Fluid resuscitation improves intestinal blood flow and reduces the mucosal damage associated with strangulation obstruction in pigs

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Background Strangulation obstruction of the small bowel is associated with local and systemic circulatory changes, local loss of fluid, and damage of the strangulated bowel segment. We wanted to examine to which extent these changes can be prevented by intravenous fluid administration. Materials and methods In anesthetized pigs, strangulation obstruction was induced by increasing the pressure in a baby pressure gasket placed around a loop of ileum until venous pressure in the loop reached 50 mm Hg. During the strangulation period (180 min), a group of eight animals (Fluid min group) received 10 ml · kg -1 · hour -1 Ringer acetate solution intravenously, whereas another eight animals (Fluid max group) received 55 ml · kg -1 · hour -1 Ringer acetate solution intravenously. Blood flow to the strangulated bowel was measured by transit time flowmetry and colored microspheres. After completed experiments, whole wall samples of the strangulated loop were selected for microscopy. Results In the Fluid min group, the heart rate increased, the arterial pressure decreased markedly, and the urine output decreased toward zero. In the Fluid max group, the heart rate and arterial pressure remained fairly constant and the urine output increased. Blood flow to the strangulated bowel decreased in both groups, but significantly more in the Fluid min group. The intestinal blood flow was highly dependent on the arterial blood pressure. The strangulated mucosa showed markedly more damage in the Fluid min group than the Fluid max group. The degree of mucosal damage correlated linearly with the mucosal blood flow. Conclusion The administration of large amounts of fluid to animals with strangulation obstruction normalized the arterial pressure and improved the intestinal blood flow thus minimizing damage to the intestinal mucosa.