The pathophysiology of septic shock: responses to different doses of live Escherichia coli injection in rats.

Responses to different doses of Escherichia coli (E coli; 0-18) injection were studied from the pathological standpoint. Various amounts of live E coli were intravenously injected through the tail vein (group A: 2.7-3.3 X 10(9); B: 1.7-2.0 X 10(9); C: 1.2-1.5 X 10(9); D: 0.3-0.5 X 10(9) organisms/100 g of body weight). All rats from group A died within 6 h; 14 out of 15 rats from group D survived. Hypothermia was commonly seen in the lethal groups (groups A, B, and C) prior to death, and hyperthermia was observed only in groups C and D. Leukopenia was seen in all groups and remained in the lethal groups, whereas in group D, leukocytosis following leukopenia was observed at 12 and 24 h. Light microscopic studies were performed in the lethal groups, showing the following differences among the three lethal groups; a dose-related depletion of white pulp of the spleen, cortical hemorrhage of the adrenal glands (only in groups A and B), foci of bacterial colonies in the heart and small intestine with aggregated leucocytes (only in group C); focal liver necrosis was found in group C, but not in group A. Tubular necrosis and cast formation were also predominant in the kidneys of group C animals. The above findings indicate that the milder, lethal group shows more severe morphological changes in all organs except the spleen and adrenal glands, and suggest that sudden death from bacteremia may involve a depleted host defense.