Effects of norepinephrine on the distribution of intestinal blood flow andtissue adenosine triphosphate content in endotoxic shock

Objective: To investigate, during endotoxic shock, the effect of a treatmen t of norepinephrine (NE) administration on the distribution of blood flow a nd adenosine triphosphate (ATP) content in the intestinal wall. Design: Randomized controlled trial. Setting: Animal laboratory. Subjects: Domestic pigs. Intervention: A total of 18 pigs were anesthetized with ketamine and pentob arbital, mechanically ventilated, hemodynamically monitored, and then chall enged with a continuous infusion of Escherichia coli endotoxin (ET) (15 mu g/kg) for 2 hrs. Three groups of six animals were studied; one served as ti me control, one group received ET and fluid resuscitation, and a third grou p received ET, fluid resuscitation, and a perfusion of NE to maintain const ant mean arterial pressure (MAP). Measurements and Main Results: Cardiac output, mesenteric arterial blood fl ow, MAP, pulmonary pressure, and portal pressure were measured. Intestinal mucosal intracellular pH (pHi) was determined with saline-filled balloon to nometers. Tissue blood flows to the intestinal mucosa and to the muscular l ayer were independently measured with fluorescent microspheres, using the a rterial reference sample method. Measurements were performed before and 3 hrs after the start of the ET chal lenge. At the end of the experiments, muscularis and mucosal samples were q uickly frozen for further enzymatic ATP measurements. ET administration wit h fluid resuscitation induced a distributive shock with increased mucosal b lood flow and decreased muscularis blood flow, whereas pHi decreased and mu cosal ATP content was significantly lower than in the control group. In the group receiving ET plus NE, MAP remained constant, mucosal blood flow did not increase, and mucosal ATP content was equal to the time control group. Meanwhile, mucosal acidosis was not prevented. Conclusions: Normodynamic endotoxic shock may induce an alteration in mucos al oxygenation, despite an increased tissue blood flow. A treatment of NE c ombined with fluid resuscitation has complex effects on tissue blood flow, ATP content, and pHi.