Article révisé par les pairs
Résumé : 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 (mes-ERO2) 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 mes-ERO2 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 mes-ERO2 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 mes-ERO2, respectively). Variations in villi-PPV were paralleled by variations in mes-ERO2 (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.

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