OBJECTIVE: Oxidative cell damage due to the production of free radical species has been implicated in the pathogenesis of cardiovascular disease for which dialysis patients are at increased risk. Plasma lipid peroxides (malon-dialdehyde), the antioxidants plasma albumin thiol, and red cell superoxide dismutase (SOD) were therefore measured in 18 patients undergoing continuous ambulatory peritoneal dialysis (CAPD), 20 hemodialysis patients, and 30 normal controls. SETTING: Renal dialysis unit. RESULTS: Malondialdehyde (MDA) concentrations were significantly higher in dialysis patients compared to controls (p less than 0.001) and were significantly higher in CAPD patients compared to hemodialysis patients, p less than 0.001 (CAPD, median and range: 11.25 (8.4-15.5) nmol/mL; hemodialysis: 8.75 (7.0-12.6) nmol/mL; controls: 6.65 (5.2-9.6) nmol/mL). Plasma thiol and red cell SOD were significantly lower in dialysis patients compared to controls, but there was no significant difference between CAPD and hemodialysis patients (CAPD thiol: 333.5 (282-480) mumol/L; hemodialysis thiol: 344 (203-468) mumol/L; control thiol: 421.5 (351-504) mumol/L; CAPD SOD: 78.2 (42.4-112.8) u/1/2 mL red cells; hemodialysis SOD: 89.4 (44.6-121.1) u/1/2 mL red cells; control SOD: 96.8 (66.8-153.4) u/1/2 mL red cells). Red cell SOD was significantly negatively correlated with duration of dialysis in CAPD patients (r = -0.683, p less than 0.01). CONCLUSION: In dialysis patients there is indirect evidence for increased free radical activity, which may be further influenced by the mode of dialysis.

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