Normal saline flushing for maintenance of peripheral intravenous sites

Based on a report indicating that the presence of heparin, even a dilute solution of 3.3 U/ml heparin, was significantly more effective in maintaining intravenous (i.v.) lock patency than normal saline alone (Holford et al. 1977), heparin flushing has been still used to maintain the patency of peripheral venous catheters in Japan. However, a recent systematic review evaluating use of normal saline flushing for peripheral intermittent infusion concluded that the effect of normal saline flushes was equivalent to heparin flushes at dose of 10 U/ml (Randolph et al. 1998). It is assumed that heparin flushing is still widely practised for maintaining peripheral i.v. catheters. The purpose of this study was to re-evaluate the effects of normal saline flush on duration of catheter patency and catheter-related complications. A prospective study was conducted on two surgical units of community-based university hospital with 618 beds over the four-month period from July to October 2003. Participants were 170 men and 151 women who were to receive a peripheral intermittent i.v. lock. All patients in this study received a 20- or 22-gauge polyurethane catheter connected to a closed intermittent i.v. access system. All patients on a given nursing unit received one of the two flushing solutions at least every 12 hours for a two-month period; 3 ml normal saline or 3 ml dilute heparin. Heparin flushing was carried out using a commercially available single use vial of heparin 10 U/ml. For the following two months, flush solutions were switched on each unit. By using this procedure, a cross-over was created, such that both units used each flushing solution type during the different months. Intravenous lock sites were evaluated at least every 12 hours. Catheter site changes were not done at a regular interval. Reason for catheter replacement or removal was failure or completion of infusion. Infusion failure included phlebitis, extravasation and clotting. As some patients required restarts of peripheral intermittent infusion, the total number of i.v. lock sites was 361. Differences in duration of catheter patency between the two groups were analysed using the Mann–Whitney U-test. The comparison of categorical data was made with the chi-squared test. Differences were considered significant at P < 0.05. There was no significant difference in age, sex or diagnosis according to surgical subspecialty and types of therapy between the two groups. No difference was found in the incidence of phlebitis (5% in saline, 8% in heparin), extravasations (34% in saline, 26% in heparin) and clotting (4% in saline, 2% in heparin) between the two groups. As shown in Table 1, flushing with 10 U/ml of heparin instead of normal saline did not prolong the duration of catheter patency. The current study demonstrated the equivalency of normal saline to 10 U/ml heparin flushes in maintaining catheter patency and reducing the incidence of catheter-related complications. The longest time of catheter survival was 312 hours in a saline group, and 360 hours in a heparin group. It has been proposed that the flushing action itself is responsible for improving patency rate and not necessarily the heparin. A re-sealable injection site maintains a positive pressure in the closed device used for the current study. It is assumed that use of a needleless closed device resulted in a longer survival time of peripheral i.v. catheters. By discontinuing the use of heparin, we estimated the cost savings per year at 203,347 Euro at our hospital. This includes pharmacy costs only and does not include an estimate of nursing time saved. Peripheral intermittent infusion devices are now flushed routinely with 3 ml of normal saline after drug administration or flushed every 12 hours. Study design: TF, TN; data analysis: TF and data collection: TS, EY.