Transmembrane passage of cytokine-inducing bacterial products across new and reprocessed polysulfone dialyzers

Abstract

The widespread use of bicarbonate dialysate and reprocessed high- efficiency and 'high-flux' dialyzers has raised concerns about the increased risk of reverse-transfer of dialysate contaminants into the blood compartment to evaluate this concern, the reverse-transfer at bacterial products tram contaminated bicarbonate dialysate into the blood compartment was compared during in vitro dialysis with new or reprocessed high-flux polysulfone dialyzers. In vitro dialysis was carried out at 37°C by use of a counter- current recirculating loop dialysis circuit with either new high-flux polysulfone dialyzers or dialyzers reprocessed once or 20 times with formaldehyde (0.75%) and bleach (<1%) with an automated system. Heparinized whole blood from healthy volunteers was circulated through the blood compartment, and bicarbonate dialysate was circulated in the dialysate compartment. The dialysate was challenged sequentially by 1:1000 and 1:100 dilutions of a sterile Pseudomonas aeruginosa culture supernatant (bacterial challenge). Samples were drawn from the blood and dialysate compartments 1 h after each challenge. Peripheral blood mononuclear cells (PBMC) were harvested by Ficoll-Hypaque separation from whole blood in the blood compartment and a 5 x 106 PBMC/mL cell suspension was prepared. Likewise, dialysate samples (0.5 mL) were added to 0.5 mL suspension of 5 x 106 PBMC/mL drawn at baseline. All PBMC suspensions were incubated upright in a humidified atmosphere at 37°C with 5% CO2 for 24 h, and total interleukin- 1α (IL-1α) and tumor necrosis factor-α (TNFα) cytokine production (cell- associated and secreted) was measured by radioimmunoassay. Eight experiments were performed for each arm of the study with the same donor for each arm. One hour after contaminating the dialysate with a 1:1000 dilution of the bacterial challenge, IL-1α production by PBMC harvested from the blood compartment was 160 ± 0, 171 ± 11 and 270 ± 35 pg, respectively, for new dialyzers, dialyzers reprocessed once, and dialyzers reprocessed 20 times (P = 0.004). One hour after challenging the dialysate with a 1:100 dilution, IL- 1α production by PBMC harvested from the blood compartment was 188 ± 20, 228 ± 35, and 427 ± 67 pg, respectively, for new dialyzers, dialyzers reprocessed once, and dialyzers reprocessed 20 times (P = 0.006). IL-1α production by PBMC from dialyzers reprocessed 20 times was significantly greater than both new and dialyzers reprocessed once. However, there were no significant differences between new dialyzers and dialyzers reprocessed once. Similarly, after the 1:1000 challenge, TNFα production by PBMC harvested from the blood compartment was 160 ± 0. 160 ± 0, and 213 ± 22 pg, respectively, far new dialyzers, dialyzers reprocessed once, and dialyzers reprocessed 20 times (P = 0.008). After the 1:100 challenge, TNFα production was 168 ± 8. 188 ± 20, and 225 ± 32 pg, respectively, for new dialyzers, dialyzers reprocessed once, and dialyzers reprocessed 20 times (P = 0.20). These results demonstrate that reprocessing of high-flux polysulfone dialyzers with bleach increases the risk of reverse-transfer of bacterial products from contaminated dialysate, and this risk appears to increase with the number of reuses. Consequently, units that reprocess membranes with bleach and have suboptimal water quality might subject their patients to a higher risk of cytokine-related morbidity.