Differential impairment of vascular reactivity of small pulmonary and systemic arteries in hyperdynamic sepsis

We postulated that the redistribution of organ blood flow that occurs in hyperdynamic sepsis is secondary to organ-specific alterations in vascular reactivity. Chronically instrumented rats were randomized to cecal ligation and perforation (CLP) (n = 12) or to a control procedure (n = 11). Cardiac output increased from 107 +/- 23 ml/min at baseline to 152 +/- 32 ml/min at 24 h after CLP (p = 0.037 versus control values). Mean blood pressure did not change in either group. Small arterial ring segment (100- to 200-microns effective lumen radius) from the pulmonary, renal, celiac, and femora arteries were obtained for determination of in vitro responsiveness. Maximal contractile responses to three receptor-operated contractile agonists were significantly depressed in the pulmonary (p = 0.001) and the celiac (p = 0.001) arteries from CLP versus control rats. The renal artery showed a trend toward decreased responsiveness (p = 0.049), but not difference was seen in the femoral artery (p = 0.172). EC50 values were unchanged. A similar, but less marked, pattern was observed for KCI-induced contractions in that depressed responses were noted in the pulmonary (p = 0.045) and celiac (p = 0.064) arteries. Vasodilator responses to acetylcholine were normal in all vessels. Nitroprusside relaxant responses were enhanced in the pulmonary artery (p = 0.022), but they were normal in the other vessels. We conclude that hyperdynamic, normotensive sepsis is associated with an organ-specific alteration of vascular smooth muscle function that particularly affects receptor-operated contractile responses. The differential expression of this altered vascular responsiveness between organs may contribute to the observed variance in regional blood flows in sepsis.