DOPAMINE AND MUCOSAL OXYGENATION IN THE PORCINE JEJUNUM

The effect of intravenously delivered dopamine on jejunal tissue oxyge nation was studied in 12 pigs anesthetized with midazolam and sufentan il and mechanically ventilated. A small segment of the jejunal mucosa and serosa was exposed by midline laparotomy and antimesenteric incisi on. Mucosal and serosal tissue Po-2, mucosal microvascular hemoglobin oxygen saturation, and mucosal hemoglobin concentration were measured by means of Clark-type oxygen electrodes and tissue reflectance spectr ophotometry, respectively. In five animals electromyogenic potentials of the jejunal wall were recorded. Measurements were performed under b aseline conditions and after intravenous infusion of 2, 4, 8, 16, 32, and again 2 mu g.kg(-1).min(-1) of dopamine. The drug produced a dose- related increase in mucosal Po-2 (from 26.5 Torr at baseline to 49 Tor r at 32 mu g of dopamine; P < 0.001) and mucosal hemoglobin oxygen sat uration (from 55.1 to 70.1%; P < 0.03) but no change in serosal Po-2 ( from 70.6 to 65.5 Torr). In nine animals baseline mucosal Po-2 and muc osal hemoglobin oxygen saturation showed rhythmic oscillations with a frequency of 2.5-5 cycles/min that could not be related to electromyog enic potentials. Dopamine decreased the oscillation amplitude of these two parameters (P < 0.001), and at doses > 16 mu.kg(-1) min(-1) they were no longer present. Dopamine therefore improves mucosal oxygenatio n of the porcine jejunum in a selective and dose-related manner. At hi gher doses the preexisting oscillatory pattern of mucosal oxygenation, which is most likely due to vasomotion, is impeded.