Bacterial endotoxin retention by inline intravenous filters.

Filters used in i.v. administration sets were tested for their ability to retain bacterial endotoxins for up to 96 hours of continuous infusion. Inline filters composed of cellulose ester, polyacrylate, polypropylene, polyethylene, or Posidyne Nylon 66 were used during continuous infusion of 5% dextrose injection at 83 mL/hr. One milliliter of inoculum containing 10(8) Escherichia coli was injected through a port upstream from the filter. A bacterial filter was used to monitor the sterility of effluent from the inline filters. The effluent was tested with limulus amebocyte lysate (LAL) that could detect endotoxin concentrations greater than 50 pg/mL. A control solution was monitored for viability of the bacteria throughout the course of the study, and positive endotoxin controls were used to confirm the sensitivity of the LAL. Samples of effluent were tested at 0, 4, 19, 24, 48, 72, and 96 hours. Effluent from all filters was sterile throughout the study. LAL assay indicated that only the effluent from filters containing Posidyne Nylon 66 was free of endotoxins for 96 hours. Effluent from the other filters contained endotoxins immediately after injection of the E. coli. Of the inline filters tested, only the one composed of Posidyne Nylon 66 was able to retain E. coli endotoxin for 96 hours. Further study is needed with E. coli and other microorganisms that are likely contaminants of i.v. infusions.