour intervals. A comparison of 22- and 24-gauge catheters revealed that there was no difference in longevity based on size. Also, use of medications did not affect catheter longevity. Age differences in catheter longevity were noted (greater longevity in older children) and is a result that needs further research. Based on the results of this study, if longer flushing intervals were used, fewer i.v.'s would have to be restarted and nursing time caring for i.v.'s would be decreased.