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The aim of the study was to investigate the changes of the activity of superoxide dismutase (SOD) and the level of malondialdehyde (MDA) in plasma and organ damage during the acute severe hemorrhagic shock (ASHS), as well as to analyze their relationship.Twenty male Wistar rats (230–270 g) were randomly divided into sham hemorrhage shock (SHS) group and ASHS group. Acute severe hemorrhagic shock rats were induced by drawing blood through a femoral arterial catheter for 15 minutes with the final mean arterial blood pressure decreased to 35 to 40 mm Hg. The animals were killed after the mean arterial blood pressure was maintained at this level for 1 hour. The activity of SOD and the level of MDA in plasma were measured, and pathologic changes of the major organs (heart, liver, spleen, lung, kidney, and brain) were observed by microscopy.The SOD activities and MDA levels in the ASHS group both increased continuously during the whole experiment. The SOD activities and MDA levels in plasma were not significantly different between the prehemorrhagic stage of ASHS and that of SHS (P > .05). The SOD activities and MDA levels were significantly higher in the ASHS initial stage than in the prehemorrhagic stage (P < .01). Compared with the ASHS initial stage, there was a significant (P < .01) increase in SOD activities and MDA levels in the ASHS end stage. Severe microscopic injuries appeared in the major organs (heart, liver, spleen, lung, kidney, and brain) of ASHS rats.The changes of the activity of SOD and the level of MDA in ASHS may have a positive correlation.