Trauma- and sepsis-induced hepatic ischemia and reperfusion injury: Role of angiotensin II

Hypothesis: We hypothesized that angiotensin II, a potent vasoconstrictor, is involved in the occurrence of hepatic ischemia after burn and sepsis, and that administration of angiotensin II antagonist DuP753 would ameliorate this process. Design: Randomized animal study. Setting: University laboratory, investigational intensive care unit, University of Texas Medical Branch, Galveston. Materials: Female pigs (n = 18, weighing 20-25 kg). Interventions: All animals were prepared with ultrasonic flow probes on the portal vein and the common hepatic artery. Catheters were inserted in the superior mesenteric and left hepatic veins. After 5 days all animals were anesthetized and 12 of them received 40% total body surface area third-degree burn. Escherichia coli lipopolysaccharide (100 μg/kg) was intravenously administered at 18 hours postburn DuP753 was administered intravenously in a dose of 1 μg/kg to 6 pigs immediately after the burn. All animals were studied for 42 hours. Main Outcome Measures: Systemic and hepatic hemodynamics were measured and blood samples were drawn for determinations of arterial, mixed venous, and portal blood gases at baseline and at 14 consecutive time points, starting 1 hour after the burn. Results: Burn caused a 4.6-fold increase in hepatic arterial vascular resistance and a 49% decrease in hepatic arterial blood flow. Postburn administration of angiotensin II receptor blocker DuP753 yielded a significant improvement in the hepatic arterial hemodynamics (only 12% increase in hepatic arterial vascular resistance and 8% decrease in hepatic arterial blood flow, P<.05 vs nontreated group, analysis of variance [ANOVA]). Postlipopolysaccharide hepatic arterial blood flow was significantly reduced (12% of baseline, P<.05, ANOVA), in contrast to DuP753-treated animals (64% of baseline, P<.05 vs nontreated group, ANOVA). Postburn blocking of angiotensin II receptors yielded a significant improvement in postlipopolysaccharide portal venous blood flow (85% of baseline vs 48% of baseline in nontreated animals, P<.05, ANOVA). Postburn endotoxemia resulted in a significant decrease of hepatic oxygen delivery (22% of baseline) and hepatic oxygen consumption (30% of baseline), while no marked changes were observed in the DuP753-treated group (P<.05 vs nontreated group, ANOVA). Conclusions: Angiotensin II seems to play a pivotal role in burn- and sepsis-induced hepatic ischemia and reperfusion injury. Blocking angiotensin II receptors by DuP753 seems to abrogate this adverse effect of thermal injuries and sepsis on hepatic perfusion and oxygenation.