Changes of small intestinal villi microcirculation in sidestream dark-field imaging with different target blood pressure in rabbits during endotoxin shock

Abstract

Changes of small intestine villus microcirculation perfusion in sidestream dark-field (SDF) imaging in the rabbits during endotoxic shock after fluid resuscitation with different target mean arterial pressure (MAP), and evaluation of feasibility of monitoring small intestine villus microcirculation by SDF were studied. Sixty standard New Zealand white rabbits were randomly divided into two groups: low target MAP group (group A, n = 30) and high target MAP group (group B, n = 30). Fistula operation of ileum was made in vitro, and lipopolysaccharide (LPS, 2 mg/kg) was injected to establish endotoxic shock model. Group A was administered with the lower dose fluid resuscitation (lactated Ringer solution, 20 mL×kg-1×h-1) for target MAP of 65 mmHg (1 mmHg = 0.133 kPa); group B was administered with the higher dose fluid resuscitation (lactated Ringer solution, 30 mL×kg-1×h-1) for MAP of 80 mmHg. Continuous norepinephrine intravenous injection (0.5-1.0 μg×kg-1×min-1) was administered only after fluid therapy couldn't reach the target MAP. The changes of small intestine villus microcirculation perfusion indexes such as vessels per villus (VV), proportion of perfused villi (PPV), microvascular flow index (MFI), borders of villus score (BVS), vessels villus score (VVS) were continuously observed and recorded before the shock, during the shock and after fluid resuscitation using SDF imaging. The differences of microcirculation perfusion were compared between two groups using the specific parameter evaluation system to determine severity of villi microcirculation and injury scores at different stages. VV and borders of villus were clear and contact before shock in two groups. After shock, VV, PPV were significantly decreased in both two groups, the borders of villus were destroyed, MFI, BVS, VVS and the total score of villi injury microcirculation were obviously and severely decreased. Partial blood flow of villous capillaries after fluid resuscitation was recovered in two groups, but the perfusion of some region was un-balanced with the outworn borders of villus. VV were rose as compared before and after fluid resuscitation in groups A and B (vessels: 1.21±0.22 vs. 0.81±0.12, 1.54±0.28 vs. 0.79±0.13), and PPV [(31±4)% vs. (12±2)%, (38±5)% vs. (13±3)%], MFI (1.55±0.09 vs. 1.09±0.03, 1.97±0.11 vs. 1.05±0.03), VVS (points: 1.22±0.08 vs. 0.89±0.02, 2.06±0.15 vs. 0.90±0.02) and the sum of MFI, BVS, VVS (3.70±0.19 vs. 2.85±0.07, 5.01±0.29 vs. 2.88±0.08) were significant rose (all P < 0.05). The recovery of group B was better than that of group A, and the injury score was reduced. But BVS were not increased in both groups compared with before and after shock (points: 0.93±0.05 vs. 0.87±0.03, 0.98±0.09 vs. 0.93±0.05, both P > 0.05). For the small intestine villus microcirculation perfusion, the higher target MAP (80 mmHg) after fluid resuscitation or/and vasoconstrictor drugs usage were probably better than the relatively lower target MAP (65 mmHg) during endotoxic shock. SDF imaging is a very promising technique for intestinal villi microcirculatory visualization and assessment.