[Heterogeneity of small intestinal microcirculation].

INTRODUCTION

Microcirculatory disorders play important roles in the impairment of the mucosal barrier of the small intestine. Circulatory failures may increase the heterogeneity of microvascular perfusion, however, conventional methods are inadequate to describe an evolving heterogeneity in time or space. The authors aims were to examine and characterize the microcirculatory reactions in the mucosa and longitudinal muscle of the small intestine in clinically relevant experimental models of circulatory disorders.

METHODS

Intravital videomicroscopy with orthogonal polarization spectral imaging technique was used to visualize the microcirculation. A mathematical approach was applied to describe the temporal variability in perfusion based on the calculation of average red blood cell velocity from the relative time periods of observed velocity, while spatial heterogeneity was calculated as a function of the perfused area. The authors' experiments were performed after 1. sham operation, 2. during hemorrhagic shock and crystalloid resuscitation, 3. during 2-hr endotoxin infusion, 4. in response to nitric oxide synthesis inhibition, and 5. after superior mesenteric artery occlusion and reperfusion.

RESULTS

During hemorrhagic shock a fluctuating flow pattern appeared in the mucosa, the average red blood cell velocity decreased by 40% in the villi and by 60% in the muscle. Ischemia caused 20% flow reduction in both layers, while endotoxin caused a temporary 20% decrease in the mucosa, and a persistent, over 25% decrease in the muscle layer. Nitric oxide synthesis inhibition resulted in a 40% decrease in both structures.

CONCLUSIONS

Heterogeneity of microcirculatory perfusion may appeared both spatially (between or within anatomical layers) and in time (periodically) after the insults. A redistribution of blood flow favouring the mucosa evolves in the small intestine after systemic circulatory disorders. Heterogenous perfusion-related microcirculatory changes can be characterized with mathematical approaches, and these calculations should be taken into account during the comparison of the consequences of distinct circulatory failures involving the small intestine.