Evidence for oxidative stress during in vitro dialysis

The evidence for oxidative stress during haemodialysis is controversial. We therefore examined markers of oxidative stress and lipid peroxidation using an in vitro dialysis circuit. A unit of fresh blood (500 ml) therapeutically removed from each of 7 haemochromatosis patients was oxygenated and circulated for 4 h at 37 degrees C through a cuprophane dialyser (Clirans C08) against saline dialysate (1,000 ml recirculating; +FIL group). In a second series of experiments (n = 7), the dialyser was omitted from the circuit (-FIL group). Concentrations of anti-oxidants and malondialdehyde (MDA) were measured at 7 time points during the study. Blood thiol concentrations decreased by 25.6% in the +FIL group (p < 0.05) but were unchanged in the -FIL group (p > 0.05; group comparison, p = 0.006). There were no significant differences between the groups, for the lipid-soluble anti-oxidants alpha-tocopherol, retinol and beta-carotene. Plasma MDA concentrations increased in both circuits (p < 0.001, respectively, no difference between groups). However, the susceptibility of red blood cells to lipid peroxidation (as determined by MDA production following a challenge with hydrogen peroxide) was unchanged by 120 min of dialysis. These in vitro experiments provide supporting evidence that haemodialysis is accompanied by measurable oxidative stress and plasma lipid peroxidation.