Comparison between intravital microscopy and laser Doppler microcirculation monitoring methods in experimental sepsis: preliminary results

Introduction

Sepsis (S) produces regional perfusion abnormalities by causing vasodilatation and blood flow redistribution, and this process mostly affects the mesenteric circulation. In addition, gut mucosal hypoperfusion can perpetuate the inflammatory process and contributes to the multiple organ failure. Thus, following experimental sepsis induction we examined gut blood flow by intravital microscopy and the gut tissue perfusion by laser Doppler, in order to detect the onset of the intestinal microcirculation changes at the acute phase of sepsis.

Methods

Adult female Wistar rats (200–250 g) were submitted to sublethal sepsis (DL₈₅ 27 hours) by inoculation of 10⁹ CFU/ml/100 g body weight of Escherichia coli R-6 into the jugular vein and were monitored at 3 hours (n = 4) and 6 hours (n = 5) periods, examining 50 villi mucosal blood flow at the distal ileum by intravital microscope and external and internal mucosal surface tissue perfusion by laser Doppler using a type-S probe (3 hours, n = 4 and 6 hours, n = 3). Saline was used in control groups and all procedures were realized under general anesthesia.

Results

Intravital analysis showed more than 90% of normal villi microcirculation in all S groups at all time periods, similar to the control groups (100% normal). Concerning tissue perfusion analysis with laser Doppler at the gut external surface, no significant statistical difference could be seen among all groups. Nevertheless, there was a statistical difference at the mucosal surface between the sham and 6 hours S groups, showing that signs of gut hypoperfusion at the mucosal site were not detectable by the intravital microscopy method although they were detectable by laser Doppler at only the late period. These data highlight that intestinal microcirculation is quite stable even during severe sepsis conditions, in contrary to the concept of fragile gut microcirculation related to sepsis shock.

Conclusion

The laser Doppler mucosal tissue perfusion method can be a useful tool for the detection of microcirculation changes in sepsis. Ongoing studies are being performed to better evaluate microcirculation-measuring tools in sepsis.