RESUMO
OBJECTIVE: To investigate the mechanism of better result of limited resuscitation in a model of uncontrolled hemorrhagic shock. METHODS: Uncontrolled hemorrhagic shock was produced in 54 rats by a standardized massive splenic injury with transection of the middle branch of splenic artery (MSIA). The rats were randomly assigned to six groups (n=6) by maintenance of the level of mean arterial pressure (MAP): sham-operated group (SS), 40 (RS40), 50 (RS50), 60 (RS60), 80 (RS80) and 100 mm Hg (RS100, 1 mm Hg=0.133 kPa). When the MAP reached 40 mm Hg, resuscitation was begun. Ringer's solution was continued as needed to maintain the following desired endpoints for 45 minutes (T45 point): MAP of 40, 50, 60, 80 and 100 mm Hg. After the bleeding was controlled, resuscitation was continued with Ringer's solution and whole blood (2:1) to raise the MAP to 100 mm Hg for 120 minutes (T165 point), followed by a 240 minutes observation period (T405 point). All animals were observed for 240 minutes or till death. The blood samples were withdrawn from artery for hematocrit (Hct), blood lactate (BL), base excess(BE) at T0, T45, T165, T405 points. At the end of the experiment, a small amount of hepatic tissue was collected for measuring tissue blood perfusion, total antioxidative capacity (T-AOC), Na(+)-K(+)-ATPase, and malondialdehyde (MDA). RESULTS: At T45, T405 points, Hct in SS, RS50 and RS60 were significantly higher than in RS80 and RS100(P<0.05). At T405 point, BL and BE levels in RS80 and RS100 were significantly higher than that of the other groups (P<0.05). The contents of MDA in SS, RS40, and RS50 were significantly lower than in RS80 and RS100(P<0.05). T-AOC level, Na(+)-K(+)-ATPase were significantly lower in RS80 and RS100 than that in the other groups. Blood perfusion was significantly lower in RS80 and RS100 than that in SS, RS40, and RS50. CONCLUSION: In the setting of uncontrolled hemorrhagic shock, limited resuscitation could balance well the needs of organ perfusion and decrease lactate level. It might also exert a protective effect against ischemia/reperfusion injury to liver tissue.
