Effects of dobutamine on intestinal microvascular blood flow heterogeneity and O(2) extraction during septic shock

Derangements of microvascular blood flow distribution might contribute to disturbing O(2) extraction by peripheral tissues. We evaluated the dynamic relationships between the mesenteric O(2) extraction ratio ([Formula: see text]) and the heterogeneity of microvascular blood flow at the gut and sublingual mucosa during the development and resuscitation of septic shock in a swine model of fecal peritonitis. Jejunal-villi and sublingual microcirculation were evaluated using a portable intravital-microscopy technique. Simultaneously, we obtained arterial, mixed-venous, and mesenteric blood gases, and jejunal-tonometric measurements. During resuscitation, pigs were randomly allocated to a fixed dose of dobutamine (5 µg·kg(−1)·min(−1)) or placebo while three sham models with identical monitoring served as controls. At the time of shock, we observed a significant decreased proportion of perfused intestinal-villi (villi-PPV) and sublingual percentage of perfused small vessels (SL-PPV), paralleling an increase in [Formula: see text] in both dobutamine and placebo groups. After starting resuscitation, villi-PPV and SL-PPV significantly increased in the dobutamine group with subsequent improvement of functional capillary density, whereas [Formula: see text] exhibited a corresponding significant decrease (repeated-measures ANOVA, P = 0.02 and P = 0.04 for time × group interactions and intergroup differences for villi-PPV and [Formula: see text] , respectively). Variations in villi-PPV were paralleled by variations in [Formula: see text] (R(2) = 0.88, P < 0.001) and these, in turn, by mesenteric lactate changes (R(2) = 0.86, P < 0.001). There were no significant differences in cardiac output and systemic O(2) delivery throughout the experiment. In conclusion, dynamic changes in microvascular blood flow heterogeneity at jejunal mucosa are closely related to the mesenteric O(2) extraction ratio, suggesting a crucial role for microvascular blood flow distribution on O(2) uptake during development and resuscitation from septic shock. NEW & NOTEWORTHY Our observations suggest that dynamic changes in the heterogeneity of microvascular blood flow at the gut mucosa are closely related to mesenteric O(2) extraction, thus supporting the role of decreasing functional capillary density and increased intercapillary distances on alterations of O(2) uptake during development and resuscitation from septic shock. Addition of a low-fixed dose of dobutamine might reverse such flow heterogeneity, improving microcirculatory flow distribution and tissue O(2) consumption.