RESUMEN
Decreased plasma selenium (Se) levels are common in critically ill patients. Oxidative stress is regarded as one possible cause of the Se deficiency. We investigated in 20 critically ill patients with decreased plasma selenium concentrations the antioxidant metabolism during parenteral selenium supplementation (week 1: 2 x 500 micrograms; week 2:1 x 500 micrograms, week 3:3 x 100 micrograms sodium selenite). As marker of oxidative stress we measured the plasma malondialdehyde levels on days 0, 1, 3, 7, 14, and 21. The content of reduced and oxidized glutathione as well as the leucocyte activity marker elastase were estimated on the same days. Initial plasma Se levels were considerably decreased (0.44 +/- 0.1 mumol/l, mean +/- SEM). After one day of supplementation Se concentrations were in the reference range. Plasma malondialdehyde levels and the ratio of oxidized and reduced glutathione were initially elevated and decreased beginning on day 3 of supplementation. The mean elastase level was 113 +/- 10 micrograms/l on day 0. On day 3 elastase values decreased significantly (85 +/- 13 micrograms/l, p < 0.05; day 21, 19 +/- 7 micrograms/l, p < 0.001). Antioxidant metabolism showed significant changes beginning after 72 hours of therapy. This latency may be explained with the induction of the enzyme glutathione peroxidase. The lowered plasma Se concentrations measured in the critically ill patients and the significant effects on antioxidant metabolism during supplementation emphasized the importance of selenium administration in these patients.