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.