[Does plasmapheresis affect the production of free radicals and the antioxidant system?]

Free radicals cause lipid peroxidation, damage cell membranes and DNA. At present attention is paid to the relationship between extracorporeal methods of blood clearance, free radicals and the antioxidant system. The objective of the present study was to ascertain the effect of membrane plasmapheresis (PF) on the antioxidant defence of the organism and whether it has an impact on lipid peroxidation.

Patients with inflammatory polyneuropathy (n = 7), pemphigus (n = 1) and pulmonary fibrosis (n = 1) were subjected to 3 PF each (apparatus Fresenius 2008 PF, filter Plasmaflux P2S). The following were assessed: superoxide dismutase activity (SOD) in red blood cells, the antioxidant capacity (AOK) and malondialdehyde (MDA) in plasma, glutathione peroxidase (GSHPx and selenium (Se) in blood, AOK, MDA and Se in the filtrate. The values were compared with those of 43 healthy volunteers using the t-test, changes of parameters during PF, using Wilcoxon's paired test. The baseline SOD, GSHPx, AOK and MDA values of patients did not differ from those of controls. SOD did not change in the course of PF. GSHPx declined during the 30th minute of PF and after PF (44.3 +/- 16.9 U/g, haemoglobin before vs. 37.5 +/- 12.2 during the 30th minute, p < 0.01, 36.7 +/- 14.6 after PF, p < 0.01). AOK rose during the 30th minute (p < 0.01) and after PF (p < 0.01). MDA after PF declined (p < 0.05). The baseline Se was higher than in controls (132.9 +/- 43.2 micrograms/l vs. 90.5 +/- 17.3, p < 0.01), after PF Se declined (100.1 +/- 28.3, p < 0.01).

The authors did not provide evidence of increased lipid peroxidation during PF. During PF the GSHPx activity declines, most probably due to Se losses. The decline of GSHPx involves the risk of deterioration of hydrogen peroxide elimination and of increased free radical formation.