Investigation of in-line filter replacement intervals for infusion

Abstract

In-line filters in peripheral and central venous catheters are used to mechanically remove bacterial cells. A recent study indicated the extension of the use of infusion sets to seven days. There is no evidence regarding replacement intervals for in-line filters. We tested in-line filters that were continuously used for seven days for ability to remove bacteria as well as flow rate. Three different in-line filters were attached to an ELNEOPA-NF No.2® premixed infusion bag of intravenous hyperalimentation, into which Staphylococcus epidermidis ATCC12228 or Escherichia coli ATCC25922 was inoculated. These experiments were compared with a control infusion. The infusion was dropped at a flow rate of 40 mL/h and replaced at 24-h intervals for seven days. Samples were collected 24 h after drop initiation. S. epidermidis was not detected in droplets between Days 1 and 6, while in-line filters 1 and 2 showed droplets containing 6-10 CFU/mL on Day 7. E. coli was not detected in any of the filters. Flow rates below 40 mL/h were observed on Day 7 in in-line filter 3 in studies of S. epidermidis, and on Days 4 and 3 in in-line filters 2 and 3, respectively, in studies of E. coli. Our study revealed differences in bacterial removal and flow rate under high inoculation among each of three tested in-line filters. We suggest the continuous use of in-line filters for a maximum of six days, while reductions in flow rate after 48 h of continuous use should be carefully noted.