Effects of dobutamine on intestinal microvascular blood flow heterogeneity and O₂ extraction during septic shock

Derangements of microvascular blood flow distribution might contribute to disturbing O₂ extraction by peripheral tissues. We evaluated the dynamic relationships between the mesenteric O₂ 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] (R² = 0.88, P < 0.001) and these, in turn, by mesenteric lactate changes (R² = 0.86, P < 0.001). There were no significant differences in cardiac output and systemic O₂ delivery throughout the experiment. In conclusion, dynamic changes in microvascular blood flow heterogeneity at jejunal mucosa are closely related to the mesenteric O₂ extraction ratio, suggesting a crucial role for microvascular blood flow distribution on O₂ 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 O₂ extraction, thus supporting the role of decreasing functional capillary density and increased intercapillary distances on alterations of O₂ 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 O₂ consumption.