Microcirculation in intestinal villi: a comparison between hemorrhagic and endotoxin shock.

Using intravital microscopy, we studied the effects of hemorrhagic and endotoxin (ETX) shock on the velocity of erythrocytes (red blood cells [RBC]) and the density of perfused villi in mouse small intestine. The mice were divided into four groups: control, normotensive sepsis (a low ETX group, 1.5 mg/kg intravenously), hypotensive sepsis (a high ETX group, 10 mg/kg intravenously), and a hemorrhagic group. One hour after endotoxemia or hemorrhage was induced, mean arterial pressure significantly decreased in the high ETX and hemorrhagic groups (72.5 +/- 1.0 mm Hg in the control group, 71.0 +/- 2.4 in the low ETX group, 42.7 +/- 1.8 in the high ETX group, 43.0 +/- 1.4 in the hemorrhagic group, respectively). We found significant decreases in RBC velocities in the villous tip and capillaries in both ETX groups but not in the hemorrhagic group (in villus tip arteriole, 1.25 +/- 0.02 mm/s, 0.80 +/- 0.02, 0.15 +/- 0.01, 1.20 +/- 0.08; in villus capillaries, 0.55 +/- 0.02, 0.38 +/- 0.02, 0.10 +/- 0.01, 0.61 +/- 0.02, for control, low ETX, high ETX, and hemorrhagic groups, respectively). We also found a significant decrease in the density of RBC-perfused villi in the high ETX and hemorrhagic groups but not in the low ETX or control groups. However, the change in the hemorrhagic group was much less than in the high ETX group (100.0 %, 95.2 +/- 1.6, 32.5 +/- 1.9, 87.3 +/- 3.4, for control, low ETX, high ETX, and hemorrhagic groups, respectively). We concluded that ETX induces a significant decrease in mucosal perfusion characterized by a diminution in RBC velocity and flux in villi found even in a normotensive situation. At a high dose of ETX, these changes are associated with a significant decrease in the number of perfused villi. In addition, we found that at the same level of hypotension, hemodynamics and mucosal perfusion disorders are considerably larger in ETX-induced hypotension than in hemorrhagic hypotension.