Diffusive vs. convective therapy: Effects on mediators of inflammation in patients with severe systemic inflammatory response syndrome

Objective: to compare two forms of continuous renal replacement therapy, co ntinuous venovenous hemofiltration (CVVH) vs. continuous venovenous hemodia lysis (CVVHD), in terms of the removal of inflammatory mediators from the b lood of patients with systemic inflammatory response syndrome and acute ren al failure. Design: Randomized crossover, clinical study. Setting: University teaching hospital. Patients: Thirteen patients with systemic inflammatory response syndrome an d acute renal failure receiving continuous renal replacement therapy. Intervention: Patients were randomized to receive either convective clearan ce using CVVH or diffusive clearance using CVVHD for the first 24 hrs, foll owed by the other modality for 24 hrs. All treatments utilized AN69 hemofil ters. CVVH was performed with an ultrafiltration rate of 2 L/hr and CVVHD w ith a dialysis outflow rate of 2 L/hr. Measurements and Main Results: Plasma and ultrafiltrate concentrations of t umor necrosis factor (TNF)-alpha, interleukin (IL)-6, IL-10, and sL-selecti n were measured at 0, 1, 3, 6, 12, and 24 hrs by radioimmunoassay. Plasma e ndotoxin concentrations were also measured at 0, 12, and 24 hrs by chromoge nic assay. CVVH was associated with a 13% decrease in plasma TNF-alpha conc entrations compared with a 23% increase while on CVVHD (p < .05). Mean plas ma concentrations of IL-6, IL-10, and sL-selectin were unchanged over time and between therapies. Only minimal amounts of mediators were recovered in the effluents with either therapy except for IL 6. The clearances for IL-6 were different between therapies, 1.9 +/- 0.8 (SD) mL/min for CVVHD and 3.3 +/- 1.5 mL/min for CVVH, (p < .01). Plasma endotoxin concentrations were n ot different between therapies. Conclusion: CVVH resulted in a decrease in plasma TNF a concentrations as c ompared with CVVHD, while the type of transport mechanism used did not infl uence plasma concentrations of IL-6, IL-10, soluble L-selectin, or endotoxi n. Differences in clearance for IL-6 between CVVH and CVVHD did not transla te into significant changes in circulating IL-6 concentrations.