Endotoxin Retention Capabilities of Positively Charged Nylon and Positively Charged Polysulphone Membrane Intravenous Filters

Abstract

We have studied the endotoxin retention capabilities of two filters claimed to be suitable for 96-h use. The filters were, a positively charged nylon membrane filter (Pall Biomedical Ltd) and a positively charged polysulphone membrane filter (Gelman Sciences Ltd). Simulated patterns of intravenous therapy that would be used over a 96-h period were set up. The administration sets were injected with either a 1-mL bolus of an Escherichia coli (108 cells suspension in 5% glucose or in a parenteral nutrition solution. After 96 h, 2-mL filter effluent samples were tested for endotoxin using the Limulus amoebocyte lysate test (sensitivity: 0.015 endotoxin units (EU) mL−1). In the E. coli in 5% glucose experiments, no endotoxin was found downstream of the positvely charged nylon membrane filters, but large amounts of endotoxin (5 min= > 10.0 EU mL−1, 72 h = 0.153 EU mL−1) were found downstream of the positively charged polysulphone membrane filters. After challenging the filters with endotoxin in parenteral nutrition solution, again no endotoxin was detected downstream with the positively charged nylon membrane filters, but one of the positively charged polysulphone membrane filters allowed endotoxin to pass through after 48 h (4.45 EU mL−1). These results indicate that only the positively charged nylon membrane can be safely used for up to 96 h without detecting the presence of endotoxin downstream to the filter.