Objectives:To determine whether continuous venovenous hemodiafiltration (CVVHD) is associated with the extraction of interleukin-6 (IL-6) and interleukin-8 (IL-8) from the circulation of critically ill patients with septic acute renal failure. To quantitate their clearance and assess any possible effect of CVVHD on these cytokines’serum concentrations.Design:Prospective controlled study of IL-6 and IL-8 removal by CVVHD in patients with septic acute renal failure.Setting:Intensive care unit of a tertiary institution.Patients:Ten critically ill patients with sepsis, acute renal failure, and multiorgan failure. A control group of five patients experiencing an acute illness while undergoing chronic hemodialysis.Interventions:Collection of blood samples before CVVHD. Simultaneous collection of prefilter blood and ultradiafiltrate after 4 and 24 h of treatment. IL-8 concentrations were measured in blood and ultradiafiltrate. Their clearances and daily extractions were calculated.Measurements and Main Results:IL-6 and IL-8 were detected in the blood of all patients with septic acute renal failure prior to CVVHD. The median IL-6 blood level was 103 pg/mL (range: 19 to 900) and the median IL-8 blood level was 200 (range: 32 to 2925). Both cytokines were cleared by the hemofilter during CVVHD. The median hemofilter clearance ofIL-6 were 1.99 L/day (range: 0 to 8.5) and the median clearance of IL-8 was 3.95 L/day (range: 0.31 to 42.8). These blood levels and clearances resulted in median daily extraction rates of 194 ng ofIL-6 (range: 0 to 9031) and of 915 ng of IL-8 (range 47.5 to 3562). Control patients had negligible amounts of either IL-6 or IL-8 In their ultrafiltrate. The rate of extraction for IL-6 correlated with its blood levels (p<0.0001). This was not true for IL-8. A correlation between IL-6 levels and the patients’white cell counts was found after 24 h ofhemofiltration.Conclusions:CVVHD is associated with the extraction of IL-6 and IL-8 from the circulation of patients with septic multiorgan and renal failure. The biological significance of such extraction is undetermined, but such cytokine removal highlights the complexity of the effect of continuous hemofiltration on the soluble mediators of inflammation activated during human sepsis.