INOTROPIC TREATMENT AND INTESTINAL MUCOSAL TISSUE OXYGENATION IN A MODEL OF PORCINE ENDOTOXEMIA

Objective: To evaluate the dose-related effects of dopamine, dopexamin e, and dobutamine on intestinal mucosal tissue oxygenation following s hort-time infusion of Escherichia coil lipopolysaccharide, which has p reviously been shown to decrease mucosal tissue oxygenation by 60% of control values. Design: Prospective, randomized, unblinded study. Sett ing: Animal research laboratory. Subjects: Anesthetized, mechanically ventilated domestic pigs. Interventions: Pigs were infused with 2 mu g /kg of E. coli lipopolysaccharide over 20 mins via the superior mesent eric artery. Pulmonary artery occlusion pressure was maintained near 1 5 mm Hg, using a mixed infusion regimen of Ringer's lactate solution a nd hydroxyethyl starch. Following endotoxemia, a small segment of the jejunal mucosa was exposed by midline laparotomy and antimesenteric in cision. The control group (n = 7) received no further interventions. P igs in the dopamine (n = 7), dopexamine (n = 7), and dobutamine (n = 7 ) groups were infused with 2.5, 5, 10; and 20 mu g/kg/min of the respe ctive drug via a central Venous catheter. Measurements and Main Result s: Systemic hemodynamics as well as systemic, mesenteric, and femoral blood gas variables were measured using an arterial, a thermodilution pulmonary artery, a superior mesenteric venous, and a femoral Venous c atheter. Jejunal mucosal tissue Po-2 was measured by means of two Clar k-type surface oxygen electrodes. Oxygen saturation of jejunal mucosal microvascular hemoglobin was determined by tissue reflectance spectro photometry. Infusion of endotoxin resulted in pulmonary hypertension. Systemic hemodynamics remained unchanged except for brief decreases in cardiac output and arterial blood pressure. Dopamine, dopexamine, and dobutamine increased systemic oxygen delivery in a dose-related manne r by 80% (p < .01), 96% (p = .00), and 129% (p = .00) of Values before inotropic treatment. Dopamine increased mucosal tissue Po-2 by 109% ( 10-mu g dose, p<.01) and 164% (20-mu g: dose, p = .00), and mucosal he moglobin oxygen saturation by 61% (5-mu g dose, p < .05), 102% (10-mu g dose, p < 01) and 121% (20-mu g dose, p = .00). Dopexamine increased mucosal tissue Po-2 by 89% (20-mu g dose, p < .01)and mucosal hemoglo bin oxygen saturation by 26% (2.5-mu g dose, p < .05) and 35% (5-, 10- , and 20-mu g dose, p < .05). In the dobutamine and control groups, no significant effect on either mucosal tissue Po-2 or hemoglobin oxygen saturation was observed. Conclusions: In this model of porcine endoto xemia, dopamine and, to a lesser extent, dopexamine increase intestina l mucosal tissue oxygenation. Of all three inotropes used, dobutamine has the most pronounced effect on systemic oxygen delivery, but it doe s not improve mucosal tissue oxygenation. Selective vasodilation withi n the intestinal mucosa; mediated mainly by dopamine-1 receptors, seem s to explain the observed intestinal mucosal effect of dopamine and do pexamine.