Hemodynamics during increased intraluminal pressure in the ileum of suckling swine

Studies of intestinal hemodynamics during increased abdominal and intraluminal pressure in adult animals (canine and feline) have shown that blood flow is practically unchanged at pressures up to 35-40 mm Hg. In the young animal, however, decreased total intestinal blood flow has been shown at pressures of 15 mm Hg or greater. To help characterize the effect of intraluminal pressure on intestinal circulation, we have studied pressure-flow relationships in an isolated loop of terminal ileum in piglets 2-14 days of age (mean, 6.1 +/- 3.7 SD, n = 14) with a mean weight of 1,745 +/- 345 SD. Intraluminal pressure was increased from 0-50 cm of water pressure in 10-cm steps of two min' duration. Blood flow was reduced with every increase in intraluminal pressure and significantly reduced at pressures of 20 cm of water or more. The calculated peripheral vascular resistance increased with every increment of intraluminal pressure. Analysis of the relationship of arterial blood pressure to changes in blood flow suggests that blood flow reductions are greater in animals with lower blood pressure at every level of intraluminal pressure studied. Increased intraluminal pressure could be a mechanism of intestinal mucosal ischemia in the newborn, particularly affecting those with low arterial blood pressure.