Super high flux hemofiltration: a new technique for cytokine removal

Objective: To test whether hemofiltration using a hemofilter with large pores (super high flux hemofiltration) achieves effective cytokine removal. Design: Ex vivo study. Setting: Laboratory of an intensive care unit in a tertiary hospital. Patients and participants: Five healthy volunteers. Interventions: Blood was spiked with I mg of endotoxin and then circulated through a closed hemofiltration circuit with a large pore polyamide super high flux hemofilter (nominal cut-off point: 100 kDa). Hemofiltration was conducted at I l/h or 6 l/h of ultrafiltrate flow. Samples were taken from the arterial, venous and ultrafiltration sampling ports. Measurements and results: Sieving coefficients (SC) above 0.6 were achieved for interleukin (IL)-1beta, IL-6 and IL-10 and SCs above 0.3 were achieved for IL-8 and TNF-alpha at I l/h. SCs of all cytokines (except IL-1) were reduced when the ultrafiltration rate was increased from I l/h to 6 l/h (p<0.01), but cytokine clearances still increased (p<0.01). The highest SC for albumin was 0.1 at I l/h and fell to 0.01 at 6 l/h. No adsorption of cytokines and albumin was observed. Conclusion: High volume ultrafiltration using a super high flux filter achieved cytokine clearances comparable to, or greater than, those currently achieved for urea during standard continuous renal replacement therapy.