Microcirculatory heterogeneity in the rat small intestine during compromised flow conditions

To characterize and compare microcirculatory changes in the rat small intestinal tissue layers when temporal or spatial microvascular perfusion heterogeneity is present.

Intravital videomicroscopy with an orthogonal polarization spectral imaging technique was used to visualize the microcirculation of the intestinal mucosa and the longitudinal muscle during systemic (hemorrhagic shock, endotoxemia, and nitric oxide synthesis inhibition) and local (ischemia-reperfusion) circulatory disorders. The average capillary red blood cell velocity (A-RBCV) was calculated from the relative durations of the observed velocity or as a function of the perfused area, respectively.

During hemorrhagic hypotension/resuscitation, timewise (flowmotion) and spatial heterogeneity were found to evolve in the mucosal villi and muscle layer. During resuscitation, the A-RBCV decreased by 40% in the villi and by 60% in the muscle. Reperfusion after a 30-min period of mesenteric ischemia caused a 20% reduction in A-RBCV in both layers, while endotoxin infusion caused a temporary 20% decrease in the mucosa, and a persistent, >25% decrease in the muscle. Nitric oxide synthesis inhibition resulted in spatial heterogeneity within the villi and in a 40% decrease in A-RBCV in both structures.

Calculations of timewise variability and of heterogeneity within and between layers can be used for the comparison of distinct intramural microcirculatory changes.