DIFFERENTIAL IMPAIRMENT OF VASCULAR REACTIVITY OF SMALL PULMONARY ANDSYSTEMIC 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 v ascular reactivity. Chronically instrumented rats were randomized to c ecal 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 value s). Mean blood pressure did not change in either group. Small arterial ring segments (100- to 200-mum effective lumen radius) from the pulmo nary, renal, celiac, and femoral arteries were obtained for determinat ion of in vitro responsiveness. Maximal contractile responses to three receptor-operated contractile agonists were significantly depressed i n the pulmonary (p = 0.001) and the celiac (p = 0.001) arteries from C LP versus control rats. The renal artery showed a trend toward decreas ed responsiveness (p = 0.049), but no difference was seen in the femor al artery (p = 0.172). EC50 values were unchanged. A similar, but less marked, pattern was observed for KCl-induced contractions in that dep ressed 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 vesse ls. We conclude that hyperdynamic, normotensive sepsis is associated w ith an organ-specific alteration of vascular smooth muscle function th at particularly affects receptor-operated contractile responses. The d ifferential expression of this altered vascular responsiveness between organs may contribute to the observed variance in regional blood flow s in sepsis.