Fig. 2. Effect of high-volume continuos venovenous hemofiltration (CVVH) on endotoxin-induced nitrate–nitrite concentrations, a marker of nitric oxide production. Plasma nitrate–nitrite concentrations were determined 1 and 5 h after an intravenous infusion of 500 μg/kg endotoxin (E. coli lipopolysaccharide). In one group of animals (endotoxin plus hemofiltration [HF], n = 6), treatment with CVVH was initiated 1 h after the end of endotoxin infusion (start of hemofiltration) and performed for 4 h (end of hemofiltration). The other group (endotoxin alone, n = 6) served as control. CVVH was zero-balanced, and the ultrafiltration rate was set at 4,500 ml/h. Values are percent of baseline and expressed as mean ± SD. *P < 0.05 compared to baseline within group; †P < 0.05, endotoxin versus endotoxin-plus-hemofiltration group at 4 h of treatment (5 h after endotoxin). Note that after 5 h of endotoxin challenge, there was an increase in plasma nitrate–nitrite concentrations in animals not treated with CVVH (endotoxin alone). Endotoxin-challenged pigs treated with CVVH for 4 h showed a reduction of this endotoxin-induced increase in plasma nitrate–nitrite concentrations.