DYSREGULATION OF THE VENOARTERIAL RESPONSE IN THE SUPERIOR MESENTERIC-ARTERY DURING ENDOTOXIC-SHOCK

Objective: To investigate whether the vascular dysfunction in endotoxic shock is associated with inhibition of the veno-arterial response of the superior mesenteric artery, Design: Prospective, concurrent trial, Setting: Animallaboratory. Subjects: Domestic pigs, Interventions: Two groups of pigs were anesthetized with ketamine and pentobarbital, mechanically ventilated, and hemodynamically monitored, One group (n = 8) was challenged with Escherichia coli endotoxin (30 mu g/ kg iv), while the other group (n = 4) served as time controls, Portal vein pressure was transiently increased in a series of steps from baseline to 25 mm Hg by partially obstructing portal venous flow, Measurements and Main Results: The effects of increases in portal pressure on superior mesenteric artery resistance, superior mesenteric artery fractional flow, and cardiac output were assessed, Under pre-endotoxin conditions, raising portal pressure induced an increase in superior mesenteric artery resistance, a decrease in superior mesenteric artery fractional flow, and no significant change in cardiac output (i.e., a normally regulating veno-arterial response), After endotoxin administration, raising portal pressure induced a decrease in superior mesenteric artery resistance, no change in superior mesenteric artery fractional flow, and a decrease in cardiac output (i.e., a dysregulated veno-arterial response), Conclusions: Under baseline conditions, a normally regulating veno-arterial response in the mesenteric vascular bed should minimize intestinal blood pooling with acute portal hypertension, Under conditions of endotoxemic shock, the dysregulation of the veno-arterial response could substantially contribute to blood pooling and edema formation in the intestinal vascular bed during septic shock, This phenomenon may account for many of the macro- and microcirculatory manifestations of septic shock.